JP2013050874A - Voltage generating circuit and power-on reset circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage generating circuit capable of quickly outputting a reference voltage, even in a case where a power supply voltage is transiently lowered, after the power supply voltage is subsequently raised, and further to provide a power-on reset circuit capable of quickly outputting a reset signal.SOLUTION: Transistors MP5 and MP6 are connected in series between a first power line N1 and a node N6. The transistor MP5 senses a starting current Is and the transistor MP6 senses a reference current Ip. Even if a power supply voltage VDD is lowered, for both transistors MP5 and MP6, there is no possibility that voltages not less than a threshold voltage are applied among gates and sources, and a charging circuit 8 is hardly charged with a charging current Io. Accordingly, when the power supply voltage VDD is restored and the power supply voltage VDD is raised, a transistor MP4 can quickly supply the starting current Is to a node N5 and a current generating circuit 6 can quickly generate the reference current Ip.

Description

  The present invention relates to a voltage generation circuit that generates a reference voltage, and a power-on reset circuit using the voltage generation circuit.

  FIG. 7 shows a main part of the prior art represented by Patent Document 1, for example, and FIG. 8 shows its operation by a timing chart. In addition, in order to make it easy to understand the difference between the present invention and the background art, the reference numerals given to the circuit components in FIG. 7 are circuits having the same or similar functions in the “Mode for Carrying Out the Invention” section below. The same reference numerals are assigned to the constituent elements.

  In the circuit shown in FIG. 7, the current of the current mirror circuits MP1 and MP2 is sensed by the transistor MP6. When a current flows through the current mirror circuits MP1 and MP2, a current mirror current is output from the transistor MP3. At this time, the sensing transistor MP6 supplies a charging current Io to the charging circuit 8, thereby generating a current from the startup circuit 3. The supply of the starting current Is flowing through the circuit 6 is stopped.

JP-A-8-186484 Japanese Patent Laid-Open No. 10-133758 JP 61-26117 A JP 2004-86750 A

  When determining the element value of the transistor of this semiconductor integrated circuit, various characteristics such as the threshold voltage Vt and current amplification factor of the transistor are determined by determining the gate width and gate length of the transistor. Since the sensing transistor MP6 of FIG. 7 senses the currents of the constituent transistors MP1 and MP2 of the current mirror circuit, the threshold voltage Vt1 is made lower than the threshold voltage Vt2 of the constituent transistors MP1 and MP2 of the current mirror circuit and the current amplification factor. In such a case, it is preferable to shorten the gate length L of the transistor MP6 and widen the gate width W.

  However, when the power supply voltage temporarily decreases due to a momentary power interruption or the like, when the power supply voltage VDD decreases to an intermediate voltage (for example, about 1 V), the intermediate voltage remains while the transistors MP1 and MP2 of the current mirror circuit remain off. The current corresponding to the current flows through the sensing transistor MP6. Then, as shown in the timing chart of FIG. 8, even if the power supply voltage is restored thereafter, almost no current flows through the transistor MP4 for supplying the starting current Is in the subsequent stage, and the supply of the starting current Is is delayed. As a result, the function of the start-up circuit 3 does not operate sufficiently, and a rise delay occurs in the output reference voltage VREF of the bandgap reference circuit. In such a case, the power-on reset does not function normally.

  The threshold voltage Vt of the transistor MP6 can be increased by increasing the gate length L of the sensing transistor MP6. However, if the threshold voltage Vt is increased while maintaining the ratio of the gate width W / gate length L, the gate length L Since the gate width W must be enlarged in accordance with the enlargement ratio, the gate width W is not practical and is not desirable in consideration of the semiconductor chip size. Therefore, a configuration that can quickly start the output reference voltage without changing the length of the gate length L as much as possible is desired.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to generate a voltage that can quickly output a reference voltage if the power supply voltage subsequently increases even when the power supply voltage temporarily decreases. It is an object of the present invention to provide a circuit and a power-on reset circuit that can quickly output a reset signal.

  According to the first aspect of the present invention, when the current generating means (6) is activated through the activation current input means (MN1), the current output transistor (6) corresponds to the power supply voltage applied between the first and second power supply lines. MP1) generates a reference current. The reference voltage generation means (7) generates a reference voltage according to the generated current of the current generation means (6).

  The first sensing means (MP6) includes a sensing transistor (MP6) having a lower threshold voltage than the current output transistor (MP1), and senses the generated current of the current generating means (6).

  Here, it is considered that the power supply voltage has temporarily decreased to a voltage lower than the threshold voltage of the current output transistor (MP1). A voltage lower than the threshold voltage is applied to the control terminal of the current output transistor (MP1), but the sensing transistor (MP6) tries to flow a charging current to the charging means (8) because the threshold voltage is low.

  Although the current tends to flow from the sensing transistor (MP6) to the charging means (8), the sensing transistor (MP5) is connected in series to the sensing transistor (MP6). The energization of (MP6) is hindered.

  Then, when the charging voltage of the charging means (8) is low, the starting current applying means (MP4) can apply a large amount of starting current to the starting current input means (MN1) when the power supply voltage increases after a momentary interruption. The starting current input to the current input means (MN1) can be increased rapidly.

  Therefore, since the current generation means (6) is activated quickly through the activation current input means (MN1), the reference current output from the current generation means (6) can be increased rapidly, and the reference voltage The rise of the reference voltage output by the generating means (7) is also quick. Thereby, even if the power supply voltage temporarily decreases, the reference voltage can be quickly output if the power supply voltage increases thereafter.

  According to the second aspect of the present invention, the current generating means (6) includes the first and fourth transistors (MP1, MN2) connected in series between the first power supply line and the second power supply line together with the resistor (R1). Therefore, these circuits can supply the reference current as a control signal for the reference voltage generating means (7), and the reference voltage generating means (7) can generate the reference voltage according to the generated current of the current generating means (6).

  The second transistor (MP2) is current-mirror connected to the first transistor (MP1), and the fourth transistor (MN2) is current-mirror connected to the third transistor (MN1). The second and third transistors (MP2) , MN1) are connected in series between the first power supply line and the second power supply line, and the first and fourth transistors (MP1, MN2) are connected in series between the first power supply line and the second power supply line together with the resistor (R1). Therefore, if a starting current is applied to the starting current input means (MN1), the reference current (Ip) can be stably output by self-bias.

  Here, the first conductivity type fifth transistor (MP4) is connected so as to apply a starting current from the first power supply line to the common connection control terminals of the third and fourth transistors (MN1, MN2).

  The first sensing means (MP6) includes a first conductivity type sixth transistor (MP6), and the sixth transistor (MP6) senses the energization current of the first transistor (MP1). Since the threshold voltage of (MP6) is lower than the threshold voltages of the first and second transistors (MP1, MP2), the power supply voltage is temporarily reduced to a predetermined voltage equal to or lower than the threshold voltage of the first and second transistors (MP1, MP2). Even if the voltage drops, the sixth transistor (MP6) tries to pass the charging current to the charging means (8).

  The current tends to flow to the sixth transistor (MP6), and the seventh transistor (MP5) of the second sensing means (MN3, MP7, MP5) is connected in series to the sixth transistor (MP6). The seventh transistor (MP5) prevents the sixth transistor (MP6) of the first sensing means (MP6) from being energized.

  The charging means (8) is charged through a series connection of the sixth transistor (MP6) of the first sensing means (MP6) and the seventh transistor (MP5) of the second sensing means (MN3, MP7, MP5). When the energization of the sixth transistor (MP6) of the first sensing means (MP6) is hindered, the charging voltage of the charging means (8) is kept low. Then, since the charging voltage of the charging means (8) is low, the starting current applying means (MP4) can apply a large amount of starting current to the control terminal of the third transistor (MN1) when the power supply voltage rises after an instantaneous interruption, The starting current of the control terminal of the third transistor (MN1) can be increased rapidly.

  Therefore, since it is quickly activated through the third transistor (MN1) serving as the activation current input means, the reference current (Ip) output from the current generation means (6) can also be rapidly increased, and the reference voltage The rise of the reference voltage output by the generating means (7) is also quick. Thereby, even if the power supply voltage temporarily decreases, the reference voltage can be quickly output if the power supply voltage increases thereafter.

  According to the third aspect of the present invention, in the power-on reset circuit for generating the reset signal after the power supply voltage is cut off, the reference voltage generated by the reference voltage generating means (7) according to the first or second aspect is used as the reset signal. Since it is used to generate the reset signal, the reset signal can be output quickly.

  According to the fourth aspect of the present invention, when the current generating means (6) is activated through the activation current input means (MN1), the current output transistor (6) corresponds to the power supply voltage applied between the first and second power supply lines. MP1) generates a reference current. The reference voltage generation means (7) generates a reference voltage according to the generated current of the current generation means (6).

  The third sensing means (MP6) includes a sensing transistor (MP6) having a lower threshold voltage than the current output transistor (MP1), and senses the generated current of the current generating means (6).

  Here, when the power supply voltage is temporarily lowered to a predetermined voltage lower than the threshold voltage of the current output transistor (MP1), the current tends to flow to the sensing transistor (MP6), but the third sensing means (MP6) Since the sensing transistor (MP5) of the fourth sensing means (MN3, MP7, MP5) is connected in series to the sensing transistor (MP6), the third sensing means (MP6, MN3, MP7, MP5) Energization is hindered by the sensing transistors (MP6, MP5).

  The mask signal of the reset signal is the inversion of the voltage generated in the sensing transistor (MP6) of the third sensing means (MP6), the sensing transistor (MP5) of the fourth sensing means (MN3, MP7, MP5), and the resistance connected in series. It is a signal. For this reason, when the power supply voltage is cut off, the sensing transistors (MP6 and MP5) prevent the energization of the resistor, and an inverted signal of the (logic) signal whose energization has been reduced is output as a mask signal for the reset signal. Therefore, even if the power supply voltage temporarily decreases, when the power supply voltage rises, the inverted signal rises according to the increased power supply voltage, and this inverted signal can be quickly used as a mask signal for the reset signal. It is possible to output the compensated reset signal quickly.

  According to the fifth aspect of the present invention, the current generating means (6) includes the first and fourth transistors (MP1, MN2) connected in series between the first power supply line and the second power supply line together with the resistor (R1). Therefore, these circuits (MP1, MN2, R1) can supply the reference current (Ip) as a control signal for the reference voltage generation means (MP3, R2, D1), and the reference voltage generation means (MP3, R2, D1) The reference voltage can be generated according to the generated current of the current generating means (MP1, MP2, MN1, MN2, R1).

  The second transistor (MP2) is current-mirror connected to the first transistor (MP1), and the fourth transistor (MN2) is current-mirror connected to the third transistor (MN1). The second and third transistors (MP2) , MN1) are connected in series between the first power supply line and the second power supply line, and the first and fourth transistors (MP1, MN2) are connected in series between the first power supply line and the second power supply line together with the resistor (R1). Therefore, if a starting current is applied to the starting current input means (MN1), the reference current (Ip) can be stably output by self-bias.

  Here, the output terminal of the first conductivity type fifth transistor (MP4) is connected to the common connection control terminal of the third and fourth transistors (MN1, MN2) of the current generating means, and the first power line is connected to the first transistor. A starting current is applied to the common connection control terminals of the third and fourth transistors (MN1, MN2).

  The third sensing means (MP6) is configured to include an eighth transistor (MP6), and the eighth transistor (MP6) senses the energization current of the first transistor (MP1). The eighth transistor (MP6) Since the threshold voltage is lower than that of the first and second transistors (MP1, MP2), when the power supply voltage temporarily drops to a predetermined voltage lower than the threshold voltage of the first and second transistors (MP1, MP2), the current is The eighth transistor (MP6) of the third sensing means (MP6) is connected in series with the ninth transistor (MP5) of the fourth sensing means (MN3, MP7, MP5). As a result, the ninth transistor (MP5) prevents the eighth transistor (MP6) from being energized. To become.

  The mask signal of the reset signal is the voltage generated in the resistor in which the eighth transistor (MP6) of the third sensing means (MP6), the ninth transistor (MP5) of the fourth sensing means (MN3, MP7, MP5), and the resistors are connected in series. Is an inverted signal.

  For this reason, when the power supply voltage is cut off, the eighth transistor (MP6) and the ninth transistor (MP5) prevent the energization of the resistor, and the inversion signal of the decreased (logic) signal serves as a mask signal for the reset signal. Will be output. Therefore, even if the power supply voltage temporarily decreases, when the power supply voltage rises, the inverted signal rises according to the increased power supply voltage, and this inverted signal can be quickly used as a mask signal for the reset signal. It is possible to output the compensated reset signal quickly.

  The above-described transistors have almost the same operational effects regardless of whether they are, for example, MOS transistors or bipolar transistors.

1 is an electrical configuration diagram showing a first embodiment of the present invention. Timing chart schematically showing transient changes in voltage and current at each node FIG. 1 equivalent view showing a second embodiment of the present invention 2 equivalent diagram FIG. 1 equivalent view showing the third embodiment of the present invention (No. 1) Figure 1 equivalent (part 2) 1 equivalent diagram showing the prior art FIG. 2 equivalent diagram showing the prior art

(First embodiment)
Hereinafter, a first embodiment in which the present invention is applied to a power-on reset circuit including a reference voltage generation circuit will be described with reference to FIGS. 1 and 2.
FIG. 1 shows the electrical configuration of the power-on reset circuit. As shown in FIG. 1, the power-on reset circuit 1 mainly includes a reference voltage output circuit 2, a startup circuit 3, a voltage dividing circuit 4, and a comparator 5. The reference voltage output circuit 2 includes a current generation circuit (current generation means) 6 and a reference voltage generation circuit (reference voltage generation means) 7.

  The current generation circuit 6 includes a P-channel type (first conductivity type) between a first power supply line N1 on the high potential side to which a positive power supply voltage VDD is applied and a second power supply line N2 on the low potential (ground) side. MOS transistors MP1 and MP2, N channel type (second conductivity type) MOS transistors MN1 and MN2, and a resistor R1 are connected to each other. Hereinafter, each MOS transistor will be described simply as a transistor.

  The transistor MP1 is diode-connected by electrically connecting between its gate and drain. The gates of the transistors MP1 and MP2 are commonly connected, and the sources of the transistors MP1 and MP2 are commonly connected by the first power supply line N1, thereby forming a current mirror circuit.

  In addition, the transistor MN1 is diode-connected by electrically connecting the gate and drain thereof. The gates of the transistors MN1 and MN2 are commonly connected. The source and drain of the transistor MP1 and the drain and source of the transistor MN2 are connected between the first and second power supply lines N1 and N2 together with the resistor R1. Further, the source and drain of the transistor MP2 and the drain and source of the transistor MN1 are connected between the first and second power supply lines N1 and N2. Thus, a self-bias circuit is configured. The drain connection node N3 of the transistors MP1 and MN2 becomes the output of the current generation circuit 6.

  The reference voltage generation circuit 7 generates a reference voltage VREF by connecting the forward direction of a P-channel MOS transistor MP3, a resistor R2, and a diode D1 between the first and second power supply lines N1 and N2. The node N3 is connected to the gate of a P-channel type MOS transistor MP3 and serves as an input to the reference voltage generation circuit 7. The transistors MP1 and MP3 are connected in a current mirror manner. The reference voltage VREF is output from the common connection node N4 of the transistor MP3 and the resistor R2.

  The reference voltage VREF output from the reference voltage generation circuit 7 is given to the non-inverting input terminal of the comparator 5. The voltage dividing circuit 4 is connected to the inverting input terminal of the comparator 5. The voltage dividing circuit 4 includes a plurality of resistors R3 and R4 that divide the power supply voltage VDD applied between the first and second power supply lines N1 and N2. The comparator 5 outputs a POR (Power On Reset) signal.

  A common connection node N5 of the transistors MN1 and MN2 constituting the current generation circuit 6 is an input (starting current supply node) of the current generation circuit 6. The startup current supply node N5 is configured to be supplied with the startup current Is from the startup circuit 3.

  The startup circuit 3 mainly includes a P-channel type MOS transistor MP4 having a source and drain connected between the first power supply line N1 and a node N5. A charging circuit (charging means) 8 is connected to the gate of the transistor MP4. The charging circuit 8 is a circuit in which a resistor R5 and a capacitor C1 are connected in parallel. The charging circuit 8 is connected between a node N6 of the gate of the transistor MP4 and the second power supply line (ground) N2, and a gate control signal (control voltage) of the transistor MP4. Is generated.

  The node N6 serves as a charging supply node for the charging circuit 8, but a plurality of source / drains of P-channel MOS transistors MP5 and MP6 are connected in series between the first power supply line N1 and the node N6. The gate widths of these MOS transistors MP5 and MP6 are the same width, and the gate lengths of the transistors MP5 and MP6 are also set to the same length (that is, the same size). The threshold voltages of these transistors MP5 and MP6 Vt1 and current supply capability (Vds-Ids characteristics, current amplification capability) are substantially the same.

  Of the transistors MP5 and MP6, the gate of the transistor MP6 is commonly connected to the gates of the transistors MP1 and MP2, and the transistor MP6 senses the reference current Ip output from the transistor MP1. At this time, in order to increase the sensing sensitivity, the threshold voltage Vt1 of the transistor MP6 is smaller than the threshold voltage Vt2 of the transistors MP1 and MP2, and the current amplification factor of the transistor MP6 is higher than the current amplification factors of the transistors MP1 and MP2. Is also high.

  The starting current supply node N5 is connected to the gate of an N-channel MOS transistor MN3, and the source of the transistor MN3 is connected to a second power supply line (ground) N2. The drain of the transistor MN3 is connected to the transistor MP7 that is diode-connected to the first power supply line N1. The gates of the transistors MP5 and MP7 are commonly connected, and these transistors MP5 and MP7 are current mirror connected.

  Thereby, the transistor MN3 senses the starting current Is supplied from the transistor MP4 to the node N5, and a mirror current corresponding to the sensing current of the transistor MN3 can be output as the drain current of the transistor MP5.

The operation of the above configuration will be described with reference to FIG.
FIG. 2 schematically shows changes over time in current and voltage at important points. An example in which each element value is applied and considered as follows is shown. Of the following, the parentheses of the transistors MP1 to MP7 and MN1 to MN3 indicate (gate width W [μm] / gate length L [μm]).

MP1 = (86/96), MP2 = (86/96), MP3 = (86/96),
MP4 = (3/12), MP5 = (480/1), MP6 = (480/1),
MP7 = (1/1)
MN1 = (80/20), MN2 = (900/20), MN3 = (80/20)
R2 = 1.5 [MΩ], R5 = 760 [kΩ], C1 = 22 [pF],
R1, R3, R4 = several [kΩ], power supply voltage VDD = 5 [V]
<Operation at power-on>
When the power supply voltage VDD is turned on, the gate of the transistor MP4 is grounded through the resistor R5. Since the gate voltage of the transistor MP4 is low, the transistor MP4 is turned on and the starting current Is is supplied to the node N5. This starting current Is is charged in the gate input capacitances of the transistors MN1 and MN2, and the gate voltages of the transistors MN1 and MN2 rise. Then, a current through the transistor MP1 and the resistor R1 flows through the transistors MN1 and MN2, and a reference current Ip flows through self-bias.

  The starting current Is is sensed by the transistor MN3, and the reference current Ip is sensed by the transistor MP6. Therefore, when both these currents Is and Ip flow, the charging current Io flows to the charging circuit 8 through the sources and drains of the transistors MP5 and MP6 constituting the startup circuit 3. When the charging current Io is charged in the capacitor C1, the gate voltage of the transistor MP4 rises and the transistor MP4 is turned off when it approaches the power supply voltage VDD. Then, the supply of the startup current Is by the startup circuit 3 is stopped. During this time, the reference voltage generation circuit 7 outputs a reference voltage VREF corresponding to the reference current Ip to the non-inverting input terminal of the comparator 5. The comparator 5 outputs a high level signal as a reset signal while the reference voltage Vref exceeds the divided voltage Va of the voltage dividing circuit 4. In this way, the power-on reset circuit 1 operates.

<Operation at momentary power interruption>
As shown in FIG. 2, the operation when the power supply voltage VDD temporarily decreases due to some influence will be described. For example, consider the case where the power supply voltage VDD drops to an intermediate voltage (Vt2-α (predetermined value)) [V] that is less than the threshold voltage Vt2 of the transistors MP1 and MP2.

  Since the threshold voltage Vt1 of the transistor MP6 is lower than the threshold voltage Vt2 of the transistors MP1 and MP2, and the current amplification factor is high, the transistor MP6 tries to pass the charging current Io. However, since the transistors MP5 and MP6 are connected in series between the first power supply line N1 and the node N6, each of the transistors MP5 and MP6 has a voltage sufficiently lower than the threshold voltage Vt1 of the plurality of transistors MP5 and MP6. The charging current Io does not flow compared to the configuration of FIG. 7 (see the description in the background art column).

  Normally, the capacitor C1 is charged, but when the charging current Io stops flowing, the charge of the capacitor C1 is consumed through the resistor R5, and the voltage of the node N6 becomes almost 0V (initial voltage). Therefore, both the voltage and current of the main node shown in FIG. 2 are close to zero.

  Here, when the power supply voltage VDD rises again from the intermediate voltage (Vt2-α) [V] and returns to the power-on reset voltage (POR voltage: power supply voltage VDD), the node N3 is matched with the rising gradient of the power supply voltage VDD. (See the voltage at the node N3 in FIG. 2B).

  At the same time, when the starting current Is flows between the source and drain of the transistor MP4, charges are injected into the gate input capacitances of the transistors MN1 and MN2, the gate voltage rises, and the current flows through the transistors MN1 and MN2. It begins to flow between the drain and source. At this time, the power supply voltage VDD starts to rise from below the threshold voltage of the transistor MP4. When the power supply voltage VDD further rises, the transistor MP4 is turned on and the voltage at the node N5 rises rapidly (FIG. 2 (d)). (Refer to the rising operation of the starting current Is).

  When the starting current Is increases, the reference current Ip is generated by the current generation circuit 6 (see the increase operation of the reference current Ip in FIG. 2F). When the reference current Ip is generated, the gate input capacitance of the transistor MP3 is charged with the current Ip, and the reference voltage VREF is generated according to the amount of current Ip (FIG. 2 (g)). (Refer to the reference voltage VREF rising operation). When the reference voltage VREF exceeds the divided voltage Va of the voltage dividing circuit 4, the comparator 5 becomes a reset signal (POR (power-on reset signal)) which becomes a high level (however, rises in accordance with the rising gradient of the power supply voltage VDD). Is output.

  The starting current Is is sensed by the transistor MN3, and the reference current Ip is sensed by the transistor MP6. Therefore, when these currents Is and Ip flow, the charging current Io flows through the charging circuit 8 through the source and drain of the transistors MP5 and MP6 in the startup circuit 3 (see the charging current Io in FIG. 2E).

  When the charging current Io is charged in the capacitor C1, the gate voltage of the transistor MP4 rises and the transistor MP4 is turned off when it approaches the power supply voltage VDD. Then, the start-up current Is rapidly decreases (see the start-up current Is decrease operation in FIG. 2D), and the supply of the start-up current Is by the start-up circuit 3 is weakened and almost stops.

  Thereafter, the power supply voltage VDD continues to recover, but when the divided voltage Va of the voltage dividing circuit 4 becomes higher than the reference voltage VREF, the comparator 5 detects that the power supply voltage VDD has reached a predetermined POR voltage, and the comparator The output reset signal 5 is turned off (released).

<Summary of main features of this embodiment>
According to this embodiment, the transistors MP5 and MP6 are connected in series between the first power supply line N1 and the node N6, the transistor MP5 senses the starting current Is, and the transistor MP6 senses the reference current Ip. For this reason, even if the power supply voltage VDD drops to an intermediate voltage (Vt2-α (predetermined value)) [V] that is less than the threshold voltage Vt2 of the transistors MP1 and MP2, both the transistors MP5 and MP6 are equal to or higher than the threshold voltage. The voltage is no longer applied between the gate and the source, the charging current Io is hardly charged in the charging circuit 8, and the transistor MP4 continues to maintain the on state.

  Therefore, when the power supply voltage VDD rises again and the power supply voltage rises, the starting current Is can be quickly supplied from the transistor MP4 to the node N5, and the current generation circuit 6 can quickly generate the reference current Ip. Therefore, when the reference current Ip flows, the reference voltage generation circuit 7 can output the reference voltage VREF quickly, and the comparator 5 can output the reset signal quickly.

(Second Embodiment)
3 and 4 show a second embodiment of the present invention. The difference from the previous embodiment is that this compensation circuit is provided separately without providing a series circuit of transistors MP5 and MP6 in the startup circuit 3. FIG. There is. Parts having the same parts, the same functions, and similar functions as those of the above-described embodiment will be described with the same reference numerals, and different parts from those of the above-described embodiment will be described below.

  FIG. 3 shows an electrical configuration in place of FIG. As shown in FIG. 3, P-channel MOS transistors MP5 and MP6 and a resistor R6 are connected in series between the first power supply line N1 and the second power supply line N2.

  Instead, a transistor MP8 instead of the transistors MP5 and MP6 is connected between the first power supply line N1 and the node N6 (charging node of the charging circuit 8). This transistor MP8 corresponds to MP6 in FIG. The gate width and gate length of the transistor MP8 are (gate width W / gate length L) = (240 μm / 1 μm). Note that the gate width and gate length of the transistors MP5 and MP6 are (gate width W / gate length L) = (480 μm / 1 μm) (similar to the above embodiment), and the transistors MP5, MP6, MP8 Both threshold voltages are low.

  A common connection node N7 of the transistor MP6 and the resistor R6 is connected to an input of a NOT gate (inverting circuit) 9. The NOT gate 9 outputs an inverted signal obtained by logically inverting the voltage of the node N7 to the OR gate 10 as a mask signal. The OR gate 10 logically sums the output signal (logic signal) of the comparator 5 and the output signal of the NOT gate 9. Output.

FIG. 4 is a timing chart showing temporal changes in the voltage and current of the main part when the power supply voltage is restored.
The configuration of the start-up circuit 3 is the same as the circuit described with reference to FIG. Therefore, after the power supply voltage VDD drops to an intermediate voltage (Vt2-α (predetermined value)) [V] lower than the threshold voltage Vt2 of the transistors MP1 and MP2, even if the power supply recovers and the power supply voltage VDD rises, it starts Since the rise of the current Is is slow and the rise of the reference current Ip is also slow, the reference voltage VREF cannot obtain a desired rise timing. Therefore, it becomes difficult to output the reset signal (POR) based on the reference voltage VREF.

  However, since the voltage of the node N7 is output to the NOT gate 9 from the series circuit of the transistors MP5 and MP6 provided separately from this circuit and the resistor R6, the return power is supplied to the NOT gate 9 and the OR gate 10. Then, the NOT gate 9 can output the input signal using the buffer output (inverted output) as a mask signal, and can output the reset signal (POR ′) after compensation through the OR gate 10.

  In this case, as shown in FIG. 4A, when the power supply voltage VDD recovers from the intermediate voltage and rises, the gates 9 and 10 output according to the rising gradient of the power supply voltage VDD. A high level (however, rising according to the power supply voltage rising gradient) can be output as a compensated reset signal (POR ′) with only a delay of 10 delay times.

  During this time, a small amount of the starting current Is flows, but when the gate input capacitances of the transistors MN1 and MN2 are charged and their gate voltages rise, both the transistors MN1 and MN2 are turned on and the reference current Ip begins to flow. VREF increases (see the operation of increasing the reference voltage VREF in FIG. 4G). Even if the reference voltage VREF increases, the power supply voltage VDD has already increased, so that a voltage exceeding the divided voltage Va of the voltage dividing circuit 4 is not applied to the non-inverting input terminal of the comparator 5. In such a case, the output of the comparator 5 remains at a low level and is not output as the reset signal POR (see the non-output of the reset signal POR in FIG. 4H).

  On the other hand, since the transistors MP5 and MP6 sense the starting current Is and the reference current Ip, respectively, the starting current Is continues to flow, and when the reference current Ip starts to flow, the sensing current Ie of the transistors MP5 and MP6 also changes. Start flowing.

  In this case, since the voltage at the node N7 increases, when this increased voltage is input to the NOT gate 9, an inverted signal of the input logic signal of the NOT gate 9 is obtained (the voltage at the node N7 in FIG. 4 (i)). (See dotted line). Therefore, the output of the NOT gate 9 also becomes low level at the timing when the reference voltage VREF increases. As a result, after the power supply voltage VDD rises and VREF completely rises, the mask signal at the node N8 is disabled (low level), and the comparator 5 outputs the power-on reset signal POR.

  At this time, since VREF has risen normally, the comparator 5 can normally perform power-on reset determination. Therefore, after returning to the power-on reset voltage (POR voltage) or higher, the compensated reset signal (POR ′) is also canceled (see the compensated reset signal POR ′ in FIG. 4J).

<Summary of main features of this embodiment>
According to this embodiment, the transistors MP5 and MP6 and the resistor R6 are connected between the first power supply line N1 and the second power supply line N2, the transistor MP5 senses the starting current Is, and the transistor MP6 receives the reference current Ip. Sensing. For this reason, even if the power supply voltage VDD drops to an intermediate voltage (Vt2-α (predetermined value)) [V] that is less than the threshold voltage Vt2 of the transistors MP1 and MP2, both the transistors MP5 and MP6 are both equal to or higher than the threshold voltage. No voltage is applied between the gate and source.

  Therefore, the voltage of the node N7 is held approximately near the ground voltage (the voltage of the second power supply line N2 (= 0V)). Therefore, when the power supply voltage VDD recovers, the NOT gate 9 outputs a voltage corresponding to the rising gradient of the power supply voltage VDD, and this voltage is output as a compensated power-on reset signal (POR '). Further, after the power supply voltage VDD rises and VREF completely rises, the mask signal of N8 is disabled (low level) and the power-on reset signal POR is output by the comparator 5. At this time, since VREF has risen normally, the comparator 5 can normally perform power-on reset determination. Therefore, the power-on reset signal (POR ') can be canceled after returning to the power-on reset voltage (POR voltage) or higher. Therefore, even if the power supply voltage VDD is temporarily lowered and the rising of the reference voltage VREF is delayed, the mask signal is enabled (high level) and the reset output signal (POR ′) is forced until VREF rises normally. Enabled (high level). As a result, the reset is not mistakenly removed at a low voltage that does not reach the power-on reset voltage, and malfunction of the system can be prevented.

(Third embodiment)
5 and 6 show a third embodiment of the present invention. The difference from the first embodiment is that a cascode current mirror circuit is used as a current mirror circuit constituting the reference voltage output circuit 2. FIG. is there. Parts that are the same as or similar to those in the above-described embodiment are given the same reference numerals, and descriptions thereof are omitted. Hereinafter, different parts will be described.

  5 and 6 show an example in which a cascode current mirror circuit is used as the current mirror circuit constituting the reference voltage output circuit 2. As shown in FIGS. 5 and 6, an N-channel MOS transistor MN5 is inserted as a current buffer between the transistors MP1 and MN2.

  With this configuration, even if the voltage at the node N3 changes greatly, the influence of the drain-source voltage change of the transistor MN2 can be reduced, so that the influence of the channel length modulation effect can be reduced. Further, when the transistors MN1 and MN2 are composed of low withstand voltage transistors, the rise of the respective drain voltages can be suppressed, and there is an effect of preventing destruction. Note that the difference between the circuit of FIG. 5 and the circuit of FIG. 6 is the difference in the supply node of the starting current Is, and the operation is almost the same.

In the first to third embodiments, the MOS transistor is used. However, other transistors such as a bipolar transistor may be applied.
In the above-described embodiment, the present invention is particularly applied to the power-on reset circuit 1, but a voltage generation circuit for quickly outputting the reference voltage VREF can be applied alone.

  In the drawings, 1 is a power-on reset circuit, 2 is a reference voltage output unit, 3 is a startup circuit, 6 is a current generation circuit (current generation means), 7 is a reference voltage generation circuit (reference voltage generation means), and 8 is a charging circuit. (Charging means), MP1 to MP8, MN1 to MN5 are transistors, N1 is a first power supply line, and N2 is a second power supply line.

Claims (5)

A starting current input means (MN1) and a current output transistor (MP1) are provided, and when activated through the starting current input means, a reference is made using the current output transistor according to a power supply voltage applied between the first and second power supply lines. Current generating means (6) for generating current;
A reference voltage generating means (7) for generating a reference voltage according to a generated current of the current generating means (6);
A starting current applying means (MP4) for applying a starting current to the starting current input means (MN1) of the current generating means;
A first sensing means (MP6) configured to include a sensing transistor (MP6) having a lower threshold voltage than the current output transistor (MP1), and sensing a generated current of the current generating means (6);
Second sensing means (MN3, MP7, MP5) for sensing the starting current applied to the starting current input means (MN1) by the starting current applying means (MP4);
Charging means (8) for charging through a series connection of a sensing transistor (MP6) of the first sensing means (MP6) and a sensing transistor (MP5) of the second sensing means (MN3, MP7, MP5). ,
The starting current applying means (MP4) applies a large amount of starting current to the starting current input means (MN1) when the charging voltage of the charging means (8) is low. The current generation means (6) includes a first conductivity type first transistor (MP1) diode-connected to a first power supply line, and a first conductivity type second transistor (MP2) connected to the first transistor in a current mirror connection. ), A second conductivity type third transistor (MN1) diode-connected to the second power line, a second conductivity type fourth transistor (MN2) connected to the third transistor in a current mirror, and a resistor (R1) The second and third transistors (MP2, MN1) are connected in series between the first power line and the second power line, and the first and fourth transistors (MP1, MN2) are the resistors (R1) is connected in series between the first power line and the second power line,
The starting current applying means (MP4) has its output terminal connected to the common connection control terminal of the third and fourth transistors (MN1, MN2) of the current generating means, and connected to the control terminal of the third transistor (MN1). A first conductive type fifth transistor (MP4) for applying a starting current from the first power line;
The first sensing means (MP6) is a transistor having a threshold voltage lower than the threshold voltages of the first and second transistors (MP1, MP2), the control terminal of which is connected to the control terminal of the first transistor (MP1). And comprising a sixth transistor (MP6) of the first conductivity type that senses the energization current of the first transistor (MP1),
The second sensing means (MN3, MP7, MP5) includes a second sensing transistor (MN3) that senses the start-up current with a control terminal connected to the output current supply node of the fifth transistor (MP4). A seventh transistor (MP5) that current-mirrors the sensing current of the two sensing transistors (MN3) and is connected in series from the first power supply line to the sixth transistor (MP6); )
The charging means (8) corresponds to a series connection of a sixth transistor (MP6) of the first sensing means (MP6) and a seventh transistor (MP5) of the second sensing means (MN3, MP7, MP5). The voltage generation circuit according to claim 1, wherein the voltage generation circuit is charged. In a power-on reset circuit that generates a reset signal after the power supply voltage is cut off,
3. A power-on reset circuit, wherein the reference voltage generated by the reference voltage generating means (MP3, R2, D1) of the reference voltage generating circuit according to claim 1 or 2 is used for generating a reset signal. In the power-on reset circuit that outputs the reset signal after the power supply voltage is cut off,
A startup current input means (MN1) and a current output transistor (MP1) are provided, and when activated through the startup current input means, the current output transistor (MP1) is controlled according to the power supply voltage applied between the first and second power supply lines. Current generating means (6) for generating a reference current using,
Reference voltage generating means (MP3, R2, D1) for generating a reference voltage according to the generated current of the current generating means (6);
A starting current applying means (MP4) for applying a starting current to the starting current input means (MN1) of the current generating means (6);
A third sensing means (MP6) configured to include a sensing transistor (MP6) having a lower threshold voltage than the current output transistor (MP1), and sensing a generated current of the current generating means (6);
And fourth sensing means (MN3, MP7, MP5) for sensing the starting current applied to the starting current input means (MN1) by the starting current applying means (MP4),
A sensing transistor (MP6) of the third sensing means (MP6) connected between the first power supply line and the second power supply line; a sensing transistor (MP5) of the fourth sensing means (MN3, MP7, MP5); And a power-on reset circuit that outputs an inversion signal of a voltage generated in the resistors connected in series as a mask signal of a reset signal. The current generation means (6) includes a first conductivity type first transistor (MP1) diode-connected to a first power supply line, and a first conductivity type second transistor (MP2) connected to the first transistor in a current mirror connection. ), A second conductive type third transistor (MN1) diode-connected to the second power supply line, a second conductive type fourth transistor (MN2) connected to the third transistor in a current mirror, and a resistor (R1) The second and third transistors (MP2, MN1) are connected in series between the first power line and the second power line, and the first and fourth transistors (MP1, MN2) are the resistors (R1) is connected in series between the first power line and the second power line,
The starting current applying means (MP4) has an output terminal connected to a common connection control terminal of the third and fourth transistors (MN1, MN2) of the current generating means, and the third and fourth transistors (MN1, MN2). ) Having a first conductivity type fifth transistor (MP4) for applying a starting current from the first power supply line to the common connection control terminal of
The third sensing means (MP6) has its control terminal connected to the control terminal of the first transistor (MP1), and its threshold voltage is lower than the threshold voltages of the first and second transistors (MP1, MP2), An eighth transistor (MP6) of the first conductivity type that senses an energization current of the first transistor (MP1);
The fourth sensing means (MP5) includes a sensing terminal (MN3) that senses the starting current with a control terminal connected to a starting current supply node of the fifth transistor (MP4), and a current flowing through the sensing transistor (MN3). A ninth transistor (MP5) that is mirror-connected and includes a first conductivity type ninth transistor (MP5) connected in series from the first power supply line to the eighth transistor (MP6);
Inversion of a voltage generated in the resistor in which the eighth transistor (MP6) of the third sensing means (MP6) and the ninth transistor (MP5) of the fourth sensing means (MN3, MP7, MP5) are connected in series to the resistor. 5. The power-on reset circuit according to claim 4, wherein the signal is output as a mask signal for the reset signal.

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