JP2003263231A - Shunt regulator, its adjustment method and noncontact ic card - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shunt regulator for compensating variations in the characteristics of a MOS transistor and increasing accuracy of the transistor. <P>SOLUTION: The shunt regulator is composed of a Vt (a threshold voltage of a P-type MOS transistor) adjustment circuit 30, capable of adjusting outputs from resister dividing between a power supply voltage VDD and a reference voltage VSS by resistors R11-R16 and switches S11-S16 and a β adjustment circuit 31, capable of adjusting sizes of transistors by P-type MOS transistors M1-M6 and switches S1-S6. Characteristics fluctuations of the MOS transistors can be compensated by the adjustment circuit 30 and 31 so that it becomes possible for the accuracy of the shunt regulator to be increased. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shunt regulator, a method of adjusting the shunt regulator, and a non-contact IC card.

[0002]

2. Description of the Related Art Generally, this type of shunt regulator is a circuit for preventing an excessive rise in voltage, and is used for the purpose of preventing damage to the elements of the circuit.

FIG. 5 is a diagram showing the structure of a conventional shunt regulator. In FIG. 5, VDD is the power supply voltage, V
SS is a reference voltage, R1 and R2 are resistors, and M0 is a P-type MOS.
It is a transistor.

The resistors R0 and R1 are connected in series between the power supply voltage VDD and the reference voltage VSS, and the resistance-divided voltage is input to the gate of the P-type MOS transistor M0.
The source of the P-type MOS transistor M0 is the power supply voltage VDD.
, And the drain is connected to the reference voltage VSS, respectively.

The gate-source voltage Vgs of the P-type MOS transistor M0 is Vgs = -R1 / (R1 + R2) * VDD, and if the threshold voltage of the P-type MOS transistor is Vt, then | Vgs |> | Vt | Under the condition, the P-type MOS transistor M0 turns on, and the current Ids flows. That is, when the power supply voltage VDD rises and the condition of | Vgs |> | Vt | is satisfied, the current Ids flows and power is consumed from the power supply voltage VDD, so that the rise of the power supply voltage VDD can be suppressed. FIG. 6 shows the characteristics of this shunt regulator. If VDD <R1 / (R1 + R2) × | Vt |
The current Ids does not flow, but VDD ≧ R1 / (R1 + R
2) × | Vt |, the current Ids flows, and the current value increases as the power supply voltage VDD increases.

Next, a non-contact IC card equipped with a shunt regulator will be described. FIG. 7 is a diagram showing a configuration of a non-contact IC card. In FIG. 7, 1 is an antenna coil, 2 is a rectifier, and 3 is a shunt regulator.

The non-contact IC card receives the AC magnetic field emitted from the reader / writer by the antenna coil 1,
It is converted into direct current by the rectifier 2. The shunt regulator 3 prevents the power supply voltage VDD from rising too much when the received power is excessive.

FIG. 8 shows the characteristics of the input power and the power supply voltage VDD in this non-contact IC card. When the input power is small, the power supply voltage VDD rises following the increase in the input power, but the power supply voltage VDD is R1 / (R1 + R2) × |
When it exceeds Vt |, the shunt regulator 3 suppresses the rise of the power supply voltage VDD.

[0009]

However, in the above-mentioned conventional structure, there is a problem that the characteristics of the shunt regulator greatly vary with variations in the transistor characteristics of the P-type MOS transistor M0. For example, R1
When / (R1 + R2) = 4 and the configuration is such that the P-type MOS transistor M0 is turned on when VDD> 4 | Vt |
The voltage at which the type MOS transistor M0 turns on varies four times as much as the variation in Vt. Since the characteristic variation of the shunt regulator is large, there is a problem that the limiting voltage for protecting the element largely varies and the power consumption characteristic also largely varies.

Further, in the non-contact IC card equipped with the shunt regulator having the conventional structure, the communication performance characteristics vary between samples and it is difficult to secure reliability due to the fluctuations of the limiting voltage characteristics and the power consumption characteristics. Occurs.

An object of the present invention is to provide a highly accurate shunt regulator that compensates for variations in the characteristics of MOS transistors.

Another object of the present invention is to provide an adjusting method relating to the shunt regulator, which allows more accurate adjustment.

Another object of the present invention is to provide a high quality non-contact IC card in which the characteristic variation between samples is small.

[0014]

In order to achieve the above object, a shunt regulator according to the present invention is a voltage for outputting a voltage between a first input and a second input at a predetermined division ratio. Output means, the first input and the second
A first MOS transistor having a source and a drain connected between the respective inputs and a gate connected to the voltage output of the voltage output means, and a switch between the first input and the second input. A plurality of second MOS transistors having a source and a drain connected to each other and a gate connected to the voltage output of the voltage output means, adjusting means for adjusting the predetermined division ratio, and switch control for controlling the switch. And means are provided.

According to the shunt regulator of the first aspect of the present invention, since the adjusting means is provided, the MOS
Even if the characteristic of the transistor changes, the characteristic change of the shunt regulator can be suppressed, and a highly accurate shunt regulator can be provided.

A shunt regulator according to a second aspect of the present invention is the shunt regulator according to the first aspect, wherein a fuse is used for the adjusting means for adjusting the predetermined division ratio and the switch control means for controlling the switch. It is characterized by

According to the shunt regulator of the second aspect of the present invention, in addition to the effect of increasing the accuracy, it becomes possible to normally operate the shunt regulator immediately after the power is turned on.

The invention according to claim 3 is the same as claim 1 or 2
A method for adjusting a shunt regulator according to the invention described above,
The adjustment means for adjusting the predetermined division ratio is adjusted first, and then the setting of the switch control means for controlling the switch is determined using the correction coefficient of the adjustment result.

According to the shunt regulator adjusting method of the invention described in claim 3, the characteristics of the shunt regulator can be adjusted with higher accuracy.

The invention according to claim 4 relates to a non-contact IC card, which is characterized in that the shunt regulator according to claim 1 or 2 is mounted.

According to the non-contact IC card of the present invention as defined in claim 4, it is possible to provide a high-quality non-contact IC card with a small variation in characteristics between samples by mounting a high precision shunt regulator. Becomes

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
2 shows the configuration of the shunt regulator in FIG. In FIG. 1, VDD is a power supply voltage, VSS is a reference voltage, R
1, R2, R11 to R16 are resistors, M0 to M6 are P-type M
OS transistors, S1 to S6, S11 to S16 are switches, A1 to A6, A11 to A16 are control signals, 30 is a Vt adjusting circuit, and 31 is a β adjusting circuit. Also, Ids
Is a current flowing through the entire P-type MOS transistors M0 to M6, and Vgs is a gate-source voltage of the P-type MOS transistors M0 to M6.

The resistors R1, R2, R11 to R16 are connected in series between the power supply voltage VDD and the reference voltage VSS,
The resistor R1 and the resistors R11 to R13 are on the power supply voltage VDD side,
The resistor R2 and the resistors R14 to R16 are provided on the reference voltage VSS side, respectively. P-type MOS transistor M0
The gate of M6 is connected to the connection node between the resistors R1 and R2, and the source is connected to the power supply voltage VDD. P type M
The drain of the OS transistor M0 is connected to the reference voltage VSS, and the drains of the P-type MOS transistors M1 to M6 are connected to the reference voltage VSS via the switches S1 to S6, respectively.
Connected to. The switches S11 to S16 are connected in parallel to the resistors R11 to R16, respectively. Switches S1 to S
6, S11 to S16 are control signals A1 to A6 and A, respectively.
On and off are controlled by 11 to A16. As standard settings, as shown in FIG. 1, S1 to S3 are turned on, S4 to S6 are turned off, and S11 to S16 are turned on. In FIG. 1, switches S1 to S6, resistors R11 to R16, and switches S11 to S16 are respectively 6
Although they are provided one by one, this number is arbitrary. Further, the on resistance of the switches S1 to S6 and S11 to S16 is 0Ω, and the off resistance is infinite.

Next, the operation of the shunt regulator shown in FIG. 1 will be described. When the power supply voltage VDD rises, the resistance ratio of the resistance R1 and the resistance R2 is output | Vg
s | also becomes large. When | Vgs | exceeds the threshold voltage | Vt | of the P-type MOS transistor, the P-type MOS transistors M0 to M6 are turned on and the current Ids flows. Figure 1
In the case of, the switches S1 to S3 are turned on and the switch S
Since 4 to S6 are off, the current Ids is P-type M
It is the sum of the currents of only the OS transistors M0 to M3. The voltage Vgs is Vgs because the switches S11 to S16 are turned on and the resistors R11 to R16 are short-circuited.
= −R1 / (R1 + R2) × VDD

Next, the Vt adjusting circuit 30 and the β adjusting circuit 3
1 will be described with reference to FIGS. 2 (a) and 2 (b). First, the characteristics of the MOS transistor will be briefly described. Strong inversion region of P-type MOS transistor (Vgs <V
The current Ids at t) is represented by Ids = (β / 2) × (Vgs−Vt) ² . Where β = μ0 × Cox × (W / L),
μ0 is the mobility, Cox is the gate oxidation capacity, W is the gate width of the transistor, and L is the gate length of the transistor.
The square root of the current Ids is √Ids = √ (β / 2) × | Vgs−Vt | 2A and 2B, the vertical axis represents √Ids and the horizontal axis represents the power supply voltage VDD. From the above, since Vgs = −R1 / (R1 + R2) × VDD, √Ids = √ (β / 2) × (R1 / (R1 + R2) × VDD− | Vt |). Here, the relationship between √Ids and VDD is represented by a straight line, the intercept of the horizontal axis is R1 / (R1 + R2) × VDD, and the slope is √ (β / 2) × R1 / (R1 + R2).

In the Vt adjusting circuit 30 of FIG. 1, for example, when the switch S11 is turned off, the formula of √Ids is √Ids = √ (β / 2) × ((R1 + R11) / (R1
+ R11 + R2) × VDD− | Vt |), and the intercept on the horizontal axis is (R1 + R11) / (R1 + R1).
1 + R2) × VDD. Further switch S1
When 2 and the switch S13 are turned off, the intercept of the horizontal axis becomes large. On the other hand, when the switch S14 is turned off while the switches S11 to S13 are turned off, the formula of √Ids is √Ids = √ (β / 2) × (R1 / (R1 + R2 + R1
4) × VDD− | Vt |), and the intercept on the horizontal axis is R1 / (R1 + R2 + R14) ×
It becomes as small as VDD. Further switches S15 and S16
When turned off, the intercept on the horizontal axis becomes smaller. In the Vt adjusting circuit 30, by controlling ON / OFF of the switches S11 to S16, the intercept of the horizontal axis can be changed as shown in FIG.

Next, in the β adjusting circuit 31 of FIG. 1, for example, when the switch S1 is turned off, the current flowing through the P-type MOS transistor M1 stops, so β = μ0 × Cox ×
The parameter of the transistor width W in (W / L) decreases, and β becomes smaller. That is, the slope of the straight line becomes smaller in the relationship between √Ids and VDD in FIG. Further, when the switches S2 and S3 are turned off, the slope of the straight line becomes smaller. On the other hand, when the switch S4 is turned on while the switches S1 to S3 are turned on, a current flows through the P-type MOS transistor M4, and the parameter of the transistor width W in β = μ0 × Cox × (W / L) increases, Grows larger. That is, √Ids and power supply voltage VD in FIG.
In relation to D, the slope of the straight line becomes large. When the switches S5 and S6 are further turned on, the inclination of the straight line becomes large. In the β adjustment circuit 31, by controlling the on / off of the switches S1 to S6, as shown in FIG.
The slope of the straight line of Ids can be changed. At this time,
The intercept on the horizontal axis does not change.

In this embodiment, as described above, the MOS
Even if the characteristic of the transistor changes from the standard value, the MOS transistor characteristic can be compensated by the Vt adjusting circuit 30 and the β adjusting circuit 31, so that it is possible to obtain a shunt regulator with a small change in the characteristic. The variations in the MOS transistor characteristics may include the threshold voltage Vt, the mobility μ0, the gate oxidation capacitance Cox, the transistor gate length L, and the transistor gate width W. For the threshold voltage Vt, the Vt adjusting circuit 30 Further, since the mobility μ0, the gate oxidation capacity Cox, the gate length L of the transistor, and the gate width W of the transistor can be adjusted by the β adjusting circuit 31, it is possible to completely compensate the variation of the MOS transistor characteristic due to the manufacturing variation. .

Next, the resistors R1, R2 and R11 to R shown in FIG.
16, setting of element constants of the P-type MOS transistors M0 to M6 will be described. First, the resistors R1 and R2 are set so that R1 / (R1 + R2) becomes a predetermined set value, assuming that the characteristics of the P-type MOS transistor are in a standard state. The resistors R11 to R16 for adjustment are determined by the assumed Vt fluctuation range of the P-type MOS transistor and the allowable error after adjustment. If you want to reduce the error after adjustment, reduce the resistance of resistors R11-R16.
To increase the Vt fluctuation range to be compensated, the resistor R1
1 to R16 and the number of switches S11 to S16 is increased.

Next, for the P-type MOS transistor, the transistor size (gate width W of the transistor) required when the characteristics of the P-type MOS transistor are standard is determined. Depending on the assumed variation range of the β parameter and the allowable error after adjustment, the switches S1 to S6 and P
The number of type MOS transistors M1 to M6 and the transistor size of P type MOS transistors M1 to M6 are determined. The size of the P-type MOS transistor M0 is set based on the difference between the transistor size required for the standard and the P-type MOS transistors M1 to M3 for adjustment. To reduce the error after adjustment, P-type MOS transistors M1 to M6
When it is desired to reduce the transistor size and increase the β parameter variation range to be compensated, the numbers of P-type MOS transistors M1 to M6 and switches S1 to S6 are increased.

In FIG. 1, the P-type MOS transistor M0
Although ~ M6 is used, an N-type MOS transistor may be used instead of the P-type MOS transistor. Regarding the control signals A1 to A6 and A11 to A16 in FIG. 1, for example, there is a method of storing control signal information in a memory and reading and setting the information at the time of startup, a method of setting by a fuse, and the like. .

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
The structure of the shunt regulator in is shown. In FIG. 3, VDD is a power supply voltage, VSS is a reference voltage, R1, R
2, R11 to R16 are resistors, M0 to M6 are P-type MOS transistors, M11 to M16 are N-type MOS transistors, F1U to F6U, F1D to F6D, F11 to F16.
Is a fuse, 32 is a Vt adjusting circuit, and 33 is a β adjusting circuit. The difference from the first embodiment shown in FIG. 1 is that the switch S1
Fuses F11 to F16 are used instead of 1 to S16,
This is that N-type MOS transistors M11 to M16 are used instead of the switches S1 to S6, and fuses F1U to F6U and F1D to F6D are used as setting circuits for the control signals A1 to A6.

In the Vt adjusting circuit 32, the fuses F11 to F11 are
By selecting and cutting F16, resistors R11-R
Since 16 can be activated, adjustment is possible. Also, β
In the adjustment circuit 33, when the fuses F1D to F6D are cut, the gates of the N-type MOS transistors M11 to M16 are turned off at Low, and when the fuses F1U to F6U are cut, the gates of the N-type MOS transistors M11 to M16 are set at High. Turn on. In the β adjustment circuit 33, the N-type MOS transistors M11 to M are provided before the fuse is blown.
Although the gate input of 16 becomes an intermediate potential of the power supply voltage VDD, if a control circuit and a fuse are further added, a predetermined setting (for example, N-type MOS transistors M11 to M13 is on and M14 to M16 is turned on before the fuse is cut). Can be turned off).

An advantage of using a fuse as in the second embodiment shown in FIG. 3 is that the shunt regulator functions normally immediately after the power is turned on. For example, when setting data is stored in the memory, it is necessary to read the setting data from the memory after turning on the power, so the shunt regulator does not operate normally during the period from turning on the power until reading the memory data. there is a possibility. In FIG. 3, the P-type MOS transistor M0
-M6 and N-type MOS transistors M11-M16 are used, N-type MOS transistors are used instead of P-type MOS transistors M0-M6, and P-type MOS transistors are used instead of N-type MOS transistors M11-M16. Good.

Next, a method of adjusting the shunt regulator according to each embodiment of the present invention will be described with reference to FIG.
It is assumed that the shunt regulator is that of the first embodiment shown in FIG. FIG. 4 shows the characteristics of the shunt regulator. The vertical axis represents √Ids and the horizontal axis represents the power supply voltage VDD. The characteristics of the shunt regulator are, as described above, √Ids = √ (β / 2) × (R1 / (R1 + R2) × V
DD- | Vt |), and the relationship between √Ids and the power supply voltage VDD can be represented by a straight line. Regarding the data acquisition at the time of adjustment, the power supply voltage VD at which the P-type MOS transistors M0 to M6 are turned on in advance.
In the range of D, the current Ids is measured at two points of different power supply voltage VDD. Here, regarding the two measurement points, the current at the time of the power supply voltage VDD1 is Ids1, and the power supply voltage VDD
The current at 2 o'clock is Ids2. From the measurement results of these two points, the slope Am of the straight line is Am = (√Ids2-√Ids1) / (VDD2-VD
D1), the intercept xm0 on the horizontal axis is: xm0 = (VDD1 × √Ids2-VDD2 × √Ids
1) / (√Ids2-√Ids1).

Next, the standard characteristic value of the P-type MOS transistor is set to β0 for the β parameter, and the threshold voltage Vt is set.
Is set to Vt0, the target value for adjustment is
For the slope A of the straight line, A = √ (β0 / 2) × R1 / (R1 + R2), and for the intercept x0 on the horizontal axis, x0 = (R1 + R2) / R1 × | Vt0 | As for the order of the adjustment method, first, the section on the horizontal axis is used. The measurement result xm0 is compared with the target value x0 to determine whether the switches S11 to S16 are on or off. As an example, here, the switch S11 is turned off, and the switch S
12 to S16 are turned on. Next, a coefficient ((R1 + R11) / (R1 + R11 + R2)) / which reflects the adjustment result of the Vt adjustment circuit 30 on the measurement result Am0 of the straight line slope.
((R1 + R2) / R1) is multiplied and this value is compared with the target value A to determine whether the switches S1 to S6 are on or off. By adjusting the Vt adjusting circuit 30, the slope Am of the straight line
0 slightly changes, but the adjustment of the β adjustment circuit 31 does not change the result of the intercept xm0 on the horizontal axis.

As described above, when the adjustment is performed, the Vt adjusting circuit 30 is adjusted first, and the adjusted correction coefficient is multiplied to obtain β.
By adjusting the adjusting circuit 31, the characteristics of the shunt regulator can be adjusted more accurately.

Further, the shunt regulator of the present invention can be used in a non-contact IC card (see FIG. 7). In that case, the characteristics of the shunt regulator can be adjusted with high accuracy even if the characteristics of the MOS transistor are changed, so that it is possible to improve the accuracy of the limiting voltage and power consumption characteristics for element protection. As a result, it is possible to provide a high-quality non-contact IC card with a small variation in characteristics between samples.

[0040]

As described above, according to the shunt regulator of the invention described in claim 1, by providing the adjusting means, the characteristic variation of the shunt regulator can be suppressed even if the characteristic of the MOS transistor varies. It becomes possible to provide a high precision shunt regulator.

According to the shunt regulator of the second aspect of the invention, since the fuse is used, the shunt regulator can function normally even immediately after the power is turned on, in addition to the effect of higher accuracy.

According to the shunt regulator adjusting method of the third aspect of the present invention, the characteristics of the shunt regulator can be adjusted more accurately.

According to the non-contact IC card of the fourth aspect of the present invention, by mounting a high-precision shunt regulator, it is possible to provide a high-quality non-contact IC card with less characteristic variation between samples. Become.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a shunt regulator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing characteristics of the shunt regulator according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a shunt regulator according to a second embodiment of the present invention.

FIG. 4 is a diagram showing characteristics of the shunt regulator according to the first and second embodiments of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a conventional shunt regulator.

FIG. 6 is a diagram showing characteristics of a conventional shunt regulator.

FIG. 7 is a diagram showing a configuration of a non-contact IC card.

FIG. 8 is a diagram showing characteristics of a non-contact IC card.

[Explanation of symbols]

R1, R2, R11 to R16 Resistors M0 to M6 P-type MOS transistors M11 to M16 N-type MOS transistors S1 to S6, S11 to S16 Switches A1 to A6, A11 to A16 Control signals F1D to F6D, F1U to F6U, F11 to F16 Fuse 1 Antenna coil 2 Rectifier 3 Shunt regulator

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C005 NA08 QA15 SA30                 5B035 AA00 BB09 CA12 CA23                 5H430 BB02 BB09 BB11 BB12 CC05                       EE04 EE09 EE13 FF02 FF12                       GG05 GG11 GG17 LA02 LA24                       LB06                 5J055 AX40 AX64 BX16 CX23 DX50                       EX07 EX17 EY00 EY03 EY21                       EZ48 FX05 FX12 GX01 GX06

Claims (4)

[Claims] 1. A voltage output means for outputting a voltage between a first input and a second input with a predetermined division ratio, and a source between the first input and the second input, respectively. And a drain, and a first MOS transistor having a gate connected to the voltage output of the voltage output means, and a source and a drain connected between the first input and the second input via a switch, respectively. A plurality of second MOS transistors that are connected to each other and have their gates connected to the voltage output of the voltage output means, and an adjustment means that adjusts the predetermined division ratio, and a switch control means that controls the switch. A shunt regulator that is characterized by 2. The shunt regulator according to claim 1, wherein fuses are used as adjusting means for adjusting the predetermined division ratio and switch control means for controlling the switch. 3. The method for adjusting a shunt regulator according to claim 1, wherein after adjusting the adjusting means for adjusting the predetermined division ratio, the switch is turned on by using the correction coefficient of the adjustment result. A method for adjusting a shunt regulator, comprising determining a setting of a switch control means to be controlled. 4. A non-contact IC card comprising the shunt regulator according to claim 1 or 2.