JPH0434168B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a power supply switching circuit for an integrated circuit used, for example, in an integrated circuit for an electronic watch using a microprocessor. The present invention relates to a power supply switching circuit that can selectively connect batteries and supply an appropriate level of power supply voltage to an integrated circuit.

[Technical background of the invention]

As a conventional watch LSI (large scale integrated circuit),
For example, two types are produced: one that uses a -1.5V silver oxide battery and one that uses a -3.0V lithium battery. The power supply circuit in the former LSI using a silver oxide battery inputs the battery voltage V _SS1 through the first power supply terminal 1 to the V _SS1 system of the booster circuit 2, as shown in Figure 1, and doubles this input voltage. The V _SS2 system output and battery voltage V _SS1 obtained by
It is supplied as a two-system power supply for LSI. In addition, the power supply circuit in the latter LSI using a lithium battery inputs the battery voltage V _SS2 through the second battery terminal 11 to the V _SS2 system of the step-down circuit 12 as shown in FIG. The V _SS1 system output obtained by stepping down the voltage and the battery voltage V _SS1 system are supplied as two power supplies for the LSI. In this case, the internal resistance of the lithium battery is large, so when the LSI circuit is under heavy load, such as when driving a buzzer load, lighting a lamp (filament), running a built-in program, or using the built-in dynamic ROM (read-only memory). ) when the CPU is accessing (reading) the lithium battery, the voltage level of the lithium battery may drop significantly. As a result, when the voltage level of the V _SS1 system output decreases significantly, the logic circuits and oscillation circuits of LSIs that are normally supplied with power from the V _SS1 system output malfunction, and in particular, the oscillation of the oscillation circuit stops. Sometimes. In order to avoid such a situation, conventionally, as shown in Fig. 2, the step-down circuit 1
2 V _SS2 system input node N ₂ and V _SS1 system output node N ₁
A first MOS (insulated gate type) transistor 13 is inserted between the V _SS1 system output node N ₁ and V _SS1
A second MOS transistor 15 is inserted in series between the terminal 14 and the first transistor 13 is made conductive by a heavy load signal generated during a heavy load, thereby forcing the V _SS1 system output node N ₁ of the step-down circuit 12. to
V May be configured to _SS2 level. Note that at this time, the heavy load signal is inverted by the inverter 16, and the second transistor 15 is cut off. Further, when a heavy load signal is not generated, the second transistor 15 is turned on and the first transistor 13 is turned off.

[Problems with Background Art] However, as mentioned above, it is disadvantageous in terms of cost to produce LSIs whose power supply circuits differ depending on the type of battery used.

In addition, when measures against heavy loads are taken as shown in Figure 2, the V _SS2 level is supplied to the LSI's V _SS1 system during heavy loads, causing malfunctions in the V _SS1 system's CPU and dynamic ROM. Because it is easy to occur,
Countermeasures for heavy loads on LSIs using dynamic systems require some ingenuity.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
Regardless of which of the two types of batteries with different voltage levels are used as an external power source, a common circuit configuration can be used, reducing costs and minimizing malfunctions of the integrated circuit due to drops in battery voltage. The object of the present invention is to provide a power supply switching circuit for integrated circuits.

[Summary of the invention]

That is, the present invention provides an integrated circuit power supply switching circuit provided in an integrated circuit in which a first battery with a first power supply voltage or a second battery with a second power supply voltage is used as an external power supply. A first power supply voltage is supplied via the supply terminal to step up the first power supply voltage to generate a second power supply voltage, and the second power supply voltage is supplied from the second battery via the second power supply terminal. a step-up/down circuit that steps down the voltage to generate a first power supply voltage; a power supply switching control terminal to which a signal of a different logic level is applied depending on whether one of the two types of batteries is used; a first power supply output terminal for supplying a power supply voltage to a circuit of a first power supply system in an integrated circuit; and a first power supply terminal inserted in parallel between the first power supply terminal and the first power supply output terminal. a second switch, an intermediate voltage supply circuit that generates an intermediate voltage between the first power supply voltage and the second power supply voltage from the voltage of the second power supply terminal and supplies the generated voltage to the first power supply output terminal; The first switch is turned on so that when a logic level signal corresponding to the use of the first battery is applied to the switching control terminal, the first switch is turned on and the intermediate voltage supply circuit is put into a non-operating state. and controlling the intermediate voltage supply circuit so that the second switch is turned on after the step-up operation of the step-up/down circuit is stabilized after the signal at the logic level is applied; When a logic level signal corresponding to the use of the second battery is applied to the power supply switching control terminal or when a heavy load circuit in the integrated circuit is operating, the intermediate voltage supply circuit is set to be in an operating state. The second switch controls the voltage supply circuit so that the second switch is turned on after the step-down operation of the buck-boost circuit is stabilized after the signal at the logic level is applied, or after the operation of the heavy load circuit is finished. The present invention is characterized by comprising a control circuit for controlling the switch.

Therefore, since the power supply switching circuit has a common circuit configuration regardless of whether the first battery or the second battery is used, it is possible to reduce costs.
Moreover, even if the voltage drop due to the internal resistance of the second battery is large when the battery is connected or under heavy load, the appropriate power supply voltage can be supplied from the intermediate voltage supply circuit to the first power supply circuit, minimizing malfunctions. It is possible to suppress the

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 3 shows, for example, a power supply switching circuit provided in a watch LSI, and 31 is a first power supply terminal to which a battery voltage V _SS1 is supplied when, for example, a silver oxide battery is used as an external power supply; Reference numeral 32 denotes a second battery terminal to which the battery voltage V _SS2 is supplied from the outside when a lithium battery is used, for example. 33 is a buck-boost circuit, which connects the first power supply terminal 31 to the first power supply terminal 31.
When the V _SS1 voltage is supplied to the V _SS1 node N ₁ , the voltage 2V _SS1 obtained by boosting it by, for example, twice (Here, if V _SS1 = -1.5V and V _SS2 = -3.0V, _{. _ _ _ _ _}
V _SS2 =V _SS1 is output to V _SS1 node _N1 . This operation is performed based on, for example, a 512 Hz clock input from an oscillation circuit (not shown).

On the other hand, 34 is a V _SS1 system circuit (logic circuit, oscillation circuit, etc.) inside the LSI, such as a buzzer drive circuit, etc.
This is the first power output terminal for supplying the power voltage to the lamp (filament circuit, etc., which is a V _SS2 system circuit). A switch circuit 35, for example, a first MOS transistor 36 and a second MOS transistor 37, is connected in parallel between the first power supply output terminal 34 and the V _SS1 node _N1 of the buck-boost circuit 33. . Further, _{an intermediate} voltage supply circuit 38, for example, a _third
A series circuit of a MOS transistor 39 and a fourth MOS transistor 40 is provided, and a connection point between the transistors 39 and 40 is connected to the first power output terminal 34.

On the other hand, in the control circuit 41, each set input terminal S of the first shift register 42 and the second shift register 43 each has a heavy load signal and a power-on clear signal generated when a used battery is connected to the LSI. A signal is applied, a voltage from an internal terminal 44 for power supply switching control (described later) is applied to each forced reset terminal (a terminal for giving priority to reset input over set input), and to each clock terminal CL (not shown). For example, a 1 Hz clock is applied from an oscillation circuit. The V _SS2 voltage is applied to the data input terminal D of the first shift register 42, and the data input terminal D of the second shift register 43 is connected to the data output terminal Q of the first shift register 42. ing.
Furthermore, the output of the data output terminal of the second shift register 43 is guided to a first inverter 45, and the output of this inverter 45 is guided to each gate of the series-connected transistors 39 and 40, and the second The output of the inverter 46 is led to the gate of one of the transistors 36 and 37 connected in parallel, and the voltage of the switching control internal terminal 44 is connected to the gate of the other transistor 37. being guided.

When the power supply used is a silver oxide battery, the internal terminal 44 for power supply switching control has, for example, a V _DD voltage,
In the case of lithium batteries, V _SS2 voltage is now applied, for example at the LSI production stage or
At the stage of assembling the LSI into a watch, wire bonding is used to connect the terminal 44 and the V _DD terminal or the V _SS2 terminal.

Note that the operating power supply for the shift registers 42 and 43 and the inverters 45 and 46 is the V _SS2 voltage.

Next, the operation shown in FIG. 3 will be explained. Currently, in LSIs that use silver oxide batteries as external power sources,
Since the internal terminal 44 is at the V _DD voltage (logic level "1"), the shift registers 42 and 43 are in a reset state. Therefore, the second shift register 43
The data output terminal of the first inverter 45 becomes "1" level (V _DD ), the output of the first inverter 45 becomes "0" level (V _SS2 voltage), transistors 39 and 40 are both turned off, and the second inverter 46 The output becomes “1” level and the first transistor 3
6 is turned on. Further, the second transistor 37 is also led to its gate by the "1" level of the internal terminal 44, so that it is turned on. Therefore, the V _SS1 voltage at the V _SS1 node N ₁ of the step-up/down circuit 33 is supplied to the LSI internal circuit from the first power output terminal 34 via the on-state transistors 36 and 37 . Here, the reason for the existence of the second transistor 37 will be described. In other words, the output of the second inverter 46 of the V _SS2 system is applied to the gate of the first transistor 36, and after the power supply is connected to the LSI, the voltage is increased by the step-up operation of the buck-boost circuit _33. Due to boost characteristics, it takes, for example, 250ms until voltage is generated.
As a result, the output of the second inverter 46 is delayed in rising to the "1" level, and the first transistor 36 cannot be completely turned on during this time. Therefore, the second transistor 37 is turned on by the "1" level of the internal terminal 44, so that a stable V _SS1 voltage can be quickly derived from the first power supply output terminal 34.

On the other hand, in an LSI that uses a lithium battery as an external power source, by connecting the battery to the LSI, the internal terminal 44 becomes V _SS2 voltage (“0” level), so the shift registers 42 and 43 Not reset. Then, when the battery is connected, a power-on clear signal is generated, both shift registers 42 and 43 are set, and the output of the second shift register 43 becomes "0" level. As a result, the output of the first inverter 45 becomes "1" level, and the output of the third and fourth transistors 3
9 and 40 are both turned on, and the second inverter 4
The output of transistor 6 becomes "0" level and the first transistor 36 is turned off, and the second transistor 37 is also turned off since the "0" level of the internal terminal 44 is guided to its gate. In _{this case} , _both transistors 39, It is assumed that a dimension ratio of 40 is set. Therefore, immediately after the battery is connected, the 2/3V _SS2 voltage is applied from the first power output terminal 34.
It is supplied to the V _SS1 system circuit, and the operation of the V _SS1 system starts up quickly. Then, the first 1 from the oscillation circuit
The first shift register 42 is controlled by the Hz clock.
V _SS2 (“0” level) input is taken in, and “0” level appears at its Q output, and the second 1Hz clock causes the second shift register 43 to shift the Q output (“0” level) of the first shift register 42. "level)" and its output becomes "1" level. As a result, the output of the first inverter 45 goes to "0" level, turning both transistors 39 and 40 off, and the output of the second inverter 46 goes to "1" level, so that the first Transistor 36 is turned on. That is, about 2 seconds after the battery is connected, the previous state is canceled, and during this time, the V _SS1 voltage obtained by being stepped down by the buck-boost circuit 33 passes through the first transistor 36 that is in the on state, and is transferred to the first
A steady power source is supplied from the power output terminal 34 to the V _SS1 system circuit. Thereafter, even when a heavy load signal is generated, a 2/3V _SS2 voltage appears at the first power output terminal 34 by the same operation as when the battery is connected as described above, and after the heavy load signal is no longer generated, After about 2 seconds, the V _SS1 voltage appears at the first power output terminal 34.

Note that even if the power supply voltage V _SS2 decreases due to the internal resistance of the battery during heavy loads, and the V _SS1 voltage decreases accordingly, the V _SS1 system circuit will output 2/2/2 instead of the V _SS1 voltage.
Since the 3V _SS2 voltage is supplied, it is sufficiently operable, and the 2/3V _SS2 voltage at this time is not as high as the V _SS2 voltage as a power supply for the V _SS1 system circuit, and the V _SS1 system circuit has a dynamic system circuit. Even if it is included, normal operation can be expected. The above 2/3V _SS2 voltage is applied to the third transistor 39 and the fourth transistor 4.
By changing the dimension ratio with respect to 0, specifically, by changing the dimension of the fourth transistor 40 while setting the dimension of the third transistor 39 to a predetermined value, V _SS1 (=1/2V _SS2 )
It is possible to change to a more appropriate value between V SS2 and V _SS2 .

〔Effect of the invention〕

As described above, according to the power supply switching circuit for integrated circuits of the present invention, no matter which of two types of batteries with different voltage levels are used as an external power supply, a common circuit configuration is required, which makes it possible to reduce costs. Malfunctions of the integrated circuit due to a drop in battery voltage can be minimized.

[Brief explanation of drawings]

1 and 2 are configuration explanatory diagrams showing a conventional integrated circuit power supply circuit, respectively, and FIG. 3 is a configuration explanatory diagram showing an embodiment of an integrated circuit power supply switching circuit according to the present invention. 31, 32... Power supply terminal, 33... Buck-boost circuit, 34... First power output terminal, 35... Switch circuit, 38... Intermediate voltage supply circuit, 41...
Control circuit, 44... Internal terminal for power supply switching control,
V _SS1 ...First power supply voltage, V _SS2 ...Second power supply voltage.

Claims (1)

[Claims] 1. A first battery with a first power supply voltage or a second battery with a second power supply voltage is used as an external power supply, and is installed in an integrated circuit having circuits of a first power supply voltage system and a second power supply voltage system. In a power supply switching circuit for an integrated circuit, the power source is connected from the first battery to the first power supply terminal via the first power supply terminal.
When the power supply voltage is supplied, it is boosted to generate a second power supply voltage, and a second power supply voltage is generated from the second battery.
A step-up/down circuit that generates the first power supply voltage by lowering the second power supply voltage when it is supplied through the power supply terminal, and a logic that differs depending on which of the two types of batteries is used. a power supply switching control terminal to which a level signal is applied; a first power supply output terminal for outputting a power supply voltage to a first power supply voltage system circuit in the integrated circuit; the first power supply terminal and the first power supply terminal; first and second switches inserted in parallel between the output terminal and the second power supply terminal; generating an intermediate voltage between the first power supply voltage and the second power supply voltage from the voltage of the second power supply terminal; an intermediate voltage supply circuit that supplies the power to the power output terminal; and when a logic level signal instructing the use of the first battery is applied to the power supply switching control terminal, the first switch is turned on and the intermediate voltage is turned on. the first voltage supply circuit so that the voltage supply circuit is inactive;
and the intermediate voltage supply circuit, and controls the second switch so that the second switch is turned on after the step-up operation of the buck-boost circuit is stabilized after the signal at the logic level is applied. , when a logic level signal instructing the use of the second battery is applied to the power supply switching control terminal or when a heavy load circuit in the integrated circuit is operating, the intermediate voltage supply circuit is set to be in an operating state. The intermediate voltage supply circuit is controlled such that the second switch is turned on after the step-down operation of the buck-boost circuit is stabilized after the signal of the logic level is applied or after the operation of the heavy load circuit is completed. A power supply switching circuit for an integrated circuit, comprising a control circuit that controls a second switch and operates at the second power supply voltage.