JP3510974B2 - Semiconductor integrated circuit device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit device, and more particularly to a technique effective when it is mainly used for a liquid crystal drive circuit and a boosted voltage generating circuit used therein.

[0002]

2. Description of the Related Art In liquid crystal display devices such as STN and TFT,
In some cases, low power consumption has been achieved in liquid crystal displays by lowering the voltage by devising a driving method. Along with this, the semiconductor integrated circuit device for a driver (driving circuit) for liquid crystal display is replaced with a special process capable of applying a high voltage by the same MOS process as a semiconductor integrated circuit device such as a normal one-chip microcomputer. Some are manufactured. On the other hand, in a liquid crystal display device for a small portable device, a liquid crystal power supply circuit for boosting a voltage of a battery or the like, which is a voltage lower than a liquid crystal display voltage by N times, and other circuits required for liquid crystal display for the purpose of downsizing. There is one in which a semiconductor integrated circuit device is built in one chip.

In a one-chip semiconductor integrated circuit device containing a power supply circuit necessary for liquid crystal display and a drive circuit for liquid crystal elements, a battery voltage for driving a system of a small portable device such as a CPU (central processing unit) is also generated. In addition, a booster circuit for generating a boosted voltage of N times, a plurality of bias voltage (display voltage) generating circuits for driving the liquid crystal element from the boosted voltage, and a liquid crystal element using the plurality of generated bias voltages. Some have a built-in liquid crystal driver circuit for controlling display on / off.

[0004]

However, in a semiconductor integrated circuit device having a built-in power supply circuit or the like for liquid crystal display of a small portable device, when a drive system for displaying a liquid crystal element at a low voltage is adopted, the system power supply voltage is low. A booster circuit that boosts the voltage by N times often generates a voltage higher than the liquid crystal drive voltage, and as a result, some MOSFETs having a high breakdown voltage corresponding to the high voltage are required. There is a problem that the advantage that the semiconductor integrated circuit device such as a one-chip microcomputer can be manufactured by the same MOS process is lost.

An object of the present invention is to provide a semiconductor integrated circuit device equipped with a boosting power supply circuit capable of obtaining the minimum boosted voltage required for driving a liquid crystal. Another object of the present invention is to provide a semiconductor integrated circuit device which is provided with a liquid crystal drive circuit and has flexibility in mounting in a system. The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0006]

The outline of a typical one of the inventions disclosed in the present application will be briefly described as follows. That is, the signal source circuit includes a signal source circuit, a liquid crystal drive circuit that receives a display signal formed by the signal source circuit to form a liquid crystal drive signal, and a power supply circuit necessary for a display operation of the liquid crystal drive circuit. The variable voltage circuit that can adjust the power supply voltage of the circuit generates an internal voltage commensurate with the boosting ratio, and the charge pump circuit boosts the internal voltage to an integral multiple to generate the maximum voltage required for the liquid crystal drive signal. Then, the voltage is divided to form another display voltage required for the liquid crystal drive signal.

[0007]

FIG. 1 is a block diagram showing an embodiment of a semiconductor integrated circuit device according to the present invention.
Each circuit element in the figure is formed on one semiconductor substrate by a known MOS integrated circuit manufacturing technique. The semiconductor integrated circuit device of this embodiment is directed to a small portable device using a liquid crystal display device.

The semiconductor integrated circuit device (LS) of this embodiment
I) 100 constitutes a small portable device together with the liquid crystal display device 200. Although not particularly limited, the semiconductor integrated circuit device 100 is supplied with the voltage of the battery E as an operating voltage via the terminal P1. This battery voltage is C
It is supplied as an operating voltage for a PU (microprocessor) 6 and a RAM (random access memory) 5.

The booster circuit 1 uses capacitors C1 and C2 connected via external terminals P2 to P5, and switches S1 to S4 connect the capacitors C1 and C2 in parallel at a first timing to provide a variable voltage circuit 4. Is charged up by the internal voltage formed by, and at the second timing, the capacitors C1 and C2 are connected in series and the internal voltage is applied to form a voltage boosted three times as a whole, and the external terminal P6 The maximum voltage V1 required for driving the liquid crystal is held by the capacitor C3 connected via
Generate.

The variable voltage circuit 4 applies the battery voltage supplied from the terminal P1 to a variable resistor VR and a fixed resistor R.
The voltage dividing circuit consisting of 1 divides the internal voltage to form an internal voltage, and the operational voltage amplifying circuit OP1 has a voltage follower form.
Power is amplified through and output. When the triple booster circuit is used as the booster circuit 1 as described above, the variable voltage circuit 4 generates a voltage obtained by equally dividing the maximum voltage V1 required for the liquid crystal drive operation into three parts. The boosted voltage formed can be set to the maximum voltage V1.

The voltage V1 formed by the booster circuit is supplied as it is as an operating voltage of the liquid crystal drive circuit (DRV) 3, and at the same time, a resistor R constituting the display voltage generating circuit 2 is provided.
The voltage is divided by 2 to R4 to form the other display voltages V2 and V3 necessary for driving the liquid crystal, and the power is amplified through the operational amplifier circuits OP2 and OP3 of the same voltage follower type as described above, so that the drive circuit 3 of It is supplied as a display voltage. The liquid crystal drive circuit 3 is also supplied with the ground potential of the circuit as an operating voltage.

The liquid crystal drive circuit 3 is a liquid crystal display panel LCD.
Is a TFT type, the above voltages V1, V2 and V
3 can be used to display three gradations. Further, in the STN type, since the dynamic driving is performed, the effective voltage applied between the scanning line electrode and the signal line electrode of the liquid crystal panel LCD corresponds to lighting / non-lighting by the combination of the above V1 to V3 and the ground potential. The voltage that gives the specified voltage is selected and output.

In this embodiment, the liquid crystal display panel is directed to a small portable device, and the liquid crystal display panel is not particularly limited, but is a relatively small display panel having 65 scanning lines and 132 signal lines. A RAM 5 having a storage capacity corresponding to display pixels (dots) of 65 × 132 is provided, and characters or figures are displayed by writing data corresponding to the dots in the memory cells of this RAM. The CPU 6 is the RAM 5 as the image memory.
The pixel data for one line is read from the RAM 5 in accordance with the cycle of the timing of selecting the scanning line of the liquid crystal display panel LCD from the RAM 5 and supplied to the liquid crystal drive circuit 3. In this case, if one line (132 bits) is read at the same time, the number of signal lines becomes enormous. Therefore, for example, 4 bits are read 33 times.

In this embodiment, considering the magnification of the booster circuit 1, the variable voltage circuit 4 generates an internal voltage so that the maximum voltage required for driving the liquid crystal and the boosted voltage match. Is. With such a configuration, the maximum voltage generated in the semiconductor integrated circuit device can be made equal to the maximum voltage required for driving the liquid crystal, so that the breakdown voltage of the MOSFET formed in the semiconductor integrated circuit device also corresponds to the maximum voltage V1. Can be lowered. As a result, the MOSFET that constitutes the liquid crystal drive circuit DRV can be formed in the same process as the MOSFET that constitutes the internal circuit of the CPU and the like, and a special process for increasing the withstand voltage is not required, so that the cost can be reduced. become.

The variable resistor VR is not particularly limited, but a plurality of resistors are formed in series, and both ends thereof are formed so as to be short-circuited by fuses, and are selectively connected in series. The number of resistors is adjusted to generate the required internal voltage. In addition, a MOSFET that acts as a switch instead of the above fuse
May be provided, and the MOSFET may be switch-controlled by a control voltage formed by the fuse that is selectively cut to select the number of resistors connected in series in the same manner as above. Of course, such a variable resistor VR may be provided outside and adjustable by a so-called volume resistor outside.

FIG. 2 is a block diagram of another embodiment of the semiconductor integrated circuit device according to the present invention. In this embodiment, in addition to the embodiment of FIG. 1, a variable resistor VR is also provided between the terminal P6 and the display electron generating circuit 2. The variable resistor VR is used when the liquid crystal display voltage is directly supplied from the external terminal P6. That is, when the display voltage V1 is formed by using the boosted voltage formed by the variable voltage circuit 4 and the booster circuit 1 as in the embodiment of FIG. 1, the resistance value is set to almost zero.

In a system in which the semiconductor integrated circuit device according to the present invention is installed, when there is a relatively high voltage that can be used for liquid crystal display, the operation of the booster circuit 1 is stopped, and specifically, The voltage is directly supplied from the external terminal P6 by setting the capacitors C1 and C2 in a non-connected state or stopping the supply of the timing required for the operation. In this case, when there is a difference between this voltage and the maximum voltage V1 required for the liquid crystal display operation, the variable resistor VR is adjusted to reduce it to the required voltage V1. Even when an external voltage is used in this way, a higher voltage than necessary is not applied, so that the MOSFET forming the liquid crystal drive circuit DRV is formed in the same process as the MOSFET forming the internal circuit such as a CPU. Since no special process for increasing the breakdown voltage is required, the cost can be reduced.

FIG. 3 is a block diagram of another embodiment of the semiconductor integrated circuit device according to the present invention. In this embodiment, the switch SW is connected to the output of the variable voltage circuit 4.
The internal voltage is supplied to the booster circuit 1 through the external terminal P9. In this embodiment, two operation modes can be selected. In one form thereof, the internal voltage can be boosted by the booster circuit 1 in the state where the switch SW is turned on and nothing is connected to the terminal P7 as in the embodiment of FIG. In another mode, the switch SW is turned off, the voltage adjusted by the external circuit OP4 is supplied to the external terminal P9, and the booster circuit 1 boosts the voltage. With this configuration, the degree of freedom in voltage adjustment can be increased.

FIG. 4 is a block diagram showing still another embodiment of the semiconductor integrated circuit device according to the present invention.
In this embodiment, a plurality of variable voltage circuits 41 to 43 are provided, and the capacitors S1 to S4 of the booster circuit 1 are used by the switches C1 to S4 during the precharge operation.
And C2 are supplied with the voltage formed by the variable voltage circuits 42 and 43. At the time of boosting operation, the voltage of the variable voltage circuits 42 and 43 held in the capacitors C1 and C2 is added to the output voltage of the variable voltage circuit 41, and the switches S5 and S6 are turned on to turn on the respective switches. The voltage is held in the capacitors C31, C32 and C33. With this configuration, the display voltages V1 to V3 can be directly formed by the booster circuit 1 without providing the resistors R2 to R4 and the operational amplifier circuits OP2 and OP3 as in the embodiment of FIG.

FIG. 5 is a block diagram showing still another embodiment of the semiconductor integrated circuit device according to the present invention.
In this embodiment, the variable resistor of the variable voltage circuit 4 is MO
SFET Q1 is used. Operational amplifier circuit OP1
The reference constant voltage Vref is supplied to the non-inverting input terminal (+) of
Resistors R5 and R6 for gain setting at the inverting input terminal (-)
Is provided, the potential V on the output side of the MOSFET Q1 is divided by the resistance circuits R5 and R6, and the reference constant voltage Vref.
The gate voltage of the MOSFET Q1 is controlled so that

In this structure, even if the voltage of the battery E drops, the internal voltage V = Vref × R6 / (R5 + R6)
It can be made constant regardless of the battery voltage. Therefore, a stable display operation can be performed without depending on the voltage of the battery E. The reference voltage uses the threshold voltage of the MOSFET, and if the accuracy is higher, a known constant voltage using the silicon band gap may be used.

The operational effects obtained from the above embodiment are as follows. That is, (1) a signal source circuit, a liquid crystal drive circuit for receiving a display signal formed by the signal source circuit to form a liquid crystal drive signal, and a power supply circuit necessary for the display operation of the liquid crystal drive circuit, A voltage generator that can adjust the power supply voltage of the signal source circuit generates an internal voltage commensurate with the boosting ratio, and this internal voltage is boosted to an integral multiple by the charge pump circuit, and the maximum required for the liquid crystal drive signal is generated. By generating a voltage and dividing the voltage to form another display voltage required for the liquid crystal drive signal, the MOSFET forming the liquid crystal drive circuit DRV is formed into an internal circuit such as a CPU.
Since it can be formed in the same process as the SFET and a special process for increasing the breakdown voltage is unnecessary, the effect that the cost can be reduced can be obtained.

(2) A signal source circuit, a liquid crystal drive circuit for receiving a display signal formed by the signal source circuit to form a liquid crystal drive signal, and a power supply circuit necessary for the display operation of the liquid crystal drive circuit. , A voltage generation circuit capable of adjusting the power supply voltage of the signal source circuit generates an internal voltage commensurate with the boosting ratio, and the internal voltage is boosted to an integral multiple by a charge pump circuit to be necessary for the liquid crystal drive signal. By generating the maximum voltage and outputting it via a variable resistor, the desired voltage is generated by adjusting the variable resistor when operating with an external power supply by using the external terminal for the charge pump. Therefore, the flexibility of application to the system is obtained and the liquid crystal drive circuit DR is provided.
The MOSFET forming V can be formed in the same process as the MOSFET forming the internal circuit of the CPU and the like, and a special process for increasing the withstand voltage is not required, so that the cost can be reduced. To be

(3) A signal source circuit, a liquid crystal drive circuit for receiving a display signal formed by the signal source circuit to form a liquid crystal drive signal, and a power supply circuit necessary for the display operation of the liquid crystal drive circuit. , An internal voltage commensurate with the step-up ratio is generated by a voltage generation circuit that can adjust the power supply voltage of the signal source circuit, and the internal voltage is supplied to the charge pump circuit via a switch and an external terminal to be an integral multiple. By boosting to generate the maximum voltage required for the liquid crystal drive signal, it is possible to operate with an external power source by using the external terminal, and to obtain flexibility of application to the system and to realize the liquid crystal drive circuit DRV. Since the constituent MOSFETs can be formed in the same process as the MOSFETs forming the internal circuit of the CPU and the like, a special process for increasing the withstand voltage is not required, so that the cost can be reduced. The effect that it can be converted into

(4) A signal source circuit, a liquid crystal drive circuit for receiving a display signal formed by the signal source circuit to form a liquid crystal drive signal, and a power supply circuit necessary for the display operation of the liquid crystal drive circuit. , A plurality of variable voltage circuits capable of adjusting the power supply voltage of the signal source circuit are used to generate a plurality of internal voltages commensurate with the boosting operation, and the respective voltages when the plurality of internal voltages are added are stored in a capacitor. By holding it, it is possible to directly form a plurality of display voltages required for display operation, and the MOSFET that constitutes the liquid crystal drive circuit DRV is formed in the same process as the MOSFET that constitutes an internal circuit such as a CPU. Therefore, a special process for increasing the withstand voltage is not required, so that the cost can be reduced.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention of the present application is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say. For example, the signal source circuit may be a control circuit formed by a gate array or the like in addition to a general-purpose CPU or the like. When the CPU also controls the display operation, a ROM storing a program for controlling the display operation may be installed. Data for setting the resistance value of the variable resistor may be stored in the ROM. INDUSTRIAL APPLICABILITY The present invention can be widely used for a semiconductor integrated circuit device including a liquid crystal drive circuit and its signal source circuit.

[0027]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows. That is, the signal source circuit includes a signal source circuit, a liquid crystal drive circuit that receives a display signal formed by the signal source circuit to form a liquid crystal drive signal, and a power supply circuit necessary for a display operation of the liquid crystal drive circuit. A voltage generator that can adjust the power supply voltage of the circuit generates an internal voltage commensurate with the boosting ratio, and the charge pump circuit boosts the internal voltage to an integral multiple to generate the maximum voltage required for the LCD drive signal. By dividing the voltage and forming another display voltage necessary for the liquid crystal drive signal, the MOSFET forming the liquid crystal drive circuit DRV can be formed in the same process as the MOSFET forming the internal circuit such as the CPU. Therefore, it is possible to reduce the cost because a special process for increasing the withstand voltage is unnecessary.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a semiconductor integrated circuit device according to the present invention.

FIG. 2 is a block diagram showing another embodiment of the semiconductor integrated circuit device according to the present invention.

FIG. 3 is a block diagram showing another embodiment of the semiconductor integrated circuit device according to the present invention.

FIG. 4 is a block diagram showing still another embodiment of the semiconductor integrated circuit device according to the present invention.

FIG. 5 is a block diagram showing still another embodiment of the semiconductor integrated circuit device according to the present invention.

[Explanation of symbols]

1 ... Booster circuit, 2 ... Display voltage generation circuit, 3 ... Liquid crystal drive circuit, 4, 41-43 ... Variable voltage circuit, 5 ... RAM, 6 ...
CPU, OP1 to OP4 ... Operational amplifier circuit, S1 to S6,
SW ... Switch, VR ... Variable resistance, R1-R6 ... Resistance,
C1 to C3, C31 to C33 ... Capacitor, 100 ... Semiconductor integrated circuit device, 200 ... Liquid crystal display panel.

Front page continued (72) Inventor Makoto Omura, 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd. (72) Inventor, Makoto Obata 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd. (72) Invention Satoshi Notomi 3681 Hayano, Mobara-shi, Chiba, Hitachi Device Engineering Co., Ltd. (56) Reference JP-A-9-197366 (JP, A) JP-A-10-112977 (JP, A) JP-A-2-275989 (JP, A) Actual Kaihei 1-79027 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/133 505 G09G 3/36

Claims (5)

(57) [Claims] 1. A signal source circuit for forming a display signal, a liquid crystal drive circuit for receiving a display signal formed by the signal source circuit and forming a liquid crystal drive signal, and a power supply used for the operation of the signal source circuit. A variable voltage circuit that receives a voltage and generates an adjustable internal voltage; a charge pump circuit that boosts the internal voltage to an integral multiple to generate a maximum display voltage required for the liquid crystal drive signal; A semiconductor integrated circuit device comprising: a voltage generation circuit that divides the formed voltage and forms another display voltage required for the liquid crystal drive signal. 2. A signal source circuit for forming a display signal, a liquid crystal drive circuit for receiving a display signal formed by the signal source circuit and forming a liquid crystal drive signal, and boosting the internal voltage to an integral multiple. A charge pump circuit that forms an output voltage greater than or equal to the maximum display voltage required for the liquid crystal drive signal and outputs the output voltage to an external terminal, and an adjustable voltage generator that lowers the voltage of the external terminal to form the maximum display voltage of the liquid crystal. And a voltage generating circuit that divides the maximum display voltage that has passed through the resistance element to form another display voltage necessary for the liquid crystal drive signal, and connects a capacitor to the external terminal. The output voltage formed by the charge pump circuit is held or the operation of the charge pump circuit is substantially stopped, and the display voltage formed by an external power supply device is input from the external terminal. The semiconductor integrated circuit device according to claim and. 3. A signal source circuit for forming a display signal, a liquid crystal drive circuit for receiving a display signal formed by the signal source circuit and forming a liquid crystal drive signal, and a power supply used for the operation of the signal source circuit. A variable voltage circuit that receives a voltage and generates an adjustable internal voltage, a switch that selectively transmits the internal voltage to an external terminal, and a voltage that is an integral multiple of the internal voltage or the voltage supplied from the external terminal. A charge pump circuit that generates a maximum display voltage required for the liquid crystal drive signal, and a voltage generation circuit that divides the voltage formed by the charge pump circuit to generate another display voltage required for the liquid crystal drive signal. A semiconductor integrated circuit device comprising: 4. A signal source circuit for forming a display signal, a liquid crystal drive circuit for receiving a display signal formed by the signal source circuit and forming a liquid crystal drive signal, and a power supply used for the operation of the signal source circuit. A variable voltage circuit that receives a voltage and generates a plurality of adjustable internal voltages, and a charge pump that generates a plurality of display voltages necessary for the liquid crystal drive signal by adding the plurality of internal voltages to boost the voltage. A circuit and a plurality of capacitors respectively holding a plurality of added voltages formed by the charge pump circuit, and using the voltages held in the plurality of capacitors as a display voltage source for forming the liquid crystal drive signal. A semiconductor integrated circuit device comprising: 5. The semiconductor integrated circuit device according to claim 1, wherein the signal source circuit includes a microprocessor and a memory circuit that stores display data.