JP2000148064A - Device for adjusting characteristic of electronic circuit, liquid crystal drive device and portable telephone set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a characteristic adjusting device for an electronic circuit self-returning even when a latch error of the trimming data occurs due to a noise, etc. SOLUTION: The trimming data according to states of respective trimming elements are held into fuse trimming latch circuits 11(a-n) by an input of a sampling signal E, and an operation characteristic of a CR oscillation circuit 20 is adjusted with a characteristic adjustment part 14 based on the held trimming data F. Then, since the sampling signal E is supplied periodically from a sampling signal generation circuit 13 to the fuse trimming latch circuits 11(a-n), the trimming data are re-held periodically. Thus, even when the trimming data F are changed due to the noise from pads 12(a-n), etc., the trimming data F are returned again to a normal state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for adjusting the characteristics of an electronic circuit, a liquid crystal driving device, and a portable telephone. TECHNICAL FIELD The present invention relates to a device for adjusting characteristics of an electronic circuit, a liquid crystal driving device, and a mobile phone, which adjusts the electronic circuit to a standard value.

[0002]

2. Description of the Related Art Conventionally, CR oscillation circuits, constant voltage circuits,
Various electronic circuits such as an amplifier circuit and a filter circuit are widely used. In these electronic circuits, trimming for adjusting characteristics using a trimming element such as a polysilicon fuse or a zener diode is performed in order to suppress a variation in operation due to a manufacturing variation in each circuit element.
For example, in a CR oscillation circuit used in a liquid crystal driving device or the like, trimming is performed to keep the oscillation frequency constant, and in a constant voltage circuit used in an electronic device such as a microcomputer to prevent power supply voltage variations. Trimming has been performed. Each trimming element is connected or disconnected,
An initial state such as conduction or opening is determined by the element, and the state is changed by applying a high voltage to the trimming element from an external terminal or irradiating laser. The adjustment of the characteristics of the electronic circuit by changing the state of the trimming element includes adjusting the operating characteristics by directly changing the resistance value and the like in the electronic circuit when cutting the trimming element, and adjusting the state of the trimmed element after cutting. May be latched by a latch circuit as trimming data consisting of a plurality of bits, and the operating characteristics may be adjusted by selecting the resistance value of the electronic circuit based on the trimmed data latched. When operating characteristics are adjusted based on latched trimming data, the state of each trimming element after trimming, such as conduction and release, is physically determined and the state of each trimming element does not change. At the time of turning on the power or resetting the device in which the device is used, a sampling signal is generated to latch the trimming data.

[0003]

However, even if the state of the trimming element does not change, the trimming data held by the latch circuit may be inverted due to external noise or the like. In such a case, the conventional trimmed electronic circuit does not latch the trimming data except at the time of power-on or reset, so if the data changes once due to the influence of noise, the trimming data will not be latched. However, there is a problem that the operation characteristics adjusted based on the condition remain changed, and a stable operation cannot be obtained. In addition, when such a trimming data latch error occurs, the user of the device or apparatus using the electronic circuit needs to turn on the power again or perform a reset process, which is complicated. In particular, when a high voltage is applied from an external terminal to change the state of a predetermined trimming element, there is a high possibility that external noise is generated from the external terminal.

The present invention has been made in order to solve the above-described problems, and provides an electronic circuit characteristic adjustment device capable of self-recovery even if a trimming data latch error occurs due to noise or the like. The purpose is to do.

[0005]

According to the present invention, trimming data corresponding to the state of each trimming element is held in trimming data holding means by input of a sampling signal, and operation of an electronic circuit is performed based on the held trimming data. The characteristics are adjusted. In the present invention, the sampling signal is periodically supplied to the trimming data holding means, so that the trimming data is periodically held again,
Even if the trimming data changes due to noise or the like, it returns to a normal state by itself. In the present invention, preferably, the electronic circuit is an oscillation circuit, a constant voltage circuit, an amplifier circuit, or a filter circuit, and the adjusting means adjusts the operation characteristics by adjusting a time constant or a resistance value according to the electronic circuit. Preferably, a polysilicon fuse or a Zener diode is used as the trimming element. Further, in the present invention, preferably, there is provided a pad for voltage application which is connected to the trimming element and changes its initial state. As described above, the present invention is particularly effective because the trimming circuit having a configuration easily affected by external noise via the pad for voltage application is self-recovered.
In the present invention, the oscillation frequency of the liquid crystal drive unit that controls the driving of the liquid crystal panel based on the oscillation clock by the oscillation circuit is
The adjustment is performed by such an electronic circuit characteristic adjustment device.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows the configuration of a characteristic adjustment device for an electronic circuit. As shown in FIG. 1, the characteristic adjustment device transmits n sets of fuse trimming latch circuits 11 a to 11 n, n pads 12 a to 12 n connected to each fuse trimming latch circuit 11, and a sampling signal E. Sampling signal generating circuit 13 to be supplied to fuse trimming latch circuit 11, and characteristic adjustment unit 1 connected to (or incorporated in part of) the CR oscillation circuit 20 as an electronic circuit whose characteristics are to be adjusted by trimming.
4 is provided.

The fuse trimming latch circuit 11 latches (holds) the trimming data F of “0” or “1” according to the state of the trimming element, and inputs the corresponding input terminal BITk (k = 0 to 0) of the characteristic adjustment unit 14. n). FIG. 2 shows a configuration of the fuse trimming latch circuit 11 for the P substrate. As shown in this figure, the fuse trimming latch circuit 11 includes a polysilicon fuse 111 as a trimming element. One end of the polysilicon fuse 111 is connected to the ground GND, and the other end is connected to the pad 12. The polysilicon fuse 111 is in a connected state (non-cut state) in its initial state, and takes two states of connection and cut by applying a high voltage from the pad 12 and cutting.

The fuse trimming latch circuit 11 further includes two P-channel transistors (MOSFETs) 115 and 116 functioning as trimming holding means.
And an inverter 117. The two transistors 115 and 116 have their source terminals connected to the power supply VCC.
, And the drain terminals are connected to the other end of the polysilicon fuse 111 (the side opposite to the ground GND) and the input terminal of the inverter 117. Transistor 1
The 15 gate terminals are connected to the sampling signal generating circuit 13 so that the sampling signal E is supplied. The gate terminal of the transistor 116 is connected to the output terminal of the inverter 117, and the output of the inverter 117 is output from the fuse trimming latch circuit 11 as trimming data F.

The operation of latching data according to the state (connected state, disconnected state) of the polysilicon fuse 111 by the fuse trimming latch circuit 11 will be described. First, the operation when the polysilicon fuse 111 is in the connected state will be described. In this case, H
When the sampling signal E (L active signal) that changes from the (high) state to the L (low) state is supplied to the fuse trimming latch circuit 11, the transistor 115 turns on. Then, the on-resistance of the transistor 115 and the resistance ratio of the polysilicon fuse 111 cause the transistor 11
The input of the inverter 117 connected to the drain of the drain 5 becomes L (low), and the inverter 117 outputs the H signal as the fuse trimming data F. The H signal is simultaneously supplied to the gate of the transistor 116 to turn off the transistor 116, so that the output of the inverter 117 is fixed at the H state. On the other hand, when the polysilicon fuse 111 is blown, when the transistor 115 to which the sampling signal E is supplied is turned on, since the polysilicon fuse 111 is blown, the input of the inverter 117 becomes H state, From 117, L as fuse trimming data F
A signal is output. This L signal is simultaneously applied to transistor 1
Since the transistor 116 is supplied to the gate of the transistor 16 to turn on the transistor 116, the output of the inverter 117 is fixed at the L state.

In the fuse trimming latch circuit 11 shown in FIG. 2, by connecting the gate terminal of the transistor 115 to the ground GND,
It is also possible to keep the state of the polysilicon fuse 111 fixed at all times by setting the state of the polysilicon fuse 111 to be always on. However, when the transistor 115 is always turned on, the transistor 11
5, a through current always flows from the power supply VCC, which leads to an increase in overall power consumption. According to the present embodiment, the H state and the L state corresponding to the state (connection, disconnection) of the polysilicon fuse 111 are again held by periodically supplying the sampling signal E to the fuse trimming latch circuit 11. However, since the output time of the sampling signal E is as short as 200 μs, the power consumption can be extremely low.
Note that the output time 200 μs of the sampling signal E is determined in consideration of the transistor size of the transistor 115 so that the transistor 115 is turned on with the polysilicon fuse 111 cut and the input of the inverter 117 can be fixed at the VCC level. It was done.

FIG. 3 shows a fuse trimming latch circuit 1.
1 shows another configuration. FIG. 3 shows the configuration of the fuse trimming latch circuit 11 for the N substrate, and the configuration is reversed as compared with the case for the P substrate shown in FIG. That is, the trimming holding means
Two N-channel transistors (MOSFET) 1
15 'and 116' and an inverter 117. When a high-level sampling signal E (H active signal) is supplied, a signal corresponding to the state of the polysilicon fuse 111 is latched.

FIG. 4 shows the configuration of the sampling signal generating circuit 13. Sampling signal generation circuit 1
Reference numeral 3 denotes a circuit that outputs an L-level sampling signal E, and includes a power-on-clear circuit 131, a periodic signal generation circuit 132, and two-input AND circuits 133 and 134. The AND circuit 133 includes a power-on-clear circuit 1
A power-on signal A output from the power supply 31 when the power is turned on;
A reset signal B generated when the reset button is turned on (or when the reset process is executed) is input. The output signal of the AND circuit 133 and the periodic signal D output from the periodic signal generating circuit 132 are input to the AND circuit 134, and the output signal of the AND circuit 134 is output from the sampling signal generating circuit 13 as the sampling signal E. . That is, the sampling signal generation circuit 13
Thereafter, a power-on signal A and a reset signal B that occur irregularly, and a periodic signal D that periodically occurs are output as a sampling signal E.

The periodic signal generating circuit 132 includes a frequency dividing circuit (frequency dividing means) (not shown).
The oscillation clock signal C supplied from FIG. 1 is frequency-divided to periodically output a periodic signal D (L active signal) at L level. When the fuse trimming latch circuit 11 is configured for the N substrate shown in FIG. 3, an H active signal is output from the sampling signal generation circuit 13 as a periodic signal D. The output timing of the periodic signal D output from the periodic signal generating circuit 132 is based on a change in the characteristic value of the electronic circuit whose characteristics are adjusted by the trimming data due to a change in the trimming data due to external noise or the like, and then due to the characteristic change. Output at a time interval shorter than the time until the effect occurs. For example, when a constant voltage circuit is used as an electronic circuit and this is used for an electronic device such as a microcomputer, the periodic signal D is output at a time interval shorter than a time until a malfunction due to a voltage change occurs. . In the present embodiment, CR is used as the electronic circuit whose characteristic is to be adjusted.
Although the oscillation circuit 20 is used, the CR oscillation circuit 2
0 is used for the liquid crystal driving device, the CR oscillation circuit 2
The effect of the characteristic change of 0 corresponds to the case where it is visually recognized as the occurrence of flicker on the liquid crystal screen. Therefore, in the present embodiment, the period before one screen is displayed is 75H, which is the period before the screen flicker occurs visually.
The periodic signal D is output at z. Then, as the periodic signal D, an L level signal is output for a time of about 200 μs. Note that the output period of the periodic signal D by the periodic signal generation circuit 132 may be 35 Hz, which is a period for displaying two screens, because it is not visually affected. However, the output cycle of the periodic signal D does not necessarily need to be linked to the screen display interval, and may be output at a cycle shorter than a visual effect is generated.

Here, one screen refers to a frame screen in the case of an interlace system in which a complete image (frame) is displayed on two screens (fields), but the frame screen is referred to. The output period of the signal D may be determined. In the case of the non-interlace method, since a field screen does not exist, a frame screen naturally corresponds to one screen.

The characteristic adjustment unit 14 (FIG. 1) is supplied from each of the fuse trimming latch circuits 11a to 11n.
N composed of trimming data F of “0” or “1”
A trimming circuit (not shown) for selecting the resistance value of the CR oscillation circuit 20 according to the bit trimming data is provided. The time constant is changed by changing the resistance value of the CR oscillation circuit 20 by the trimming circuit, and thereby the characteristic (the oscillation frequency of the CR oscillation circuit) is adjusted. The CR oscillation circuit 20 oscillates with the time constant adjusted by the characteristic adjustment unit 14 and outputs an oscillation clock C. The oscillating clock C is supplied to the sampling signal generating circuit 13 and is also frequency-divided by a frequency divider to a predetermined frequency and supplied to a liquid crystal driving unit and the like.

Next, the operation of the thus-configured electronic circuit characteristic adjusting apparatus will be described. (1) Trimming Operation (Selection of State of Polysilicon Fuse) First, in a state where the characteristics are not adjusted, the CR oscillation circuit 20 is selected.
The oscillation frequency and the time constant are examined, and a resistance value as a characteristic adjustment amount is obtained from the values. Then, trimming data for selecting the obtained resistance value by the characteristic adjustment unit 14 is determined (n-bit trimming data corresponding to the obtained resistance value is determined). Next, the polysilicon fuse 111 of the fuse trimming latch circuit 11 corresponding to the bit value of each trimming data F corresponding to "0" is cut. That is, the fuse is cut by applying a high voltage from the pad 12 connected to the polysilicon fuse 111 to be cut.

(2) Operation of Characteristic Adjustment Device for Electronic Circuit after Trimming State of polysilicon fuse 111 so that each fuse trimming latch circuit 11 outputs trimming data corresponding to the characteristic adjustment amount required for CR oscillation circuit 20. Is determined, the CR oscillation circuit 20 and the characteristic adjustment device whose characteristics have been adjusted are set in a liquid crystal driving device or the like of the mobile phone. FIG. 5 is a timing chart of signals in each section of the electronic circuit characteristic adjustment device. This timing chart shows the timing in one fuse trimming latch circuit 11, and it is assumed that the polysilicon fuse 111 is in a cut state.
As shown in this figure, when a power supply of a mobile phone or the like is first turned on, a power-on signal A is output from a power-on clear circuit 113, which is used as a sampling signal E from a sampling signal generating circuit 13 to a fuse trimming latch circuit 11. Supplied to When the sampling signal E is supplied, a state L corresponding to the cutting state of the polysilicon fuse 111 is latched by the transistors 115 and 116 of the fuse trimming latch circuit 11, and the signal “0” is output as the trimming data F by the characteristic adjustment unit 14. Supplied to

At the point indicated by arrow a in FIG.
Trimming data F caused by extraneous noise from
It is assumed that the value has been inverted from 0 "to" 1 ". In this case, the conventional electronic circuit characteristic adjustment device requires fuse trimming unless the user turns on the power again or turns on the reset button. Since the state after the inversion held by the latch circuit 11 continues, the characteristics of the CR oscillation circuit oscillation 20 change, and problems such as flickering, display failure, and malfunction of the liquid crystal display device occur. On the other hand, according to the present embodiment, the periodic signal D is output from the periodic signal generation circuit 132 in addition to the sampling signal E which is output irregularly due to power-on or reset, and this is the sampling signal E as the sampling signal E. The data is supplied from the generation circuit 13 to the fuse trimming latch circuit 11. For this reason, it is assumed that data inversion due to external noise or the like has occurred at the time point of the arrow a. Also, the sampling signal E by an arrow b point before the influence of the data inversion occurs is supplied to the fuse trimming latch circuit 11 latches the state L in accordance with the state of the polysilicon fuse 111 again,
Correct "0" is output as the trimming data F.
As described above, according to the present embodiment, even if an error occurs in the trimming data F due to external noise or the like, the self-recovery is performed before the influence of the noise occurs, so that the user can turn on the power again or execute the reset. There is no need to do it.

FIG. 6 shows a liquid crystal driving device and a liquid crystal (LCD) panel in which an electronic circuit characteristic adjusting device is used. The liquid crystal driving device 50 and the liquid crystal panel 60 shown in this figure are, for example, a display device of a portable telephone such as a PHS (personal phone system), a mobile phone, a car phone, or a portable electronic terminal such as an electronic organizer. It is used for various display devices such as display devices for facsimile machines, display devices for laser printers and copiers, and display devices for home telephones. As shown in this figure, the mobile phone or the like has a liquid crystal panel (LCD panel) 60 for displaying characters and images.
And a liquid crystal driving device 50 for driving and displaying the LCD panel.
And The liquid crystal driving device 50 includes the characteristic adjustment device 40 of the electronic circuit described in FIGS. The latch circuit 41 of the electronic circuit characteristic adjusting device 40 shown in FIG. 6 includes the fuse trimming latch circuit 11 except for the polysilicon fuse 111 described with reference to FIGS. The adjustment unit 14 is configured. As shown in FIG. 6, the liquid crystal driving unit includes a display timing generating circuit 51 that generates a display timing by dividing the oscillation clock from the CR transmission circuit 20 whose characteristics have been adjusted (frequency adjusted), a line counter, and the like. 52, a liquid crystal drive circuit 54 for driving and displaying the display image data stored in the display data RAM 53 in accordance with the timing supplied from the display timing generation circuit 51, and other components for driving an ordinary LCD panel.

In the liquid crystal driving device 50 shown in FIG. 6, the oscillation clock C output from the CR oscillation circuit 20 is not supplied to the sampling signal generation circuit 13, but is output from the display timing generation circuit 51. The display timing signal is supplied to the sampling signal generation circuit 13. In this case, since the display timing signal is obtained by dividing the frequency of the oscillation clock C output from the CR oscillation circuit 20 in accordance with the display timing, the periodic signal generation circuit 132 of the sampling signal generation circuit 13 can be omitted. The circuit can be simplified. Therefore, the display timing signal is directly supplied to the AND circuit 134 of the sampling signal generating circuit 13 and is supplied as it is to the fuse trimming latch circuits 11 as the sampling signal E.

Liquid crystal driving device and LCD described above
According to a mobile phone, a facsimile apparatus, or the like having a panel and a liquid crystal driving device, the transmission frequency of the CR transmission circuit, which is a reference for determining the display timing of the LCD panel, is changed according to the state of the polysilicon fuse 111 which is a trimming element. Can be adjusted by the characteristic adjustment unit 14 according to
More accurate display control can be performed. Also, even if noise is generated from the pad 12 or the like for cutting the polysilicon fuse 111 and the trimming data for characteristic adjustment is inverted, the normal state is automatically restored within a predetermined time. The effect of the above does not occur.

Although the configuration and operation of the electronic circuit characteristic adjusting device according to the present embodiment have been described above, the present invention is not limited to this configuration, and various modifications are possible within the scope described in each claim. It is. For example, in the embodiment, the case where the polysilicon fuse is used as the trimming element in the electronic circuit characteristic adjustment device has been described. However, another trimming element such as a Zener diode may be used. When a Zener diode is used as the trimming element, the anode is connected to ground GND and the cathode is connected to the pad 12.
Connect to However, in the polysilicon fuse 111, the initial state is the connection state, and the high state is applied by applying a high voltage from the pad 12, but in the case of the Zener diode, the initial state is the non-conductive state, and the high voltage is applied from the pad 12. The difference is that a short circuit occurs when t is applied. Therefore, before being output from the fuse trimming latch circuit 11, the data is inverted by an inverter and then output as trimming data F, or the trimming data F of the characteristic adjustment circuit 14 is output.
This can be handled by reversing the treatment for.

In the embodiment described, the pad 12
By applying a high voltage to the polysilicon fuse 111
Was cut, but a laser trimming method of cutting by irradiating the polysilicon fuse 111 with a laser may be used. In this case, the pad 12 becomes unnecessary. For this reason, external noise does not occur from the pad 12, but external noise such as magnetic influence may occur and the trimming data F output from the fuse trimming latch circuit 11 may be inverted. The self-recovery system works effectively.

Further, in the sampling signal generation circuit 13 of the present embodiment, the oscillation clock signal C used in the periodic signal generation circuit 132 is obtained from the CR oscillation circuit 20, but the oscillation circuit may be provided independently. Good. Since the sampling signal generation circuit 13 includes a unique oscillation circuit in this manner, the periodic signal D can be output without being affected by a characteristic change due to external noise of the CR oscillation circuit 20.

The sampling signal generating circuit 1 of the present embodiment
3, the reset signal B is sampled because the periodic signal D is periodically output as the sampling signal E, and the fuse trimming latch circuit 11 self-recovers and holds and outputs the correct trimming data according to the state of the trimming element. It is not necessary to output the signal E. That is, the sampling signal generation circuit 13 includes a power-on-clear circuit 131, a periodic signal generation circuit 132, and one AND circuit 134. And AND circuit 1
The output terminal of the power-on-clear circuit 131 and the output terminal of the periodic signal generation circuit 132 are connected to the input terminals of the power-on-clear circuit 34. As a result, the number of AND circuits is reduced by one, and the circuit can be simplified.

In the present embodiment, a CR oscillation circuit has been described as an electronic circuit whose characteristic is to be adjusted. However, in the present invention, an LC oscillation circuit may be used as another electronic circuit. In this case, the characteristic adjustment unit 14 changes the time constant of the LC oscillation circuit according to the trimming data.
In addition, a constant voltage circuit (voltage regulator) is used as another electronic circuit whose characteristics are to be adjusted.
The characteristics of the filter circuit may be adjusted by using the filter circuit as an electronic circuit.

As holding means, two transistors 11
5, 116 and the inverter 117, but another self-holding circuit may be used.

[0028]

According to the present invention, the sampling signal is periodically supplied to the trimming data holding means, so that the trimming data is periodically held again, and the trimming data returns to a normal state even if the trimming data changes due to noise or the like. Can self-return. Further, in the present invention, the oscillation frequency of the liquid crystal driving unit that controls the driving of the liquid crystal panel based on the oscillation clock of the oscillation circuit is adjusted by such an electronic circuit characteristic adjustment device. It can return to its own state. Therefore, the user does not need to turn on the power again or perform a reset process in order to normalize the change of the trimming data due to noise.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electronic circuit characteristic adjustment device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a fuse trimming latch circuit for a P substrate in the electronic circuit characteristic adjustment device.

FIG. 3 is another configuration diagram of the fuse trimming latch circuit in the electronic circuit characteristic adjustment device.

FIG. 4 is a configuration diagram of a sampling signal generation circuit in the electronic circuit characteristic adjustment device.

FIG. 5 is a timing chart of signals in each unit of the electronic circuit characteristic adjustment device.

FIG. 6 is a configuration diagram of a liquid crystal driving device and a liquid crystal (LCD) panel that use the electronic circuit characteristic adjustment device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 fuse trimming latch circuit 12 pad 13 sampling signal generation circuit 14 characteristic adjustment unit 20 CR oscillation circuit 40 characteristic adjustment device 41 latch circuit 50 liquid crystal drive device 60 liquid crystal panel 111 polysilicon fuse 115, 116 transistor 117 inverter 131 power-on-clear circuit 132 Periodic signal generation circuit 133, 134 AND circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H093 NA06 NC21 NC27 NC29 NC49 NC59 ND49 ND60 5C006 AC29 AC30 AF44 AF52 AF67 AF72 BB11 BF02 BF04 BF11 BF15 BF22 BF23 BF26 BF27 BF34 BF36 BF37 BF49 FA23 FA47 5C05 A06 DD06 KK07 5J081 AA08 CC22 CC27 JJ23

Claims (6)

[Claims] A plurality of trimming elements; sampling signal output means for periodically outputting a sampling signal; and trimming data corresponding to a state of each of the trimming elements by inputting a sampling signal output from the sampling signal output means. Characterized by: trimming data holding means for holding the data; and adjusting means for adjusting the operating characteristics of the electronic circuit based on the trimming data held in the trimming data holding means. . 2. The electronic circuit is an oscillating circuit, a constant voltage circuit, an amplifier circuit, or a filter circuit, and the adjusting unit adjusts a time constant or a resistance value according to the electronic circuit to change an operation characteristic. The characteristic adjusting device for an electronic circuit according to claim 1, wherein the characteristic is adjusted. 3. The characteristic adjusting device according to claim 1, wherein the trimming element is a polysilicon fuse or a Zener diode. 4. The electronic circuit according to claim 1, further comprising a pad for voltage application connected to said trimming element and changing an initial state thereof. Characteristic adjustment device. 5. A characteristic adjusting device for an electronic circuit according to claim 1, an oscillation circuit whose characteristic is adjusted by the characteristic adjusting device for an electronic circuit, and driving of a liquid crystal panel based on an oscillation clock by the oscillation circuit. And a liquid crystal drive unit for controlling the operation of the liquid crystal display. 6. A portable telephone comprising: the liquid crystal driving device according to claim 5; and a liquid crystal panel driven by the liquid crystal driving device.