UPD16681A Просмотр технического описания (PDF) - NEC => Renesas Technology

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UPD16681A

LCD CONTROLLER/DRIVER FOR DOT MATRIX DISPLAY OF JIS LEVEL 1 AND JIS LEVEL 2 KANJI SETS

NEC => Renesas Technology 

µPD16681A

4.2 Regulation of LCD Driver Voltage

4.2.1 When not using internal power supply select or D/A converter (VEXT = L, DACHA = L)

When using the internal power supply, the boosted voltage is used as the power supply for the op amp incorporated

in the IC for the LCD driver’s voltage. A common mode amplifier circuit can be configured by connecting external

resistors R1 and R2 and inputting the reference voltage VREF to AMPIN(+), and this configuration can be used to

regulate the potential of the LCD driver voltage VLC1. If using a thermistor to regulate the LCD driver voltage to suit

the liquid crystals’ temperature characteristics, we recommend connecting in parallel to R2.

The LCD driver voltage VLC1 can be determined using the following formula.

VLC1

=

AMPOUT

=

1+



R2'

R1





VREF

Remark

R2' =

R2 × Rth

R2 + Rth

Figure 4−2. When Not Using Internal Power Supply Select or D/A Converter

DACHA

VREF

AMPIN(+)

D/A

converter

+

−

To internal drive circuit

AMPIN(−)

AMPOUT

Rth

VLC1

R2

R1

C1

4.2.2 When using internal power supply select and D/A converter (VEXT = L, DACHA = H)

Using the D/A converter enables commands to be entered to control the reference voltage VREF that is input to the +

input of the op amp for the LCD driver voltage.

The D/A converter function sets 6-bit data to the D/A converter set register to set one of the 64 modes for the

reference voltage VREF between VDD and 1/2 VDD.

The formula for VLC1 is the same as in 4.2.1 When not using internal power supply select or D/A converter

(VEXT = L, DACHA = L) above.

Data Sheet S14207EJ3V0DS

9

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