Rev. 1.00

21

November 22, 2011

HT16C21

Internal Voltage Adjustment (IVA) Setting Command

setting the LCD operating voltage adjustment command.

Function Byte (MSB)

Bit7

Bit6 Bit5 Bit4

Bit3

Bit2

Bit1 (LSB)

Bit0

Note

R/W Def

Internal

Voltage

Adjustment

(IVA)

Setting

1

0

0

0

1

0

1

0

W

Internal

Voltage

Adjust

control

X

X

DE

VE

DA3 DA2 DA1 DA0

● The Segment/VLCD

shared pin can be

programmed via the

“DE” bit.

● The “VE” bit is used

to enable or disable

the internal voltage

adjustment for bias

voltage.

● The DA3~DA0 bits can

be used to adjust the

W 30H

Note:

Bit

Segment /

VLCD Shared

Pin Select

Internal

Voltage

Adjustment

Note

DE

VE

0

0

VLCD pin

off

● The Segment/VLCD pin is set as the VLCD pin.

● Disable the internal voltage adjustment function

● One external resister must be connected between

VLCD pin and VDD pin to determine the bias voltage,

and internal voltage follower (OP4) must be enabled by

setting the DA3~DA0 bits as the value other than “0000”.

● If the VLCD pin is connected to the VDD pin, the internal

voltage follower (OP4) must be disabled by setting the

DA3~DA0 bits as “0000”.

0

1

VLCD pin

on

● The Segment/VLCD pin is set as the VLCD pin.

● Enable the internal voltage adjustment function.

● The VLCD pin is an output pin of which the voltage can

be detected by the external MCU host.

1

0

Segment pin

off

● The Segment/VLCD pin is set as the Segment pin.

● Disable the internal voltage adjustment function.

● The bias voltage is supplied by the internal VDD power.

● The internal voltage-follower (OP4) is disabled

automatically and DA3~DA0 don’t care.

1

1

Segment pin

on

● The Segment/VLCD pin is set as the Segment pin.

● Enable the internal voltage adjustment function.

● Power on status: Disable the internal voltage adjustment and the Segment/VLCD pin is set as the Segment pin.

● When the DA0~DA3 bits are set to “0000”, the internal voltage-follower (OP4) is disabled. When the DA0~DA3

bits are set to other values except “0000”, the internal voltage follower (OP4) is enabled.

● If the programmed command is not defined, the function will not be affected.