Pad Description

Pad No.

Pad Name

I/O

Function

1~3

SA1~SA3

O

LCD segment drive

4~6

SB1~SB3

O

LCD segment drive

7~19

SC1~SC3

O

LCD segment drive

10~12

SD1~SD3

O

LCD segment drive

13

SE1

O

LCD segment drive

14

VEE

O

Generate negative voltage (–1.5V)

15

CAP

O

For negative voltage, NMOS output

16

C512

O

For negative voltage, inverter output

17

TV

B

Test pin for IC

18

TEST1

I

Test pin for IC

19

LOWC

B

For the supply voltage detector. Open the pin when not in use.

20

VSS

I

Power supply GND

21

SC

B

Common point, NMOS open drain

22

RF

O

Connect reference resistor, PMOS open drain

23

RS

O

Connect sensor resistor, PMOS open drain

24

VDD

I

Positive power supply

25

PSW

I

Pull low input pin, push switch to turn the power on or off

26

TEST2

I

Pull low test pin, for production test, floating LCD displays

the real time value, when connected to VDD, LCD displays

the highest value.

27

ML

I

Connect to VDD for memory function, otherwise floating.

28

FEVL

I

Floating with fever function, otherwise connect to VDD.

29

S804KL

I

Floating buzzer is 4kHz, connect to VDD if buzzer is 8kHz.

30

OSCI

I

For system oscillator in

31

OSCO

O

For system oscillator out

32

BZ1

O

Buzzer output 1

33

BZ2

O

Buzzer output 2

34~36

COM1~COM3

O

LCD backplane drive, 3-level voltage out

HT7501

3

8th Feb ’99