SM8132A

NIPPON PRECISION CIRCUITS INC.—8

FUNCTIONAL DESCRIPTION

LED Drive Current Setting

The SM8132A LED drive current setting is controlled by the combination of resistance connected to ISET and

the EN input signals.

(1) Setting LED Drive Current using RSET

The maximum drive current per LED (when DATA = 1) is determined by the external resistance connected to

nected between ISET and GND. Note that while RSET can have a maximum resistance 50k

Ω, the total LED

output current must not exceed the maximum output current of 80mA.

(2) Setting LED Drive Current using EN Input Signals

The EN input ENABLE/DISABLE circuit, also simultaneously counts the number of input pulses using an

internal counter and adjusts the LED drive current setting in response. The internal 4-bit counter provides 16-

On the 16th pulse (DATA = 16), the LED drive current control circuit shuts down. On the 17th pulse (DATA =

1), the LED drive current is reset to the maximum current value. As the current is set to the maximum value on

the first pulse, applications without pulse input can also be employed (by controlling brightness using RSET).

ISET

RSET

GND

LED drive current maximum setting using RSET

0

10

20

30

40

50

0

10

20

30

40

50

RSET [k

Ω]

EN

EN input

pulse

12 3

GND

LED drive current setting variation using EN input

pulse modulation

0

5

10

15

20

25

04

8

12

16

DATA set by EN input pulse

RSET=10k

Ω

RSET=15k

Ω

RSET=20k

Ω

Table. LED drive current setting and EN input pulse count

DATA

123456789

10

11

12

13

14

15

16

EN

pulse

count

123456789

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

0