SM8121A Datasheet, PDF (13/19 Pages) Nippon Precision Circuits Inc – White LED Driver IC

SM8121A
Current Switching using External Transistors
If only a few brightness steps are required, the LED current can be adjusted by switching the LED current set-
ting resistance using external transistors (Tr).
VIN
3.6V
L
10µH
CIN
4.7µF
SBD
COUT
1.0µF
SW
VDD
VSS
SM8121
LED
FB
CE
Select signal 1
Select signal 2
R3
40Ω
Tr2
R2
100Ω
Tr1
R1
250Ω
Select signal 2
Low
Low
High
High
Select signal 1
Low
High
Low
High
I_LED
2mA
2 + 5 = 7mA
2 + 12.5 = 14.5mA
2 + 5 + 12.5 = 19.5mA
NIPPON PRECISION CIRCUITS INC.—13