SM8121A
White LED Driver IC
OVERVIEW
The SM8121A is a high efficiency step-up DC-DC converter. Due to high voltage CMOS process realizing
25V output supply as maximum value, 2 to 6 lights of white LED connected in series can be lighted. By con-
necting in series, current variation among LED is eliminated. Current value sent to white LED can be set by
external resistors. In addition, brightness can also be adjusted by control to FB pin or CE pin.
FEATURES
I
I
PINOUT
(Top view)
I
I
I
I
I
I
I
I
I
I
I
I
I
Boost-up control using PWM
2 to 6 lights of white LED (connected in series)
lighted
Output current value can be set by external resis-
tors (51
Ω
: 9.8mA, 33
Ω
: 15.2mA, 24
Ω
: 20.8mA)
Brightness adjustable by control to FB pin or CE
pin
Current variation among LED decreased by high
precision
High efficient drive by step-up model
Supply voltage range: 2.3 to 5.5V
Maximum output voltage: 25V
Quiescent current: 400
µ
A (typ)
Standby current: 1.0
µ
A (max)
R
ON
(Switching MOS-Tr): 2
Ω
(typ)
Switching frequency: 1.0MHz (typ)
Output current detection accuracy:
±
2%
Small package: SOT23-5 (SM8121AH)
SON-6 (SM8121AD)
SOT23-5
SW
1
5
VDD
VSS
2
FB
3
4
CE
I
SON-6
APPLICATIONS
I
I
I
I
I
I
I
I
I
SW
VSS
VDD
1
6
FB
VSS
Cellular phone
Pager
Digital still camera
Handy terminal
PDAs
Portable games
White LED drive
LCD bias supply
Flash memory supply
3
4
CE
ORDERING INFORMATION
Device
SM8121AH
SM8121AD
Package
SOT23-5
SON-6
NIPPON PRECISION CIRCUITS INC.—1
SM8121A
BLOCK DIAGRAM
SW
FB
VDD
Buff
PWM
COMP
ERR
AMP
VREF
RAMP
GENERATOR
CE
OSC
SOFT
START
VSS
PIN DESCRIPTION
Number
Name
SOT23-5
1
2
3
4
5
SON-6
1
2, 5
6
4
3
SW
VSS
FB
CE
VDD
O
–
I
Ip
1
–
Coil switching
GND
Feed back (Output current detection)
Chip enable (High active)
Power supply
I/O
Description
1. Input with built-in pull-down resistor
NIPPON PRECISION CIRCUITS INC.—3
SM8121A
SPECIFICATIONS
Absolute Maximum Ratings
Parameter
Supply voltage range
Input voltage range
SW output voltage range
SW input current
Power dissipation
Operating temperature range
Storage temperature range
Symbol
V
DD
V
IN
V
SW
I
SW
P
D
T
opr
T
stg
Rating
−
0.3 to 6.5
V
SS
– 0.3 to V
DD
+ 0.3
–0.3 to 27
500
250 (Ta = 25
°
C)
–40 to 85
−
55 to 125
Unit
V
V
V
mA
mW
°
C
°
C
Electrical Characteristics
V
DD
= 3.6V, V
SS
= 0V, Ta = 25
°
C unless otherwise noted
Rating
Parameter
Supply voltage
Maximum output voltage
Standby current
Quiescent current
SW-Tr ON resister
SW-Tr leak current
Switching frequency
Maximum duty
Input voltage
Pin
VDD
SW
VDD
VDD
SW
SW
SW
SW
CE
CE
Input current
FB
Soft-start time
FB voltage
Coil inductance
SW
FB
SW
Symbol
V
DD
V
OUT
I
STB
I
DD
R
ON
I
LEAK
f
OSC
Duty
V
IH
V
IL
I
CE
I
FB
T
SS
V
FB
L
SW
V
CE
= 3.6V
V
FB
= 0.5V
V
CE
= 0V
V
FB
= 1.0V
V
FB
= 0V
I
SW
= 100mA, V
DD
= 3.6V
V
SW
= V
DD
V
FB
= 0V
V
FB
= 0V
Condition
min
2.3
–
–
–
–
–
–
0.9
65
2.0
–
–
–1.0
–
0.49
–
typ
3.6
–
–
150
400
2.0
–
1.0
75
–
–
5.0
–
500
0.50
–
max
5.5
25
1.0
300
800
3.0
1.0
1.1
85
–
0.6
10
1.0
–
0.51
10
V
V
µ
A
µA
µA
Ω
µA
MHz
%
V
V
µA
µA
µs
V
µ
H
Unit
NIPPON PRECISION CIRCUITS INC.—4
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