Micro Power Constant-Current
DC-DC Converter
POWER MANAGEMENT
Description
The SC104 is a micro power dc-dc step-up converter
which converts an input voltage, in the range of 1.55V to
10V, to a constant current. The part features a range of
user programmable voltages and currents including
dynamic adjustment of the “constant” current. The
converter is capable of generating output voltages as
low as the input supply voltage and up to 38V. During
shutdown, the part draws a typical 500nA standby
current.
The output current is set by the external resistor R1.
Dynamic adjustment of the output current can be made
by the application of an analog voltage to the ADJ
input, or by PWMing this pin.
The peak switch current is programmable through the
external resistor R
LIM
enabling the use of a wide range of
inductors and battery technologies.
SC104
Features
Adjustable output current using pulse width
modulation or analog voltage input
38V output capability supports up to 10 white LEDs
Wide range of input voltages 1.55V to 10V
Low quiescent current
0.5µA standby current in shutdown
Programmable cycle by cycle current limit
Surface mount packaging (3x3mm 8pin MLP)
Output voltage and over-temperature protection
Applications
White LED supplies
Color LED supplies
Cellular phones
PDAs
Electronic books
Handheld computers
Wireless web appliances
Typical Application Circuit - 6 LEDs
VIN = 3V to 5V
IOUT ADJUST
1
2
U1
ADJ
FB
GND
OUT
SC104
EN
LIM
IN
LX
CIN
4.7uF
8
7
6
5
L1
12uH
RLIM
7.50k
ENABLE
IOUT = 15mA
LED4
LED5
LED6
3
4
LED3
LED2
LED1
RSET
23.2R
COUT
0.47uF
D1
March 22, 2005
1
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SEMTECH [ SEMTECH CORPORATION ]
