SC1417B Datasheet, PDF (1/11 Pages) Semtech Corporation – MicroPower, 620kHz PWM, Step-up DC/DC Converter

POWER MANAGEMENT
Description
The SC1417B is a fixed frequency, current mode step-up
dc-dc converter. It operates over a wide input supply range
of 1.5V to 12V, making it suitable for battery input and
TFT-LCD applications. The 620kHz constant frequency
oscillator minimizes the size of external components and
allows simple filtering for noise sensitive environments.
The integrated power NPN supports peak currents of up
to 0.9A enabling the device to support 150mA at 15V
from a 5V supply. The maximum switch duty cycle of
85% (typical) allows output to input voltage ratios as high
as 6.5 in step-up configurations, thus allowing 2V to 12V
boost operation.
The SC1417B features a low battery detector and a
200mV reference circuit which remains active during shut
down. The part consumes less than 50µA in shutdown.
The low battery detect output goes low when the input
battery voltage has dropped below a user programmable
level. Pulse-by-pulse current limit and thermal shutdown
protect the converter during load faults.
The SC1417B is available in a MSOP-8 surface mount
package.
SC1417B
MicroPower, 620kHz PWM,
Step-up DC/DC Converter
Features
‹ Operates from 1.5V to 12V supply voltage
‹ High efficiency >85%
‹ 150mA @ 15V from 5V input
‹ Internal switch peak current of 0.9A
‹ Programmable output voltage
‹ Powers up into full load
‹ Pulse-by-pulse current limit/thermal shutdown
‹ 620kHz fixed frequency current mode converter
‹ Low current shutdown mode extends battery life
‹ 18V output capability
‹ Low battery detector
‹ MSOP-8 package. Available in Lead-free package,
fully WEEE and RoHS compliant
‹ Pin-for-pin compatible with LT1317B
Applications
‹ TFT-LCD Bias supplies
‹ Constant current LED bias supplies
‹ Pagers
‹ GPS receivers
‹ Battery backup
‹ SEPIC converters
Typical Application Circuit
C1
47uF
2 Cells
(Alkaline)
R2
R3
1M
1M
R6
130k
L1
D1
10uH
U1
6
IN
7
LBI
3
EN
1
COMP
5
LX
2
FB
8
LBO
4
GND
SC1417B
SMB5819
3.3V@250mA
R1
1.0M
C2
V_OUT
= 1.22 • (1+
R1
R4
)
47uF
R4
604k
R5
33k
C3
3.3nF
LBO OUT
Revision: August 1, 2006
1
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