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
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
L1
10uH
R2
1M
C1
47uF
R3
1M
U1
6
7
3
1
IN
LBI
EN
COMP
LX
FB
LBO
GND
5
2
8
4
C2
47uF
R4
604k
D1
SMB5819
R1
1.0M
3.3V@250mA
V
OUT
=
1.22
•
(1
+
R1
)
R4
SC1417B
(Alkaline)
2 Cells
R6
130k
LBO OUT
R5
33k
C3
3.3nF
Revision: August 1, 2006
1
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