SS6639
1-Cell, 3-Pin, Step-Up DC/DC Controller
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FEATURES
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Guaranteed start-up from less than 0.9 V.
High efficiency.
Low quiescent current.
Fewer external components needed.
Low ripple and low noise.
Fixed output voltage: 2.7, 3.0V, 3.3V, and 5V.
Driver for external transistor.
Space-saving package: SOT-89 and TO-92.
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GENERAL DESCRIPTION
The SS6639 is a high efficiency step-up DC/DC
controller for applications using 1 to 4 battery cells. Only
three external components are required to deliver a
fixed output voltage of 2.7, 3.0V, 3.3V, or 5V. The
SS6639 starts up from less than 0.9V input with a 1mA
load. The Pulse Frequency Modulation scheme offers
optimized performance for applications with light output
loading and low input voltages. The output ripple and
noise are lower than with circuits operating in PSM
mode.
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APPLICATIONS
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Pagers.
Cameras.
Wireless Microphones.
Pocket Organizers.
Battery Backup Suppliers.
Portable Instruments.
The PFM control circuit operating up to 100 KHz
switching rate results in smaller passive components.
The space-saving SOT-89 and TO-92 packages make
the SS6639 an ideal choice of DC/DC controller for
space-conscious
applications,
such
as
pagers,
electronic cameras, and wireless microphones.
Using an external transistor driver pin (EXT), the
SS6639 is recommended for applications requiring
currents from several tens to several hundreds of
milliamperes.
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TYPICAL APPLICATION CIRCUIT
VIN
D1
V
OUT
L1
33µH
R1
+
C1
47µF
GS SS14
SS6639-27
SS6639-30
EXT
SS6639-33
SS6639-50
GND
VOUT
*Q1
2SD1803
300
+
C3
100µF
C2
10nF
*Q1: Sanyo 25D1803S-TC 60V/5A/20W
100mA Load Current Step-Up Converter
Rev.2.01 6/26/2003
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