ZXSC100
SINGLE CELL DC-DC CONVERTER SOLUTION
DESCRIPTION
The ZXSC100 series is designed for DC-DC
applications where step-up voltage conversion from
very low input voltages is required. These applications
mainly operate from single nickel cadmium or nickel
metal hydride battery cells.
The ZXSC100 devices are non-synchronous PFM,
DC-DC controller ICs which drive an external
transistor. Zetex SuperSOT4
™
switching transistors,
with saturation resistance as low as 13mΩ, are
recommended as the external switching element.
These bipolar transistors are the best switching
devices available for this type of DC-DC conversion,
enabling high efficiency conversion with input
voltages down to below 1 volt.
The circuit can start up under full load with regulation
maintained down to an input voltage of only 0.926
volts. The solution configuration ensures optimum
FEATURES
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SuperSOT4™ switching transistor
ZXT14N20DX:V
CE(sat)
45mV max @ 1A load
Efficiency maintained over a wide range of input
voltages and load currents
82% efficiency @ V
BATT
=1V
Startup under full load
Minimum operating input voltage V
BATT
=0.926V
Adjustable output voltage down to V
BATT
Quiescent current typically 150µA referred to
input voltage
MSOP8 Package
SO8 Package
Demonstration boards available
U1
EM
V
DRIVE
I
SENSE
FB
G
ND
BAS
RE
V
CC
efficiency over a wider range of load currents, several
circuit configurations are possible with power
dissipation up to 2W. The step up output voltage is
easily programmed with external resistors, the
non-synchronous architecture and SuperSOT4™
device enabling an output voltage down to the input
voltage level. For best performance the ZXSC100
quiescent current is a small 150µA ensuring minimum
battery drain in no load conditions.
For the best in space saving the ZXSC100 is offered in
the MSOP8 package, however the devices are also
available in SO8 packaging for applications where
space saving is not so critical.
The IC and discrete combination offers the ultimate
cost vs performance solution for single cell DC-DC
conversion.
APPLICATIONS(continued)
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Hand Held Instruments
Portable Medical Equipment
Solar Powered Equipment
LED Flashlight
LED Backlight
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TYPICAL APPLICATION CIRCUIT
V
BATT
L1
D1
ZHCS2000
3.3V/0.1A
R1
Q1
ZXT14N20DX
R3
C3
C2
APPLICATIONS
Cordless Telephones
MP3 Players
PDA
Pagers
Battery Backup Supplies
Electronic toothbrush
GPS Receivers
Digital Camera
Palmtop Computers
ZXSC100
C1
R2
R4
ISSUE 1 - JANUARY 2001
1
ZETEX [ ZETEX SEMICONDUCTORS ]
