UM3433 Datasheet, PDF (6/9 Pages) Union Semiconductor, Inc. – 600mA, 600kHz Step-Up DC-DC Converter

UM3433
Pin Functions
SW (Pin 1): Switch Pin. Connect inductor between SW and V_IN. Keep these PCB trace lengths as
short and wide as possible to reduce EMI and voltage overshoot.
GND (Pin 2): Signal and Power Ground. Provide a short direct PCB path between GND and the
(–) side of the output capacitor(s).
NC (Pin 3): Not Connect.
FB (Pin 3): Feedback input. Connect resistor divider tap to this pin. The output voltage can be
adjusted from 2.5V to 5V by:
V_OUT=V_FB×(1+R1/R2)
____________
SHDN (Pin 4): Logic Controlled Shutdown Input.
____________
SHDN=High: Normal free running operation, 600kHz typical operating frequency.
____________
SHDN=Low: Shutdown, quiescent current <1μA.Output capacitor can be completely discharged
through the load.
VOUT (Pin 5): Output Voltage Sense Input and Drain of the Internal Synchronous Rectifier
MOSFET. Bias is derived from V_OUT. PCB trace length from V_OUT to the output filter capacitor(s)
should be as short and wide as possible.
VIN (Pin 6): Battery Input Voltage. The device gets its start-up bias from V_IN. Once V_OUT
exceeds V_IN, bias comes from V_OUT. Thus, once started, operation is completely independent from
VIN. Operation is only limited by the output power level and the battery’s internal series
resistance.
Typical Application Circuits
4.7uH
VIN ₊
-
4.7uF
SW
VIN
VOUT
UM3433-3.3/3.0
VOU T
3.3V/3.0V
OFF ON
SHDN
GND
10uF
VIN ₊
-
Figure 1 Fixed output application circuit
4.7uH
4.7uF
OFF ON
SW
VIN
VOUT
UM3433-ADJ
SHDN
FB
GND
VOUT
R1
AD J
10uF
R2
Figure 2 Adjustable output application circuit
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http://www.union-ic.com Rev.05 Dec.2009
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