SC251 Datasheet, PDF (7/19 Pages) Semtech Corporation – Step-down DC-DC Converter with Bias LDO for WCDMA Amplifi ers

SC251
POWER MANAGEMENT
Pin Description
Pin#
1
2
3
4
5
6
7
8
9
10
T
Pin Name Pin Function
VIN
VREF
GD
EN
VMODE
VDAC
GND
VOUT
PGND
LX
Thermal Pad
Input supply pin.
A 2.85V LDO reference voltage supply - 10mA max load that can be used as a supply
for power amplifier bias inputs.
A push pull external PFET Gate drive control output - connect to the gate of an external
MOSFET to control a low resistance path between V_IN and V_OUT when low voltage
drop is needed (optional - if not used leave floating). A low state turns on the MOSFET.
Enable pin - controls both the switching converter and the VREF output. Active high.
Input control to select the V_DAC to V_OUT profile (high = low power, low = high power).
Analog control voltage input - ranges between 0.3 and 1.2V for exponential control of
V_OUT , V_DAC > 1.28 enables pass-through mode (using internal pass MOSFET or
optional low R_DSON MOSFET controlled by GD).
System and logic ground.
Output voltage pin.
Ground reference for internal N-channel MOSFET.
Switch node connection to inductor. This pin connects to the drains of the internal
main and synchronous power MOSFET switches.
Pad for heatsinking purposes. Connect to ground plane using multiple vias.
Not connected internally.
© 2006 Semtech Corp.
7
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