MP38873 – 15A, 16V, HIGH FREQUENCY STEP-DOWN WITH SYNCHRONOUS GATE DRIVER
MP38873 Rev. 0.9 www.MonolithicPower.com 4
9/17/2009 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2009 MPS. All Rights Reserved.
PIN FUNCTIONS
Pin # Name Description
1 VCC BG Driver Bias Supply. Decouple with a 1µF ceramic capacitor.
2 SYNCOUT
Timing output to drive another MP38873 (or similar device) SYNCIN for phase-shift
operation.
3 SYNCIN External Frequency Synchronization. Connect to V
CC
if not used.
4 EN On/Off Control.
5 SS/TRK Soft-Start/Track Input. Connect a capacitor to ground.
6 FB
Feedback. An external resistor divider from the output to GND, tapped to the FB pin,
sets the output voltage. To prevent current limit run away during a short circuit fault
condition the frequency foldback comparator lowers the oscillator frequency when the
FB voltage is below 400mV.
7 COMP Compensation. Connect R/C network to ground.
8 PG
Power Good Indicator. Connect this pin to V
CC
or V
OUT
by a 100k pull-up resistor.
The output of this pin is an open drain if the output voltage is within 10% of the
nominal voltage, otherwise it is LOW. If PG is initially at open drain, there is a 20µs
delay to pull PG if the output voltage is less than 10% regulation window.
9 BST
Bootstrap. This capacitor is needed to drive the power switch’s gate above the supply
voltage. It is connected between SW and BS pins to form a floating supply across the
power switch driver.
10, 18,
Exposed Pad
VIN
Supply Voltage. The MP38873 operates from a +4.5V to +16V unregulated input. C1
is needed to prevent large voltage spikes from appearing at the input.
11-17 SW Switch Output. These pins are fused together.
19 GATE Gate Driver Output. Connect this pin to the synchronous MOSFET.
20 GND Ground.
