Copyright © 2013 Microsemi Page 3
Rev. 1.1, 01/10/2013 Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA 1-800-713-4113, 1-949-380-6100, fax 1-949-215-4996
LX7157B
3V Input, High Frequency, 3A Step-Down Converter
Production Datasheet
Pin Description
Pin Number Pin Designator Description
1 FB
Voltage feedback pin. Connect to the output terminal through a
resistor divider network to set the output voltage of the
regulator to the desired voltage. The upper resistor of the divider
is part of the closed loop stability and must be selected properly
to insure the stability of the regulator. Table 1 shows the proper
values of this network for selected output voltages.
2 VOUT Output sense pin.
3, 4, 13 GND Ground pin.
5,6 SW
Switch-node pin. Connect the output inductor between this pin
and output capacitor.
7,8 PVIN
Input voltage pin of the regulator. A minimum of 10µF, X5R type
ceramic capacitor must be connected as close as possible from
this pin to GND plane to insure proper operation.
9 VCC
Internal chip supply. Decouple this pin to GND with a 1µF, X5R
type (or better) ceramic capacitor and connect it via a 10Ω
resistor to the input rail.
10 EN
Pulling this pin higher than 1.7V will enable the regulator. When
pulled below 0.4V, the regulator will turn off.
11 PGOOD
Power-good pin. This is an open-drain output and should be
connected to a voltage rail (for example, VIN) with an external
pull-up resistor. During the power on, this pin switches from low
to high state when FB voltage reaches above the power good
threshold and the internal soft start has finished its operation. It
will be pulled low,
when the FB falls below the power good
threshold minus the hysteresis. It will turn back on, when the
pull FB rises above the threshold.
12 MODE
This PIN should be connected to GND; skip mode is enabled to
improve the light load efficiency.
