Datasheet

LTC3101
11
3101fb
PIN FUNCTIONS
RESET (Pin 13): Active-Low µP Reset and Fault Signal.
This pin provides an active-low microprocessor reset
signal. During the power-up sequence, the µP reset sig-
nal is held low until all converters are in regulation for a
duration programmed by the C
RS
capacitor. In addition,
this pin is held low during a fault condition and when the
IC is disabled in order to prevent spurious turn-on of the
microprocessor.
BAT2 (Pin 14): Battery Power Input for the Buck-Boost
Converter. A 10F or larger bypass capacitor should be con-
nected between this pin and ground. The bypass capacitor
should be located as close to the IC as possible and should
via directly down to the ground plane. Pins BAT1 and BAT2
must be connected together in the application.
SW3A (Pin 15): Buck-Boost Switch Pin. This pin should
be connected to one side of the buck-boost inductor.
USB2 (Pin 16): USB or Wall Adapter Power Input for the
Buck-Boost Converter. A 10F or larger bypass capacitor
should be connected from this pin to ground. The bypass
capacitor should be located as close to the IC as pos-
sible and should via directly down to the ground plane.
Pins USB1 and USB2 must be connected together in
the application.
OUT3 (Pin 17): Buck-Boost Output Voltage. This pin is the
power output for the buck-boost regulator. It should be
connected to a low ESR capacitor with a value of at least
10F. For higher output current applications (>400mA), it
is recommended that a 22µF or larger output capacitor be
used. The capacitor should be placed as close to the IC as
possible and should have a short return path to ground.
HSO (Pin 18): Hot Swap Output. An internal current-limited
switch connects the HSO output to the buck-boost output
voltage after the buck-boost output reaches regulation.
With the buck-boost operating in PWM mode, this output
is guaranteed to support a 100mA load and is short-circuit
protected.
ENA3 (Pin 19): Enable Pin for Buck-Boost Converter.
Forcing this pin above 1V will turn on the buck-boost
converter when the IC is enabled (via the pushbutton
interface). Forcing this pin below 0.3V will disable the
buck-boost converter.
SW3B (Pin 20): Buck-Boost Switch Pin. This pin should
be connected to one side of the buck-boost inductor.
ENA1 (Pin 21): Enable Pin for Buck Converter 1. Forcing
this pin above 1V will turn on the buck converter when the
IC is enabled (via the pushbutton interface). Forcing this
pin below 0.3V will disable buck converter 1.
FB2 (Pin 22): Feedback Voltage Input for Buck Converter 2.
The resistor divider connected to this pin sets the output
voltage for buck converter 2.
FB1 (Pin 23): Feedback Voltage Input for Buck Converter 1.
The resistor divider connected to this pin sets the output
voltage for buck converter 1.
ENA2 (Pin 24): Enable Pin for Buck Converter 2. Forcing
this pin above 1V will turn on the buck converter when the
IC is enabled (via the pushbutton interface). Forcing this
pin below 0.3V will disable buck converter 2.
GND (Exposed Pad Pin 25): Small-Signal and Power
Ground for the IC. The Exposed Pad must be soldered to
the PCB and electrically connected to ground through the
shortest and lowest impedance connection possible.