Datasheet

LTC3127
7
3127f
pin FuncTions
SW1 (Pin 1): Switch Pin Where Internal Switches A and
B Are Connected. Connect inductor from SW1 to SW2.
Minimize trace length to reduce EMI.
V
IN
(Pin 2): Input Supply Pin. Internal V
CC
for the IC. A
10μF or greater ceramic capacitor should be placed as
close to V
IN
and PGND as possible.
SHDN (Pin 3): Logic-Controlled Shutdown Input.
SHDN = High: Normal Operation
SHDN = Low: Shutdown
MODE (Pin 4): Pulse Width Modulation/Burst Mode
Selection Input.
MODE = High: Burst Mode Operation
MODE = Low: PWM Operation Only. Forced continuous
conduction mode.
PROG (Pin 5): Sets the Average Input Current Limit
Threshold. Connect a resistor from PROG to ground. See
below for component value selection.
R
PROG
= 54.92 • I
LIMIT
(A) + 4.94 (kΩ)
SGND (Pin 6): Signal Ground for the IC. Terminate the
PROG resistor, compensation components and the output
voltage divider to SGND.
FB (Pin 7): Feedback Pin. Connect resistor divider tap here.
The output voltage can be adjusted from 1.8V to 5.25V.
The feedback reference voltage is 1.195V.
V
R
R
V
OUT
= • +






1 195 1
2
1
.
V
C
(Pin 8): Error Amplifier Output. Place compensation
components from this pin to SGND.
V
OUT
(Pin 9): Output of the Synchronous Rectifier. Connect
the output filter capacitor from this pin to GND. A minimum
value of 22µF is recommended. Output capacitors must
be low ESR.
SW2 (Pin 10): Switch Pin Where Internal Switches C and
D Are Connected. Minimize trace length to reduce EMI.
PGND (Exposed Pad Pin 11): Power Ground. The exposed
pad must be soldered to the PCB ground plane.
(DD Package)