LTC3538
6
3538fb
PIN FUNCTIONS
FB (Pin 1): Feedback Input to Error Amplifer. Connect
resistive divider tap from V
OUT
to this pin to set the output
voltage. The output voltage can be adjusted from 1.8V to
5.25V. Referring to the Block Diagram the output voltage
is given by:
V
OUT
= 1V • (1 + R1/R2)
V
C
(Pin 2): Error Amplifi er Output. A frequency compensa-
tion network should be connected between this pin and FB
to compensate the loop. See Closing the Feedback Loop
section of the datasheet for further information. Pulling
V
C
below 0.25V disables the LTC3538.
GND (Pin 3): Ground.
BURST (Pin 4): Burst Mode Select Input.
BURST = Low for fi xed frequency PWM operation
BURST = High for Burst Mode operation
V
OUT
(Pin 5): Power Supply Output. This pin should be
connected to a low ESR output capacitor. The capacitor
should be placed as close to the IC as possible and should
have a short return to GND.
SW2 (Pin 6): Switch Pin where the Internal Switches
C and D are Connected. An optional Schottky diode can
be connected from SW2 to V
OUT
for a moderate effi ciency
improvement. Keep the trace length as short as possible
to minimize EMI.
SW1 (Pin 7): Switch Pin where the Internal Switches A and
B are Connected. Connect an inductor from SW1 to SW2.
An optional Schottky diode can be connected from SW1 to
ground for a moderate effi ciency improvement. Keep the
trace length as short as possible to minimize EMI.
V
IN
(Pin 8): Input Supply. This input provides power to
the IC and also supplies current to switch A. A ceramic
bypass capacitor (4.7μF or larger) is recommended as
close to V
IN
and GND as possible.
Exposed Pad (Pin 9): GND. The exposed pad must be
electrically connected to the board ground for proper
electrical and thermal performance.
