LTC3442
PI FU CTIO S
SHDN/SS (Pin 1):
Combined Soft-Start and Shutdown.
Applied voltage <0.4V shuts down the IC. Tie to >1.4V to
enable the IC and >2.4V to ensure the error amp is not
clamped from soft-start. An RC network from the shut-
down command signal to this pin will provide a soft-start
function by limiting the rise time of the V
C
pin.
R
T
(Pin 2):
Programs the Frequency of the Internal Oscil-
lator. Place a resistor from this pin to ground. See the
Applications Information section for component value
selection.
SGND (Pin 3):
Signal Ground for the IC.
SW1 (Pin 4):
Switch Pin Where Internal Switches A and B
are Connected. Connect inductor from SW1 to SW2. An
optional Schottky diode can be connected from SW1 to
ground for a moderate efficiency improvement. Minimize
trace length to reduce EMI.
PGND (Pin 5, 13):
Power Ground for the Internal NMOS
Power Switches. The exposed pad must be soldered to
PCB ground to provide both electrical contact and a good
thermal contact to the PCB.
SW2 (Pin 6):
Switch Pin Where Internal Switches C and D
are Connected. An optional Schottky diode can be con-
nected from SW2 to V
OUT
for a moderate efficiency im-
provement. Minimize trace length to reduce EMI.
BURST (Pin 7):
Used to set the Automatic Burst Mode
Operation Threshold. Place a resistor and capacitor in
parallel from this pin to ground. See the Applications
Information section for component value selection. For
manual control, ground the pin to force Burst Mode
operation, connect to V
OUT
to force fixed frequency mode.
V
OUT
(Pin 8):
Output of the Synchronous Rectifier. A filter
capacitor is placed from V
OUT
to GND. A ceramic bypass
capacitor is recommended as close to the V
OUT
and GND
pins as possible.
V
IN
(Pin 9):
Input Supply Pin. Internal V
CC
for the IC. A
10µF ceramic capacitor is recommended as close to V
IN
and SGND as possible.
R
LIM
(Pin 10):
Sets the Average Input Current Limit
Threshold. Place a resistor and capacitor in parallel from
this pin to ground. See the Applications Information
section for component value selection.
V
C
(Pin 11):
Error Amp Output. A frequency compensation
network is connected from this pin to FB to compensate
the loop. During Burst Mode operation, V
C
is internally
connected to a hold circuit.
FB (Pin 12):
Feedback Pin. Connect resistor divider tap
here. The output voltage can be adjusted from 2.4V to
5.25V. The feedback reference voltage is typically 1.22V.
6
U
U
U
3442f
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
