Datasheet

LTC3428
5
3428fb
PIN FUNCTIONS
PGNDA, PGNDB (Pins 1, 10, 11 (Exposed Pad)): Power
Ground for the IC. Tie directly to local ground plane.
SWA (Pin 2), SWB (Pin 9): Phase B and Phase A Switch
Pins. The inductor and Schottky diodes for each phase
are connected to these pins. Minimize trace length to
reduce EMI.
V
OUT
(Pin 3): Power Supply Output and Bootstrapped
Power Source for the IC. Connect low ESR output fi lter
capacitors from this pin to the ground plane.
SHDN (Pin 4): Shutdown Pin. Grounding this pin shuts
down the IC. Connect to a voltage greater than 1.5V to
enable.
V
C
(Pin 5): Error Amp Output. A frequency compensation
network is connected to this pin to compensate the boost
converter loop.
FB (Pin 6): Feedback Pin. A resistor divider from V
OUT
is
connected here to set the output voltage according to
V
OUT
= 1.243 • (1 + R1 / R2)
AGND (Pin 7): Signal Ground for the IC. Connect to ground
plane near feedback resistor divider.
V
IN
(Pin 8): Input Supply Pin. Bypass V
IN
with a low ESR
ceramic capacitor of at least 4.7µF. X5R and X7R dielectrics
are preferred for their superior voltage and temperature
characteristics.
BLOCK DIAGRAM
–
+
–
+
–
PWM
COMP
+
–
–
PWM
COMP
PWM
LOGIC
PWM
LOGIC
TSD
CURRENT
LIMIT
CURRENT
LIMIT
1.243V
V
C
ERROR AMPLIFIER/SOFT-START
RAMP/
SLOPE COMP
OSCILLATOR
CLK B
CLK A
CHANNEL B
CHANNEL A
RAMP/
SLOPE COMP
I
SENA
I
SENB
FB
DRIVER
DRIVER
I
SENA
I
SENB
SWB
V
OUT
PGNDB
SWA
PGNDA
V
C
SHDN SHUTDOWN
AGND
3428 BD
V
IN
FB
5pF