Datasheet

LTC3534
7
3534fb
For more information www.linear.com/LTC3534
GND Pads (Pins 1, 8, 9, 16; GN Package): IC Substrate
Grounds. These pins MUST be soldered to the printed
circuit board ground to provide both electrical contact
and a good thermal contact to the PCB.
RUN/SS (Pin 2): Combined Shutdown and Soft-Start. Ap
-
plying a voltage below 400mV shuts down the IC. Apply
a voltage above 1.4V to enable the IC and above 2.4V to
ensure that the error amp is not clamped from soft-start.
An R-C from the enable command signal to this pin will
provide a soft-start function by limiting the rise time of
the V
C
pin. PWM mode operation must be commanded
to properly enable the IC.
GND (Pin 3): Signal Ground for the IC.
PGND1, PGND2 (Pins 4, 7): Power Ground for the Internal
N-channel MOSFET Power Switches (Switches B and C).
SW1 (Pin 5): Switch Pin where Internal Switches A and
B are Connected. Connect inductor from SW1 to SW2.
Minimize trace length to reduce EMI.
SW2 (Pin 6): Switch Pin where Internal Switches C and
D are Connected. Minimize trace length to reduce EMI.
PWM (Pin 10): Burst Mode Select. PWM must be driven
HIGH during start-up. When V
OUT
is in regulation, the
PWM pin may be driven LOW to command Burst Mode
operation. Applying a voltage below 400mV enables Burst
Mode operation, providing a significant efficiency improve
-
ment at light loads. Burst Mode operation will continue
until this pin is driven high. Applying a voltage above 1.4V
disables Burst Mode operation, enabling low noise, fixed
frequency operation.
V
OUT
(Pin 11): 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
OUT
is given by the following equation:
V
OUT
= 1.000 •
R1+R2
R2
V
PV
IN
(Pin 12): Power V
IN
Supply Pin. A 10µF ceramic
capacitor is recommended as close to the PV
IN
and PGND
pins as possible.
V
IN
(Pin 13): Input Supply Pin. Connect the power source
to this pin.
V
C
(Pin 14): Error Amp Output. An R-C network is con-
nected from this pin to FB for loop compensation. Refer
to “Closing the Feedback Loop” section for component
selection guidelines.
FB (Pin 15): Feedback Pin. Connect V
OUT
resistor divider
tap to this pin. The output voltage can be adjusted from
1.8V to 7V. The feedback reference voltage is typically 1V.
Exposed Pad (Pin 17; DHC Package): IC Substrate Ground.
This pin MUST be soldered to the printed circuit board
ground to provide both electrical contact and a good
thermal contact to the PCB.
pin FuncTions