LTC3499/LTC3499B
6
3499fc
PIN FUNCTIONS
SHDN (Pin 1): Shutdown Input for IC. Connect to a voltage
greater than 1.2V to enable and a voltage less than 0.2V
to disable the LTC3499/LTC3499B.
V
IN
(Pin 2): Input Supply Voltage. The valid operating
voltage is between 1.8V to 5.5V. V
IN
has reverse battery
protection. Since the LTC3499/LTC3499B use V
IN
as the
main bias source, bypass with a low ESR ceramic capaci-
tor of at least 2.2µF.
SW (Pin 3): Switch Pin. Connect an inductor from V
IN
to
this pin with a value between 2.2µH and 10µH. Keep PCB
trace lengths as short and wide as possible to minimize
EMI and voltage overshoot. If the inductor current falls to
zero or SHDN is low an internal 250Ω antiringing switch
is connected from V
IN
to SW to minimize EMI.
GND (Pin 4/Exposed Pad, DD Package Pin 9): Signal
and Power Ground. The DD package exposed pad must
be soldered to the PCB power ground plane for electrical
connection and rated thermal performance.
SS (Pin 5): Soft-Start Input. Connect a capacitor from
SS to ground to control the inrush current at start-up.
An internal 3µA current source charges this pin. SS will
be discharged if SHDN is pulled low, thermal shutdown
occurs or V
IN
is below the minimum operating voltage.
V
OUT
(Pin 6): Power Supply Output. Connect a low ESR
output filter capacitor from this pin to the ground plane.
FB (Pin 7): FB Input to Error Amplifier. Connect a resistor
divider tap from V
OUT
to this pin to set the output voltage.
The output voltage can be adjusted between 2V and 6V.
Referring to the Functional Block Diagram, the output
voltage is given by:
V
OUT
=1.22 • 1+
R1
R2
VC (Pin 8): Error Amplifier Output. A frequency com-
pensation network is connected from this pin to GND to
compensate the boost converter loop. See Closing the
Feedthrough Loop section for guidelines.
