LTC3499 datasheet(6/16 Pages) LINER

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LTC3499/LTC3499B

3499f

PI FU CTIO S

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.

VIN (Pin 2): Input Supply Voltage. The valid operating

voltage is between 1.8V to 5.5V. VIN has reverse battery

protection. Since the LTC3499/LTC3499B use VIN as the

main bias source, bypass with a low ESR ceramic capaci-

tor of at least 2.2

µF.

SW (Pin 3): Switch Pin. Connect an inductor from VIN to

this pin with a value between 2.2

µH 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 250

Ω antiringing switch is

connected from VIN to SW to minimize EMI.

GND (Pin 4): Signal and Power Ground for the IC.

SS (Pin 5): Soft-Start Input. Connect a capacitor from SS

to ground to control the inrush current at start-up. An

internal 3

µA current source charges this pin. SS will be

discharged if SHDN is pulled low, thermal shutdown

occurs or VIN is below the minimum operating voltage.

VOUT (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 VOUT 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:

OUT =+

⎛

⎝⎜

⎞

⎠⎟

⎡

⎣

⎢

⎤

⎦

⎥

122

.•

VC (Pin 8): Error Amplifier Output. A frequency compen-

sation network is connected from this pin to GND to

compensate the boost converter loop. See Closing the

Feedthrough Loop section for guidelines.

Exposed Pad—DD Only (Pin 9): Ground. Must be sol-

dered to the PCB power ground plane for electrical con-

nection and rated thermal performance.

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