Datasheet LTC3499, LTC3499B (Analog Devices) - 6

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