LTC3252 datasheet(6/14 Pages) AD

6 / 14 page

LTC3290

Rev. 0

For more information www.analog.com

PIN FUNCTIONS

VAUX (Pin 1): Auxiliary Input Supply Voltage. VAUX should

be bypassed with a low impedance ceramic capacitor.

EN (Pin 2): Enable Logic Input. A logic high on the EN pin

enables the part and regulates the output voltage to the

desired value depending on the circuit configuration and

the state of the VSET pin. Do not float this pin.

C+ (Pin 3): Flying Capacitor Positive Connection.

C– (Pin 4): Flying Capacitor Negative Connection.

VIN (Pin 5): Input Supply Voltage. VIN should be bypassed

with a low impedance ceramic capacitor.

BIAS (Pin 6): Internal BIAS Voltage, 4.5V (typ). Connect

this pin to a 4.7µF bypass capacitor to GND. A ceramic

capacitor of at least 6.3V rating is recommended. The bias

pin is for internal operation only and should not be loaded

or driven externally.

PGOOD (Pin 7): Power Good Output. This open drain

output is low when the part is enabled and the output is

not in regulation. Once the part reaches regulation, this

pin transitions to a Hi-Z state. An external resistor pull-up

to a suitable voltage ≤ 3.6V is required to interface this pin

with external circuitry such as a microprocessor.

FB (Pin 8): Feedback Input Voltage. When the VSET pin is

settoGND,theFBpinfunctionsasaconventionalfeedback

input pin. An external resistor divider from the VOUT pin

to GND sets the output voltage at the VOUT pin. The FB

pin servos to 1V to achieve the desired output voltage at

the VOUT pin. In tracking mode, an external resistor from

the FB pin to GND generates a reference current. This

current is replicated at the VSET pin. An external resistor

from VOUT to the VSET pin sets the effective voltage at the

VOUT Pin. This configuration is used in the tracking mode,

when VOUT is desired to be set to a fixed offset voltage

above the input voltage VIN.

VSET (Pin 9): Output Voltage Set Pin. An external resis-

tor from this pin to the VOUT pin sets the output voltage

of the part in VIN tracking mode. For conventional boost

charge pump operation, this pin must be grounded. Do

not float this pin.

VOUT(Pin10):OutputVoltage.Thispinshouldbebypassed

with a low impedance ceramic capacitor to GND in normal

boost charge pump mode or to the VIN pin in VIN track-

ing mode. When the VSET pin is set to GND, the VOUT pin

voltage is set by an external divider between the VOUT, FB

and GND pins. In VIN tracking mode, the VOUT pin oper-

ates at a fixed offset voltage above the VIN pin. The value

of the offset voltage is set by a pair of external resistors,

one from the VOUT pin to the VSET pin and another from

the FB pin to GND.

GND(ExposedPadPin11):Ground.Theexposedpackage

is ground and must be soldered to the PC board ground

plane for proper functionality and for rated thermal per-

formance.

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