LTC3265 datasheet(8/20 Pages) LINER

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LTC3265

3265fa

For more information www.linear.com/LTC3265

PIN FUNCTIONS (DFN/TSSOP)

CBST– (Pin 1/Pin 2): Boost Charge Pump Flying Capacitor

Negative Connection.

NC (Pins 1, 11 TSSOP Only): No Connect. These pins are

not connected to LTC3265 die. These pins should be left

floating or connected to ground.

CBST+ (Pin 2/Pin 3): Boost Charge Pump Flying Capacitor

Positive Connection.

VIN_P (Pin 3/Pin 4): Input Voltage for Boost Charge Pump.

VIN_P should be bypassed with a low impedance ceramic

capacitor.

EN– (Pin 4/Pin 5): Logic Input. A logic “high” on the

EN– pin enables the inverting charge pump as well as the

negative LDO regulator. Do not float this pin.

BYP– (Pin 5/Pin 6): LDO– Reference Bypass Pin. Connect

a capacitor from BYP– to GND to reduce LDO– output

noise. Leave floating if unused.

ADJ– (Pin 6/Pin 7): Feedback Input for the Negative Low

Dropout Regulator. This pin servos to a fixed voltage of

–1.2V when the control loop is complete.

LDO– (Pin 7/Pin 8): Negative Low Dropout (LDO–) Linear

Regulator Output. This pin requires a low ESR (equivalent

series resistance) capacitor with at least 2µF capacitance

to ground for stability.

VOUT–(Pin8/Pin9):InvertingChargePumpOutputVoltage.

Inconstantfrequencymode(MODE=low)thispinisdriven

to –VIN_N. In Burst Mode operation, (MODE = high) this

pin voltage is regulated to – 0.9 • VIN_N using an internal

burst comparator with hysteretic control.

CINV– (Pin 9/Pin 10): Inverting Charge Pump Flying

Capacitor Positive Connection.

CINV+ (Pin 10/Pin 12): Inverting Charge Pump Flying

Capacitor Negative Connection.

VIN_N (Pin 11/Pin 13): Input Voltage for Inverting Charge

Pump. This pin should be tied to VIN_P or VOUT+ pins

depending on the desired output voltage at the VOUT– pin.

If VIN_N is tied to VOUT+, the output at VOUT– will be –VOUT+

or –2 • VIN_P. This configuration is suitable for symmetric

outputs at LDO+ and LDO– pins. If VIN_N is tied to VIN_P,

the output at VOUT– will be –VIN_P. This configuration is

suitableforasymmetricoutputsatLDO+andLDO–pins.See

ApplicationsInformationforadditionaldetails.VIN_Nshould

be bypassed with a low impedance ceramic capacitor.

RT (Pin 12/Pin 14): Input Connection for Programming

the Switching Frequency. The RT pin servos to a fixed

1.2V when the EN+ or EN– pin is driven to a logic “high”.

A resistor from RT to GND sets the charge pump switch-

ing frequency. If the RT pin is tied to GND, the switching

frequency defaults to a fixed 500kHz.

EN+ (Pin 13/Pin 15): Logic Input. A logic “high” on the

EN+ pin enables the boost charge pump as well as the

positive LDO regulator. Do not float this pin.

MODE (Pin 14/Pin 16): Logic Input. The MODE pin

determinesthechargepumpoperatingmode.Alogic“high”

on the MODE pin forces the charge pumps to operate in

Burst Mode operation. The boost charge pump regulates

the VOUT+ pin to 0.94 • 2 • VIN_P with hysteretic control.

The inverting charge pump regulates the VOUT– pin to

(–0.94 • VIN_N). A logic “low” on the MODE pin forces

the charge pumps to operate in open-loop mode with a

constant switching frequency. The boost charge pump

doubles the input to 2 • VIN_P in this mode while the

inverting charge pump inverts its input to (–VIN_N). The

switching frequency in both modes is determined by an

external resistor from the RT pin to GND. In Burst Mode

operation,thisrepresentsthefrequencyoftheburstcycles

beforethepartentersthelowquiescentcurrentsleepstate.

Do not float this pin.

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