LTC7802EUFDM datasheet(9/34 Pages) AD

9 / 34 page

LTC7802

Rev. 0

For more information www.analog.com

PIN FUNCTIONS

INTVCC pins and the BOOST2 and INTVCC pins. Voltage

swing at the BOOST pins is from INTVCC to (VIN + INTVCC).

SW1, SW2 (Pins 22,14): Switch Node Connections to

Inductors.

TG1, TG2 (Pins 23,13): High Current Gate Drives for Top

N Channel MOSFETs. These are the outputs of floating

drivers with a voltage swing of INTVCC superimposed on

the switch node voltage SW.

PGOOD1, PGOOD2 (Pins 24,12): Open-Drain Power

Good Outputs. The VFB1,2 pins are monitored to ensure

that VOUT1,2 are in regulation. When VOUT is not within

±10% of its regulation point, the corresponding PGOOD

pin is pulled low.

TRACK/SS1, TRACK/SS2 (Pins 26,11): External Tracking

and Soft-Start Input. The LTC7802 regulates the VFB1,2

voltage to the lesser of 0.8V or the voltage on the TRACK/

SS1,2 pin. Internal 12.5µA pull-up current sources are

connected to these pins. A capacitor to ground sets the

start-up ramp time to the final regulated output voltage.

The ramp time is equal to 0.65ms for every 10nF of capac-

itance. Alternatively, a resistor divider on another voltage

supply connected to the TRACK/SS pins allows the

LTC7802 output to track the other supply during start-up.

ITH1, ITH2 (Pins 27,10): Error Amplifier Outputs and

Switching Regulator Compensation Points. Each asso-

ciated channel’s current comparator trip point increases

with this control voltage. Place compensation compo-

nents between the ITH pins and ground.

VFB1, VFB2 (Pins 28,9): Controller Feedback Inputs.

Connect an external resistor divider between the output

voltage and the VFB pin to set the regulated output voltage.

Tie VFB2 to INTVCC to configure the channels for a 2-phase

single output application, in which both channels share

VFB1, ITH1, and TRACK/SS1.

GND (Exposed Pad Pin 29): Ground. Connects to the

sources of the bottom N-Channel MOSFETs and the (–)

terminal(s) of decoupling capacitors. The exposed pad

must be soldered to PCB ground for rated electrical and

thermal performance.

Tying this pin to INTVCC forces continuous inductor cur-

rent operation. Tying this pin to INTVCC through a 100k

resistor selects pulse-skipping operation.

RUN1, RUN2 (Pins 5,6): Run Control Inputs for Each

Controller. Forcing either of these pins below 1.1V disables

switching of the corresponding controller. Forcing both of

these pins below 0.7V shuts down the entire LTC7802,

reducing quiescent current to approximately 1.5µA. These

pins can be tied to VIN for always-on operation. Do not

float the RUN pins.

INTVCC (Pin 17): Output of the Internal 5.1V Low Dropout

Regulator. The driver and control circuits are powered by

this supply. Must be decoupled to ground with a minimum

of 4.7μF ceramic or tantalum capacitor.

EXTVCC (Pin 18): External Power Input to an Internal LDO

Connected to INTVCC. This LDO supplies INTVCC power,

bypassing the internal LDO powered from VIN whenever

EXTVCC is higher than 4.7V. See INTVCC Regulators in the

Applications Information section. Do not exceed 30V on

this pin. Connect this pin to ground if the EXTVCC LDO

is not used.

VIN (Pin 19): Main Bias Input Supply Pin. A bypass capac-

itor should be tied between this pin and GND.

PLLIN/SPREAD (Pin 25): External Synchronization Input

and Spread Spectrum Selection. When an external clock

is applied to this pin, the phase-locked loop will force the

rising TG1 signal to be synchronized with the rising edge

of the external clock. When an external clock is present, the

regulators operate in pulse-skipping mode if it is selected

by the MODE pin, or in forced continuous mode otherwise.

When not synchronizing to an external clock, tie this input

to INTVCC to enable spread spectrum dithering of the oscil-

lator or to ground to disable spread spectrum.

BG1, BG2 (Pins 20,16): High Current Gate Drives for

Bottom (Synchronous) N-Channel MOSFETs. Voltage

swing at these pins is from ground to INTVCC.

BOOST1, BOOST2 (Pins 21,15): Bootstrapped Supplies to

the Top Side Floating Drivers. Connect capacitors between

the corresponding BOOST and SW pins for each channel.

Also connect Schottky diodes between the BOOST1 and

LTC7802EUFDM 数据表(PDF) 9 Page - Analog Devices

LTC7802EUFDM 数据表(HTML) 9 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

数据表下载