LT8705 datasheet(11/42 Pages) LINER

11 / 42 page

LTC7813

7813f

For more information www.linear.com/LTC7813

pin FuncTions

PLLIN/MODE (Pin 10): External Synchronization Input

to Phase Detector and Forced Continuous Mode Input.

When an external clock is applied to this pin, the phase-

locked loop will force the rising TG1 and BG2 signals

to be synchronized with the rising edge of the external

clock, and the regulators will operate in forced continuous

mode. When not synchronizing to an external clock, this

input, which acts on both controllers, determines how the

LTC7813 operates at light loads. Pulling this pin to ground

selects Burst Mode® operation. An internal 100k resistor

to ground also invokes Burst Mode operation when the

pin is floated. Tying this pin to INTVCC forces continuous

inductor current operation. Tying this pin to a voltage

greater than 1.1V and less than INTVCC – 1.3V selects

pulse-skipping operation. This can be done by connecting

a 100k resistor from this pin to INTVCC.

GND (Pin 11, Exposed Pad Pin 33): Ground. The exposed

pad must be soldered to the PCB for rated electrical and

thermal performance.

PGOOD1 (Pin 14): Open-Drain Logic Output. PGOOD1 is

pulled to ground when the voltage on the VFB1 pin is not

within ±10% of its set point.

INTVCC (Pin 15): Output of the Internal 5V Low Dropout

Regulator. The low voltage analog and digital circuits

are powered from this voltage source. A low ESR 0.1µF

ceramic bypass capacitor should be connected between

INTVCC and GND, as close as possible to the IC.

RUN1, RUN2 (Pins 16, 17): Run Control Inputs for Each

Controller. Forcing either of these pins below 1.2V shuts

down that controller. Forcing both of these pins below

0.7V shuts down the entire LTC7813, reducing quiescent

current to approximately 3.6µA.

ILIM (Pin 18): Current Comparator Sense Voltage Range

Input. Tying this pin to GND or INTVCC or floating it sets

the maximum current sense threshold (for both channels)

to one of three different levels (50mV, 100mV, or 75mV,

respectively).

VFB2 (Pin 19): If VPRG2 is grounded, this pin receives the

remotely sensed feedback voltage for the boost control-

ler from an external resistive divider across the output. If

VPRG2 is floated or tied to INTVCC, this pin receives the

remotely sensed output voltage of the boost controller.

DRVUV (Pin 21): Determines the higher or lower DRVCC

UVLO and EXTVCC switchover thresholds, as listed on

the Electrical Characteristics table. Connecting DRVUV to

GND chooses the lower thresholds whereas tying DRVUV

to INTVCC chooses the higher thresholds.

DRVSET (Pin 22): Sets the regulated output voltage of the

DRVCC LDO regulator. Connecting this pin to GND sets

DRVCC to 6V whereas connecting it to INTVCC sets DRVCC

to 10V. Voltages between 5V and 10V can be programmed

by placing a resistor (50k to 100k) between the DRVSET

pin and GND.

DRVCC (Pin 24): Output of the Internal or External Low

Dropout (LDO) Regulator. The gate drivers are powered

from this voltage source. The DRVCC voltage is set by the

DRVSETpin.Mustbedecoupledtogroundwithaminimum

of 4.7µF ceramic or other low ESR capacitor. Do not use

the DRVCC pin for any other purpose.

EXTVCC (Pin 25): External Power Input to an Internal LDO

Connected to DRVCC. This LDO supplies DRVCC power,

bypassing the internal LDO powered from VBIAS whenever

EXTVCC is higher than its switchover threshold (4.7V or

7.7V depending on the DRVSET pin). See EXTVCC Connec-

tion in the Applications Information section. Do not float

or exceed 14V on this pin. Do not connect EXTVCC to a

voltage greater than VBIAS. Connect to GND if not used.

VBIAS(Pin26):MainSupplyPin.Abypasscapacitorshould

be tied between this pin and the GND pin.

BG1, BG2 (Pins 31, 27): High Current Gate Drives for

Bottom N-Channel MOSFETs. Voltage swing at these pins

is from ground to DRVCC.

BOOST1, BOOST2 (Pins 32, 28): Bootstrapped Supplies

to the Topside Floating Drivers. Capacitors are connected

betweentheBOOSTandSWpins.VoltageswingatBOOST1

is from approximately DRVCC to (VIN1 + DRVCC). Voltage

swing at BOOST2 is from approximately DRVCC to (VOUT2

+ DRVCC).

LT8705 Datasheet(PDF) 11 Page - Linear Technology

LT8705 Datasheet(HTML) 11 Page - Linear Technology

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 35 36 37 38 39 40 41 42

Datasheet Download

Link URL