LTC3370 datasheet(15/44 Pages) LINER

15 / 44 page

LTC3372

Rev. A

For more information www.analog.com

PIN FUNCTIONS

WDI (Pin 20): Watchdog Timer Input. The WDI pin must

be toggled either low to high or high to low every 1.62

seconds. Failure to toggle WDI results in the WDO pin

being pulled low for 202ms. All times correspond to a

10nF capacitor on the CT pin.

WDO (Pin 21): Watchdog Timer. Open-drain output. WDO

is pulled low for 202ms during a watchdog timeout period.

The WDO pin pulls low if the WDI input does not transition

in less than 1.62 seconds since its last transition or 12.9

seconds after a watchdog timeout period. An UVLO event

resets the watchdog timer and WDO asserts itself low for

the 202ms watchdog timeout period. All times correspond

to a 10nF capacitor on the CT pin.

CT (Pin 22): Timing Capacitor Pin. A capacitor connected

to GND sets a time constant which is scaled for use by

the WDI, WDO, and RST pins. Tying the CT pin to INTVCC

disables the watchdog timer to reduce quiescent current.

EN3 (Pin 23): LV Buck Regulator 3 Enable Input. Active

high. In configurations where LV Regulator 3 is not used,

tie EN3 to ground. Do not float.

FB3 (Pin 24): LV Buck Regulator 3 Feedback Pin. Receives

feedbackbyaresistordividerconnectedacrosstheoutput.

In configurations where LV Regulator 3 is not used, FB3

should be tied to ground.

VINE (Pin 25): LV Power Stage E Input Supply. Bypass to

GND with a 10μF or larger ceramic capacitor.

SWE (Pin 26): LV Power Stage E Switch Node. External

inductor connects to this pin.

SWF (Pin 27): LV Power Stage F Switch Node. External

inductor connects to this pin.

VINF (Pin 28): LV Power Stage F Input Supply. Bypass to

GND with a 10μF or larger ceramic capacitor.

VING (Pin 29): LV Power Stage G Input Supply. Bypass to

GND with a 10μF or larger ceramic capacitor.

SWG (Pin 30): LV Power Stage G Switch Node. External

inductor connects to this pin.

SWH (Pin 31): LV Power Stage H Switch Node. External

inductor connects to this pin.

VINH (Pin 32): LV Power Stage H Input Supply. Bypass to

GND with a 10μF or larger ceramic capacitor.

FB4 (Pin 33): LV Buck Regulator 4 Feedback Pin. Receives

feedbackbyaresistordividerconnectedacrosstheoutput.

EN4 (Pin 34): LV Buck Regulator 4 Enable Input. Active

high. Do not float.

INTVCC (Pin 35): Internal VCC Pin. Output of an internal

linear low-dropout (LDO) regulator powered from VIN.The

HV buck gate drive and control circuits are powered from

this voltage source when VOUT is < 4.7V. When VOUT >

4.7V the bias connects to Vout and the LDO is shutdown.

Must be de-coupled to GND pin with a minimum of 4.7μF

low ESR (ceramic) capacitor.

BG (Pin 36): HV Controller High Current Gate Drive for

Bottom(Synchronous)N-channelMOSFET.Voltageswing

at this pin is from ground to INTVCC.

TG (Pin 37): HV Controller High Current Gate Drive for Top

N-channel MOSFET. This is the output of floating driver

with a voltage swing equal to INTVCC superimposed on

the switch node voltage SW.

SW (Pin 38): HV Controller Switch Node Connection to

Inductor.

BOOST(Pin39):HVControllerBootstrappedSupplytothe

Topside Floating Driver. A capacitor should be connected

between the BOOST and SW pin and a Schottky diode

should be connected between the BOOST and INTVCC

pins. Voltage swing at the BOOST pin is from INTVCC to

(VIN + INTVCC).

RUN (Pin 40): HV Controller Enable Input. Forcing this

pin above 1.2V turns on the HV controller. This pin has a

0.5µA internal pull-up current from ground to around 4V,

and can be forced up to 65V (absolute maximum).

VIN (Pin 41): HV Input Supply Pin. A bypass capacitor

should be tied between this pin and the GND pin.

TRACK/SS (Pin 42): HV Controller External Tracking and

Soft-StartInput.Whenthispinisabove 1.2V,thecontroller

regulates the output voltage VOUT to the programed 5V or

3.3V level. When this pin is below 1.2V, the output voltage

LTC3370 Datasheet(PDF) 15 Page - Linear Technology

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