LTC3838-1_15 Datasheet, PDF(12/52 Page) Linear Technology – Dual, Fast, Accurate Step-Down DC/DC Controller with Dual Differential Output Sensing

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LTC3838-1_15 Datasheet, PDF (12/52 Pages) Linear Technology – Dual, Fast, Accurate Step-Down DC/DC Controller with Dual Differential Output Sensing

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LTC3838-1

PIN FUNCTIONS

SW1, SW2 (Pin 21, Pin 30): Switch Node Connection to

Inductors. Voltage swings are from a diode voltage below

ground to VIN. The (â) terminal of the bootstrap capacitor,

CB, connects to this node.

BG1, BG2 (Pin 22, Pin 29): Bottom Gate Driver Outputs.

The BG pins drive the gates of the bottom Nâchannel power

MOSFET between PGND and DRVCC.

DRVCC1, DRVCC2 (Pin 23, Pin 28): Supplies of Bottom

Gate Drivers. DRVCC1 is also the output of an internal 5.3V

regulator. DRVCC2 is also the output of the EXTVCC switch.

Normally the two DRVCC pins are shorted together on the

PCB, and decoupled to PGND with a minimum of 4.7ÂµF

ceramic capacitor, CDRVCC.

VIN (Pin 24): Input Voltage Supply. The supply voltage

can range from 4.5V to 38V. For increased noise immunity

decouple this pin to SGND with an RC filter. Voltage at

this pin is also used to adjust top gate on-time, therefore

it is recommended to tie this pin to the main power input

supply through an RC filter.

PGND (Pin 25, Exposed Pad Pin 39): Power Ground.

Connect this pin as close as practical to the source of the

bottom N-channel power MOSFET, the (â) terminal of

CDRVCC and the (â) terminal of CIN. Connect the exposed

pad and PGND pin to SGND pin using a single PCB trace

under the IC. The exposed pad must be soldered to the

circuit board for electrical and rated thermal performance.

INTVCC (Pin 26): Supply Input for Internal Circuitry (Not

Including Gate Drivers). Normally powered from the DRVCC

pins through a decoupling RC filter to SGND (typically

2Î© and 1ÂµF).

EXTVCC (Pin 27): External Power Input. When EXTVCC

exceeds the switchover voltage (typically 4.6V), an internal

switch connects this pin to DRVCC2 and shuts down the

internal regulator so that INTVCC and gate drivers draw

power from EXTVCC. The VIN pin still needs to be powered

up but draws minimum current.

VDFB2â (Pin 38): Differential Feedback Amplifier (â) Input

of Channel 2. Connect this pin to the negative terminal of

the output load capacitor of VOUT2.

For more information www.linear.com/3838-1

38381f

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