RT8205A datasheet(8/28 Pages) RICHTEK

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RT8205A/B/C

DS8205A/B/C-06 July 2012

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

GND [Pin 15 (RT8205A), Exposed Pad (25)]

Analog Ground for SMPS controller. The exposed pad

must be soldered to a large PCB and connected to GND

for maximum power dissipation.

PGND (Pin 15) (RT8205B/C)

Power Ground for SMPS controller. Connect PGND

externally to the underside of the exposed pad.

VIN (Pin 16)

High Voltage Power Supply Input for 5V/3.3V LDO and

Feed-forward ON-Time circuitry.

VREG5 (Pin 17)

5V Linear Regulator Output.VREG5 is also the supply

voltage for the low-side MOSFET driver and analog supply

voltage for the device.

NC (Pin 18) (RT8205A)

No Internal Connection.

LG1_CP (Pin 18) (RT8205B)

Alternative LGATE1 Output for 14V charge pump.

SECFB (Pin 18) (RT8205C)

The SECFB is used to monitor the optional external 14V

charge pump. Connect a resistive voltage-divider from 14V

charge pump output to GND to detect the output. If SECFB

drops below the threshold voltage, LGATE1 turns on for

300ns (typ.). This will refresh the external charge pump

driven by LGATE1 without over-discharging the output

voltage.

LGATE1 (Pin 19)

SMPS1 Synchronous-Rectifier Gate-Drive Output.

LGATE1 swings between GND and VREG5.

PHASE1 (Pin 20)

Inductor Connection for SMPS1. PHASE1 is the internal

lower supply rail for the UGATE1 high-side gate driver.

PHASE1 is also the current-sense input for the SMPS1.

UGATE1 (Pin 21)

High-Side MOSFET Floating Gate-Driver Output for

SMPS1. UGATE1 swings between PHASE1 and BOOT1.

BOOT1 (Pin 22)

Boost Flying Capacitor Connection for SMPS1. Connect

to an external capacitor according to the typical application

circuits.

PGOOD (Pin 23)

Power Good Output for channel 1 and channel 2. (Logical

AND)

VOUT1 (Pin 24)

SMPS1 Output Voltage-Sense Input. Connect to the

SMPS1 output. VOUT1 is an input to the on-time one-

shot circuit. It also serves as the SMPS1 feedback input

in fixed-voltage mode.

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