RT8105 Просмотр технического описания (PDF) - Richtek Technology

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RT8105

5V/12V Synchronous Buck PWM DC/DC Controller

Richtek Technology 

RT8105

Typical Application Circuit

+5V to +12V D1

BAT54

RBOOT

0

R1

10

C1

1µF

1 BOOT UGATE 2

5 VCC

PHASE 8

6 FB

RT8105

OPS

7

3 GND

LGATE 4

C2

0.1µF

RUGATE

0

ROCSET

Disable >

Q3

3904

R2

R3

32

68

VIN

+3.3V/+5V/+12V

C3

C4

1µF

470µF

Q1

MU

L1

3µH

VOUT

Q2 R

ML

C

C6 to C8

1000µFx3

VOUT

=

VREF

× (1+

R3 )

R2

VREF : Internal reference voltage

(0.8V ± 2%)

R4

C5

200 to 1k 0.1 to 0.33µF

Functional Pin Description

BOOT (Pin 1)

Bootstrap supply pin for the upper gate driver. Connect

the bootstrap capacitor between BOOT pin and the PHASE

pin. The bootstrap capacitor provides the charge to turn

on the upper MOSFET.

UGATE (Pin 2)

Upper gate driver output. Connect to the gate of high side

power N-MOSFET. This pin is monitored by the adaptive

shoot-through protection circuitry to determine when the

upper MOSFET has turned off.

GND (Pin 3)

Both signal and power ground for the IC. All voltage levels

are measured with respect to this pin. Ties the pin directly

to the low side MOSFET source and ground plane with

the lowest impedance.

LGATE (Pin 4)

Lower gate drive output. Connect to the gate of low side

power N-MOSFET. This pin is monitored by the adaptive

shoot-through protection circuitry to determine when the

lower MOSFET has turned off.

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2

VCC (Pin 5)

Connect this pin to a well-decoupled 5V or 12V bias

supply. It is also the positive supply for the lower gate

driver, LGATE.

FB (Pin 6)

Switcher feedback voltage. This pin is the inverting input

of the error amplifier. FB senses the switcher output

through an external resistor divider network.

OPS (OCSET, POR and Shut-Down) (Pin 7)

This pin provides multi-function of the over-current setting,

UGATE turn-on POR sensing, and shut-down features.

Connecting a resistor (ROCSET) between OPS and PHASE

pins sets the over-current trip point.

Pulling the pin to ground resets the device and all external

MOSFETs are turned off allowing the output voltage power

rails to float.

This pin is also used to detect VIN in power on stage and

issues an internal POR signal.

PHASE (Pin 8)

Connect this pin to the source of the upper MOSFET and

the drain of the lower MOSFET.

DS8105-03 April 2011

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