ERROR

AMPLIFIER

R

Q

S

Boot

Charge

Boot

UVLO

UVLO

Current

Sense

Oscillator

with PLL

Logic

Slope

Compensation

Logic

PWM

Latch

PWM

Comparator

Minimum

COMP Clamp

Maximum

Clamp

Voltage

Reference

Overload

Recovery

VSENSE

SS/TR

COMP

RT/CLK

PH

BOOT

VIN

GND

Thermal

Shutdown

EN

Enable

Comparator

Shutdown

Logic

Shutdown

Enable

Threshold

Logic

Shutdown

PWRGD

POWERPAD

PGND

Logic

Shutdown

105 %

93%

TPS54678 Block Diagram

S

TPS54678

SLVSBF3 – JUNE 2012

www.ti.com

FUNCTIONAL BLOCK DIAGRAM

Overview

The TPS54678 is a 6-V, 6-A, synchronous step-down (buck) converter with two integrated n-channel MOSFETs.

To improve the performance during line and load transients the device implements a constant frequency, peak

current mode control which reduces output capacitance and simplifies external frequency compensation design.

The wide switching frequency range of 200 kHz to 2000 kHz allows for efficiency and size optimization when

selecting the output filter components. The switching frequency is adjusted using a resistor to ground on the

RT/CLK pin. The device has an internal phase lock loop (PLL) on the RT/CLK pin that is used to synchronize the

power switch turn on to a falling edge of an external system clock.

The TPS54678 has a typical default start up voltage of 2.4 V. The EN pin has an internal pull-up current source

that can be used to adjust the input voltage under voltage lockout (UVLO) with two external resistors. In addition,

the pull up current provides a default condition when the EN pin is floating for the device to operate. The total

operating current for the TPS54678 is typically 570 µA when not switching and under no load. When the device

is disabled, the supply current is less than 3 µA.

6

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Product Folder Link(s): TPS54678