Wide Range Input, Synchronous,

Step-Down DC-to-DC Controller

Data Sheet

ADP1851

Rev. B

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FEATURES

Input voltage range: 2.75 V to 20 V

Maximum output current of more than 25 A

Current mode architecture

Configurable to voltage mode

±1% output voltage accuracy over temperature

Voltage tracking

Programmable frequency: 200 kHz to 1.5 MHz

Synchronization input

Power saving mode at light load

Precision enable input

Power good with internal pull-up resistor

Adjustable soft start

Programmable current sense gain

Integrated bootstrap diode

Starts into a precharged load

Externally adjustable slope compensation

Suitable for any output capacitor

Overvoltage and overcurrent-limit protection

Thermal overload protection

Input undervoltage lockout (UVLO)

Available in 16-lead, 4 mm × 4 mm LFCSP

Supported by ADIsimPower design tool

APPLICATIONS

Intermediate bus and POL systems requiring sequencing and

tracking, including

Telecom base station and networking

Industrial and instrumentation

Medical and healthcare

GENERAL DESCRIPTION

The ADP1851 is a wide range input, dc-to-dc, synchronous

buck controller capable of running from commonly used 3.3 V

to 12 V (up to 20 V) voltage inputs. The device nominally

operates in current mode with valley current sensing providing

the fastest step response for digital loads. It can also be config-

ured as a voltage mode controller with low noise and crosstalk

for sensitive loads.

The ADP1851 is ideal in system applications requiring multiple

output voltages. The ADP1851 includes a synchronization feature

to eliminate beat frequencies between switching devices. It also

provides accurate tracking capability between supplies and

includes precision enable and power-good functions for simple,

robust sequencing.

TYPICAL OPERATION CIRCUIT

VIN

M2

M1

FB

SW

PGND

L

DH

BST

DL

RAMP

PGOOD

SYNC

SS/TRK

ILIM

EN

AGND (EP)

COMP

FREQ

VCCO

ADP1851

HIGH

LOW

Figure 1.

The ADP1851 provides a high speed, high peak current gate

driving capability to enable energy efficient power conversion.

The device can be configured to operate in power saving mode

by skipping pulses, reducing switching losses, and improving

efficiency at light load and standby conditions.

The accurate current limit allows design within a narrower

range of tolerances and can reduce overall converter size and

cost. The ADP1851 can regulate down to 0.6 V output using a

high accuracy reference with ±1% tolerance over the

temperature range of −40°C to +125°C.

With its wide range input voltage, the ADP1851 provides the

designer with maximum flexibility for use in a variety of system

configurations; loop compensation, soft start, frequency setting,

power saving mode, current limit, and current sense gain can

all be programmed using external components. In addition, the

external RAMP resistor allows the selection of optimal slope

excellent line rejection. The linear regulator and the bootstrap

diode for the high-side driver are internal.

Protection features include undervoltage lockout, overvoltage,

overcurrent/short circuit, and overtemperature.