ADP1851 Step-Down DC-DC Controller Reference Solution

Analog Devices’ ADP1851 is a wide input range, synchronous step-down DC-DC controller with voltage tracking and synchronization capabilities. The versatile ADP1851 can be configured for input feed-forward voltage mode or current mode. Input voltage range: 2.75-20V, output voltage range is 0.6V-0.9Vin. This document describes the design, operation, and test results of the ADP1851-EVALZ evaluation board. The input voltage range of this evaluation board is 9-15V, the output voltage regulation is set to 1.8V, and the maximum output current can reach 25A. The ADP1851 evaluation board includes externally adjustable soft-start, output overvoltage protection, externally programmable current limit, Power output, and a programmable good oscillator frequency ranging from 200KHz to 1.5MHz. This article describes the ADP1851 key features, block diagram, evaluation board ADP1851-EVALZ key features, circuit diagram, bill of materials, and PCB component layout.

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.

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℃.

ADP1851 main features:

Input voltage range: 2.75V to 20V

Output voltage range: 0.6 V to 90% VIN

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

ADP1851 application:

Intermediate bus and POL systems requiring sequencing and tracking, including

Telecom base station and networking

Industrial and instrumentation

Medical and healthcare

ADP1851 Step-Down DC-DC Controller Reference Solution

Figure 1. LT3791 block diagram

ADP1851-EVALZ main features:

Input voltage range: 9V to 15V

Output voltage: 1.8V

Output current: up to 25A

Switching frequency: 600 kHz

Operates in PWM or PSM

Designed for evaluation of the ADP1851 functionality

Flexible and easy to re-configure and modify

ADP1851-EVALZ circuit diagram:

Figure 2. ADP1851-EVALZ Circuit Diagram

ADP1851-EVALZ Bill of Materials:

PCB component layout:

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