ANALOG DEVICES UG-407 Service Manual

ADP2441-EVALZ User Guide

UG-407

10694-101

One Technology Way • P. O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: [phone] • Fax: [phone] • www.analog.com

ADP2441 Evaluation Board

FEATURES

Full-featured evaluation board for the ADP2441
Configurable synchronous step down dc-dc switching

regulator
Operating voltage range of board: V
Output voltage is set to 5 V or can be adjusted
Maximum load 1 A
Switching frequency set to 500 kHz or adjustable switching

frequency of 300 kHz to 1 MHz
Power saving mode at light load
Precision enable input pin
Current limit protection
Power good output
External soft start set to 6 ms or external tracking available
Board size: 53 mm × 53 mm

DOCUMENTS NEEDED

ADP2441 data sheet

UG-407

= 6 V to 36 V

IN

GENERAL DESCRIPTION

The ADP2441 evaluation board is a complete, dc-to-dc switch­ing regulator design based on the ADP2441, a configurable, 1 A,
synchronous step-down, dc-to-dc regulator.

The ADP2441 is a synchronous, step-down dc-to-dc switching
regulator that uses a current mode pulse-width modulation
(PWM) control scheme at medium-to-heavy load currents for
high efficiency and smoothly transitions to a pulse skip mode
at light loads to conserve power. The power switch and
synchronous rectifier are integrated for minimal external part
count and high efficiency. The ADP2441 is optimized for
operation with small ferrite core inductors and ceramic
capacitors to deliver the maximum output power per square
millimeter of the PCB board area.

The ADP2441-EVALZ is available with 5 V at 1 A output,
switching frequency set to 500 kHz. If needed, the ADP2441
evaluation board configuration can be modified by changing
the values of the appropriate passive components.

Complete specifications for the ADP2441 device can be found
in the ADP2441 data sheet, which is available from Analog
Devices, Inc., and should be consulted in conjunction with this
user guide when using the evaluation board.

PLEASE SEE THE LAST PAGE FOR AN IMPORTANT
WARNING AND LEGAL TERMS AND CONDITIONS.

ADP2441-EVALZ

Figure 1.

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UG-407 ADP2441-EVALZ User Guide

TABLE OF CONTENTS

Features .............................................................................................. 1

Documents Needed .......................................................................... 1

General Description ......................................................................... 1

ADP2441-E VALZ ............................................................................. 1

Revision History ............................................................................... 2

Using the Evaluation Board ............................................................. 3

Powering Up the Evaluation Board ............................................ 3

Measuring Evaluation Board Performance ............................... 4

REVISION HISTORY

6/12—Initial Version: Revision 0

Modifying the Evaluation Board .....................................................5

Changing the Output Voltage ......................................................5

Changing the Switching Frequency ............................................5

Changing the Soft Start Time ......................................................5

Typical Performance Characteristics ..............................................6

Evaluation Board Schematics and Artwork ...................................8

Ordering Information .................................................................... 10

Bill of Materials ........................................................................... 10

Rev. 0 | Page 2 of 12

ADP2441-EVALZ User Guide UG-407

PGOOD

TP2: EXTERNAL
SUPPLY: 5V

JP1

10694-001

R7
50kΩ

R10

OPEN

R11

OPEN

C11
10nF

SS

SS/TRK

TRK

10694-002

USING THE EVALUATION BOARD

POWERING UP THE EVALUATION BOARD

The ADP2441 evaluation board is provided fully assembled
and tested. Before applying power to the evaluation board,
follow the procedures in this section.

Input Power Source

The power source voltage must not exceed 36 V, the maximum
operation input voltage of the ADP2441.

Make sure the power source is switched off before connecting it
to the ADP2441 evaluation board. Connect the positive
terminal of the power source to the evaluation board V
terminal (T1), and the negative terminal of the power source to
the evaluation board GND terminal (T2). If the power source
includes an ammeter, connect the ammeter in series with the
input source voltage. Connect the positive lead (+) of the power
source to the ammeter positive (+) connection, the negative
lead (−) of the ammeter to the evaluation board V
(T1), and the negative lead (−) of the power source to the
evaluation board GND terminal (T2).

Output Load

Make sure the evaluation board is switched off before connect­ing the load. Connect the load directly to the evaluation board,
with the positive (+) load connection to the V

OUT

(T3) and the negative (−) load connection to the GND terminal
(T4). If an ammeter is used, connect it in series with the load:
connect the positive (+) ammeter terminal to the evaluation
board V

terminal (T3), the negative (−) ammeter terminal

OUT

to the positive (+) load terminal, and the negative (−) load
terminal to the evaluation board GND terminal (T4).

Once the load is connected, make sure it is set to the proper
current before powering the ADP2441 evaluation board. Before
connecting a load to the output of the evaluation board, make
sure that the output voltage does not exceed the maximum
operating voltage range of the load.

Enabling and Disabling the DC-to-DC Switching Regulator

In the evaluation board, a voltage divider is used to generate
an enable signal for the IC. As soon as voltage is applied to
V

(24 V), IC is enabled.

IN

Alternatively, header TP1 (EN) is available to enable and disable
the evaluation board. To enable the output, connect the header
TP1 to the V

supply or to an external voltage source. To disable

IN

the output connect the header TP1 to the GND.

IN

terminal

IN

terminal

PGOOD Signals

When the output is enabled and the output voltage, VOUT, is in
regulation, the logic signal at the PGOOD test point is high. In
a typical application, a pull-up resistor from the PGOOD pin to
the external supply is used to generate this logic signal.

On the evaluation board, the pull-up resistor (R7) is available to
connect to the external supply through the jumper (JP1). Test
Point TP2 is available to connect the external supply of 5 V.

Figure 2 PGOOD Signal

External SS/Track Signal

The SS/TRK pin is multipurpose. It can be used either for
tracking the external supply or for soft start.

A header, TRK, is available on the board for connecting an
external signal to be tracked by the regulator output voltage.
Before applying a signal to the TRK header, make sure the
voltage divider resistor values (R10, R11) connected on the
evaluation board are the correct values (see the ADP2441
data sheet).

Alternatively, to program soft start time, a capacitor can be
connected to SS/TRK pin. On the evaluation board, a 10 nF
capacitor, C11, is connected for a soft start time of 6 ms.

Figure 3. Soft Start Signal

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UG-407 ADP2441-EVALZ User Guide

ININ

OUTOUT

IVIV×

×

=

η

10694-104

MEASURING EVALUATION BOARD PERFORMANCE

Output Voltage Ripple

To observe the output voltage ripple, place an oscilloscope
probe tip at Terminal T3 and connect the probe ground lead at
the negative (−) Terminal T4. Set the oscilloscope to an ac­coupled, 100 mV/division and 2 μs/division time base.

Switching Waveform

To observe the switching waveform with an oscilloscope, place
the oscilloscope probe tip at the end of the inductor that is
connected to the SW pin with the probe ground at Terminal T4,
GND. Set the scope to dc, 5 V/division, and 2 µs/division time
base. The switching waveform should alternate between 0 V
and approximately the input voltage.

Figure 4. Switch Node Measurement

Measuring Load Regulation

The load regulation should be measured by increasing the
load at the output and looking at the change in output voltage.
To minimize voltage drop, use short low-resistance wires,
especially for heavy loads.

Measuring Line Regulation

Vary the input voltage and examine the change in the output
voltage. In PWM mode, the output voltage ripple should be
small (<50 mV) but in pulse skip mode, the output voltage
ripple can be as large as 100 mV.

Measuring Efficiency

The efficiency, η, is measured by comparing the input power
with the output power.

Measure the input and output voltages as close as possible to the
input and output capacitors to reduce the effect of IR drops.

Inductor Current

The inductor current can be measured by removing one end
of the inductor from its pad and connecting a current loop in
series with it. Then a current probe can be used to measure
the current flowing through the current loop.

Line Transient Response

Generate a step input voltage (VIN) and observe the behavior
of the output voltage, with an oscilloscope.

Load Transient Response

Generate a load current transient at the output, V

OUT

, and
observe the output voltage response with an oscilloscope.
Use a current probe attached to the wire between the output
and the load to visualize the current transient.

Loop Stability Measurement

Closed-loop response can be measured using a network
analyzer. To measure the loop response, Header IN and
Header OUT are available.

Rev. 0 | Page 4 of 12