Analog Devices ADP2442-EVALZ Manuel utilisateur

Evaluation Board User Guide

UG-456

One Technology Way •P. O. Box 9106 •Norwood, MA 02062-9106, U.S.A. •Tel: 781.329.4700 •Fax: 781.461.3113 •www.analog.com

Evaluation Board for the ADP2442 36 V, 1 A, Synchronous, Step-Down DC-to-DC

Regulator with External Clock Synchronization

PLEASE SEE THE LAST PAGE FOR AN IMPORTANT

WARNING AND LEGAL TERMS AND CONDITIONS.Rev. 0 | Page 1 of 12

FEATURES

Full featured evaluation board for the ADP2442

Configurable synchronous step-down dc-to-dc switching

regulator

Operating voltage range: VIN = 6 V to 36 V

Output voltage: 5 V or adjustable

1 A maximum load

Switching frequency: 500 kHz or adjustable switching

frequency of 300 kHz to 1 MHz

Power saving mode at light load

Precision enabled input pin

Current limit protection

Power good output

SYNC/MODE pin for external synchronization or mode

selection

53 mm × 53 mm board size

DOCUMENTS NEEDED

ADP2442 data sheet

UG-407 user guide

GENERAL DESCRIPTION

The ADP2442-EVA L Z evaluation board is a complete, dc-to-dc

switching regulator design based on the ADP2442, a configurable,

1 A, synchronous, step-down dc-to-dc regulator.

The ADP2442 is a synchronous, step-down dc-to-dc switching

regulator that uses a current mode pulse-width modulation

(PWM) control scheme. The ADP2442 can be configured for

pulse skip mode at light load or forced PWM mode. The power

switch and synchronous rectifier are integrated for minimal

external part count and high efficiency. The ADP2442 is

optimized for operation with small ferrite core inductors and

ceramic capacitors to deliver the maximum output power per

square millimeter of the printed circuit board (PCB) area.

The ADP2442-EVA L Z is available with 5 V at a 1 A output, with

a switching frequency set to 500 kHz. If needed, the ADP2442-

E VA L Z configuration can be modified by changing the values

of the appropriate passive components.

Complete specifications for the ADP2442 device can be found

in the ADP2442 data sheet, which is available from Analog

Devices, Inc., and should be consulted in conjunction with this

user guide when using the evaluation board.

ADP2442-EVALZ

Figure 1.

10949-001

UG-456 Evaluation Board User Guide

Rev. 0 | Page 2 of 12

TABLE OF CONTENTS

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

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

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

ADP2442-E VA L Z ............................................................................. 1

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

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

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

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

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

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

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

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

Evaluation Board Schematic and Artwork.....................................8

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

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

REVISION HISTORY

11/12—Revision 0: Initial Version

Evaluation Board User Guide UG-456

Rev. 0 | Page 3 of 12

USING THE EVALUATION BOARD

POWERING UP THE EVALUATION BOARD

The ADP2442-EVA L Z evaluation board is provided fully

assembled and tested. Before applying power to the evaluation

board, follow the procedures in the following sections.

Input Power Source

The power source voltage must not exceed 36 V, the maximum

operation input voltage of the ADP2442.

Ensure that the power source is switched off before connecting

it to the ADP2442-E VA L Z evaluation board. Connect the positive

terminal of the power source to the evaluation board VIN 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 VIN terminal (T1), and the

negative lead (−) of the power source to the evaluation board

GND terminal (T2).

Output Load

Ensure that 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 VOUT terminal (T3) and

the negative (−) load connection to the PGND terminal (T4). If

an ammeter is used, connect it in series with the load: connect

the positive (+) ammeter terminal to the evaluation board VOUT

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

(+) load terminal, and the negative (−) load terminal to the

evaluation board PGND terminal (T4).

When the load is connected, ensure that it is set to the proper

current before powering the ADP2442-E VA L Z evaluation board.

Before connecting a load to the output of the evaluation board,

ensure 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 VIN

(24 V), IC is enabled.

Alternatively, the TP1 (EN) header is available to enable and

disable the evaluation board. To enable the output, connect the

TP1 header to the VIN supply or to an external voltage source. To

disable the output, connect the TP1 header to the GND.

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). The TP2

test point is available to connect the external supply of 5 V.

Figure 2. PGOOD Signal

SYNC/MODE Pin

The SYNC/MODE pin is a multifunctional pin. When the

SYNC/MODE pin is connected to VCC or a high logic, the

PWM mode is enabled. When the SYNC pin is connected to

AGND, the pulse skip mode is enabled. The external clock can

be applied for the synchronization.

On the evaluation board, the SYNC/MODE pin can be connected

to VCC or AGND through JP2 (as shown in Figure 3). Users can

apply a clock input to the SMB connector, which is connected to

the SYNC pin.

Table 1. Mode Selection

SYNC Pin Mode of Operation

Low Pulse skip mode

High Forced PWM mode

Clock signal Forced PWM mode

Figure 3. SYNC/MODE Signal

PGOOD

TP2: EXTERNAL

SUPPLY: 5V

JP1

50kΩ

10949-002

VCC

JP2

SYNC/MODE

CLOCK

10949-003

UG-456 Evaluation Board User Guide

Rev. 0 | Page 4 of 12

MEASURING EVALUATION BOARD PERFORMANCE

Output Voltage Ripple

To observe the output voltage ripple, place an oscilloscope probe

tip at the T3 terminal and connect the probe ground lead at the

negative (−) the T4 terminal. Set the oscilloscope to an ac-coupled,

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,

PGND. Set the scope to dc, 5 V/division, and 2 µs/division time

base. Alternate the switching waveform between 0 V and

approximately the input voltage.

Measuring Load Regulation

Measure the load regulation by increasing the load at the output

and looking at the change in the 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, ensure that the output voltage ripple is

small (<50 mV); however, in pulse skip mode, the output voltage

ripple can be as large as 100 m V.

Measuring Efficiency

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

the output power.

ININ

OUTOUT IV IV

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

By removing one end of the inductor from its pad and connecting a

current loop in series with it, the inductor current can be measured.

Once this is done, 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, VOUT, 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, the IN and OUT headers are

available.

Evaluation Board User Guide UG-456

Rev. 0 | Page 5 of 12

MODIFYING THE EVALUATION BOARD

The ADP2442-E VA L Z evaluation board is provided fully

assembled and tested for proper operation. The evaluation

board has a fixed 5 V output voltage.

CHANGING THE OUTPUT VOLTAGE

The ADP2442-EVA L Z output regulation voltage is set by a

resistive voltage divider consisting of the R2 and R3 resistors. R2

corresponds to the RTOP resistor in the ADP2442 data sheet, and

R3 corresponds to the RBOTTOM resistor in the ADP2442 data sheet.

The output regulation voltage is determined by











+

×= 3

V6.0 R

R3R2

OUT

where:

R2 is the value of the top resistor of the voltage divider (RTOP).

R3 is the value of the bottom resistor of the voltage divider

(RBOTTOM).

VOUT is the output regulation voltage in volts.

To set the output regulation voltage to the desired value, first

determine the value of the bottom resistor, R3, by

STRING

R3 =

where:

VFB = 0.6 V, the internal reference.

ISTRING is the resistor divider string current (greater than 20 µA

nominally).

Once R3 is determined, calculate the value of the top resistor,

R2, by











−

OUT

R3R2

For example, to set the output regulation voltage of the

ADP2442-E VA L Z to 3.3 V, calculate the R2 and R3 values

as shown in the following equations:

kΩ10

μA60

V0.6 ===

STRING

ΩΩ

k45.3

0.6V

V0.6V3.3

k10 =











−

×=











−

×=

OUT

R3R2

When the output voltage of the ADP2442-E VA L Z is changed, the

output capacitors (C7 and C8), inductor (L1), and compensation

components (R5 and C10) must be recalculated and changed to

ensure stable operation according to the Applications Information

section in the ADP2442 data sheet.

Table 2. Programming Output Voltage

Voltage (V) R2 (kΩ) R3 (kΩ)

12 190 10

5 73 10

3.3 45 10

1.2

CHANGING THE SWITCHING FREQUENCY

The switching frequency (fSW) setpoint can be changed by

replacing the R9 resistor with a different value by using

following equation:

R500,92

where:

R9 is the frequency resistor in kΩ.

fSW is the switching frequency in kHz.

Table 3. Programming Frequency

R9 (kΩ) Frequency (kHz)

308 300

132 700

92.5 1000

When the switching frequency (fSW) is changed, the L1, C7, C8,

R5, and C10 values must be recalculated and changed to ensure

stable operation (see the ADP2442 data sheet for details on

external component selection).

UG-456 Evaluation Board User Guide

Rev. 0 | Page 6 of 12

TYPICAL PERFORMANCE CHARACTERISTICS

Figure 4. Efficiency vs. Load Current, VOUT = 5 V, fSW = 500 kHz, Pulse Skip Mode

Figure 5. Efficiency vs. Load Current, VOUT = 5 V, fSW = 500 kHz, PWM Mode

Figure 6. Load Regulation, VOUT = 5 V, fSW = 500 kHz

Figure 7. Line Regulation, VOUT = 5 V, fSW = 500 kHz

Figure 8. Pulse Skip Mode Waveforms, VIN = 24 V, VOUT = 5 V, fSW = 500 kHz,

No Load, SYNC/MODE: AGND

Figure 9. PWM Waveform, VIN = 24 V, VOUT = 5 V, fSW = 500 kHz, Load = 1 A

100

0.01 0.1 1

EFFICIENCY (%)

LOAD (A)

VIN = 12V

VIN = 24V

VIN = 36V

10949-005

100

0.01 0.1 1

EFFICIENCY (%)

VIN = 12V

VIN = 24V

VIN = 36V

10949-006

LOAD (A)

10949-007

4.980

4.985

4.990

4.995

5.000

5.005

5.010

5.015

5.020

5.025

5.030

5.035

5.040

00.2 0.4 0.6 0.8 1.0 1.2

OUT

(V)

= 12V

= 24V

= 36V

10949-008

4.97

4.98

4.99

5.00

5.01

5.02

5.03

5.04

5.05

5.06

712 17 22 27 32 37 42

OUT

(V)

NO LOAD

LOAD 1A

CH1 100mV CH2 10V M20µs A CH4 150mA

T46.8%

CH4 500mAΩ

OUT

SWSW

INDUCTOR CURRENT

10949-009

CH1 50mV CH2 10V M2µs A CH2 7.6V

T46.8%

CH4 500mA Ω

OUT

INDUCTOR CURRENT

SWSW

10949-010

Evaluation Board User Guide UG-456

Rev. 0 | Page 7 of 12

Figure 10. Load Transient, VIN = 24 V, VOUT = 5 V, 500 mA Step

Figure 11. Load Transient, VIN = 12 V, VOUT = 5 V, 500 mA

Figure 12. Startup, VIN = 24 V, VOUT = 5 V, Load 5 Ω, PWM Mode

Figure 13. Shutdown, VIN = 24 V, VOUT = 5 V, Load 5 Ω

Figure 14. Clock Synchronization, VIN = 24 V, VOUT = 5 V

Figure 15. Bode Plot, VIN = 24 V, VOUT = 5 V, fSW = 500 kHz, Load = 1 A,

fCO = 37 kHz, Phase Margin = 55

CH1 100mV CH2 10V M200µs A CH4 720mA

T71.2%

CH4 500mAΩ

LOAD STEP 500mA

SWSW

10949-011

VOUT

CH1 100mV CH4 500mAM200µs A CH4 800mA

T71.4%

CH2 5V

Ω

OUT

LOAD STEP 500mA

10949-012

CH2 10V

CH3 5V M1ms ACH1 1.32V

T23.2%

CH1 2V

10949-013

ENABLE, CHANNEL 1 VOUT, AND CHANNEL 2 SW

SWSW

ENABLE

OUT

CH2 10V

CH3 5V M1ms ACH1 1.52V

T52.4%

CH1 2V

10949-014

SWSW

ENABLE

VOUT

CH2 10V

CH3 2V M1µs A CH3 2.8V

T50.4%

CH1 50mV

10949-015

SYNC

VOUT

200

–200

160

–160

120

–120

–80

–40

110

1k 10k 100k

–90

–70

–50

–30

–10

PHASE (Degrees)

MAGNITUDE (dB)

FREQUENCY(Hz)

10949-016

UG-456 Evaluation Board User Guide

Rev. 0 | Page 8 of 12

EVALUATION BOARD SCHEMATIC AND ARTWORK

Figure 16. ADP2442-EVALZ Evaluation Board Schematic

10949-017

Evaluation Board User Guide UG-456

Rev. 0 | Page 9 of 12

Figure 17. ADP2442-EVALZ Evaluation Board Top Layer

Figure 18. ADP2442-EVALZ Evaluation Board Third Layer

Figure 19. ADP2442-EVALZ Evaluation Board Second Layer

Figure 20. ADP2442-EVALZ Evaluation Board Bottom Layer

10949-018

10949-019

10949-020

10949-021

UG-456 Evaluation Board User Guide

Rev. 0 | Page 10 of 12

ORDERING INFORMATION

BILL OF MATERIALS

Table 4.

Quantity Reference Designator Description Manufacturer/Part Number

2 C1, C2 Capacitor MLCC, 4.7 µF, 50 V, 1206, X7R Murata GRM31CR71H475KA12L

2 C3, C4 Capacitor MLCC, 1 µF, 25 V, 0603, X7R Murata GRM188R71E105KA12D

1 C5 Capacitor, MLCC, 10 nF, 50 V, 0603, X7R Murata GRM188R71H103KA01D

2 C7, C8 Capacitor, MLCC, 22 µF, 25 V, 1210, X7R Murata GRM32ER71E226K

1 L1 Shielded surface-mount power inductor Coilcraft MSS1038T-273

1 C6 Capacitor MLCC, 0.1 µF, 50 V, 0603, X7R Murata GRM188R71H104KA93D

1 C10 Capacitor MLCC, 270 pF, 50 V, 0603, X7R Determine by the user

1 R1 Resistor, 49.9 Ω, 1/10 W, 1%, 0603, SMD Determined by user

2 R3, R8 Resistor, 10 kΩ, 1/10 W, 1%, 0603, SMD Determined by user

Resistor, 50 kΩ, 1/10 W, 1%, 0603, SMD

Determined by user

1 R2 Resistor, 73.2 kΩ, 1/10 W, 1%, 0603, SMD Determined by user

1 R5 Resistor, 118 kΩ, 1/10 W, 1%, 0603, SMD Determined by user

1 R6 Resistor, 182 kΩ, 1/10 W, 11%, 0603, SMD Determined by user

1 R9 Resistor, 185 kΩ, 1/10 W, 1%, 0603, SMD Determined by user

2 IN, OUT Headers Sullins PBC01SAAN

1 J1 SYNC SMB5PIN_JACK Johnson J613-ND

4 TP1, TP2, TP3, TP4 Headers Sullins PBC01SAAN

1 JP1 PGOOD Jumper Sullins PBC03SAAN

1 JP2 SYNC Jumper Sullins PBC03SAAN

4 T1, T2, T3, T4 Terminal, double turret, brass, 0.078” Keystone 1502-1

36 V, 1 A, synchronous, step-down DC-to-DC regulator

Analog Devices ADP2442

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