ADP2441-EVALZ

ADP2441-EVALZ User Guide UG-407 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 ADP2441 Evaluation Board FEATURES GENERAL DESCRIPTION Full-featured evaluation board for the ADP2441 Configurable synchronous step down dc-dc switching regulator Operating voltage range of board: VIN = 6 V to 36 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 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. DOCUMENTS NEEDED ADP2441 data sheet UG-407 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. 10694-101 ADP2441-EVALZ Figure 1. PLEASE SEE THE LAST PAGE FOR AN IMPORTANT WARNING AND LEGAL TERMS AND CONDITIONS. Rev. 0 | Page 1 of 12 UG-407 ADP2441-EVALZ User Guide TABLE OF CONTENTS Features .............................................................................................. 1 Modifying the Evaluation Board .....................................................5 Documents Needed .......................................................................... 1 Changing the Output Voltage ......................................................5 General Description ......................................................................... 1 Changing the Switching Frequency ............................................5 ADP2441-EVALZ ............................................................................. 1 Changing the Soft Start Time ......................................................5 Revision History ............................................................................... 2 Typical Performance Characteristics ..............................................6 Using the Evaluation Board............................................................. 3 Evaluation Board Schematics and Artwork ...................................8 Powering Up the Evaluation Board ............................................ 3 Ordering Information .................................................................... 10 Measuring Evaluation Board Performance ............................... 4 Bill of Materials ........................................................................... 10 REVISION HISTORY 6/12—Initial Version: Revision 0 Rev. 0 | Page 2 of 12 ADP2441-EVALZ User Guide UG-407 USING THE EVALUATION BOARD PGOOD Signals POWERING UP THE EVALUATION BOARD 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. 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 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 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 VOUT terminal (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 VOUT terminal (T3), the negative (−) ammeter terminal to the positive (+) load terminal, and the negative (−) load terminal to the evaluation board GND terminal (T4). 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. PGOOD R7 50kΩ JP1 10694-001 The ADP2441 evaluation board is provided fully assembled and tested. Before applying power to the evaluation board, follow the procedures in this section. TP2: EXTERNAL SUPPLY: 5V 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. 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. SS SS/TRK C11 10nF TRK Enabling and Disabling the DC-to-DC Switching Regulator R11 OPEN 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. 10694-002 R10 OPEN Figure 3. Soft Start Signal Alternatively, header TP1 (EN) is available to enable and disable the evaluation board. To enable the output, connect the header TP1 to the VIN supply or to an external voltage source. To disable the output connect the header TP1 to the GND. Rev. 0 | Page 3 of 12 UG-407 ADP2441-EVALZ User Guide Measuring Line Regulation 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. Vary the input voltage and examine the change in the output voltage. In PWM mode, the output voltage ripple should be small (