ADP2442-EVALZ

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 FEATURES GENERAL DESCRIPTION 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 The ADP2442-EVALZ 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-EVALZ is available with 5 V at a 1 A output, with a switching frequency set to 500 kHz. If needed, the ADP2442EVALZ configuration can be modified by changing the values of the appropriate passive components. DOCUMENTS NEEDED ADP2442 data sheet UG-407 user guide 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. 10949-001 ADP2442-EVALZ Figure 1. PLEASE SEE THE LAST PAGE FOR AN IMPORTANT WARNING AND LEGAL TERMS AND CONDITIONS. Rev. 0 | Page 1 of 12 UG-456 Evaluation Board 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 ADP2442-EVALZ ............................................................................. 1 Typical Performance Characteristics ..............................................6 Revision History ............................................................................... 2 Evaluation Board Schematic and Artwork.....................................8 Using the Evaluation Board............................................................. 3 Ordering Information .................................................................... 10 Powering Up the Evaluation Board ............................................ 3 Bill of Materials ........................................................................... 10 Measuring Evaluation Board Performance .................................. 4 REVISION HISTORY 11/12—Revision 0: Initial Version Rev. 0 | Page 2 of 12 Evaluation Board User Guide UG-456 USING THE EVALUATION BOARD PGOOD Signals 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-EVALZ 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-EVALZ 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. 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. PGOOD R7 50kΩ JP1 TP2: EXTERNAL SUPPLY: 5V 10949-002 The ADP2442-EVALZ evaluation board is provided fully assembled and tested. Before applying power to the evaluation board, follow the procedures in the following sections. 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 Low High Clock signal Enabling and Disabling the DC-to-DC Switching Regulator Mode of Operation Pulse skip mode Forced PWM mode Forced PWM mode SYNC/MODE J1 CLOCK JP2 VCC 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. Rev. 0 | Page 3 of 12 10949-003 POWERING UP THE EVALUATION BOARD Figure 3. SYNC/MODE Signal UG-456 Evaluation Board User Guide MEASURING EVALUATION BOARD PERFORMANCE η= 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 (