Evaluation Board for Step-Down DC-to-DC Converter Solution EVAL-ADP2107 FEATURES GENERAL DESCRIPTION Efficiency > 95% Input voltage range: 2.7 V to 5.5 V Output voltage range: 0.8 V to VIN Maximum output current: 2.0 A Switching frequency: 1.2 MHz Quiescent current: 20 μA Shutdown current: 0.1 μA Enable/shutdown logic input Optimized for small ferrite core inductors Optimized for tiny ceramic input and output capacitors Programmable soft start with single capacitor Programmable compensation for optimizing transient performance The ADP2107 evaluation board is a complete step-down dc-to-dc converter solution using the ADP2107 step-down dc-to-dc converter. It provides a ±1% accurate (±3% over all conditions), regulated output voltage with load currents up to 2 A. It comes in two versions: the ADP2107-1.8-EVAL with fixed output voltage of 1.8 V, and the ADP2107-EVAL with adjustable output voltage initially set to 2.5 V. The ADP2107 is a synchronous, step-down dc-to-dc converter that uses a current-mode pulse width modulation (PWM) control scheme at medium-to-heavy load currents for high efficiency, but smoothly transitions to a pulse frequency modulation (PFM) scheme at light loads to conserve power. The power switch and synchronous rectifier are integrated for minimal external part count and high efficiency. The ADP2107 has been optimized for operation with small ferrite core inductors and tiny ceramic capacitors to deliver the maximum output power per square inch of the PCB board area. For more details, see the ADP2107 data sheet. FUNCTIONAL BLOCK DIAGRAM ADP2107 EVALUATION BOARD VIN J1 R2 GND ENB GND R3 C4 C7 C1 L1 R4 R5 R1 ADP2107 VOUT C6 C2 C3 VOUT: ANALOG DEVICES, POWER MANAGEMENT (STP) 06314-001 C5 Figure 1. Rev. 0 Evaluation boards are only intended for device evaluation and not for production purposes. Evaluation boards as supplied “as is” and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability or fitness for a particular purpose. No license is granted by implication or otherwise under any patents or other intellectual property by application or use of evaluation boards. Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Analog Devices reserves the right to change devices or specifications at any time without notice. Trademarks and registered trademarks are the property of their respective owners. Evaluation boards are not authorized to be used in life support devices or systems. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2006 Analog Devices, Inc. All rights reserved. EVAL-ADP2107 TABLE OF CONTENTS Features .............................................................................................. 1 Changing the Load Transient Response.....................................4 General Description ......................................................................... 1 Measurement Setup...........................................................................5 Functional Block Diagram .............................................................. 1 Typical Performance Characteristics ..............................................6 Using the Evaluation Board............................................................. 3 Ordering Information.......................................................................7 Powering Up the Evaluation Board............................................ 3 Bill of Materials..............................................................................7 Measuring Evaluation Board Performance............................... 3 Ordering Guide .............................................................................9 Modifying the Evaluation Board .................................................... 4 ESD Caution...................................................................................9 Changing the Output Voltage ..................................................... 4 REVISION HISTORY 12/06—Revision 0: Initial Version Rev. 0 | Page 2 of 12 EVAL-ADP2107 USING THE EVALUATION BOARD POWERING UP THE EVALUATION BOARD Turning on the Evaluation Board The ADP2107 evaluation board is supplied fully assembled and tested. Before applying power to the evaluation board, follow the procedures in this section. Once the power source and the load are connected to the ADP2107 evaluation board, it can be powered up for operation. Slowly increase the input power source voltage until the input voltage exceeds the minimum input operating voltage of 2.7 V. Insert Jumper J1, and check to see if the output voltage rises to the regulated output voltage (1.8 V for the ADP2107-1.8-EVAL and 2.5 V for the ADP2107-EVAL). If the load is not already enabled, enable the load, and check that it is drawing the proper current and that the output voltage maintains voltage regulation. Jumper J1 Before turning on the ADP2107 evaluation board, make sure that all the components are present, but Jumper J1 is removed. Input Power Source Before connecting the power source to the ADP2107 evaluation board, make sure that it is turned off. If the input power source includes a current meter, use that meter to monitor the input current. Connect the positive terminal of the power source to the VIN terminal on the evaluation board and the negative terminal of the power source to the GND terminal of the evaluation board. If the power source does not include a current meter, connect a current meter 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 power source to the GND terminal on the evaluation board, and the negative lead (−) of the ammeter to the VIN terminal on the board. Output Load Although the ADP2107 evaluation board can sustain the sudden connection of the load, it is possible to damage the load if it is not properly connected. Make sure that the board is turned off before connecting the load. If the load includes an ammeter, or if the current is not measured, connect the load directly to the evaluation board with the positive (+) load connection to the VOUT terminal and the negative (−) load connection to the GND terminal. If an ammeter is used, connect it in series with the load; that is, connect the positive (+) ammeter terminal to the evaluation board VOUT terminal, the negative (−) ammeter terminal to the positive (+) load terminal, and the negative (−) load terminal to the evaluation board GND terminal. Once the load is connected, make sure that it is set to the proper current before powering the ADP2107 evaluation board. Input and Output Voltmeters Measure the input and output voltages with voltmeters. Make sure that the voltmeters are connected to the appropriate evaluation board terminals, not the load or power source. If the voltmeters are not connected directly to the evaluation board, the measured voltages are incorrect due to the voltage drop across the leads and/or connections between the evaluation board, the power source, and/or the load. Connect the input voltage measuring the voltmeter positive terminal (+) to the evaluation board VIN terminal and the negative (−) terminal to the evaluation board GND terminal. Connect the output voltage measuring voltmeter positive (+) terminal to the evaluation board VOUT terminal and the negative (−) terminal to the evaluation board GND terminal. MEASURING EVALUATION BOARD PERFORMANCE Measuring Output Voltage Ripple To observe the output voltage ripple, place an oscilloscope probe across the output capacitor (C3/C4) with the probe ground lead at the negative (−) capacitor terminal and the probe tip at the positive (+) capacitor terminal. Set the oscilloscope to ac, 20 mV/division, and 2 μs/division time base. In the PWM mode of operation, the output voltage ripple is small (< 20 mV), but in PFM mode, the output voltage ripple can be as large as 50 mV. Measuring the 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 LX pins with the probe ground at GND. Set the scope to dc, 2 V/division, and 2 μs/division time base. The switching waveform should alternate between 0 V and the approximate input voltage. Measuring Load Regulation Load regulation must be tested 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. Measuring Efficiency The efficiency, η, is measured by comparing the input power with the output power. η= VOUT × I OUT VIN × I IN Measure the input and output voltages as close as possible to the input and output capacitors to reduce the effect of IR drops. Measuring 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. A current probe can then be used to measure the current flowing through the current loop, as shown in Figure 2. Rev. 0 | Page 3 of 12 EVAL-ADP2107 MODIFYING THE EVALUATION BOARD The ADP2107 evaluation board is supplied fully assembled and tested for proper operation. It comes in two versions: the ADP2107-1.8-EVAL with fixed output voltage of 1.8 V and the ADP2107-EVAL with adjustable output voltage initially set to 2.5 V. The two most common modifications that can be done to the evaluation boards are changing the output voltage and changing the load transient response. CHANGING THE OUTPUT VOLTAGE The ADP2107-EVAL output regulation voltage can be changed by altering its external components. The ADP2107-1.8-EVAL output regulation voltage is fixed at 1.8 V and cannot be changed. The ADP2107-EVAL output regulation voltage is set by a resistive voltage divider consisting of Resistor R4 and Resistor R5. Resistor R4 corresponds to the RTOP resistor in the ADP2107 data sheet, and Resistor R5 corresponds to the RBOT resistor in the ADP2107 data sheet. The output regulation voltage is determined by the equation ⎡ R + RBOT ⎤ VOUT = 0.8 V × ⎢ TOP ⎥ RBOT ⎦ ⎣ where: RTOP is the value of the top resistor of the voltage divider (R4). RBOT is the value of the bottom resistor of the voltage divider (R5). 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, RBOT, by R BOT = Note that when the output voltage of the ADP2107-EVAL is changed, the output capacitors (C3 and C4), the inductor (L1), and the compensation components (R1 and C6) must be recalculated and changed according to the Application Information section in the ADP2107 data sheet to ensure stable operation. CHANGING THE LOAD TRANSIENT RESPONSE The ADP2107 evaluation board load transient response can be altered by changing the output capacitors (C3 and C4) and the compensation components (R1 and C6) as explained in the Output Capacitor section and Loop Compensation section of the ADP2107 data sheet. By default, the load transient response of both ADP2107 evaluation boards is set to 5% of the output voltage for a 1 A load transient. Consider an example where the load transient response of ADP2107-1.8-EVAL is changed to 10% of the output voltage for a 1 A load transient. First, choose the output capacitors (C3 and C4) based on the load transient response requirements. The desired load transient response is 10% overshoot for a 1 A load transient. For this condition, the % Overshoot for a 1 A Load Transient Response vs. Output Capacitor × Output Voltage figure in the Output Capacitor Selection section of the ADP2107 data sheet gives Output Capacitor × Output Voltage = 25 μC V FB ⇒ Output Capacitor = I STRING where: VFB is 0.8 V, the internal reference. ISTRING is the resistor divider string current (20 μA nominally). Once RBOT is determined, calculate the value of the top resistor, RTOP, from RTOP ⎡V ⎡ 2 V − 0.8 V ⎤ − VFB ⎤ R4 = R5 × ⎢ OUT ⎥ = 40 kΩ × ⎢ ⎥ = 60 kΩ ⎣ 0.8 V ⎦ ⎣ VFB ⎦ Next, taking into account the loss of capacitance due to dc bias as shown in the % Drop-In Capacitance vs. DC Bias for Ceramic Capacitors figure in the Output Capacitor Selection section of the ADP2107 data sheet, let C3 and C4 be two 10 μF X5R MLCC capacitors (GRM21BR61A106KE19L). Finally, calculate the compensation resistor and compensation capacitor as follows: ⎡V − VFB ⎤ = RBOT ⎢ OUT ⎥ ⎣ VFB ⎦ ⎛ ( 2 π ) FCROSS RCOMP = 0.8 ⎜⎜ ⎝ G m GCS For example, to set the output regulation voltage of ADP2107EVAL to 2.0 V, calculate the value of Resistor R4 and Resistor R5 as shown below. R5 = 25 μC ≈ 14 μF 1 .8 V ⎞ ⎛ C OUT VOUT ⎟×⎜ ⎟ ⎜ V REF ⎠ ⎝ ⎞ ⎟⎟ ⎠ ⎞ ⎛ 14 μF × 1.8 V ⎞ ⎛ ( 2 π ) × 80 kHz ⎟⎟ = 70 kΩ ⎟⎟ × ⎜⎜ = 0.8 ⎜⎜ 50 μA / V × 3 . 625 A / V 0 .8 V ⎠ ⎠ ⎝ ⎝ VFB 0.8 V = = 40 kΩ I STRING 20 μA CCOMP = 2 2 = = 120 pF πFCROSS RCOMP π × 80 kHz × 70 kΩ Therefore, choose the compensation resistor to be 70 kΩ and the compensation capacitor to be 120 pF. Rev. 0 | Page 4 of 12 EVAL-ADP2107 MEASUREMENT SETUP ELECTRONIC LOAD VOLTMETER 3A VOLTAGE SOURCE VIN IIN VOUT IOUT J1 R2 GND ENABLE VIN GND PROBE OUTPUT VOLTAGE ACROSS OUTPUT CAPACITOR R3 C4 C7 C1 R4 ADP2107 L1 R5 VOUT R1 C6 C5 C2 CURRENT PROBE C3 INDUCTOR OSCILLOSCOPE 1V SEP 1V SEP AT NORW OFF 0V H 0V V EVE OFF 0V H 0V V VD 1S DIV VD 1S DIV VPOS NVERT OUTPUT VOLTAGE WAVEFORM mV V mV DVA DVA ADD LX NODE WAVEFORM Figure 2. Typical Measurement Setup Rev. 0 | Page 5 of 12 CH INDUCTOR CURRENT WAVEFORM 06314-010 V EVAL-ADP2107 TYPICAL PERFORMANCE CHARACTERISTICS 100 100 VIN = 3.6V 95 VIN = 2.7V 90 85 VIN = 4.2V EFFICIENCY (%) 80 VIN = 5.5V 75 70 VIN = 5.5V VIN = 4.2V 80 75 70 65 65 60 60 55 1 10 100 06314-004 INDUCTOR: D62LCB, 1.5µH DCR: 21mΩ TA = 25°C 50 10000 1000 INDUCTOR: D62LCB, 2.0μH DCR: 28mΩ TA = 25°C 55 1 10 100 06314-007 EFFICIENCY (%) VIN = 3.6V 90 85 50 VIN = 3.0V 95 10000 1000 LOAD CURRENT (mA) LOAD CURRENT (mA) Figure 6. Efficiency—ADP2107-EVAL (2.5 V Output) Figure 3. Efficiency—ADP2107-1.8-EVAL (1.8 V Output) LX NODE (SWITCH NODE) LX NODE (SWITCH NODE) 3 3 1 1 OUTPUT VOLTAGE (AC-COUPLED) OUTPUT VOLTAGE (AC-COUPLED) CH4 200mAΩ M 2µs T 6% A CH3 4 CH1 20mV CH3 2V 3.88V CH4 1AΩ M 1µs T 17.4% A CH3 3.88V Figure 7. PWM Mode of Operation at Medium/Heavy Load (1.5 A) Figure 4. PFM Mode of Operation at Light Load (10 mA) OUTPUT CURRENT 3 2 OUTPUT CURRENT 2 CH2 LOW –108mV LX (SWITCH) NODE VOLTAGE CH2 100mV M 10µs T 10.4% A CH2 OUTPUT VOLTAGE (AC-COUPLED) 1 06314-006 1 CH1 2V CH3 1A CH2 LOW –140mV OUTPUT VOLTAGE (AC-COUPLED) 06314-009 3 06314-008 INDUCTOR CURRENT CH1 50mV CH3 2V INDUCTOR CURRENT 06314-005 4 LX (SWITCH) NODE VOLTAGE CH1 2V CH3 1A 100mV Figure 5. 1 A Load Transient Response for ADP2107-1.8-EVAL CH2 100mV M 10µs T 20.20% A CH2 100mV Figure 8. 1 A Load Transient Response for ADP2107-EVAL with VOUT Set to 2.5 V Rev. 0 | Page 6 of 12 EVAL-ADP2107 ORDERING INFORMATION BILL OF MATERIALS Table 1. Bill of Materials for ADP2107-1.8-EVAL with VOUT Set to 1.8 V Ref. Des. Ref. Name 1 Quantity Manufacturer Mfg. Part Number Capacitor, MLCC, 10 μF, 10 V, 0805, X5R, SMD Capacitor, MLCC, 22 μF, 6.3 V, 0805, X5R, SMD Capacitor, MLCC, 1 nF, 16 V, 0603, X7R, SMD C1, C2 CIN1, CIN2 2 Murata GRM21BR61A106KE19L C3, C4 COUT 2 Murata GRM21BR60J226ME39L C5 CSS 1 Vishay Vitramon or equivalent VJ0603Y102KXJA Capacitor, MLCC, 68 pF, 50 V, 0603, NPO Capacitor, MLCC, 0.1 μF, 25 V, 0603, X7R, SMD Resistor, 140 kΩ, 1%, 0603, SMD Resistor, 100 kΩ, 1%, 0603, SMD C6 CCOMP 1 VJ0603Y680KXJA C7 1 1 1 Resistor, 10 Ω, 1%, 0603, SMD R3 IN (filter capacitor) RCOMP EN (pull down) IN (filter resistor) Vishay Vitramon or equivalent Vishay Vitramon or equivalent Vishay Dale or equivalent Vishay Dale or equivalent 1 Vishay Dale or equivalent CRCW060310R0FRT1 Resistor, 0 Ω, 1%, 0603, SMD Bottom Resistor of Voltage Divider Inductor 1.5 μH, 6.3 mm × 6.2 mm × 2.0 mm 1.8 V, 2 A, Step-Down DC-to-DC Converter R4 R5 1 Vishay Dale or equivalent CRCW06030000ZSSF No stuff 1 Toko D62LCB—1R5M U1 1 Analog Devices, Inc. ADP2107-1.8 Headers, 0.100, Single, Straight VOUT, VIN, GND, GND, J1, EN 6 Sullins Electric or equivalent S1012-36-ND PTC36SAAN R1 R2 L1 L VJ0603Y104KXXA CRCW06031403FRT1 CRCW06031003FRT1 Refer to the Typical Applications Circuit for Fixed Output Voltage Options figure in the ADP2107 data sheet. V C7 R3 IN 0.1µF 10Ω VIN J1 16 15 14 13 FB GND IN PWIN1 1 EN 2 GND3 EN R2 100kΩ C1 10µF FB U1 ADP2107 1 LX1 10 PWIN2 9 COMP SS AGND PADDLE NC 5 OUTPUT VOLTAGE = 2.5V PGND 11 GND1 4 GND LX2 12 GND2 3 INPUT VOLTAGE: 2.7V TO 5.5V VIN 6 7 17 C5 1nF 2 VIN C2 10µF 8 OUT OUTPUT VOLTAGE: 1.8V C3 22µF C4 22µF R4 0kΩ VOUT GND R5 NS R1 140kΩ C6 68pF L1 1.5µH NC = NO CONNECT Figure 9. Evaluation Board Schematic of ADP2107-1.8-EVAL with VOUT = 1.8 V Rev. 0 | Page 7 of 12 06314-002 1 Description EVAL-ADP2107 Table 2. Bill of Materials for ADP2107-EVAL with VOUT Set to 2.5 V Ref. Des. C1, C2 Ref. Name1 CIN1, CIN2 QTY 2 Manufacturer Murata Mfg. Part Number GRM21BR61A106KE19L C3 COUT 1 Murata GRM21BR60J226ME39L C4 COUT 1 Murata GRM21BR61A106KE19L Capacitor, MLCC, 1 nF, 16 V, 0603, X7R, SMD Capacitor, MLCC, 68 pF, 50 V, 0603, NPO Capacitor, MLCC, 0.1 μF, 25 V, 0603, X7R, SMD Resistor, 140 kΩ, 1%, 0603, SMD Resistor, 100 kΩ, 1%, 0603, SMD Resistor, 10 Ω, 1%, 0603, SMD C5 CSS 1 VJ0603Y102KXJA C6 CCOMP 1 C7 1 1 1 1 Resistor, 87.6 kΩ, 0.5%, 0603, SMD Resistor, 41.2 kΩ, 0.1%, 0603, SMD Inductor 2.0 μH, 6.3 mm x 6.2 mm x 2.0 mm R4 IN (filter capacitor) RCOMP EN (pull down) IN (filter resistor) RTOP Vishay Vitramon or equivalent Vishay Vitramon or equivalent Vishay Vitramon or equivalent Vishay Dale or equivalent Vishay Dale or equivalent Vishay Dale or equivalent 1 Vishay Dale or equivalent TNPW060387K6DHTA R5 RBOT 1 Vishay Dale or equivalent TNPW060341K2BEEN L1 L 1 Toko D62LCB-2R0M 2 A Step-Down DC-to-DC Converter with Adjustable Output Headers, 0.100, Single, Straight U1 1 Analog Devices, Inc. ADP2107-ADJ VOUT, VIN, GND, GND, J1, EN 6 Sullins Electric or equivalent S1012-36-ND PTC36SAAN R1 R2 R3 VJ0603Y680KXJA VJ0603Y104KXXA CRCW06031403FRT1 CRCW06031003FRT1 CRCW060310R0FRT1 Refer to the Typical Applications Circuit for Adjustable Output Voltage Option figure in the ADP2107 data sheet. V C7 R3 IN 0.1µF 10Ω VIN 16 15 14 13 FB GND IN PWIN1 1 EN 2 GND3 EN R2 100kΩ C1 10µF FB J1 U1 ADP2107 PGND 11 PWIN2 9 COMP SS AGND PADDLE NC 5 1 LX1 10 GND1 4 GND LX2 12 GND2 3 INPUT VOLTAGE: 2.7V TO 5.5V VIN 6 7 17 C5 1nF 2 VIN C2 10µF 8 FB OUTPUT VOLTAGE: 2.5V C3 22µF R4 87.6kΩ C4 10µF VOUT GND R5 41.2kΩ R1 140kΩ C6 68pF L1 2.0µH NC = NO CONNECT 06314-003 1 Description Capacitor, MLCC, 10 μF, 10 V, 0805, X5R, SMD Capacitor, MLCC, 22 μF, 6.3 V, 0805, X5R, SMD Capacitor, MLCC, 10 μF, 10 V, 0805, X5R, SMD Figure 10. Evaluation Board Schematic for ADP2107-EVAL with Adjustable VOUT Initially Set to 2.5 V Rev. 0 | Page 8 of 12 EVAL-ADP2107 ESD CAUTION ORDERING GUIDE Model ADP2107-1.8-EVAL ADP2107-EVAL Description Evaluation Board Evaluation Board Rev. 0 | Page 9 of 12 EVAL-ADP2107 NOTES Rev. 0 | Page 10 of 12 EVAL-ADP2107 NOTES Rev. 0 | Page 11 of 12 EVAL-ADP2107 NOTES ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. EB06314-0-12/06(0) T T Rev. 0 | Page 12 of 12