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Evaluation Board for Constant-Frequency,

Current-Mode, Step-Up, DC/DC Controller

EVAL-ADP1621

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

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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

EVALUATION BOARD DESCRIPTION

This data sheet describes the design, operation and test results

of the ADP1621 Evaluation Board. The input range for the

demo board is 3.0 V to 3.6 V, and the output voltage is 5 V with

a maximum load of 2 A. The design is done in a bootstrapped

configuration as shown in

Figure 13. The switching frequency

is set to 600 kHz with a 36 kΩ resistor. This design is done in

all multilayer ceramic capacitors (MLCC), although other types

of capacitors can be used, such as the aluminum polymer or

aluminum electrolytic capacitors. The PCB is laid out in such a

way that the user can easily modify the demo board for other

input and output configurations. See the

Other Configurations

section for more information.

ADP1621 DEVICE DESCRIPTION

The ADP1621 is a fixed-frequency, pulse-width modulation

(PWM), current-mode, step-up converter controller. It drives

an external n-channel MOSFET to convert the input voltage to

a higher output voltage. The ADP1621 can also be used to drive

flyback, SEPIC, and forward converter topologies, either

isolated or nonisolated.

EVALUATION BOARD

GND

OUT

ADP1621

.5µH INDU

TOR

IRF7470

OUTPUT CAPACITORS

06358-013

Figure 1.

Summary of content (12 pages)

PAGE 1
Evaluation Board for Constant-Frequency, Current-Mode, Step-Up, DC/DC Controller EVAL-ADP1621 EVALUATION BOARD DESCRIPTION ADP1621 DEVICE DESCRIPTION This data sheet describes the design, operation and test results of the ADP1621 Evaluation Board. The input range for the demo board is 3.0 V to 3.6 V, and the output voltage is 5 V with a maximum load of 2 A. The design is done in a bootstrapped configuration as shown in Figure 13. The switching frequency fSW is set to 600 kHz with a 36 kΩ resistor.
PAGE 2
EVAL-ADP1621 TABLE OF CONTENTS Evaluation Board Description......................................................... 1 Other Configurations ...................................................................8 ADP1621 Device Description......................................................... 1 Evaluation Board Schematic and Artwork.....................................9 Evaluation Board .............................................................................. 1 PCB Layout ..........................
PAGE 3
EVAL-ADP1621 EVALUATION BOARD HARDWARE capacitance, set the switching frequency fSW to 600 kHz. Assuming a 30% ripple current of 1/(1 − D) × 2 A (the load current) in the inductor, the inductor value is calculated from the following equation: Table 1. Jumper Description Jumper J1 J2 J3 Description VIN and GND terminals VOUT and GND terminals SDSN connection Function L= Connects SDSN to VIN or drives SDSN separately Table 2.
PAGE 4
EVAL-ADP1621 Diode Selection and The diode conducts the inductor current to the output capacitor and loads while the MOSFET is off. The average diode current is the load current, I DIODE , AVE = I LOAD (8) The rms diode current in continuous conduction mode is given by I DIODE ,RMS = I LOAD × 1− D 1− D (9) where D is the duty cycle. With a 2 A load, IDIODE,RMS is calculated to be 2.6 A. A Vishay SSA33L in a SMA package meets the dc current and thermal requirements.
PAGE 5
EVAL-ADP1621 Current Limit where: The current limit in the ADP1621 limits the peak inductor current and is achieved by the COMP voltage clamp. The peak inductor current, IL,PK, is given by n = 9.5 VCOM,CLAMP = 2.1 V VCOMP,ZCT = 1.0 V. VCOMP ,CLAMP − VCOMP ,ZCT I L ,PK = n − I SC ,PK × RS × D 1 − t OFF , MIN × f SW RCS (17) where: VCOMP,CLAMP is the COMP clamp voltage (maximum 2.1 V). VCOMP,ZCT is the COMP zero-current threshold (typically 1.0 V). n is the current-sense amplifier gain (typically 9.
PAGE 6
EVAL-ADP1621 TEST WAVEFORMS 100 T VIN = 3.3V VOUT = 5V 1A LOAD 90 Δ: 33.0mV @: –21.0mV EFFICIENCY (%) OUTPUT RIPPLE 1 80 TA = 25°C VIN = 3.3V VOUT = 5V fSW = 600kHz 70 GATE 60 2 0 0.5 1.0 1.5 LOAD CURRENT (µA) 2.0 2.5 CH1 50.0mV Figure 2. Efficiency vs. Load Current T CH2 5.00V M 2.00µs A CH2 500mV Figure 5. Output Voltage Ripple, 1 A Load Δ: 57.0mV @: 23.0mV VIN = 3.3V VOUT = 5V 2A LOAD OUTPUT RIPPLE BW 06358-005 40 06358-002 50 T 0.
PAGE 7
EVAL-ADP1621 LOAD TRANSIENT RESPONSE T T LOAD STEP RESPONSE 0.5A TO 1.5A TO 0.5A 0.2A TO 1A TO 0.2A LOAD CURRENT LOAD CURRENT 4 4 1 1 OUTPUT RIPPLE 620mA CH1 200mV M 200µs A CH4 620mA CH4 1.00AΩ 06358-010 M 200µs A CH4 CH4 1.00AΩ 06358-008 CH1 200mV OUTPUT RIPPLE Figure 10. Load Step Response Figure 8.
PAGE 8
EVAL-ADP1621 PCB LAYOUT GUIDELINE drain and the output. It is recommended to add 5 Ω of resistance for every inch of PCB trace. This helps to reduce the overshoot and ringing at the drain and the output. However, this added resistance increases the rise and fall times of the MOSFET; thus, the switching loss in the MOSFET is increased. Layout is important for all switching regulators, but is particularly important for regulators with high switching frequencies.
PAGE 9
EVAL-ADP1621 EVALUATION BOARD SCHEMATIC AND ARTWORK ADP1621 BOOST DEMO BOARD VIN = 3.3V, VO = 5V @ 2A VIN TP1* 1 1 1 TP5* 1 1 2 VOUT D1 VISHAY SSA33L 1 2 TP3* 1 CSL1 J1 1 2 TP2* L1 2.5µH 1 1 + CE4 + CE5 C1 OPEN OPEN OPEN OPEN 2 2 C2 C3 47µF 6.
PAGE 10
EVAL-ADP1621 Figure 16. Bottom Layer 06358-015 Figure 14. Silk Screen 06358-016 06358-014 PCB LAYOUT Figure 15. Top Layer Rev.
PAGE 11
EVAL-ADP1621 ORDERING INFORMATION BILL OF MATERIALS The ADP1621 evaluation board schematic is shown in Figure 13. Table 4 shows the bill of materials of the evaluation board. VIN = 3.0 V to 3.6 V, VOUT = 5 V, IOUT = 2 A, bootstrapped configuration. Table 4. Qty 1 Reference Designator M1 1 1 1 4 1 1 1 1 1 1 1 1 1 2 2 3 1 1 1 1 2 2 Supplier IRF Supplier Number IRF7470 D1 L1 Description MOSFET, 8 L SOIC, 40 V, VGS = 2.8 V, 5 A, 15 mΩ @ 4.5 VGS, 30 mΩ @2.8 VGS Schottky, 3 A, 30 V, SMA 2.