DIODES AP65550 COT Synchronous DC and DC Buck Converter Owner’s Manual

DIODES AP65550 COT Synchronous DC and DC Buck Converter

Product Information

Specifications:

• Input Voltage Range: 4.5V to 18V
• Output Current: 5A
• Output Voltage: 1.05V
• Switching Frequency: 650kHz
• Efficiency: 90%

Description:
The AP65550 is a synchronous buck converter that provides high efficiency, excellent transient response, and high DC output accuracy for low-voltage regulation in digital TV and monitors. It features a constant-on-time control scheme, low external component count, and supports seamless transitions between continuous and
discontinuous conduction modes.

Product Usage Instructions

Quick Start Guide:

1. Connect a power supply to the input terminals VIN and GND. Set VIN to 12V.
2. Connect the positive terminal of the electronic load to VOUT and negative terminal to GND.
3. EN has a positive voltage through a 100K pull-up to VIN. Drive EN above 1.9V to start the converter and below 0.6V to stop it.
4. The evaluation board should power up with a 1.05V output voltage.
5. Set the load to 5A through the electronic load. Check the SW signal on the oscilloscope for stable operation and measure the switching frequency.

Measurement/Performance Guidelines:

1. When measuring output voltage ripple, maintain short ground lengths on the oscilloscope probe to avoid noise injection.
2. For efficiency measurements, connect an ammeter in series with the input supply and an electronic load to the output.

FAQs:

1. Q: How do I start and stop the converter?
   A: Drive EN above 1.9V to start the converter and below 0.6V to stop it.

2. Q: What is the recommended input voltage range?
   A: The input voltage range is from 4.5V to 18V.

Description

The AP65550 is an adaptive on-time mode synchronous buck converter providing high efficiency, excellent transient response and high DC output accuracy for low-voltage regulation in digital TV and monitor.
The constant-on-time control scheme handles wide input/output voltage ratios and provides low external component count. The internal proprietary circuit enables the device to adopt both low equivalent series resistance (ESR) output capacitors, such as SP-CAP or POSCAP and ultra-low ESR ceramic capacitors.
The adaptive on-time control supports seamless transition between continuous conduction mode (CCM) at higher load conditions and discontinuous conduction mode (DCM) at lighter load conditions. DCM allows AP65550 maintain high efficiency at light load conditions. The AP65550 also features programmable soft-start, UVLO, OTP and OCP to protect the circuit.
This IC is available in SO-8EP package.

• Gaming Consoles
• Flat Screen TV Sets and Monitors
• Set Top Boxes
• Distributed Power Systems
• Green Electronics
• Home Audio
• Consumer Electronics
• Network Systems
• FPGA, DSP and ASIC Supplies

Performance Spec of AP65550SP-EVM (Rev2)

Performance Spec of AP65550SP-EVM (Rev2)

Parameter| Conditions| Performance Value
Input voltage| Range 4.5V to 18V| 12V
Output Current| | 5A
Output Voltage| | 1.05V
Output Voltage Ripple| | 20mVP-P
Transient Response| Peak-to-peak Deviation Load step from 0A to 5A| 30mVP-P
Switching Frequency| | 650kHz
Efficiency| | 90% @VOUT=5V

PCB Layouts

Quick Start Guide

The AP65550SP-EVM has a simple layout and allows access to the appropriate signals through test points. To evaluate the performance of the AP65550, follow the procedure below:

1. Connect a power supply to the input terminals VIN and GND. Set VIN to 12V.
2. Connect the positive terminal of the electronic load to VOUT and negative terminal to GND.
3. EN has a positive voltage through a 100K pull-up to VIN. No supply input is required for EN. Note: To use the EN function drive EN above 1.9V to start the converter and below 0.6V to stop the converter.
4. The evaluation board should now power up with a 1.05V output voltage.
5. Check for the proper output voltage of 1.05V (±1%) at the output terminals VOUT and GND. Measurement can also be done with a multimeter with the positive and negative leads between VOUT and GND.
6. Set the load to 5A through the electronic load. Check for the stable operation of the SW signal on the oscilloscope. Measure the switching frequency. A test point is conveniently located at the head of the inductor.

Measurement/Performance Guidelines:

1. When measuring the output voltage ripple, maintain the shortest possible ground lengths on the oscilloscope probe. Long ground leads can erroneously inject high frequency noise into the measured ripple.
2. For efficiency measurements, connect an ammeter in series with the input supply to measure the input current. Connect an electronic load to the output for output current.

EVALUATION BOARD SCHEMATIC

BILL OF MATERIALS

REF| VALUE| DESCRIPTION| PACKAGE| MANUFACTURER| MANUFACTURER P/N
---|---|---|---|---|---
C1, C2| 10µF| Ceramic Cap, 25V, X7R| 1210| Wurth Electronics| 885012209028
C4| 8.2nF| Ceramic Capacitor, 16V, X7R| 0805| AVX| 0805YC822KAT2A
C5| 1µF| Ceramic Cap, 16V, X7R| 0805| Wurth Electronics| 885012207051
C6| 0.1µF| Ceramic Capacitor, 50V, X7R| 0805| Wurth Electronics| 885012207098
C8, C9| 22µF| Ceramic Cap, 25V, X5R| 1210| AVX| 12103D226KAT2A
L1| 1.5µH| Inductor, SMD 6.9mmWx6.9mmLx4mmH| SMD| Wurth Electronics| 744311150
R1| 8.25kΩ| Resistor, 1%| 0805| Panasonic| ERJ-6ENF8251V
R2| 22.1kΩ| Resistor, 1%| 0805| Panasonic| ERJ-6ENF2212V
R3| 100kΩ| Resistor, 1%| 0805| Panasonic| ERJ-6ENF1003V
T1| 1598| Terminal Turret Triple 0.094” L (Test Points)| Through- Hole| Keystone Circuit| 1598-2
U1| | DC/DC Converter| SO-8EP| Diodes Inc| AP65550SP

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March 2018
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