DIODES AP62500SJ 5A Synchronous Buck Converter

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DESCRIPTION

The AP62500 is a 5A, synchronous buck converter with a wide input voltage range of 4.5V to 18V. The device fully integrates a 47mΩ high-side power MOSFET and a 18mΩ low-side power MOSFET to provide high efficiency step-down DC-DC conversion.

The AP62500 device is easily used by minimizing the external component count due to its adoption of Constant On-Time (COT) control to achieve fast transient response, easy loop stabilization, and low output voltage ripple.

The AP62500 design is optimized for Electromagnetic Interference (EMI) reduction. The device has a proprietary gate driver scheme to resist switching node ringing without sacrificing MOSFET turn-on and turn-off times, which reduces high-frequency-radiated EMI noise caused by MOSFET switching.

The device is available in a V-QFN2030-12 (Type A) package.

FEATURES

• VIN: 4.5V to 18V
• Output Voltage (VOUT): 0.6V to 7V
• 5A Continuous Output Current
• 0.6V ± 1% Reference Voltage
• 195μA Quiescent Current
• Selectable Operation Modes
  • Pulse Frequency Modulation (PFM)
  • Ultrasonic Mode (USM)
  • Pulse Width Modulation (PWM)
• Selectable Switching Frequency
  • 400kHz
  • 800kHz
  • 1.2MHz
• Programmable Soft-Start Time
• Proprietary Gate Driver Design for Best EMI Reduction
• Power-Good Indicator
• Precision Enable Threshold to Adjust UVLO
• Protection Circuitry
  • Undervoltage Lockout (UVLO)
  • Cycle-by-Cycle Valley Current Limit
  • Thermal Shutdown

APPLICATIONS

• 5V and 12V Input Distributed Power Bus Supplies
• Television Sets and Monitors
• White Goods and Small Home Appliances
• FPGA, DSP, and ASIC Supplies
• Home Audio
• Network Systems
• Gaming Consoles
• Consumer Electronics
• General Purpose Point of Load

FUNCTIONAL BLOCK

Figure 1. Functional Block Diagram

RECOMMENDED OPERATING CONDITIONS

EVALUATION BOARD

Figure 2. AP62500SJ-EVM

QUICK START GUIDE

The AP62500SJ-EVM has a simple layout and allows access to the appropriate signals through test points. The board is targeted to be used in providing a simple and convenient evaluation environment for the AP62500.

To operate the EVM, set jumpers J1, J2 and J3 to the desired positions per below shown.

• J1 = EN pin input jumper. For Enable, to enable IC, leave it OPEN or jump to “ON” to program an external resistor voltage divider at R5 and R6 to set the EN level. Jump to “OFF” position to disable IC.
• J2 = PFM, PWM or USM mode selection. At J2, connect a jumper to PWM to force the device in Pulse Width Modulation (PWM) operation mode. Connect a jumper to PFM to ground the pin to operate the device in Pulse Frequency Modulation (PFM) operation mode without Ultrasonic Mode (USM). Leave J2 OPEN to float the pin to operate the device in PFM with USM mode.
• J3 = Switching frequency selection. At J3, connect a jumper to GND to set clock frequency to 400kHz. Leave J3 OPEN to float the pin to set clock frequency to 800kHz. Connect a jumper to VCC to set clock frequency to 1.2MHz.

To evaluate the performance of the AP62500SJ-EVM, 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. By default, the evaluation board should now power up with a 5.0V output voltage. Frequency is 800kHz.
4. Check for the proper output voltage of 5.0V (±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.
5. 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.

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.

APPLICATION INFORMATION

Setting the Output Voltage of AP62500

1. Setting the output voltage:
   The AP62500 features external programmable output voltage by using a resistor divider network R2 and R1 as shown in the typical application circuit. The output voltage is calculated as below;
   

First, select a value for R1 according to the value recommended in table 1. Then, R3 is determined. The output voltage is given by Table 1 for reference. For accurate output voltage, 1% tolerance is required.

Table 1. Resistor selection for output voltage setting

EXTERNAL COMPONENT SELECTION:

Table 2. Recommended inductors and output capacitor AP62500

Output Voltage

(V)

| Frequency (kHz)| R1

(kΩ)

| R2

(kΩ)

| L1

(µH)

| C1

(µF)

| C9, C10, C11

(µF)

| C5

(nF)

1.2| 400| 10| 10| 1.50| 22| 3 x 22| 100
800| 0.75
1200| 0.51
1.5| 400| 15| 10| 1.80| 22| 3 x 22| 100
800| 0.87
1200| 0.62
1.8| 400| 20| 10| 2.00| 22| 3 x 22| 100
800| 1.00
1200| 0.68
2.5| 400| 31.6| 10| 2.70| 22| 3 x 22| 100
800| 1.30
1200| 0.87
3.3| 400| 45.3| 10| 3.3| 22| 3 x 22| 100
800| 1.5
1200| 1.00
5.0| 400| 73.2| 10| 3.5| 22| 3 x 22| 100
800| 2.2
1200| 1.20

EVALUATION BOARD SCHEMATIC

Figure 4. AP62500SJ-EVM – Top Layer

PCB INNER LAYER 2 LAYOUT

Figure 5. AP62500SJ-EVM – Inner Layer 2

PCB INNER LAYER 3 LAYOUT

Figure 6. AP62500SJ-EVM – Inner Layer 3

PCB BOTTOM LAYOUT

Figure 7. AP62500SJ-EVM – Bottom Layer

BILL OF MATERIALS for AP62500SJ-EVM for VOUT=5V @800kHz

Ref| Value| Description| Qty| Size| Vendor| Manufacturer PN| PCB
Layer
---|---|---|---|---|---|---|---
C1,
C9,
C10, C11| 22µF| Ceramic
Capacitor, 25V, X6S| 4| 1206| Samsung| CL31X226KAHN3NE| Top
C4, C5| 0.1µF| Ceramic Capacitor, 50V,
X7R, 10%| 2| 0603| Wurth Electronics| 885012206095| Top
**** C6| 47nF| Ceramic Capacitor, 50V,
X7R, 10%| 1| 0603| Wurth Electronics| 885012206093| Top
C7| 1µF| Ceramic

Capacitor, 25V, X7R, 10%

| 1| **** 0603| Wurth Electronics| 885012206076| Top
L1| 2.2µH| DCR=10.5mΩ, Ir=8A| 1| 6.65×6.45×3.3
0mm| Wurth Electronics| 74439344022| Top
R1| 73.2KΩ| RES SMD 1%| 1| 0603| Panasonic| ERJ-3EKF7322V| Top
R2,
R3| 10KΩ| RES SMD 1%| 2| 0603| Panasonic| ERJ-3EKF1002V| Top
R4| 0Ω| RES SMD 1%| 1| 0603| Yageo| RC0603FR-070RL| Top
R5| 100KΩ| RES SMD 1%| 1| 0603| Yageo| AC0603FR-13100KL| Top
---|---|---|---|---|---|---|---
J1,
J2,
J3| | PCB Header, 40 POS| 3| 1X3| 3M| 2340-6111TG| Top
JH6, JH7, JH8,
JH9| 1598| Terminal Turret Triple 0.094″ L (Test Points)| 4| Through-Hole| Keystone Electronics| 1598-2| Top
U1| AP62500| 5A Sync DC/DC Converter| 1| QFN2030-12| Diodes Incorporated (Diodes)| AP62500SJ| Top

TYPICAL PERFORMANCE CHARACTERISTICS

Figure 8. Efficiency vs. Output Current, VIN = 12V, VOUT = 5V, L = 2.2μH, fSW = 800kHz

Figure 9. Efficiency vs. Output Current, VIN = 12V, VOUT = 3.3V, L = 1.5μH, fSW = 800kHz

Figure 10. Output Voltage Ripple, IOUT = 50mA VIN = 12V, VOUT = 5V PFM fSW = 800kHz

Figure 11. Output Voltage Ripple, IOUT = 5A VIN = 12V, VOUT = 5V PFM fSW = 800kHz

Figure 12. Output Voltage Ripple, IOUT = 50mA VIN = 12V, VOUT = 5V USM fSW = 800kHz

Figure 13. Output Voltage Ripple, IOUT = 5A VIN = 12V, VOUT = 5V USM fSW = 800kHz

Figure 14. Output Voltage Ripple, IOUT = 50mA VIN = 12V, VOUT = 5V PWM fSW = 800kHz

Figure 15. Output Voltage Ripple, IOUT = 5A VIN = 12V, VOUT = 5V PWM fSW = 800kHz

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