DIODES INCORPORATED

General Description

The AL88902Q is a synchronous buck converter featuring internal compensation and an adjustable switching frequency up to 2.5MHz. It integrates a 120mΩ high-side power MOSFET and a 55mΩ low-side power MOSFET to achieve high-efficiency DC-DC conversion.

The AL88902Q supports a continuous load current of up to 2.5A, delivering efficiencies as high as 95%. Its current mode control operation facilitates easy loop stabilization across a wide range of output loads, making it suitable for both Constant Voltage (CV) and Constant Current (CC) applications.

The device simplifies board layout and reduces space requirements due to its high switching frequency and integrated smaller-sized inductor and MOSFETs, making it an ideal solution for power management.

The AL88902Q is available in the standard Green U-QFN4040-16 package.

Applications

• Automotive infotainment
• Automotive exterior and interior LED lighting systems
• Automotive motor controls
• Automotive and industrial power systems

Key Features

• AEC-Q100 Grade 1 qualified
• Input Voltage (VIN) range: 3.8V to 60V
• Wide Output Voltage (VOUT) range: 0.8V to near 100% of VIN
• VOUT Accuracy: 1%
• VFB adjustable through SS/TR Pin
• Synchronous Rectification with > 95% efficiency @12V
• High-Side Power MOSFET: 120mΩ
• Low-Side Power MOSFETs: 55mΩ
• Low Quiescent Current: 43μA
• Switching Frequency: 300kHz to 2.5MHz
• Force PWM or PFM Mode via MYSNC pin
• Synchronization to External Clock
• Programmable Startup Control
• Startup with Pre-Biased Output
• External Soft-Start with Tracking
• High Voltage Enable Pin with High Precision
• Protection and Diagnosis Functions
• Power Good (PG) Detection
• Thermal Shutdown Protection
• Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
• Halogen and Antimony Free. "Green" Device (Note 3)

The AL88902Q is suitable for automotive applications requiring specific change control; this part is AEC-Q100 qualified, PPAP capable, and manufactured in IATF 16949 certified facilities.

For more product definitions, visit: https://www.diodes.com/quality/product-definitions/

Notes

1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS), 2011/65/EU (RoHS 2) & 2015/863/EU (RoHS 3) compliant.
2. See https://www.diodes.com/quality/lead-free/ for more information about Diodes Incorporated's definitions of Halogen- and Antimony-free, "Green" and Lead-free.
3. Halogen- and Antimony-free "Green" products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds.
4. Automotive products are AEC-Q100 qualified and are PPAP capable. Refer to https://www.diodes.com/quality/.

Evaluation Board

Figure 1: AL88902QFVBW EVM Top View

A photograph of the AL88902QFVBW Evaluation Module (EVM) top side, showing the AL88902Q IC, passive components (capacitors, resistors), inductors, and connectors labeled for VIN, VOUT, GND, and other test points.

Board Layout

The following figures illustrate the PCB layout for the AL88902QFVBW EVM.

Figure 2: PCB Top Layer (Top View)

A diagram showing the top copper layer of the AL88902QFVBW EVM PCB layout. It illustrates the routing of power and signal traces, component placement outlines, and via locations.

Figure 3: PCB Second Layer (Top View)

A diagram showing the second layer (internal power plane) of the AL88902QFVBW EVM PCB layout. It depicts the ground plane and power distribution.

Figure 4: PCB Third Layer (Top View)

A diagram showing the third layer (internal signal layer) of the AL88902QFVBW EVM PCB layout. It illustrates signal routing and connections.

Figure 5: PCB Bottom Layer (Top View)

A diagram showing the bottom copper layer of the AL88902QFVBW EVM PCB layout. It illustrates component placement outlines and routing.

Evaluation Board Schematic

Figure 6: Schematic Circuit

A circuit schematic diagram for the AL88902QFVBW EVM. It shows the AL88902Q IC connected to input/output capacitors, resistors for feedback and configuration, an inductor, and jumpers for setting various operational modes (FS, MSYNC, EN, BIAS).

Quick Start Guide

The AL88902QFVBW-EVM board has a simple layout and allows access to the appropriate signals through test points. To evaluate the performance of the AL88902Q, follow the procedure below:

1. Insert jumpers to configure the EVM board setting as described in the Application Information sections of the device datasheet.
2. Use jumper JP3 (100kΩ to VIN) to set the device enabled, or JP2 (GND) to disable the device.
3. Remove jumpers JP2 and JP3 and connect an external voltage source on the EN pin directly.
4. Use jumper JP5 to set FS to default 500kHz (VCC) or 2.5MHz (GND).
5. Use jumper JP1 to set MSYNC to forced PWM (VCC) or PFM (GND) operation.
6. Remove jumper JP1 and force an external clock source on the MSYNC pin for synchronization with a positive edge trigger and PWM.
7. Use jumper JP6 for default external soft start (C7) of 2ms.
8. Remove jumper JP6 and use jumper JP7 (VCC) for internal soft start of 1.7ms.
9. Use jumper JP8 to connect the BIAS pin to PGND.
10. Use jumper JP9 to connect the BIAS pin to VOUT.
11. Remove JP8 and JP9 and connect an external voltage source on the BIAS pin (<15V).
12. Connect a 12V power supply between the VIN and PGND terminals. Make sure the power supply is turned off.
13. Connect an adjustable current or resistive load to the VOUT and PGND terminals.
14. Turn on the power supply. Do not turn on the power supply until all connections are completed and fully checked.
15. The EVM board should now power up with a 5V output voltage.
16. Increase the load current and observe the output voltage change.
17. Check for the stable operation of the SW and VOUT signal on the oscilloscope.
18. Measure the switching frequency on the SW probe jack in the EVM board.
19. Measure the output ripple on the VOUT probe jack in the EVM board.

Measurement/Performance Guidelines

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.

Bill of Materials

Typical Performance Characteristics

The following graphs and oscilloscope traces illustrate the typical performance of the AL88902Q converter under various conditions (TA = +25°C, VIN = 12V, VOUT = 5V, fsw = 400kHz).

Figure 7: PWM Load Regulation

This graph shows the output voltage (VOUT) in Volts plotted against the output current (IOUT) in Amperes. Multiple lines represent different input voltages (VIN) from 24V to 60V, demonstrating how the output voltage remains stable across varying load conditions.

Figure 8: PWM Line Regulation

This graph displays the output voltage (VOUT) in Volts plotted against the input voltage (VIN) in Volts. Multiple lines represent different output currents (IOUT) from 0A to 2.5A, illustrating the output voltage stability as the input voltage changes.

Figure 9: Output Ripple, VIN=12V, VOUT = 5V @2.5A, PWM

This oscilloscope trace shows the output voltage ripple (VOUT AC) in millivolts per division, the inductor current (IL) in Amperes per division, and the switch node voltage (VSW) in Volts per division. The time base is 2µs/div, demonstrating the output ripple under a heavy load condition (2.5A) in PWM mode.

Figure 10: Output Ripple VIN = 12V, VOUT = 5V @50mA, PWM

This oscilloscope trace shows the output voltage ripple (VOUT AC) in millivolts per division, the inductor current (IL) in Amperes per division, and the switch node voltage (VSW) in Volts per division. The time base is 2µs/div, demonstrating the output ripple under a light load condition (50mA) in PWM mode.

Figure 11: Load Transient, IOUT = 50mA to 2.5A to 50mA, PWM

This oscilloscope trace captures the transient response to a load change from 50mA to 2.5A and back to 50mA. It shows the output voltage (VOUT AC) and output current (IOUT) in Amperes per division. The time base is 100µs/div, illustrating the converter's ability to handle rapid load variations in PWM mode.

Figure 12: Load Transient, IOUT = 50mA to 2.5A to 50mA, PFM

This oscilloscope trace captures the transient response to a load change from 50mA to 2.5A and back to 50mA. It shows the output voltage (VOUT AC) and output current (IOUT) in Amperes per division. The time base is 100µs/div, illustrating the converter's ability to handle rapid load variations in PFM mode.

Important Notice

1. DIODES INCORPORATED (Diodes) AND ITS SUBSIDIARIES MAKE NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO ANY INFORMATION CONTAINED IN THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY RIGHTS (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).

2. The Information contained herein is for informational purpose only and is provided only to illustrate the operation of Diodes' products described herein and application examples. Diodes does not assume any liability arising out of the application or use of this document or any product described herein. This document is intended for skilled and technically trained engineering customers and users who design with Diodes' products. Diodes' products may be used to facilitate safety-related applications; however, in all instances customers and users are responsible for (a) selecting the appropriate Diodes products for their applications, (b) evaluating the suitability of Diodes' products for their intended applications, (c) ensuring their applications, which incorporate Diodes' products, comply the applicable legal and regulatory requirements as well as safety and functional-safety related standards, and (d) ensuring they design with appropriate safeguards (including testing, validation, quality control techniques, redundancy, malfunction prevention, and appropriate treatment for aging degradation) to minimize the risks associated with their applications.

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