Switching Regulator Controllers Compatible with FPGA Power Supply Requirements : Reasons for the need for higher accuracy FPGA power supply

The BD95601MUV and BD95602MUV are switching regulator controller ICs designed to support the low-voltage, large-current requirements of power supplies in recent years. In addition to high efficiency and numerous protection functions, these ICs exhibit optimal performance as power supplies for FPGAs and CPUs, which require high voltage accuracy and superior stability.

These power supply ICs have been adopted into a power supply module board of the Mini-Module Pluse evaluation kit for Xilinx’s 7 Series FPGAs and ZynqR-7000 All Programmable SoC, developed jointly by ROHM and Avnet, Inc. There are several crucial reasons for the adoption.

While the accuracy of voltage that is required may vary somewhat by the type of power supply involved, as an example suppose that the required accuracy is ±3% for a 1V output. Because the system voltage such as 5V/3.3V normally carries a ±5% accuracy, in terms of percentages ±3% may appear stringent. However, the actual allowable voltage is naturally less.

3.3 V±3% means 3.3 V±99 mV, as opposed to 1.0 V±3% for 1.0 V±30 mV.

Because this is an accuracy requirement including ripple voltage, it is an extremely stringent condition for switching regulators. Even if the average output voltage can be set precisely to 1V, the ripple voltage needs to be ±30mV or less. Because the output voltage is subject to fluctuations due to load regulation or load transitions, the ripple voltage must be minimized while ensuring the basic accuracy.

The properties of the BD95601MUV and BD95602MUV are designed to satisfy these power supply requirements from the FPGA.

• ・H3Reg^TM synchronous rectification buck switching regulator controller enabling high-speed
   transient response characteristics
• ・1 ch: BD95601MUV, 2 ch: BD95602MUV
• ・Maximum efficiency: 95%+
• ・Selectable between light load and continuous PWM modes.
   (Quiet light load mode: BD95602）
• ・Adjustable soft start reduces inrush current during startup
• ・Power Good output
• ・Multiple protective functions: Over Current Protection (OCP), short circuit protection, Thermal Shut Down
    (TSD), Under Voltage Lockout (UVLO)

Basically, the two products are both high-efficiency, synchronous rectifying buck controllers, providing a light-load mode and capable of maintaining high efficiency when accommodating light load. The reference voltage of 0.75V/0.7V corresponds to the low voltage, the ±1% accuracy is better than the ±3% figure mentioned above, and basically they are low-ripple products. In addition, ROHM’s proprietary control mode H3Reg provides an extremely fast load transient response capability. These features permit the highly accurate and stable maintenance of the output voltage.

• Switching regulator controller IC