The accuracy of DC-DC power supply is becoming more and more precise with the accuracy of FPGA

FPGA manufacturers continue to use more advanced processes to reduce device power consumption and improve performance. At the same time, FPGAs have more stringent requirements on the accuracy of power supplies, and the voltage must be maintained within very strict tolerances. If the power supply voltage range exceeds the specification requirements , It will affect the reliability of the FPGA, and even lead to the failure of the FPGA.

Generally, in addition to power supply accuracy that affects the stability and reliability of the entire system, a higher-precision power supply can also help us reduce system power consumption.

FPGA manufacturers continue to use more advanced processes to reduce device power consumption and improve performance. At the same time, FPGAs have more stringent requirements on the accuracy of power supplies, and the voltage must be maintained within very strict tolerances. If the power supply voltage range exceeds the specification requirements , It will affect the reliability of the FPGA, and even lead to the failure of the FPGA.

Whether it is Intel (Altera) FPGA or Xilinx FPGA, the power supply accuracy requirements are clearly put forward in the data sheet, and the most demanding is the power supply of the core and high-speed transceiver. For example, Intel’s Cyclone V, Cyclone 10 GX, Arria10, and Stratix 10 require power supply accuracy within ±30mV.

The accuracy of DC-DC power supply is becoming more and more precise with the accuracy of FPGA

The power supply requirements (±30mV) on the core and transmitter data sheets of Arria10:

Stratix10 core and transmitter power supply requirements (±30mV) on the data sheet:

If Stratix10 needs to support 26.6G transceiver, the accuracy of the power supply of the transceiver must be within ±20mV:

Xilinx’s Artix 7, Kintex7, Virtex 7 and other devices also require power supply accuracy within ±30mV, while KU+ and VU+ devices require power supply accuracy within ±22mV.

Kintek Ultrascale+’s core and transmitter data sheet power requirements (±22mV):

It can be seen that the power supply accuracy of the new generation FPGA is around ±20-30mv, and it is already one of the most demanding devices on the power supply accuracy in the single board.

Since the output accuracy is theoretically calculated, and does not consider the interference and errors introduced by the single-board PCB wiring and other external equipment, when the actual product is designed, the output accuracy of the power supply must not only meet the requirements in the data manual, but also must reserve a certain amount The margin, usually in the design, we will reserve 50%-100% margin to ensure the long-term reliable operation of the system.

The steady-state DC accuracy of the power supply and its calculation method

The steady-state DC accuracy of the power supply mainly depends on two factors: voltage adjustment accuracy and output voltage ripple. There is a misunderstanding here. Many engineers only use the voltage output accuracy in the DC-DC data sheet to judge whether the device meets the requirements. In fact, this is incorrect.

First of all, many DC-DCs require an external feedback resistor to determine the final output voltage. The voltage adjustment accuracy in the data sheet refers to the output accuracy of the chip itself, and does not calculate the deviation introduced by the feedback circuit. Secondly, the voltage output accuracy on the device data sheet does not include the output voltage ripple, and the two must be superimposed to obtain the correct DC steady-state accuracy.

The calculation formula for the correct steady-state DC accuracy of the power supply is as follows:

DC steady-state accuracy of the power supply = device output accuracy (here, the accuracy at full temperature and full load is required. Many device manuals only give typical values, so be careful) + ripple + error introduced by the accuracy of the external feedback resistor.

The effect of high-precision power supply on reducing FPGA power consumption

Let’s take an example. The typical working voltage recommended by an FPGA is 0.85V, the highest working voltage is 0.88V, and the lowest working voltage is 0.82V. Assuming that the actual steady-state DC accuracy of the power supply DC-DC is ±30mV, then the DC-DC must be just right Working at 0.85V, if the voltage is lower, it will be lower than the FPGA’s requirement for the lower voltage limit.

The Links:   CM1000DU-34NF NL6448BC26-27C