R Classroom | Evaluation of Rohm's ultra-high-efficiency battery management solution evaluation board "REFLVBMS001-EVK-001" and verification of the low power consumption and load capacity of the battery management solution

※The article is reprinted from Power Network, the author is Yaxiong

Good guy, I was really shocked when I received the evaluation board. Although the board is small, there are really a lot of supporting materials. One is the precautions, one is the quick start guide, and the other is the user manual. If you look closely, the board is still a 4-layer board, which is a bit of a luxury.

The battery voltage was only 0.05V when I got it, almost gone, so I quickly charged it. The input voltage range from 4.5 to 5.5V is shown in the technical manual, so I chose 5V charging. The charging current is 15mA.

For the built-in 27mAh battery, it can be fully charged in 2 hours. Sadly, when I wanted to test the charging curve characteristics, I forgot to change the 24V back to 5V and the charging circuit smoked. The relevant charging parameters can no longer be tested.

The chip used in the charging circuit is BD71631QWZ . The schematic is shown below. The charging current can be changed, and there is also a charging indicator light function.

Disassemble the battery, use Tektronix linear power supply to simulate the battery, and connect a 6-and-a-half-digit ammeter in series. The current at the output voltage of 1.8V is: 0.5uA. To be honest, this is the DCDC circuit with the lowest power consumption I have ever seen. For a 27mAh battery, it can last for 3 years without any problem when it is turned off. It’s not that you can’t stand by for longer, but the battery itself also has a self-discharge effect. Among them, the DCDC chip only has 180nA, and the other 270nA is consumed by the voltage monitoring chip.

I have seen this thin battery used in Bitcoin electronic keys. Let me show you the real thing. This kind of situation requires very low standby power consumption. A wallet the size and thickness of a business card with an ink screen and a battery. If I had known about this solution two years earlier, I could have done it. Oh, I missed it.

The DCDC chip uses BD70522GUL , which has 9 voltage output options. The output voltage is controlled through the VSET1 and VSET2 pins. The package is also very small, only 1.76mm x 1.56mm x 0.57mm.

The nominal load capacity of BD70522GUL is 500mA in the output voltage range of 1.2V~3.3V. Let's test it with an electronic load.

After actual testing, the nominal parameters can be achieved. More complex tests will be performed below.

The probe uses a high-voltage differential probe, which has a little burr, but the results can illustrate the problem. Divided into 3 situations for testing.
A. The current changes from 0% to 100%, and the voltage output has no overshoot or undervoltage.
B. When the battery is fully loaded, the voltage output does not overshoot or undervoltage.
C. Under no-load conditions, when the battery is connected, the voltage output does not overshoot or undervoltage.

After testing the above key parameters, it is shown that Rohm's battery management solution is relatively excellent, especially in terms of low power consumption and load capacity. You can use these chips in your project with confidence.