How To Simplify USB PD 1-4s Charging Design

In this video, we'll take a look at a buck/boost battery manager IC that can charge your device battery using standard USB PD voltages—but it can also work in reverse, providing output to power or charge other devices.

The BD99954 is a battery management IC from ROHM Semiconductor. It's available in a QFN package (40-pin, 0.4mm pitch 5mm x 5mm, denoted as BD99954MWV) and a wafer-level CSP package (41-ball, 0.4mm pitch 2.6mm x 3mm, denoted as BD99954GW) which is designed for use in space-constrained applications (say, mobile devices).

In this video, we'll go through two demos using this component: one with the BD99954 charging our simulated battery from an external supply and one with the BD99954 powering the load from the battery. 

We'll be using the BD99954 eval kit, which utilizes the QFN package. That means we'll be dealing with the following specs (from the datasheet):

 

Check out the eval kit below to better follow along with the video:

 

 

Demo #1

In the first demo, you can see the BD99954 charging our internal battery.

For that, we have our 15 V power supply connected to the B bus, our SMU connected to Vbat, and a DMM connected to VSys so we can show that there's a constant output to the system, as well. The power supply is set to 15 V, although the BD99954 can take any USB PD standard voltage.

 

 

The SMU is set up to be at a 5.5 V sync so that it acts much like a depleted two-cell battery. Check out the rest of this demo in the above video.

 

Demo #2

For our second demo, we have software that can drive the BD99954 and set all of its parameters. In the software, we have the bus current limit set to 1.5 amps and we can set the parameters for our automatic JEITA-compliant charging profile.

The VSYSREG set is programmed to about a 7 V precharge. The threshold is at 6 V and the fast charge reg set is at 8.4 V. So, as we ramp up our simulated battery, we will step through each of those stages in the charging profile, and the appropriate current will be output at each stage as well. See how we set up the software side in the above video.

 

Conclusion

You can see that this single BD99954 Buck/Boost charger enables a simpler design by allowing you to use a single power path to charge from and output at standard USB PD voltages. It’s intended for use in modern designs with USB Type-C, supports 1-4 cell batteries, and pairs well with ROHM’s USB PD devices and wireless charging solutions. For datasheets and more information on the BD99954 and this evaluation kit, visit ROHM.com.

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