TPS51601A: MPPT Lead Acid Charging

Also, the datasheet shows the Vdd pin connected only to ground through a capacitor. Am assuming that this is a decoupling cap and that Vdd is also connected to +5v.

Hi Nicholas,

You are right, VDD pin should be connected to +5V supply.

I don't know what kind of FET you are considering for MPPT charger, but usually it's > 50V so a higher gate voltage is needed than 5V. In this case, TPS51601A won't be a good solution. 

TI does have a reference design for MPPT controller, please refer to below link and see if it works for you.

https://www.ti.com/lit/pdf/tiduej8a

Regards,

Weidong

Thanks!

I am planning on using the CSD18502Q5B. We currently use this MOSFET in a similar app that uses the SM72295 full bridge driver

In that app, we also use a Coilcraft SER2918H-103KL 10uH 30A inductor. I am thinking about using that in this design as well but since I only need about 15A of charge current, this part might be a bit of overkill.

I am assuming that Al electrolytics should be used for Cin and Cout

The CSD18502 looks very similar to the CSD17302 in most of its characteristics 

Other than the missing Vdd connection in the datasheet, page 11, is the example design complete with no other missing connections?

Other than the missing Vdd connection in the datasheet, page 11, is the example design complete with no other missing connections?

Thanks!

I am planning on using the CSD18502Q5B. We currently use this MOSFET in a similar app that uses the SM72295 full bridge driver

In that app, we also use a Coilcraft SER2918H-103KL 10uH 30A inductor. I am thinking about using that in this design as well but since I only need about 15A of charge current, this part might be a bit of overkill.

I am assuming that Al electrolytics should be used for Cin and Cout

Hi Nicholas,

That's right, there is no other missing connections other than VDD to +5V.

Regards,

Weidong

Thanks, any recommendations on the other parts?

Thanks

You can refer to the below E2E threads or application notes about MPPT charger design:

https://e2e.ti.com/support/power-management/f/power-management-forum/31010/mppt-based-lead-acid-charger-using-bq2031

https://e2e.ti.com/support/power-management/f/power-management-forum/71254/bq2031-based-mppt-charger

http://www.ti.com/litv/pdf/slva378

https://e2e.ti.com/support/power-management/f/power-management-forum/115676/bq24650-used-as-mppt-solar-charger-for-lead-acid-battery

Regards

Weidong

One more question: After driving PWM, how can I ensure that both gate drive pins are LOW i.e. both MOSFETS are off?

Just to be clear, I am using the 51601 as the controller. 

You can leave PWM pin floating, or drive PWM pin between 1.5V and 2.5V so that both FETs are off.

Regards,

Weidong

I understand, my controller is an AM3354.  I am using a PWM timer output to drive the 51601 and implementing my own charger algorithm. 

Since I will be driving PWM from an output, I will need a way to float that pin when necessary.

If you float PWM, TPS51601A has internal divider which can drive the voltage to 3-state voltage and turn off both FETs.

Regards,

Weidong

Thanks, I noticed that in the datasheet equ. circuit and scope shots.