nRF52840 Battery Circuit Design

[Radio]

Hi All,

I am currently designing a BLE module using nRF52840 chip which works with battery.

In the nRF52840 DK, it uses a Power Switch Driver (SC728CSTRT) from Semtech. However, the particular component from Semtech has reached End Of Life.

I found another similar chip from Semtech (SC33020HCSTRT) with reverse blocking. My question is:

1. What is the correct way of connecting this component. In the old SC728CSTRT datasheet there are two 1.0uF capacitors connected to the ground at the input (VIN) and the output VOUT. But it wasn't there in nRF52840 DK schematic. A similar connection is suggested in the new SC33020HCSTRT datasheet as well. Below I have attached snapshot of my circuitry. Is my design is OK? Do you have any suggestions?

2. As shown above, I have connected the Enable pin with VIN. Is this acceptable?

3. Is it good idea to have a Power Switch Driver circuit?

Thanks a lot!!

[Andreas]

Hi,

 

1) Ideally you should replicate the instructions from the datasheet. In this case though the idea is probably that there is enough capacitance already on the output that the one 1µF is not needed.

2 and 3) Not sure if this is going to do much in this case, as the high threshold is max 1.0V. The most critical thing I see here is there might not be enough capacitance on the supply, when nRF52840 draws a lot of current the battery will not be able to supply enough current to avoid the voltage dropping. Other than that, running the nRF52840 directly off the battery is generally not a problem.

 

Best regards,

Andreas

[Radio]

Hi Andreas,

Many thanks for the reply. I am bit not clear about the high threshold value and why it is not going to do much in the case.

In the datasheet they mention EN - GND max is 6.0 V. Also EN input high threshold is 1.0 V.

In my case if I am to enable the chip what should I do?

Thanks!

[Andreas]

Hi,

 

If you want to enable the chip you should bring the EN to 1.0V or higher. 6V is the max rating and exsceeding that might either damage the device or have it operate out of spec, I do not know this part in detail but you should avoid it.

 

Best regards,

Andreas

[Radio]

Hi Andreas,

Thank you very much for the support.