LM74930-Q1: Polarity inversion protection + battery charger

Jimmy ROUX

Part Number: LM74930-Q1
Other Parts Discussed in Thread: LM74502H, , BQ21040, LM7480-Q1, LM74800-Q1

Tool/software:

Hi,

I am working on a new design powered by an INR18650 (3.7V) cell and I would like being able to achieve these two functions :

- Protecting the circuit against polarity reverse as the cell will be removable

- Being able the charge the cell (from VOUT to VIN) from a USB port (over a BQ charger).

As far as I understand the LM74502H with common source MOSFETs should allows current to flow either from VIN to VOUT and from VOUT to VIN, so as long a cell is in place with the right polarity, it should be possible to charge it from VOUT..

Am I right ? Is it the good circuit to achieve this from your point of view ?

Thanks for your help

15 days ago

0 Shiven Dhir 15 days ago

TI__Mastermind 24845 points

Hi Jimmy,

LM74502H can't be used as its minimum startup voltage is 3.9V and your cell is rated for 3.7V.

LM74930-Q1 can be used here.

Regards,

Shiven Dhir

0 Jimmy ROUX 15 days ago in reply to Shiven Dhir

Prodigy 30 points

Hi Shiven,

Thank you for your reply.

Just to be sure, can you confirm that LM74930-Q1 can be used for dual direction current (using back to back mosfets) and so allowing to charge a battery (inr18650) with a charger such as BQ21040 ?

Best

Jimmy

0 Shiven Dhir 14 days ago in reply to Jimmy ROUX

TI__Mastermind 24845 points

Hi Jimmy,

Yes, It can be used. Although it is important to note that startup needs to happen in forward direction first.

By this I mean, battery should be plugged in, and controller should be on. After this MODE pin decides the flow of bidirectional current.

Regards,

Shiven Dhir

0 Jimmy ROUX 14 days ago in reply to Shiven Dhir

Prodigy 30 points

Hi Shiven,

Again, thank you for your help.

I noticed that the LM74930-Q1 is mentioned as 4V to 65V but also as 3V to 65V on the same page, can you confirm if 3V is correct ? : www.ti.com/.../LM74930-Q1

Also I found the LM7480-Q1 which looks very interesting (simpler) as well for the same application. Can you confirm me if this also work (i see there is no mode pin on this one) ?

Thanks a lot

Best

Jimmy

+1 Shiven Dhir 13 days ago in reply to Jimmy ROUX

TI__Mastermind 24845 points

Hi Jimmy,

LM74800-Q1 will not support bidirectional current. You can disable unwanted features of LM74930-Q1 for easier implementation.

LM74930-Q1 will work as far as VS>VS_PORR.

Regards,

Shiven Dhir

0 Jimmy ROUX 13 days ago in reply to Shiven Dhir

Prodigy 30 points

Dear Shiven,

Ok very clear, thanks a lot for your help

Best

Jimmy

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LM74930-Q1: Polarity inversion protection + battery charger