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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
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
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
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
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
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