BQ29700EVM-610: discharge over current protection threshold

Hong Liu

Part Number: BQ29700EVM-610
Other Parts Discussed in Thread: BQ29700EVM, CSD16301Q2, CSD16406Q3

BQ29700EVM user guide shows that discharge current typical is 1A, and maximum at 5A. When I try the circuit with discharge current at 2A, the circuit triggers the over current protection threshold. My application needs load current at 2.0 – 2.2A. Is there a way setting the over current threshold externally? Or I have to replace the on board FET?

Thanks,

Hong Liu

over 8 years ago

0 Vish Nadarajah over 8 years ago

TI__Expert 6085 points

Hi Hong,
The device on the EVM is bq29700SDE with a built-in OCD threshold of 100mV. Threshold are trimmed internally ONLY.The CSD16301Q2 FET have RDS-on of ~ 29mS. V= ~ 2A ( 2 * 29m Ohm) ~116mV. Hence the device will trip. If your MAX desired discharge current is 5A, V=5A*39mOhm ~ 200mV. you may want order and try the bq29708 pp3 of the d/s)

0 Hong Liu over 8 years ago in reply to Vish Nadarajah

Prodigy 40 points

Thanks for the help, is it possible to change the FET in the BQ29700EVM board for increasing discharge current? CSD16406Q3 FET have RDS-on of 7.4m Ohm (V = 3A * 2* 7.4 = 45 mV). bq29708 is not available in DIGIKEY, can I use bq29708 instead?

Hong Liu

0 Vish Nadarajah over 8 years ago in reply to Hong Liu

TI__Expert 6085 points

Ordering the bq29708 would be the most expeditious way.

0 Hong Liu over 8 years ago in reply to Vish Nadarajah

Prodigy 40 points

Hi Vish,

I can't find any ordering information for bq29708dset on TI website, are you sure this part is available (in production)? Do you think bq29732 can be the replacement part for discharge current 3A?

Thanks,

Hong Liu

0 Miguel Angel Rios over 8 years ago in reply to Hong Liu

TI__Expert 4640 points

Hi Hong,

My suggestion is to go into the bq297xx datasheet and find the table on page 3 that shows all the available permutations of the devices. I'm positive you will find something that can fulfill your application's needs. Please ignore the devices with a superscript (2) as those are unreleased parts.

Thanks

M

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BQ29700EVM-610: discharge over current protection threshold