BQ24610: sometimes LODRV FET burns

daeseon kim

Prodigy 100 points

Part Number: BQ24610

this is my shcematic

and I'm using rocker switch(J2)

when I turn on rocker switch Q5(LODRV FET) burns sometimes

I tried to change FET(larger Id) to FDS8638 but it's same

1. Is there a problem with the rocker switch on/off noise?

2. How can I select Gate resister value

3. FDS8447 that I'm using has 19~27nC Qg but sis412DN(reference part in BQ24610's datasheet) has 3.8nC. is this not good that has large Qg?

if you have another solution tell me pls

thanks

over 4 years ago

0 daeseon kim over 4 years ago

Prodigy 100 points

I upload schematic cause it's not seem

0 Kedar Manishankar over 4 years ago in reply to daeseon kim

TI__Mastermind 24075 points

Hi Daeson,

What is the purpose of the rocker switch, and can you describe the test conditions when the switch is being triggered? FDS8447 is used on the BQ24610EVM so this FET selection is not an issue. Gate resistor slows down turn off and turn on time of the switching MOSFET. You can use a 4.7 or 10 ohm gate drive resistor. The higher the value of gate drive resistance resistance, the slower the turn on/off time, the more heat dissipated and lower efficiency.

0 daeseon kim over 4 years ago in reply to Kedar Manishankar

Prodigy 100 points

Hi Kedar Manishankar,

sorry, I fogot to explain rocker switch.

The switch is connect to J2 and VDD_24V is supply to motor, wifi module, and camera.

if I use Gate resistor then should I add both Q5 and Q4 with same value?

thanks!

0 Kedar Manishankar over 4 years ago in reply to daeseon kim

TI__Mastermind 24075 points

Hi Daeson,

Generally the resistor is used to slow down gate drive to reduce EMI, so the main benefit is only from slowing down the HSFET. Is damage occurring when rocker switch is disconnecting the 24V input supply from SYS, while the part is switching? Or is it the other way around?

0 daeseon kim over 4 years ago in reply to Kedar Manishankar

Prodigy 100 points

Hi Kedar Manishankar

It never damaged while the part is switching.

It usally damaged when rocker switch connecting(24V input supply from SYS)

Thanks

0 Kedar Manishankar over 4 years ago in reply to daeseon kim

TI__Mastermind 24075 points

Hi Daeson,

When LSFET is off, both intrinsic body diode of HSFET and LSFET will block conduction path from the VIN/VSYS rail to GND. I do not see any path through which the LSFET is conducting current so that it could be damaged. If rocker switch is not used in the system, do you see any damage?

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BQ24610: sometimes LODRV FET burns