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LM7480-Q1: Issue in getting HGATE output

Avinav Anand

Prodigy 20 points

Part Number: LM7480-Q1

Tool/software:

Hi,

We are using LM74801QDRRRQ1 for reverse battery protection at input voltage of 24VDC and using it for 200V load dump protection. The output 24VDC is fed to six different High Side Drivers. The control signal for these drivers is coming from MCU. We notice that it's able to drive only 5 drivers. As soon as we try to drive sixth driver, 24V output becomes low. HGATE becomes low and hence the IC is not able to provide 24V output when the sixth driver is also connected. We are using IAUC120N06S5N017 MOSFETs at HGATE and DGATE.

Noticeable Points

1. What might be the reason that HGATE becomes low when the sixth driver is connected?

2. The system behaves as expected during steady state i.e. once it becomes ON, it remains ON.

3. When the system is switched ON/OFF, then only we encounter this issue. What can be the reason for this behavior?

Regards

Avinav

over 1 year ago

0 Shiven Dhir over 1 year ago

TI__Mastermind 47460 points

Hi Avinav,

Welcome to E2E!

Do you have waveforms to share?

Please measure VIN,VCAP,HGATE,VOUT

Regards,

Shiven Dhir

0 Avinav Anand over 1 year ago in reply to Shiven Dhir

Prodigy 20 points

The above waveforms have been captured when only 5 rivers are operating (even though we are trying to drive all 6 drivers).

The above waveforms have been captured when all drivers are switched ON. VOUT becomes low in this case.

0 Shiven Dhir over 1 year ago in reply to Avinav Anand

TI__Mastermind 47460 points

Hi Avinav,

Thanks for the waveforms. I hope charge pump is scaled according to the condition stated in the datasheet.

Regards,

Shiven Dhir

0 Avinav Anand 11 months ago in reply to Shiven Dhir

Prodigy 20 points

Hi Shiven!

Thanks for your support!

Q1 & Q2 both MOSFETs are working now,

Without Load =>> Power Cycle applying =>> Circuit is working okay

but

At Loaded Condition =>> Power cycles applying =>> Facing a new problem =>> Q1 MOSFET is getting short (Drain to Source) and burnt.

Kindly give some suggestions to resolve it.

0 Shiven Dhir 11 months ago in reply to Avinav Anand

TI__Mastermind 47460 points

Hi Avinav,

Q1(HSFET) damaging can be because of MOSFET SOA violation.

You can use this tool to scale your startup.

FET-INRUSH-SOA-CALC Calculation tool | TI.com

Regards,

Shiven Dhir

0 Avinav Anand 11 months ago in reply to Shiven Dhir

Prodigy 20 points

Hi Shiven,

we are using IAUC120N06S5N017 MOSFET for HGATE and DGATE as well.

I have attached my working circuit also. Refer this and give your suggestions.

0 Shiven Dhir 11 months ago in reply to Avinav Anand

TI__Mastermind 47460 points

Hi Avinav,

If power cycle with load is damaging the FET, it is because you are violating the FET SOA.

FET is turning on slowly and will have very high PD.

where PD= VDSxCurrent (inrush current + load)

Increasing the dvdt cap can help.

Although it is advisable to not turn-on downstream load until VOUT is charged.

Regards,

Shiven Dhir

0 Avinav Anand 11 months ago in reply to Shiven Dhir

Prodigy 20 points

capacitor is okay as per recommendations.

0 Shiven Dhir 11 months ago in reply to Avinav Anand

TI__Mastermind 47460 points

Hi Aviv,

I am unsure if there is any recommendation for dvdt cap as it depends on the system needs

Regards,

Shiven Dhir