LM7480-Q1: Omitting Reverse Battery Protection DGATE, Using Load Disconnect Switch Control HGATE

Senthil Seveelavanan18

Part Number: LM7480-Q1
Other Parts Discussed in Thread: LM74800-Q1, LM74502-Q1, LM7481-Q1,

Tool/software:

Hello,

Referring to the image from the datasheet below.

I want to omit Q1, the FET relating to ideal diode functionality.
But use Q2, the FET relating to load switch functionality.
Possibly in a back to back configuration, for reverse voltage protection.

My goal is to provide reverse voltage protection, but to allow reverse current flow.
It would be used on a battery interface, where the battery would be both charged and discharged.

What is the recommended approach?

If Pin A and Pin C are connected together, at the same voltage, and Q1 is not populated, would Q2 operate normally?

Thanks

EDIT: I don't want to use the LM74801-Q1 variation, because i will be using the LM74800-Q1 elsewhere in my design.

9.2

8 months ago

0 Shiven Dhir 8 months ago

TI__Mastermind 47230 points

Hi Senthil,

Can you check LM74502-Q1 from our portfolio once?

LM74502-Q1 data sheet, product information and support | TI.com

Regards,

Shiven Dhir

0 Senthil Seveelavanan18 8 months ago in reply to Shiven Dhir

Prodigy 160 points

Hello Shiven,

Your recommendation of the LM74502-Q1 would be exactly what I would be wanting functionally.
But I'm trying to re-use a LM7480-Q1 or LM7481-Q1, which would exist elsewhere in the design, for BOM consolidation.

How would I achieve LM74502-Q1 like behaviour with LM7480-Q1 or LM7481-Q1?

Thanks : )

0 Shiven Dhir 7 months ago in reply to Senthil Seveelavanan18

TI__Mastermind 47230 points

Hi Senthil,

Unfortunately, reverse current blocking cannot be disabled in LM74800-Q1. Removing Q1 and shorting A to C should be fine but you will lose reverse polarity protection then.

Regards,

Shiven Dhir

0 Senthil Seveelavanan18 7 months ago in reply to Shiven Dhir

Prodigy 160 points

Hi Shiven,

"Removing Q1 and shorting A to C should be fine but you will lose reverse polarity protection then".

If I used 2 back to back FETS with HGATE, would I be correct in thinking this provides reverse voltage protection but NOT reverse current protection.
Which is my goal.

Thanks

0 Shiven Dhir 7 months ago in reply to Senthil Seveelavanan18

TI__Mastermind 47230 points

Hi Senthil,

Can you show how are you planning to back-to-back FETs with only HGATE.

Regards,

Shiven Dhir

0 Senthil Seveelavanan18 7 months ago in reply to Shiven Dhir

Prodigy 160 points

0 Shiven Dhir 7 months ago in reply to Senthil Seveelavanan18

TI__Mastermind 47230 points

Hi Senthil,

This scheme cannot work. During reverse polarity, Q1 FET will turn-on. How?

Since VIN (source of Q1) will be negative, and its gate (HGATE) will be at zero volts initially, VGS will be high, and FET will be ON.

VS pin will read negative voltages and damage the controller. Even VOUT will read negative voltage, and no protection will be offered.

I would still recommend using LM7502 which is a very easy implementation.

Regards,

Shiven Dhir

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LM7480-Q1: Omitting Reverse Battery Protection DGATE, Using Load Disconnect Switch Control HGATE