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# LM74701-Q1: LM74701-Q1 Full conduction mode VdsClamp mdoe:

Part Number: LM74701-Q1

Hi  engineer:

I am evaluating LM74701-Q1 for my project, and I tested your EVM these days.

1. Full conduction mode:  I tested the EVM, the Voltage difference between Cathode and Anode is I * rds(on), not 50mV, and when load is up to 60mA， the Gate voltage is equeal wiht VCAP,  so I think the mosfet is full condution.

2.  VdsClamp  mdoe: if Anode is Negative votlage,  the voltage is under Anode POR threshold, How does the Mosfet be driven on?

3 . The absoute voltage of Anode is 65V, if we don't add TVS, how to pass ISO7637-2 2A /2B test?

Thanks

Johnsin  Tao

• Hi Johnsin,

Please find my response inline below,

1. Full conduction mode:  I tested the EVM, the Voltage difference between Cathode and Anode is I * rds(on), not 50mV, and when load is up to 60mA， the Gate voltage is equal with VCAP,  so I think the mosfet is full conduction.

The LM74701-Q1 will try to regulate the FET source-drain voltage to around V(AK REG) = 20mV. Once the load current is high enough that the product of  Iload * Rds(on) is greater than 20mV, the LM74701-Q1 will start to pull the gate high to VCAP. This is full conduction mode,

2.  Vds Clamp mode: if Anode is Negative voltage,  the voltage is under Anode POR threshold, How does the Mosfet be driven on?

When the Anode voltage drops below cathode voltage by VCLAMP = 40V, the internal circuit drives the gate-source voltage such that the voltage across the FET is maintained at  VCLAMP voltage. The internal VDS Clamp circuit is designed to operate even when Vanode is negative.

3 . The absolute voltage of Anode is 65V, if we don't add TVS, how to pass ISO7637-2 2A /2B test?

ISO7637-2 2A /2B are very short duration and low energy pulses. These can be easily suppressed using  input and output capacitances.