CSD17573Q5B: Residual voltage on the MOSFET source terminal when it's turned OFF

Part Number: CSD17573Q5B

 Hello,

 

Customer notice that there is a residual voltage measured on the MOSFET source terminal when it is turned OFF and the amplitude increased over temperature as table shown below.

 

 

Below is customer's circuit, the Gate-Source terminal is connected with a 10M resistor, during OFF state the Gate terminal is grounded with a 2K resistor. The Drain is connected to a 8V battery, the Source pin of MOSFET is connected to system side.

 

 

 

 

May we know at what temperature would the MOSFET VDS completely breakdown? Please advise

 

Application: Battery Pack for servo system backup power

Customer: in TW

Discharge MOSFET using CSD17573Q5B

 

 

Regards,

Brian

5 Replies

  • Please find the enclosure for the Vds data with temp and partial schematic

  • In reply to Brian Wang0928:

    Brian, 

    I am not entirely sure I understand your question but I have forwarded it to our apps team. 

    Naturally, the breakdown voltage of the FET increases with temperature, but I do not think this is what you are asking about. As long as you stay under the max junction temp of the FET (150, or 125deg if you want some margin), you should be fine. 

    I will let you know what our apps team's response is. 

    Brett Barr

    Product Marketing Engineer, Mid-Voltage FET

    b-barr@ti.com

    (610) 849 5114

  • In reply to Brett Barr1:

    Ok so after talking with the apps guys, it makes more sense that your issue of voltage on the source node pertains to increased leakage through the FET.

    Leakage generally increases, sometimes exponentially with temperature. Again though, as long as you stay within the junction temperatures listed on the datasheet, you should be fine, unless you have some specific minimum requirement on what you require this leakage and corresponding source voltage to be.

    Brett Barr

    Product Marketing Engineer, Mid-Voltage FET

    b-barr@ti.com

    (610) 849 5114

  • In reply to Brett Barr1:

    Hello Brett,

    Thanks for reply. Please help on below questions following up to this.

    1. In the D/S, it says the IDSS=1uA at Vgs=0V and Vds=24V at 25degree. how about the IDSS at 125degree?

    2. In this application circuit, there is a 10M Ohm resisor connected between Source pin and Gate pin, and there is a 10K Ohm resistor connected between Gate pin Groundig pin. The current flow of the IDSS should go into the 10M+2K Ohm, right? What's the source pin voltage with these connections at 125degree?

    The Source pin residual voltage of MOSFET Must to be under 100mV at TA>70degree as specified from end-customer HPE.

    Regards,

    Brian  

    Regards,

    Brian

  • In reply to Brian Wang0928:

    Brian,

    I'd rather not share this data on a public forum, please email myself and Kevin O'Connell directly. 

    However, if all this current is flowing through 10Mohm resistor, it is almost certainly the exponential increase in IDSS is what is causing this increase in voltage on the switch node. This problem will only increase with temperature. 

    Brett Barr

    Product Marketing Engineer, Mid-Voltage FET

    b-barr@ti.com

    (610) 849 5114