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DRV110: DRV110 Schematic Values

alikaan
Expert 2315 points
Part Number: DRV110

Hello, 

Could you please advise the passive component values for application ?

DC Voltage: 28V

Desired Current 2 Amper

Solenoid resistance 4 Ohm

Thanks.

  • 0
    TI__Mastermind 23421 points

    Hey Alikaan,

    The passive component values should be rated for at least 10% higher voltage than the peak voltage they will see.  For a 28V system, I would use 50V rated capacitors for items around the VIN.  Of course logic-related passive components can be rated for just 10V if they will never see higher than 5V.  

    Check out our EVM bill of materials on the EVM users guide to see what external components we used. 

    Here are some other threads discussing DRV110 schematics at similar voltages:  E2E 24V    E2E 28V  E2E 24V2

    Regards,

    Jacob

  • 0 in reply to Jacob Thompson
    Expert 2315 points

    Hello Jacob,

    Please check the scope screen with the passive component values. After few seconds, MOSFET is getting hot, nearly 130C Degree. There is no problem except mosfet's temperature. 

    Channel 1 is current probe

    Channel 2 is mosfet's gate signal. 

    MOSFET: IRF3710

    Rpeak 480k

    Rsense 25mOhm

    Rhold 168k

    Rosc 168k

    Ckeep 1uF

  • +1 in reply to alikaan
    TI__Mastermind 23421 points

    Hey Alikaan,

    Just for my own understanding I went through and calculated the system settings:

    • Rpeak 480k --> Datasheet levels are 50k or 200k, this should be read as the 200k level, so VPEAK = 300mV
    • Rsense 25mOhm  --> Datasheet discusses 1Ω or 2Ω, but this should work
    • Rhold 168k --> VHOLD = 50mV
    • Rosc 168k --> PWM frequency 25kHz
    • Ckeep 1uF --> tKEEP = 0.1second
    • IPEAK = 1Ω*0.9A*66.67kΩ/480kΩ * 1/0.025Ω = 5A
    • IHOLD = 1Ω*0.150A*66.67kΩ/168kΩ * 1/0.025Ω = 2.38A

    This looks very similar to the this E2E post's "Size for 5A" schematic:  https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1163630/drv110-schematic-check  They used the IRF7469PbF which is a less powerful version of your IRF3710PbF FET, so this design should work.  

    Can you post your full schematic for us to look at?  

    One thing you can try to reduce the temperature is by reducing the switching frequency. can you try to reduce the PWM frequency by adjusting Rosc. Test it at 1000Hz and measure the temperature. Does it go down?

    Regards,

    Jacob

  • 0 in reply to Jacob Thompson
    Expert 2315 points

    Hi Jacob,

    By the way, this written values applied to DRV110EVM board. I'll test the reducing PWM. I'll let you know the test result. Also I have custom designed board, please check the values & schematics for same application. In custom board, with these values, MOSFET is burning is several seconds.

    Mosfet: CSD18540Q5BT

    Thanks!

  • 0 in reply to Jacob Thompson
    Expert 2315 points

    Hi Jacob,

    Also I see marked gate signal form sometimes, is it normal?

  • 0 in reply to alikaan
    TI__Mastermind 23421 points

    Hey Alikaan,

    Give me another day to look into this, I'm going to get a coworker's opinion on the gate signal.  

    Regards,

    Jacob

  • 0 in reply to Jacob Thompson
    Expert 2315 points

    Hi Jacob, 

    I fixed the MOSFET temperature problem with changing the MOSFET with lower gate capacitance. Also I decreased the PWM freq. I just have abnormal gate drive signal sometimes as I mentioned above. 

    Thanks!

  • 0 in reply to alikaan
    TI__Mastermind 23421 points

    Hey Alikaan,

    Glad to hear changing MOSFETs worked! 

    The abnormal gate drive signal is an artifact of the hysteresis controller this device implements for current control - see 7.3.2 PWM Current Control.  It is nothing to worry about.  This device has a fixed frequency (25kHz).  It sensed the current was too high right before the new on-cycle, so immediately turned off the output to limit the current back to the desired level.  

    Regards,

    Jacob