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DRV401-Q1: Some questions about DRV401-Q1

Part Number: DRV401-Q1
Other Parts Discussed in Thread: DRV401, DRV421, DRV411, DRV421EVM, TPS7A19, TL720M05-Q1

Hello,

According to DRV401-Q1 overview material, it is designed for VAC sensor. 

Does it mean that DRV401-Q1 can only be used with VAC sensor?

If DRV401-Q1 can be used with other sensors,

1. Can you support Sensor matching like as Input/Output information and Magnetic core information?

2. Can DRV401-Q1 support over 300A rated current? Can you recommend Turn ratio and etc

3. Can you recommend  Icom1 & Icomp2 output spec between Compensation coil and  Compensation driver ?

Regards,

Nicky

  • Nicky,

    Hello and thank you for using the E2E fourm.  The DRV401 can be used with other flux gate sensors.

    1. When using a sensor please take note the Magnetic Probe (Sensor) Interface section.  This has information on how to interface with a sensor.  Also note on the EC table on the Probe Coil Loop that shows the limitation of the probe driver.  If you do not want to design this probe yourself I would recommend using the DRV421 which already has the fluxgate probe inside the device.
    2. Both the DRV401 and DRV421 can support the output of 300A but both would require larger coil windings to keep the resistance of the coils down.  There is a trade off with larger number of turns and larger resistance.  The DRV421 has a system parameter tool that can help with these calculations.  The DRV401 has very similar compensation coil drive capabilities.  The DRV421 also has some technical documents to help with the design and located in the DRV421 technical document section.
    3. I am confused on this question.  Are you asking what are the max capabilities of the Icomp pins?  We have EC table specification on these drive capabilities.   other than that we have a TI Design for the DRV411 that increases there drive capability but it does add circuitry.  Again the compensation coil drive is very similar the DRV401 on the DRV411 as well.

  • Hi Javier,

    You mean EC table is Electrical Characteristics in datasheet, am I right?

    1. Is there any technical documents for DRV401, not DRV421 or DRV411?
    2. Is there system parameter tool only for DRV401? DRV421 integrate fluxgate sensor, but DRV401 does not.

    Regards,
    Nicky
  • Nicky,

    Yes,  when I stated EC table it is the Electrical Characteristics in datasheet.

    1.  We do not have more technical documents for the DRV401 other than the Datasheet and the TI Design, Differential Signal Conditioning Circuit for Current and Voltage Measurement Using Fluxgate Sensors.

    2.  This is no calculator for the DRV401.  Some of the parameters are very similar for the DRV421 and can be used as a starting point.

  • Hi Javier,

    I have two more questions.

    1. Does H-Bridge Driver(Differential driver) in DRV401-Q1 block work as FET or Transistor?
    2. To make reference board, will use Figure 42. Basic Connection Circuit in datasheet 25page. Is there any recommended(or reference) value of Resistance, Capacitance, and Diode?

    Regards,
    Nicky
  • Nicky,

    1) I will double check but I believe these function as FET.

    2)For the circuit I would assume for the R and C you are mostly concerned with R3, R4, C3 and C4.  I do not have examples for these.  These are not required but can help with noise coming from the excitation of the flux-gate probe.  For R1 and R2 this will be based on your number of windings and the gain you would expect.  For the protection diodes you could use the BAT54S just like the DRV421EVM board.  I would connect them like the DRV421 on the ICOMP1 and ICOMP2 pins.  This protects the ICOMP pins as well and not just the inputs to the Diff Amp. 

  • Hello Javier,

    I have questions about DRV421_System Parameter Calculator.

    To calculate Shunt resistance for DRV401, try to use this calculator. 

    But there are input item which there cannot be found in DRV401 datasheet as below.

    How can I treat this input item?

    Please let me get your answer.....

    Regards,

    Nicky

  • Hello Nicky Lim,

    Thanks again for using the forum.  

    The inductor when using the DRV401 is expected to be lower.  We do have a gain set pin to help with the stability if you gain up your external compensation driver of your compensation coil.  The stability normally will not be an issue but you could see settling issues but your DC values should be fine.  The shunt resistor value will be determined by the range you need and the number of loop in your compensation loop.  Your inductance will be determined by your core dimensions and the number of loops you have.

    Please also recall that you could have issues trying to measure 300A if your compensation coil resistance is too high.  Please take into account that copper resistance drifts 0.4%/°C.  This increase in resistance can cause you to hit maximum compensation drive capability.  Please design the resistance of compensation coil for max operation temperature range.

  • Hi Javier,

    You mean that this GSEL value can be determined by compensation inductance value, am I right?

    Regards,
    Nicky
  • Nicky,

    The GAIN pin should be Low on the DRV401 for most applications and only if you add gain to the compensation coil circuit as described in the datasheet. The DRV421 has more gain selection features to allow for different inductance. In the GSEL for the DRV421 the GSEL helps with high frequency and stability.
  • Hi Javier,

    Customer make DRV401 circuit as attached.

    Could you check if the connection between DRV401 and Coil & MCU is correct or not?

    Regards,

    Nicky

  • Nicky,

    A few comments. 

    • The TPS7B6933 has a max output of 150mA.  Please be sure that this is enough to drive the compensation coil.  Besides powering up the DRV401 that supply also drives the compensation coil.  
    • The analog inputs to the DRV401 Difference Amplifier are not connected across the Rshunt resistor.
    • Recommended, place a small capacitor in parallel with C3.  

  • Hi Javier,

    There are a few further questions as below.

    1. The inductor when using the DRV401 is expected to be lower.
    Q1. The Inductor means both of Probe coil and compensation coil?

    We do have a gain set pin to help with the stability if you gain up your external compensation driver of your compensation coil.
    Q2. Is external compensation driver TR or FET?

    Q3. Does gain set pin mean Pin3 (GAIN) of DRV401?
    This GAIN pin is connected to GND in Recommend schematic. Is this connection right?

    Please also recall that you could have issues trying to measure 300A if your compensation coil resistance is too high.
    This increase in resistance can cause you to hit maximum compensation drive capability.
    Q4. Could you explain above comment in detail?

    The TPS7B6933 has a max output of 150mA. Please be sure that this is enough to drive the compensation coil. Besides powering up the DRV401 that supply also drives the compensation coil.
    Q5. Customer will choose LDO among below 3 parts. She can use those LDO for DRV401 schematic? or Can you recommend suitable LDO?
    TPS7A19, TPS7B6750-Q1, TL720M05-Q1

    Regards,
    Nicky
  • Hi Nicky,

    1. The inductor of the compensation coil.
    2. I am not sure what the drive is but the resistance and drive capabilities is listed in the datasheet.
    3. Yes.  Connect GAIN pin to GND.
    4. Here is an example
    • Primary Current = 300A  Max
    • VDD = 5V
    • Compensation Number Turns = 2000
    • Rshunt  = 4
    • Compensation Current Estimated max = 150mA
    • HBridge Max Vout = 4.2V

    Max Comp Current 150mA = 4.2V/ (Rshunt + RCompCoil). For this condition Rshunt + RcompCoil <28Ω

    5. The LDO must supply the current for the entire circuit.  Please let me know the maximum compensation current to determine the max current required.