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DRV8874-Q1: Described in the explanation frame（No.1～No.8）

yukio-kide
Prodigy 20 points
Part Number: DRV8874-Q1

No.1：Function mode switching

Active mode ⇔ sleep mode, switching control
Is it possible to switch modes when PMODE is set to Hi (PWM control mode) and IN1 and IN2 are connected to nSLEEP?
(Normally, the IN1 and IN2 terminals are Lo input, and one terminal is Lo input with his 100% duty during operation.)

Also, if such a control method is adopted, will there be any impact when switching from reverse control or forward control to sleep?

No.2：EN1/IN1，PH/IN2，nSLEEP pins

In the DRV8874Q1 (datasheet), the EN1/IN1, PH/IN2, and nSLEEP pins are pulled down with 100kΩ, but I would like to know the variation in resistance values.

No.3：nFAULT pin

I am considering using the IC with the fault state disabled, will this affect the IC in any way?
If not, is a pull-up resistor necessary?

No.4：IPROPI pin

If the current detection function is not used, is there any problem with OPEN?

No.5：VREF pin

If the IMODE pin is connected to GND and the IPROPI pin is open, is there any problem if the VREF pin is open?

No.6：VREF pin

If the IMODE pin is connected to GND and the IPROPI pin is open, and if the reference voltage must be input to the VREF pin, is there no problem with a 5.0V input?
It is described in the recommended operating conditions (VVREF=0 to 3.6V) in the datasheet, but what is the difference from 5V input?

No.7：Protection circuit

What are the implications of not using the VCP charge pump constant voltage lockout protection?
If not used, is the capacitor between CPH and CPL unnecessary?

No.8：Reverse voltage application

A diode is inserted upstream of the VM pin as a countermeasure against reverse voltage application. Will it affect the IC?

If the IC is not affected, are the above measures sufficient?
(No resistance is inserted between the GND terminal of the IC and the GND of the board.)

If there is any effect on the IC, please tell me the countermeasure against reverse voltage application.

  • +1
    TI__Intellectual 1020 points

    Hello Yukio,

    Thanks for reaching out! 

    No. 1: The PMODE state can be changed by taking the nSLEEP pin logic low, waiting the tSLEEP time, changing the PMODE pin input, and then enabling the device by taking the nSLEEP pin back logic high.

    Can you clarify what you mean by In1/In2 being connected to nSLEEP?

    When switching from reverse control to forward control, technically there shouldn't be an impact on the IC. That being said, you should be aware of the quick switch causing the supply to pump up. To avoid this, I would recommend decelerating the device, making the switch, and then accelerating in the new direction.

    No. 2: You can use a +/- 20% variation when choosing resistor values 

    No, 3: To clarify, you cannot disable the fault state on this device. You can choose to not monitor the fault pin. If you do that, I would be aware of Quad-Levels 3 and 4 for the IMODE. They do not have automatic retry, so if you go into overcurrent, the device will stop working and you will not know why unless you are monitoring the fault conditions. 

    No. 4:  If you do not want to use current sensing, I would tie this pin to GND with a low resistance value to avoid tripping the comparator inside the device. 

    No. 5: Vref can be left open. But once again, I wouldn't recommend leaving IPROPI open.

    No. 6: The Absolute Maximum rating for Vref is 5.75V, so a 5.0V input is fine

    No. 7: You cannot disable the VCP charge pump on this device and the capacitor between CPH/CPL is necessary

    No. 8: You can insert a diode upstream of VM. You can also use the circuit below. Please note that if you do use the diode version you suggested, you will have a higher voltage drop than if you use the version below. You want to make sure the device voltage never drops low enough to turn on Under Voltage Lockout. 

    I hope this helps! Please let me know if you need further clarification on any of these answers, or if you have any other questions.

  • 0
    Prodigy 20 points

    No.1

    Is there a problem with the connection method for switching control between active mode and sleep mode?

    No.3

    Is there any problem even if the nFAULT pin is open?

    No.4

    Can it be directly connected to GND?
    If you can't connect directly, how many ohms is the low resistance value?

    No.8

    If I protect the IC from reverse connection with the version of the diode I suggested, will it have any effect on the IC?

  • 0 in reply to Audrey Kuehler
    Prodigy 20 points

    excuse me.

    I accidentally clicked "This fixed the problem". I have submitted additional questions.

  • 0 in reply to yukio-kide
    TI__Intellectual 1020 points

    Hello Yukio,

    No. 1
    Can you explain why you want to switch between sleep mode and active mode? Technically, you can switch between active and sleep mode, but depending on your use I would probably recommend using coast mode instead of sleep mode. 

    No. 3

    You can leave it open, but I would not recommend it. 

    No. 4

    You tie directly to GND, but if you do you need to set Vref greater than ground.

    If you want to void any risk to tripping the comparator, I would add a small resistor (around 100 Ohms).

    No. 8

    You can use the diode version you suggested. That will be fine. But, if you do that, you need to make sure the device voltage never drops low enough to turn on Under Voltage Lockout. You will not know the device has gone into under voltage lockout if you are not monitoring the nFAULT pin

    Let me know if you have any more questions.

  • 0 in reply to Audrey Kuehler
    Prodigy 20 points

    No.1

    Since it will be installed in a vehicle, we want to perform low current control to prevent the battery from running out.

    What is the current consumption in coast mode?

    No.3

    Is it okay to pull up the nFAULT pin through a resistor?

    If there is no problem, how many ohms should the pull-up resistor be?

    If there is a problem, how should I connect?

  • 0 in reply to yukio-kide
    Prodigy 20 points

    No.1

    Since it will be installed in a vehicle, we want to perform low current control to prevent the battery from running out.

    What is the current consumption in coast mode?

    If the nSLEEP pin is the connection I asked about yesterday, could I set the IMODE pin to Quad-Levels 1?

    No.3

    Why is it not recommended to leave the nFAULT pin open when not monitoring for fault conditions?

    Is it okay to pull up the nFAULT pin through a resistor?

    If there is no problem, how many ohms should the pull-up resistor be?

    If there is a problem, how should I connect?

  • 0 in reply to yukio-kide
    Prodigy 20 points

    If I set the PMODE pin to Hi, do I need a 5V connection through a resistor?

    If I need a resistor, how many ohms should I set it to?

    If the IMODE pin is set to Quad-Levels 1, do I need a GND connection through a resistor?

    If I need a resistor, how many ohms should I set it to?

  • 0 in reply to yukio-kide
    Prodigy 20 points

    I didn't know if it was sent, so I sent it again.

    No.1

    Since it will be installed in a vehicle, we want to perform low current control to prevent the battery from running out.

    What is the current consumption in coast mode?

    If the nSLEEP pin is the connection I asked about yesterday, could I set the IMODE pin to Quad-Levels 1?

    No.3

    Why is it not recommended to leave the nFAULT pin open when not monitoring for fault conditions?

    Is it okay to pull up the nFAULT pin through a resistor?

    If there is no problem, how many ohms should the pull-up resistor be?

    If there is a problem, how should I connect?

  • 0 in reply to yukio-kide
    TI__Intellectual 1020 points

    Hello Yukio,

    Deepest apologies for my delay in response.

    No. 1

    Let me get back to you on the current consumption.

    Yes, the Quad-Levels are determined by the IMODE pin. You can change the Quad-Levels when you toggle the nSleep pin (please see more details in the second paragraph of 7.3.3.2 in the datasheet), but you do not have to. The IMODE pin determines the Quad-Levels

    You can set to Quad Level 1 by tying the IMODE pin directly to ground. Please see Table 7-6 in the datasheet for more details on the different Quad-Levels.

    No.3

    Let me clarify, I would not recommend choosing to not monitor fault conditions. But you can leave the pin open.

    You can pull up the nFAULT pin through a resistor. In fact, it’s listed in the recommended external components table. Blush I would recommend either 4.7k or 10k.

    For the PMODE pin, If you look at the recommended operating conditions table on the datasheet, the max logic input voltage is 5.5 V so you can have PMODE=5V. All you need is to bring the pin to logic high through the 5V connection.

  • 0 in reply to Audrey Kuehler
    Prodigy 20 points

    Question 1

    In the event of a system failure, the protection built into the device is sufficient as long as the "OCP" and "TSD" are working.
    If I don't mind if the "UVLO" and "CPUV" protection functions don't work, is it okay to not need a capacitor between the VM-VCP pin and the CPH-CPL pin?

    Question 2

    Regarding control from such a controller, is there any problem with the connection method for switching control between active mode and sleep mode? Also, does such control method affect the device? (Especially when switching between active and sleep modes)

  • 0 in reply to yukio-kide
    TI__Intellectual 1020 points

    Hello Yukio,

    1. You need the charge pump capacitor between VM-VCP. Without it, the driver will not "wake up"

    2. If you are rapidly switching back and forth between active and sleep mode (about a second in each mode) you can switch between active and sleep mode. If you are keeping the motor active longer than that with PWM anywhere around the 1-20kHz range, you need to use coast mode instead. You can calculate the Power Consumption using the parameters below. 

  • 0 in reply to Audrey Kuehler
    Prodigy 20 points

    If there is no problem even if the "CPUV" protection function does not work, is a capacitor between the CPH and CPL terminals necessary?

  • 0 in reply to Audrey Kuehler
    Prodigy 20 points

    If there is no problem even if the "CPUV" protection function does not work, is a capacitor between the CPH and CPL terminals necessary?

  • 0 in reply to yukio-kide
    TI__Intellectual 1020 points

    Hello Yukio,

    You still need this capacitor. Even if you plan on not monitoring CPUV or using the high-side FETs, the driver will still flag the under voltage fault and it will disable all the outputs. 

    Thank you,

    Audrey

  • 0
    Prodigy 20 points

    I want to connect the "PMODE" pin to 5V, is it ok to connect it directly to 5V?

    Is it okay to use the 0.1μF capacitor listed in the datasheet for the capacitor used between the "VM" and "VCP" pins?

    Is it okay to use the 0.022μF capacitor listed in the datasheet for the capacitor used between the "CPH" and "CPL" pins?

  • 0 in reply to yukio-kide
    Prodigy 20 points

    I want to connect the "PMODE" pin to 5V, is it ok to connect it directly to 5V?

    Is it okay to use the 0.1μF capacitor listed in the datasheet for the capacitor used between the "VM" and "VCP" pins?

    Is it okay to use the 0.022μF capacitor listed in the datasheet for the capacitor used between the "CPH" and "CPL" pins?

  • 0 in reply to yukio-kide
    TI__Intellectual 1020 points

    Hello Yukio,

    Yes, you can connect 5V directly to pmode

    Yes, you can absolutely use those capacitors. The capacitors listed in the datasheet are the recommended values. 

    Thank you,

    Audrey