TI中文支持网Part Number:DRV8873
IC chip: DRV8873HPWPR
Mode: PWM Mode, "Mode" pin connect to DVDD pin, H bridge, motor connect to OUT1 and OUT2
1. How to control motor from forwad to brake within 2 seconds?
I want to brake motor from full speed to stop within 2 seconds . The input pwm frequence is 20khz, in the forward mode, set IN1 pwm duty as 100% , set IN2 pwm duty as 0, the motor forward at full speed, If I set IN1 and IN2 pwm duty as 0, it will take 7 seconds stop the motor, if i set IN1 and IN2 pwd duty as 100 at the same time, it will take about 5 seconds to stop the motor. So, If I want to stop motor from full speed within 2 seconds, how to set IN1 and IN2
2. How to set ITrip to 10A
I want to set ITrip to 10A, and I have follow the datasheet descriptions, connect the nITRIP pip to DVDD, the IPROPI1 and IPROPI2 connected together with Rsensor, which value is 500R. Then I was try to forced motor stop,
the output current is about 4.5A, same as the default state which ITrip is 6.5A. I think it should output more larger current but it can't.
Cherry Zhou：
Hi,
Please allow some time for our experts to get back to you.
Thanks
,
Cherry Zhou：
Hi,
1.
In order to stop a motor quickly, the current in the motor coils must reduced quickly and the VBEMF must equal zero. Decay modes can be adjusted to reduce the current during PWM off time, however stopping a motor to quickly can cause VM pumping and send current back into the supply voltage. Please see the attached blog about stopping motors:
https://e2e.ti.com/blogs_/b/industrial_strength/posts/art-of-stopping-the-motor-vm-pumping
2.
The absolute max current is 10A but this should only be for a short time, not continuous. If the current is above 10A for to long the OCP or OTP will trigger.
It is not recommended to operate the load current above 8A.
A driver with a higher current rating may be selected to operate a load with higher current.
The following FAQ will help with IPROPI and current sensing:
https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1013146/faq-how-to-configure-ipropi-and-current-sensing
Thanks
,
?? ?：
Hi，
1. For DRV8873, in PWM mode, mcu controller drv8873 by nSLEEP, DISABLE, IN1 and IN2 pins, operat, how to set the input can operate drv8873 from forward to slow decay(or fast decay)? I'm not sure my operate is right, because when motor from full speed to stop, it will take more than 7 seconds, it's too longer for me. My question is how to operate the input pins(nSLEEP, DISABLE, IN1 and IN2) to operate drv8873 into slow decay mode or fast decay mode.
2.Here is descriptions in drv8873 datasheet:
"""
R(sensor) = k x 5 / Io (k is typically 1100)
In the hardware version of the device, the current trip limit is set to 6.5 A. The current regulation feature is enabled bydefault on both the outputs (OUT1 and OUT2). To disable current regulation in the hardware version of thedevice, the nITRIP pin must be connected to DVDD.
"""
If I want to set current trip limit to 8A, the R(sensor) should be about 688R, and need to connect the nITRIP pin to DVDD. My question is I have do this but the output current always less than 6A, the below is my test steps:
(1) Set IN1 PWM duth as100%, IN2 PWM duty as 0, the motor forward at full speed;
(2) Forced blocking motor;
I think when forced blocking motor, the output current should be about 8A, but the output current was always less than 6A and then it stoped. It seems that I didn't set the current limit to 8A success.
,
Cherry Zhou：
Hi,
I'll check with our experts and get back to you soon.
,
Cherry Zhou：
Hi,
The DRV8873H is the hardware version of this device. The hardware version offers less flexibility in terms of current regulation. The DRV8873H has a set current trip limit of 6.5 A.
The SPI version of this device can be configured to have a typical ITRIP of 7A and a max of 8A.
The hardware version also only has a fixed TOFF time of 40us.
When ITRIP is reached the device will enter slow decay by enabling both high-side FETS.
While in current regulation, the inputs can be toggled to drive the load in the opposite direction to decay the current faster.
,
?? ?：
1. For hardware version, if the ITRIP is fixed as 6.5A and can't configured, so the R(sensor) take effects when adjust output current less than 6.5A.
2. In the normal operat mode, how to configure input to operate motor stop more fast?
3. When enable current regulation, we can operate IN1/IN2 to drive the motor in the opposite direction to stop motor more fast?
,
Cherry Zhou：
Hi,
Yes, the ITRIP threshold is set to 6.5A but should be configurable for output current values less than 6.5A.
In order to decay the current faster, in current regulation, the inputs can be toggled to drive the load in the opposite direction.
This switching between forward and reverse drive should help stop the motor more quickly.
Forward: IN1 is 100% duty cycle and IN2 is 0% duty cycle
Reverse: IN1 is 0% duty cycle and IN2 is 100% duty cycle
