DRV8701 new design

Khoi Nguyen83

Expert 1180 points

Other Parts Discussed in Thread: DRV8701, DRV8701EVM

I'm designing with DRV8701.

From the DRV8701EVM

5.9 to 45V operating voltage range
15A continuous / 20A peak H-bridge output current
Drives a single bidirectional brushed DC motor

Can we increase the rating to 20A continous, 30A peak without adding additional FETs?

Is it possible to double up the FET at high/low location to increase the continuous current?

Can the chip GH2/GH1/GL2/GL1 drive two FETs?

over 8 years ago

0 Rick Duncan over 8 years ago

TI__Guru** 114905 points

Hi Khoi,

I am not sure I understand your question. The DRV8701EVM is rated at 15A continuous / 20 A peak.

The FETs on the PCB are rated for 23A continuous with adequate thermals.

The DRV8701 can drive multiple FETs. Driving multiple FETs can create challenges. If you can find one FET that meets your size and cost target, it is recommended to use it.

The FET gate charge and PWM frequency are key parameters when determining if the DRV8701 can drive the FETs. Please refer to section 8.2.1.2 for details.

0 Khoi Nguyen83 over 8 years ago in reply to Rick Duncan

Expert 1180 points

That answers my question. Also I assume we can increase peak current with Rsense to 30A or higher as well.

0 Rick Duncan over 8 years ago in reply to Khoi Nguyen83

TI__Guru** 114905 points

Hi Khoi,

The current is limited by equation 1 on page 16. The FETs used should be able to support the ICHOP value.

0 Khoi Nguyen83 over 8 years ago in reply to Rick Duncan

Expert 1180 points

Currently we are using motor driver with high inrush as shown.

48A peak < 50ms see attach photo.

Does the DRV8701 has the inrush limit so we don't exceed the battery max of 36A < 2s rating?

0 Rick Duncan over 8 years ago in reply to Khoi Nguyen83

TI__Guru** 114905 points

Hi Khoi,

Please refer to equation 1 of the datasheet.

The inrush current limit can be set by adjusting the VREF voltage and sense resistor. Depending on the system, the current level could be set lower than 36A.

0 Khoi Nguyen83 over 8 years ago in reply to Rick Duncan

Expert 1180 points

do you have orcad schematic database for the drv8701evm eval board?

0 Rick Duncan over 8 years ago in reply to Khoi Nguyen83

TI__Guru** 114905 points

Hi Khoi,

The DRV8701EVM schematic is available in Altium. You should be able to import the file into Orcad.

0 Khoi Nguyen83 over 8 years ago in reply to Rick Duncan

Expert 1180 points

Can CONTROL INPUTS (PH, EN, IN1, IN2, nSLEEP) be driven by 5V source?
I think it can be from section 6.5 of the datasheet but I just want to confirm so we don't need 3.3V to 5V translator.

Khoi

0 Rick Duncan over 8 years ago in reply to Khoi Nguyen83

TI__Guru** 114905 points

Hi Khoi,

Yes, the control inputs can be driven by 5V source.

Section 6.3 of the datasheet confirms the control inputs can be driven by 5V.

The Recommended Operating Conditions of the Logic level inputs is 0 to 5.5V. Logic Level inputs are PH, EN, IN1, IN2, nSLEEP

0 Khoi Nguyen83 over 8 years ago in reply to Rick Duncan

Expert 1180 points

Since EN, PH, SLEEP have internal pull down resistors, I don't think there would be issue if the VM is powered off while the processor is still driving the these input signals. The processor output would be seeing 115K pulldown, correct?

Khoi

0 Rick Duncan over 8 years ago in reply to Khoi Nguyen83

TI__Guru** 114905 points

Hi Khoi,

Correct, there should be no issue if the VM is powered off while the processor is still driving the inputs.

The processor would be seeing 115k pulldown typically. The resistance can vary.

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DRV8701 new design