DRV8308 - VREG not coming up

Sharath Kumar47

Other Parts Discussed in Thread: DRV8308, DRV8307Part Number: DRV8308

Application: Sensored BLDC driver for consumer electronic product

Question type: Development and troubleshooting

Description of the problem: Hi, I was using DRV8307 to run my BLDC, it worked fine. When I upgraded to DRV8308 the VREG in the chip is not coming up. I have checked for shorts in bypass capacitors, and pullup pulldown resistors, nothing is short. Programming is clear from the microcontroller side (SPI registers are written properly). Voltage at VINT is about 1.3V. VM is 15V. Enable pins state is not changing the VREG state (it is always 0V )

Thanks.

over 8 years ago

0 Rick Duncan over 8 years ago

TI__Guru** 114905 points

Hi Sharath,

Do you have a second board to try? If the device was placed on the board manually, there could an open instead of a short.

Can you confirm you have a connection to the ENABLE pin? You may be able to measure the internal pulldown.

0 Sharath Kumar47 over 8 years ago in reply to Rick Duncan

Prodigy 120 points

I checked for the resistance between ENABLE and GND it is 17.5M ohm. I also have a DRV8307 in which VINT is 1.8V and DRV8308 VINT is 1.3V, will this cause a problem? I will also try with other boards/Chips and let you now.

Thanks.

0 Rick Duncan over 8 years ago in reply to Sharath Kumar47

TI__Guru** 114905 points

Hi Sharath,

The resistance between ENABLE and GND should be less than 550kOhm. You may have an open.

We will await the results of other boards/chips.

0 Sharath Kumar47 over 8 years ago in reply to Rick Duncan

Prodigy 120 points

Hi Duncan,

I replaced the chip and now it is working fine. The VREG is coming up and VINT is 1.8V. Thanks for the support. Another problem popped up now, I programmed the registers as per the procedure, with values given in page 47 of the data sheet. But Gate pulses for U,V and W are not coming up. Faultn and lockn pin is high (I guess no fault has occured). What might be the problem?

Thanks.

0 Rick Duncan over 8 years ago in reply to Sharath Kumar47

TI__Guru** 114905 points

Hi Sharath,

What is the state of the inputs CLKIN, DIR, BRAKE, RESET, and ENABLE?

Please observe the FGOUT signal with a scope. Is it transitioning?

0 Sharath Kumar47 over 8 years ago in reply to Rick Duncan

Prodigy 120 points

Hi,
CLkIN - PWM input from ucontroller, (I am using PWM speed control mode)
ENABLE - 5V (Enable active high)
DIR, BRAKE - 0V (I programmed brake = high for braking)
Reset - 0V,
Im using Hall sensors, Hall U pin shows transitions. FGout is not connected.

My programming procedure was,
Powerup --> Enable chip --> write SPI registers --> PWM pulses

Thanks.

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DRV8308 - VREG not coming up