DRV595: DRV595 Not Working

Shaifali Jain

Part Number: DRV595

Hello,

I am using drv595 to drive a peltier 12V/7A. I have used the standard schematic given by ti. Fault and SDZ pin is shorted and pulled up.

Freq =500KHz (FS0= high, FS1= LOW, FS2=LOW)

MODSEL PIN = LOW, Master Mode selected, Gain selected is 26dB. Input voltage given to IN+ pin is 2.2v.

Supply voltage PVCC is varied from 5 to 12V but there is no output on the outp and outn.

For fault detection voltage on fault is high that means is is working in normal mode.

Why the DRV595 is not giving output in the following condition? Please suggest some solution.

over 7 years ago

0 Shawn Zheng over 7 years ago

TI__Mastermind 24835 points

Hi Shaifali,
What do you mean about 'No output'? There is no PWM swtiching on the OUTP and OUTN pins, right?
What is the volage on the IN-? What if you adapt the input volatge to make the voltage difference on the differential input is around 0.3V? If you remove the input signal, can you see the PWm switching on the output pins?

0 Shaifali Jain over 7 years ago in reply to Shawn Zheng

Intellectual 400 points

Yes there is no pwm switching at the output. The voltage developed on outp and outn pin is 0.133v approx.

I have given ground to in- pin and voltage on in+is varying through pot(variable resistor) from a different voltage source whose ground is not common with the circuit ground.

0 Shawn Zheng over 7 years ago in reply to Shaifali Jain

TI__Mastermind 24835 points

Is the issue still there when the voltage on the input pins is removed?

0 Shaifali Jain over 7 years ago in reply to Shawn Zheng

Intellectual 400 points

After applying the input or without input there is pwm switching at the output (sine waveform), but voltage magnitude is very low 0.95v. i have increased the PVCC to increase the voltage on output but there is no change in the output voltage. My peltier is not able to cool since voltage developed across outp and outn is very low.

0 Shawn Zheng over 7 years ago in reply to Shaifali Jain

TI__Mastermind 24835 points

what do you mean of "After applying the input or without input "? Could you please help to explain?
When 0.95V signal shows on the output, what is input signal? If you enlarge the input signal, the output signal amplitude is also enlarged, right?
Can you show the waveform on the input and the output? Can you try to use a larger gain setting to achieve a larger output?

0 Shaifali Jain over 7 years ago in reply to Shawn Zheng

Intellectual 400 points

If i apply or remove voltage on IN+ and IN- pin there is sin wave on the output.

the voltage difference between IN- and IN+ pin is 2.2v which is very large since there is limit on the input voltage upto 5V.
As i have already mentioned the input signal is given through a voltage divider to IN+ pin and IN- pin is connected to GND.
When i vary input voltage there is no change in the output voltage which should not happen.
For larger gain should i switch to 36dB gain settings?
What should be done to change the output wrt to input variation?

0 Shawn Zheng over 7 years ago in reply to Shaifali Jain

TI__Mastermind 24835 points

Can you please try to set the volatge on IN- to 3V, and then change the voltage on the IN+?
Please show me the SCH if possible.

0 Shaifali Jain over 7 years ago in reply to Shawn Zheng

Intellectual 400 points

Hello,

I have attached the schematic. Please suggest the settings to achieve the output.

drv595 circuit.pdf

0 Shawn Zheng over 7 years ago in reply to Shaifali Jain

TI__Mastermind 24835 points

Hi Shaifali,
Thank you for the SCH. If your PVCC is changing, the voltage on the IN- is also changing. Could you please add a fixed 3V voltage on the IN- and adapt the voltage on the IN+?

0 Shaifali Jain over 7 years ago in reply to Shawn Zheng

Intellectual 400 points

Hello,

I think you misunderstood. I am not varying PVCC or IN+ pin voltage.

I have tried the different voltage on PVCC but its now working by keeping all the other parameter constant. Similarly I have varyied IN+ pin keeping the PVCC constant to see the change in the output.

But in both cases there is no change in the output it is still around 0.9V.

Is there any suggestion about the settings which I should change to achieve the output?

0 Shawn Zheng over 7 years ago in reply to Shaifali Jain

TI__Mastermind 24835 points

How much voltage is PVCC? Did you try to set IN- to 3V biase and set IN+ to 3.2V voltage? What is the output waveform on the OUTP and OUTN pins for this case?

0 Shaifali Jain over 7 years ago in reply to Shawn Zheng

Intellectual 400 points

I set the PVCC at 6V. IN- pin is biased at 3v and input at IN+ is about 2-3V.
The voltage on the output pin is 0.9v and sine wave.
Since i have used LC filter sine wave should not come on output pins, so this can be the noise on the output

0 Shawn Zheng over 7 years ago in reply to Shaifali Jain

TI__Mastermind 24835 points

It's quite strange. One DC signal is applied on the input, why the output is a sinewave? Can you show me the captured waveform by scope? Can you rescale the time axis on the scope? Is the sinewave possibly the ripple current after LC filter? What is the DC offset on the output sinewave?

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DRV595: DRV595 Not Working