DRV103: drv103u is not giving right duty cycle.

Hey Showrya,

Showrya Mohan Avrekad Chandregowda said:

instead of TTL input I am giving input from PSU

Can you elaborate on this?  Make sure the input voltages comply with the absolute maximum ratings table 

What is your voltage on the Delay Adjust pin?  If below 2.6V device will be 100% ON.  Also what is your voltage or resistor for the Duty Cycle Adjust pin?

Best,

Jacob

Hello Jacob, 

Thanks for fast response,

circuit configuration:

pin connections:

pin1 : voltage from the DAC

pin2: floating

pin3; 100k(50KHz)

pin 4: GND

pin 5: anode of 1n5822 and terminal of valve.

pin 6: supply voltage with 22uF bypass. also cathode of fly back diode and other terminal of valve .

pin 7: floating

pin 8: input from PSU via voltage divider(2V).

today chip started working as I used the new chip. But there are some issues/doubts I have.

1. after I turn off the input signal, still it shows the PWM output(oscillator probe is connected to pin 5 and GND). (according to data sheet it should off below 1.7V

2. can I control the frequency through voltage instead of resistor?

3. right now I am giving the supply voltage as 27V which is connected  to both  Vs and valve, but what voltage should I consider for the valve of 24V?

4. I am doing voltage controlled duty cycle provided from the DAC, would it take input from the microcontroller(digital input) or I should convert it using DAC before giving it to the duty cycle adjustment pin?

"Can you elaborate on this? " 

In datasheet it says we have to provide TTL input to input pin, but I am giving dc input from Power supply unit to voltage divider and giving it to pin 8.

"What is your voltage on the Delay Adjust pin?"

it varies from the range 4.9 to 5.3V  varies based on the  the duty cycle voltage.

"Also what is your voltage or resistor for the Duty Cycle Adjust pin?"

giving voltage from DAC from 1.3 to 3.5 volts

Hey Showrya,

Showrya Mohan Avrekad Chandregowda said:

today chip started working as I used the new chip

That's good!

Showrya Mohan Avrekad Chandregowda said:

it varies from the range 4.9 to 5.3V  varies based on the  the duty cycle voltage

Make sure this voltage does not exceed 5.5V as that could damage the device.

Showrya Mohan Avrekad Chandregowda said:

2. can I control the frequency through voltage instead of resistor?

Ahh sorry looks like I was mistaken, it has to be a resistor I believe looking at its block diagram.  

Showrya Mohan Avrekad Chandregowda said:

3. right now I am giving the supply voltage as 27V which is connected  to both  Vs and valve, but what voltage should I consider for the valve of 24V?

No change, Vs on the device can be 8V to 32V no problem. 

Showrya Mohan Avrekad Chandregowda said:

4. I am doing voltage controlled duty cycle provided from the DAC, would it take input from the microcontroller(digital input) or I should convert it using DAC before giving it to the duty cycle adjustment pin?

The pin wants a voltage, so if you did use a PWM from the microcontroller I would add a low-pass filter to convert the digital PWM signal into an analog voltage.  

For testing you might want to try just using a resistor for it, so you can isolate whether the DAC is causing issues.

Best,

Jacob

1.after I turn off the input signal, still it shows the PWM output(oscillator probe is connected to pin 5 and GND). (according to data sheet it should off below 1.7V)

could you please explain what might be the reason.?

Not sure, I don't think that is expected behavior.  Could be damaged device?  Does it stay on continuously, or just for a few ms? 

Looks like voltage will stay high, but current will be zero. 

Note that the output will be disabled below 1.2V and enabled above 2.2V.  Between 1.2V and 2.2V is a gray area, don't know what the behavior will be.  

Best,

Jacob

hello,

I don't think the device is damaged, because when I vary the duty cycle Via DAC, it actually gives the right duty cycle at output. when I am doing this, if I disconnect the input, still it will give the output. also I want to know what exactly is TTL input is and what is the difference between analog input and TTL input. and how can I generate it?

regards,

Showrya

Hey Showrya,

Showrya Mohan Avrekad Chandregowda said:

what exactly is TTL input is and what is the difference between analog input and TTL input

TTL input just means it supports TTL voltage levels, which are where low is <1.2V and high is >2.2V in this case.  for TTL stands for transistor-transistor logic. This is an old-fashioned way to describe an input, just saying that it can handle up to 5V not just typical 3.3V directly from a microcontroller.    

Showrya Mohan Avrekad Chandregowda said:

disconnect the input

Ahh, well disconnecting the input is different from driving the input low.  Since the device doesn't appear to have a pull up or pull down resistor on the input pin, when the input goes Hi-Z (disconnected) then it will likely maintain the previous voltage state.  It might eventually float up/down to the other state.  Since it's Hi-Z it's unknown what voltage the device will read. 

Best,

Jacob

Hello, 

I have on more question, Lets say I used 24V valve, I will provide 26V as supply voltage to drv103, which is also connected to valve. Now if I replace the 24V valve by 12V valve and if I keep supply voltage same, it wont give right output, what might be the reason and also what might be the possible solution?. Once I give the supply voltage, I don't want to change it irrespective of the valve I am using.

Hey Showrya,

Correct, the device just switches the voltage you give.  So you would have to change supply voltage to 12V for 12V valve.  Or you could PWM the output and add a R/C filter to create a rough analog voltage from the PWM signal

Best,

Jacob