Ramp Function & Slew Rate

Hi, A1DFF. 

Thanks for your interest in AD5560 and for sending us this set of inquiries. I first have a few clarifications before we move forward.

1. When the slew rates do not change, what is the slew rate that you are measuring by current range?

2. What equipment are you using to feed RCLK to the part?

3. When the ramp sequence ends and you read back from 0x08, what do you read? Is it 0x8000 or 0x93FB?

4. Register 0x41 is only used to enable the ramp. It will not store 0xFFFF into the register memory so you are not expected to read 0xFFFF from it.

5. In your loading conditions, you are making the part drive about 200uA of current. When you do this in the two lowest ranges, the part will issue a clamp alarm (if it is turned on) and will interrupt the ramp. The third lowest current range can possibly encounter this as well due to intrinsic linearity errors.

Thanks,
Mac

Thank you so much for your quick response.

Here is my response to your clarifications:

1. Regarding the test sequence I performed:

   • (1) In the 250uA range, I accessed the 0x03 register and changed SR[2:0] from 0x0 to 0x7, measuring the slew rate each time (no change in slew rate, around 0.05V/us).
   • (2) I measured the slew rate while changing the current range to 250uA, 2.5mA, 25mA, EXT2 (500mA), and EXT1 (1.2A). There was a change in slew rate.
   • (3) I tried changing the slew rate for each current range, but there was no change in the slew rate.

2. I generated the RCLK using an Intel MAX10 (CPLD). Below is the waveform of the RCLK.           

3. The data at address 0x08 remains at 0x8000 until I write 0xFFFF to 0x41 (Enable ramp). After that, the data at 0x08 changes to 0x0.

4. I Understood.

5. I understand the loading conditions, so I started the test from the 250uA range. As mentioned in my initial post, all alarm conditions were normal.

   *(Additional information: There is no DUT Cap.)

Hi, A1DFF. 

Thanks for the responses. I'll try to do some bench experiments today and will get back to you as soon as I can.

By the way, are you using the evaluation board?

Thanks,
Mac

Thank you. I am conducting the evaluation using a self-developed board, not an evaluation board.

Additionally, I am sharing the waveforms measured by changing the slew rate under the 250uA range condition. (Load 5kOhm, 1V Setting)

1V/us Setting (0x03 : 0x0080)

0.3125V/us Setting (0x03 : 7080)

Hi, A1DFF. 

I just got back from the bench and I didn't find issues with the ramp function with the conditions you have given. The part as expected returned clamp alarm for the three lowest ranges (0x93FB is equivalent to 2V for VREF = 5V), thus the alarm in the 250uA range. I figured you must have VREF set to 2.5V, right?

Since you are not using the evaluation board, is it possible for you to share your schematic diagram or system block diagram to help add information to the existing ones?

Thanks,
Mac

Are you saying that the Ramp function worked correctly? Q1. Did you operate the Ramp function using the sequence I described? If so, how did you control the /Load function? (To verify if Ramp Start is 0x41 = 0xFFFF) Q2. If you tested under the load condition I described (5Kohm, 0x08=0x93FB setting) with VREF=5V, the 400uA range should have been output, and an alarm should have occurred. For reference, I am using VREF=2.5V. Is it okay if I share the schematic related to the DPS section via email?

Yup. It worked as expected. It alarmed on the three lowest ranges but worked on the higher two. I didn't do anything with the load function, just left it to its default setting.
You can share your schematic and related documents to my email. Please send them to mark.manato@analog.com 

Thanks!

I have shared the schematic via email.

Thank you once again for helping me solve the issue I am experiencing.