UCD9222: Controlling UCD7242, one rail doesn't work unless GUI is connected

dave k

Part Number: UCD9222
Other Parts Discussed in Thread: UCD7242

I am using a UCD9222 to sequence/control a UCD7242. Normally the design works fine but I am finding a few units that for the B side of the UCD7242 it will not work unless the USB adapter is connected at power up. If I have the USB adapter connected and power the board it boots up fine. If I don't have the adapter connected and power up the B channel on the UCD7242 does not start. If I then connect the adapter the GUI reports a fault on the B channel. If I do a soft reset in the GUI of the device it powers up fine.

over 6 years ago

0 Zhiyuan Hu over 6 years ago

TI__Genius 9845 points

Looks like the device checksum has been erased by accident. Without checksum, the device can only work when GUI is connected. Please refer to the below document to restore checksum.

Regards,

Zhiyuan

5148.Procedure for Recreating UCD9xxxx Checksum_A.pdf

0 dave k over 6 years ago in reply to Zhiyuan Hu

Intellectual 305 points

Zhiyuan, thanks for the quick reply. I tried following the pdf attached but after I select the Scan Device in ROM Mode it notes No ROM detected.

0 dave k over 6 years ago in reply to dave k

Intellectual 305 points

Although it does see the devices as is also shown in the above screen shot

0 Zhiyuan Hu over 6 years ago in reply to dave k

TI__Genius 9845 points

Once Fusion GUI is attached, the device goes into Program mode and it will operate normally. If you power cycle the board without Fusion GUI open, the device will not operate. In that case, the device will stay in ROM mode, and you can find it by scanning in ROM mode.

0 dave k over 6 years ago in reply to Zhiyuan Hu

Intellectual 305 points

Zhiyuan, that is the process I followed for the screen shot above. I turned the power on to the PCB with out the USB connection. I then connected the USB adapter and opened the GUI. I then selected the Scan Device in ROM Mode and the error in the screen shot above is what I get. I then select DEVICE ID which then gives the rest of the output in the screen shot above. I did just repeat the process to verify I get the same results.

0 dave k over 6 years ago in reply to dave k

Intellectual 305 points

It appears that it is not actually the GUI running that allows the part to work, it is actually having the USB pod connected to the device which allows the part to work properly.

0 Zhiyuan Hu over 6 years ago

TI__Genius 9845 points

What fault does GUI report on the B channel?

Thanks,

Zhiyuan

0 dave k over 6 years ago in reply to Zhiyuan Hu

Intellectual 305 points

Here is a screen shot, the USB is unconnected, I then power the PCB on, then connect the USB.

0 Zhiyuan Hu over 6 years ago in reply to dave k

TI__Genius 9845 points

Please check waveform and see if there is OC condition on UCD7242. If not, check if UCD7242 FLT-B pin is really set high (or due to noise/glitch).

Regards,

Zhiyuan

0 dave k over 6 years ago in reply to Zhiyuan Hu

Intellectual 305 points

No, the FLT-B pin is low on the UCD7242.

0 Zhiyuan Hu over 6 years ago in reply to dave k

TI__Genius 9845 points

Then I suspect there is a glitch on FLT-B that triggered the FLT fault, and somehow the glitch doesn't occur when adapter is connected. Please check if it is the case.

0 Brad over 5 years ago in reply to Zhiyuan Hu

TI__Genius 13700 points

Sorry for the delay in getting back to you.

The FLT line of the UCD7242 can be cleared between the time the FLT occurred until the UCD9222 controller ends pulsing (could be 3-4 PWM pulses) so scoping the FLT line after the rail fails may not provide any information.

Can you capture the FLT condition with an oscilloscope during the power up without the adapter attached or will the rail power up correctly with the probe connected to the FLT line? It may be present for only one or several PWM cycles.

Try to include the Output Voltage and PWM signal with the FLT line and if possible take a couple captures, one with 5-6 PWMs cycles and one with longer timebase to observe where in the power up the issue occurs.

0 dave k over 5 years ago in reply to Brad

Intellectual 305 points

Yes, if I hang a probe on the FLT line the board powers up fine. I added a pull down to the net and that appears to fix the problem on this device. It would appear this device is more susceptible to noise on this net then others. This is the first unit out of more than 800 that I have found the issue on. I was wondering if you had an idea as to why hanging the jtag pod on the 9222 would also make the unit power up fine?

0 Brad over 5 years ago in reply to dave k

TI__Genius 13700 points

JTAG pod or the USB-to-GPIO?
In either case, I have not seen that particular solution to the FLT noise.
Previously, grounding on the UCD7242 appeared to be the root of the noise on the FLT line, it was a while ago but I believe it was between the AGND and PGND.

0 dave k over 5 years ago in reply to Brad

Intellectual 305 points

It is the USB to GPIO adapter. I have AGND and PGND tied together under the device with vias on both directly to my GND plane.

0 Brad over 5 years ago in reply to dave k

TI__Genius 13700 points

Your description sounds as though you have the correct method for grounding the AGND to PGND on the UCD7242.

If you'd like I could look at the schematic/layout, we could connect through friend request rather than posting it to the forum.

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UCD9222: Controlling UCD7242, one rail doesn't work unless GUI is connected