CY7C65642-28 Unknown USB Device (Device Descriptor Request Failed)

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MXZh_4597956
Level 1
Level 1
First question asked First reply posted Welcome!

Hello everyone!

When I connect the chip to PC it show a massage "USB device not recognized" and on Device manager it shows Unknown USB Device (Device Descriptor Request Failed)

I have checked the document DOC-14871 and all of those are complied.

I tried to attach the probe to D+,seems the chip was no response to the host.

I don't know if the external 12MHz clock source is a problem.It's feed into XIN pin but there was no waveform at the XOUT.Capture.PNG

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6 Replies
MXZh_4597956
Level 1
Level 1
First question asked First reply posted Welcome!

Capture3.PNGCapture2.PNG

There are the PCB layout

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Sananya_14
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello,

For the schematic please try the following-

-Kindly connect the TEST pin to GND for normal operation.

-Please connect a 650-Ω resistor with 1 percent precision to the RREF pin.

-Please ensure that the external clock requirements are met as per the App Note (https://www.cypress.com/file/122726/download​).

Best Regards,

Sananya

Hello SananyaM_56,

Thanks for your prompt reply!

-I tried connect the TEST/SCL to ground but the problem didn't disappear.

-On the board I did use a single 649(1%) resistor to connect the RREF to ground directly.

-The external clock seems not comply the app note, the scope screenshot is shown below.DS1Z_QuickPrint1.png

Best regards,

MX Zhang

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Hello MX Zhang,

As you mentioned, the clock source does not comply with the requirements. Could you kindly try changing the external clock parameters or using a crystal instead? Then we can confirm if it is due to improper clock source or some other hardware issue.

Best Regards,

Sananya

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Hello Sananya,

Ok, I will try what you mentioned. Thanks for your help!

Best regards,

MX Zhang

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Hello Sananya,

I changed the external clock to a crystal, but it did not help. The crystal could oscillate while power on, but after 2-3 seconds it stopped, and the computer showed the massage "USB Device not recognized". The XOUT waveform is shown below.

DS1Z_QuickPrint3.png

Best regards,

MX Zhang

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