Part Number: TUSB2077A
Can you please review the attached schematic below? I am not getting any crystal. I have verified the Power on reset has 600 mS low after 90% of 3.3V. All voltages look ok. I don't know what else to try, I verified that the Hub IC is not in suspend( Suspend = high). The crystal is stuck at 1.5V and never oscillates. Thanks!
Is buspwr pin high? this will set device into self power mode. also Suspend should be low for normal operation.
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In reply to Brian Zhou:
I have tried buspwr high and buspwr low but the failure symptom is exactly the same. Yes Suspend is low but i still don't understand why there is no crystal ( crystal stuck at 1.5V) if we are not in suspend.
In reply to Mikkel Nielsen1:
what would make the crystal not turn on? is floating at 1.5V expected? Will the device do any enumeration attempt before turning on the crystal ? Or is enabling the crystal the first thing the IC will do ? Should i try a 6 Mhz clock generator/ oscillator instead?
What do you see on the upstream DP/DM lines (connection to the host)? Is anything connected downstream of the hub?
In reply to JMMN:
I get a Unknown usb device ( Decide Descriptor Request Failed ) on Windows 10 device manager. There are two downstream devices connected and 5 open USB ports, but they never get power since the PWR on signals to the TPS2044 parts never go active ( low)
Is the pullup on DP on before the host / hub are out of reset? If the hub is still in reset when the host sees the DP pullup, it could fail to enumerate the hub. Can you try manually toggling the DP pullup high-low-high to see if that changes the behavior?
I tried toggling the D+ line . This unfortunately did not solve the problem I'm still getting the same No USB Device Descriptor error from Windows.
What behavior do you see on the DP/DM lines? Can you try waiting until both the host and the hub are powered and out of reset before connecting the host and the hub as a test? This sounds like a power on reset timing issue.
I have tried powering the host & hub and then connecting just the usb data lines of host and hub but i get the same no device descriptor error. I have not put the D+/ D- lines on a scope because i don't have a differential probe set + scope.
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