Bringing up a CX3 board - issues ...

[LeLe_4350096]

Hello,

We're bringing up a CX3 based design (USB boot) and the board comes up as an "unrecogized device" in windows device explorer. Once in a while, it will

enumerate as "Cypress FX3 USB Bootloader Device", but the Cypress Control Center does not show it and I cannot download firmware.

Some board details:

- USB Boot (checked PMODE pins and they are at the right state)

- Power supply voltages OK

- 19.2 MHz external oscillator with an external buffer. The single buffer output drives both CLKIN and REFCLK. Waveforms look OK on scope

-  CLKIN_32 not used - input is grounded.

- USB type C connector - we have a mux for the USB3 signals, but this should not matter since for USB boot, the USB2 D+/D- are used instead.

Any ideas what to try next? I have a reference design board and it enumerates correctlty in USB boot mode so I am fairly sure its not a windows/driver issue.

Thanks!

p.s has Cypress terminated the free schematic review service? https://www.cypress.com/welcome-cypress-schematic-review-service

the link at the bottom of this page no longer works.

[Hemanth]

Hi,

CLKIN_32 pin if not used should be left unconnected. Can you please try by doing the same?

Regards,

Hemanth

[LeLe_4350096]

We would have to re-spin the pcb to float the CLKIN_32 on our board.

Instead, I modified a reference design board (from e-consystems) and disconnected the 32kHz oscillator and GND'ed the CLKIN_32 input.

The reference board booted from USB  without any problems with CLKIN_32 grounded - looks like that isn't the issue.

[LeLe_4350096]

One other question. We are using a 19.2MHz buffered clock that is 1.8V logic for REFCLK and CLKIN.

The Vddio1 (REFCLK power domain) and Cvddq (CLKIN power domain) power pins are both connected to 1.8V.

The datasheet says Vddio1/Cvddq can be 1.7V-3.6V power. Is 1.8V logic for the clocks more finicky than running 3.3V clocks?

Thanks!

[Hemanth]

Hi,

Please let me know if it is possible for you to share the schematic over here.

Regards,

Hemanth

[LeLe_4350096]

Hi,

I spoke to my manager and we would prefer not to post the schematic to a public forum.

I guess that makes it more difficult, but we'll do what we can.

Thanks,

Len