When the ADV7182, ADV7280, ADV7280-M, ADV7281, ADV7281-M, ADV7281-MA, ADV7282 or ADV7282-M system is first powered, you will find that the 28.63636MHz crystal will not oscillate. This is expected behavior as per design.
This has surprised some customers as the older part, the ADV7180, did not operate in this manner. In ADV7180 systems the 28.63636MHz crystal oscillated immediately after power up.
This is because the ADV7182/ADV728x parts were designed to operate in a slightly different manner than the ADV7180.
When the ADV7182/ADV728x is first powered up it still remains in a software powerdown mode. In this powerdown mode the XTALP and XTALN pins are powered down. This results in the crystal not oscillating.
Running Analog Devices' recommended script forces the ADV7182/ADV728x out of powerdown mode. The write 0x00 to the User Sub Map register 0x0F forces theADV7182/ADV728x out of powerdown mode. After this write the crystal will start oscillating.
Yes, it is absolutely right, i have observed this behavior for ADV7180.
only after chip is getting powered up, crystal is showing frequency 28.63636MHz. in power down mode it is not showing frequency even though supply is given to chip. chip will be powered up by two things 1. active High signal on PWRDWN pin. or 2. PWRDWN bit is high in register 0x0F depending on the PDBP bit in register 0x0F.
Just to state that the crystals on ADV7182/ADV728x systems will not oscillate until the system is powered up and the ADV7182/ADV728x parts are programmed.
This behavior will not occur for ADV7180 systems. The crystals in ADV7180 systems will start oscillating when powered up even before the ADV7180 is programmed.
For ADV7180, The crystals in ADV7180 systems will start oscillating when powered up even before the ADV7180 is programmed, because chip is powered up using active High signal on PWRDWN pin.
Thank you for your reply but unfortunately you are incorrect.
I am the senior applications engineer for the ADV7180, ADV7182 and ADV728x parts in Analog Devices. Many customers were asking me why the crystals do not oscillate on their ADV7182/ADV728x systems after they power up their systems. I created this FAQ to help these customers understand why. I will change the title of my FAQ to state this more clearly.
We designed the ADV7182 and ADV728x parts to operate in a slightly different manner than the ADV7180.
When the ADV7182 and ADV728x are first powered up (3.3V supplies, 1.8V supplies, powerdown and the reset pin all high) they remain in a software powerdown mode.
When in powerdown mode the pads to the XTALP and XTALN pins are deactivated. This results in the crystal not oscillating. The crystal will not oscillate until the ADV7182 or ADV728x parts are programmed out of powerdown mode.
When the ADV7180 is first powered up (3.3V supplies, 1.8V supplies, powerdown and the reset pin all high) it enters an active mode of operation.
Even if the ADV7180 is forced into powerdown mode the XTAL and XTAL1 pins are not deactivated. Therefore the crystal will oscillate even if the ADV7180 is in powerdown mode.