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UCD9090 PMBUS_Control pin goes low when connected usb interface adapter

Narasimha reddy
Prodigy 90 points

Hi,

Previously we enabled all rails with auto enable(0x00) option and that time we monitored all rails status in fusion digital power designer tool. Now, based on requirement for power on/off sequence implementation we used PMBus control pin and we changed auto enable(0x00) option to control pin only (0x14).

Issues is now, whenever we connected USB interface Adapter JTAG on our board, PMBus control pin immediately went to LOW. On board we have pull-up resistors for PMBUS_CTL pin, PMBUS_Alert pin, PMBUS_Data and PMBUS_clock.

I probed all the JTAG signals and observed that except PMBUS_CTL al signals are high. Based on that I thought issues with PMBUS_CTL. 

what are schematic changes are required to make PMBus control pin to high when we connect USB interface Adapter JTAG ? 

also see JTAG interface connection details.