DS90UB948-Q1: DS90UB948-Q1 power up charateristic

Terry Liang

Intellectual 1990 points

Part Number: DS90UB948-Q1

Hi team

Customer tested UB948 and found in some pcs there is unexpected voltage platform in OPLDI output(ch3) before PDB ramp up (pic 1), while in other pcs(in the same board) the voltage keep zero before PDB ramp up (pic 2). Also, in the unexpected case, they disconnected the link between the display panel. The voltage platform still exist. They wonder whether this voltage platform before PDB ramp up is normal? if no, what's your suggestions to dig out what does this voltage platform come from? Thanks!

note: ch1 is display panel Vcc

over 4 years ago

0 Steven(Shenzhen) Shi over 4 years ago

TI__Mastermind 30515 points

hi,

what is the VCC in your plot?

for the pulse voltage in oLVD pins, it is due to leakage from the multi-rails power-on sequence.

Regards,

Steven

0 Terry Liang over 4 years ago in reply to Steven(Shenzhen) Shi

TI__Intellectual 1990 points

Hi Steven,

Thanks for your reply. The ch1 is Vcc of display panel. So you mean the voltage platform of OLDI output before PDB ramp up is normal? But in some pcs IC, there is no voltage platform as shown in pic 2. Is that caused by IC individual difference? Both situations are normal? Is there any solution to remove this voltage platform? It's unacceptable for the customer.

Thanks!

0 Steven(Shenzhen) Shi over 4 years ago in reply to Terry Liang

TI__Mastermind 30515 points

Yes.

the leakage current is different due to process variation but this is normal behavior for the silicon IC.

to reduce this pulse, you can reduce the time latency between different supply rails.

regards,

Steven

0 Steven(Shenzhen) Shi over 4 years ago in reply to Steven(Shenzhen) Shi

TI__Mastermind 30515 points

If the vcc is the panel supply, you should capture 948's vcc, vddio, vcc12, pdb during the power-on stage...

this can help you understand the pulse in the oLDI pins during the power-on stage.

btw, pls follow up the power on sequence closely!

regards,

Steven

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DS90UB948-Q1: DS90UB948-Q1 power up charateristic