TPS92620-Q1: minimum, maximum value of t6, t7 and t8

Henry Wang3

Genius 3515 points

Part Number: TPS92620-Q1

Tool/software:

Hi Sir,

Could you share the below table about the minimum and maximum value of t6, t7 and t8?

My customer needs to get the min/max value to fix the fault bus pin unstable issue.

The fault bus pin was unstable.

over 1 year ago

0 Hailee Xu over 1 year ago

TI__Genius 10430 points

Hi Henry,

What do you mean the fault pin is unstable? could you explain more details for a better analysis or feedback? Thanks!

0 Henry Wang3 over 1 year ago in reply to Hailee Xu

Genius 3515 points

Hi Sir,

This issue cause the LED is the external, the impedance may become larger as the wire aging.
Lead to the voltage of the LED will be as high as VIN, causing the driver to to make a wrong judgment about the circuit open, but it is not open because of the 1mA detect.
So the FAULT pin always be on/off.
The customer has two solutions, one is to increase the VIN voltage, the other is to connect an external bypass capacitor to make the fault signal stable on the fault pin.
So they would like to get the min/max values of T6, T8, and T9, to calculate the voltage after stabilization.

0 Hailee Xu over 1 year ago in reply to Henry Wang3

TI__Genius 10430 points

Hi Henry,

I am checking it internally and will get back to you later.

What is your application and input voltage? if the impedance becomes larger, do you mean the wire between the Power and Supply pin? If the supply margin for the thermal is enough, it would be easier to increase the Vin to avoid this issue. Thanks!

0 Dylan Sun over 1 year ago in reply to Hailee Xu

Prodigy 105 points

hi, Hailee:

thanks for ypur reply.

We use the BUCK IC LM50410 to reduce it to 7V, and then connect it to the LED driver TPS92620.
The LED current is set to 400mA,
The LED driver output is connected to the LEDs outside the PCB through wires.
LED voltage is typical 5V, range is 4.5V~5.5V.
However, the impedance of the wire may be greater than 4ohm due to long-term aging.
So when the wire ages, VOUT=5V+0.4*4=6.6V, open protection will be activated.
But when 1mA detecting, the voltage will be lower than V(OPEN_th_falling), so the FAULT pin signal will repeat high-low.
We have thought about increasing 7V to 7.7V,
But we cannot control over how wires age.
So I want to add a capacitor to the FAULT pin to prevent the FAULT pin from actually dropping to 0V in this situation.
So we want to know the min-max range of T6, T8, and T9 to calculate the voltage value after stabilization.
Thanks

Dylan.