TPS92610-Q1: one-fails–all-fail bus pull up calculation

Hi Olivier,

1.In this application, how many devices will be put in the "One-fails-all-fail" bus?

you can refer the datasheet detailed description- 7.3.6 FAULT Bus Output With One-Fails–All-Fail and please refer the similar structure of TPS92633-Q1.

In the "one-fails-all-fail" feature, the external pull-up current of "n" devices can't exceed the max internal pull-down current.

2.TPS92610-Q1 is a single-channel linear device that has a maximum output current of 450mA.

If you have the demand of multi-devices, you can consider our new multi-channel linear devices-TPS9262x/TPS92633 family.

BR,

Hailee.

thanks. Can you please share a calculation example with 2x 610 in a one-fails-all-fail configuration ? it seems the zener characteristic as a role as well.

Hi Olivier, 

This Zener is mainly for MCU I/O protection (the limitation I/O voltage) and Fault pin protection (max 22V in the datasheet).

if you don't need these connections, you can remove this Zener and the pull-up structure, other parts are similar;

if you need these connections, please pay attention to the selection of Vsupply and the pull-up resistor.

Vsupply can provide an external strong pull-up current via the pull-up resistor, and the device has a weak internal pull-up current and strong pull-down current.

Like this example: 

the target is "I(external pull-up) + 2*I(internal pull-up) < I(max internal pull-down)"

you can find related parameters in the datasheet like below.

BR,

Hailee.

Hello,

still not clear to me : how do you assess the I(external pull up) : you have VCC but not fault voltage? please provide external resistor pull up for one-fails-all-fail with 2x TPS92610

something like :

R min (or max) ext pull up = equation

thanks

Hi Olivier,

Sorry for the wrong typo: I(external pull-up) --> I(external pull-down)

The internal VCC provide the Fault output voltage when there is no external connection on FAULT pin.

1. Set an example:

V(supply) = 12V, Rpull-up = 50kohm

When a fault occurs, Fault should be less than 0.4V, approximately to 0.

I(external pull-down) = Vsupply/Rpull-up = 240uA.

I(internal pull-down) = I(external pull-down) + 1 or 0*I(FAULT_pullup), approximately equal to I(external pull-down)

It is fine if(internal pull-down) is smaller than max I(FAULT_pulldown)=500uA~1000uA.

The above is a simplified calculation process.

2. If there is no external connection, for these devices, there are n* internal pull-up current on the fault bus.

Why do you want to keep this pull-up resistor structure? 

BR,

Hailee.

Hello Hailee,

Can we have a call on this : i still dont understand.

>> I(external pull-down) : what is this current ? there is no pull down resistor only a zener.

>> Why do you want to keep this pull-up resistor structure? : I dont care what structure please help me design the correct circuit for 2x TPS92610 in one-fails-all-fail with calculation to justify the design. I mentioned external pull up because this is what is on the 92610 EVM and on the 92633 datasheet (?)

Olivier