TPS22810: TPS22810 VOut load resistance when switch disabled

Steve Clynes

Part Number: TPS22810

I have an application switching 5V to a high impedance signal. When the switch is off the impedance to ground needs to be very high (greater than few 100K).

The TPS22810 states there is no discharge resistance when the QOD pin is left floating but I am seeing about 50K to ground, which is too high for my application.

It it expected to see about 50K to ground even when the switch is off and the QOD pin is floating?

If so, can you recommend any other load switch for ~5V at 600mA, higher than 300L with an output slew rate of less than 2mS?

BR,

Steve

over 6 years ago

0 Aleksandras_Kaknevicius over 6 years ago

TI__Genius 15780 points

Hi Steve,

We expect the output impedance to be very large when the device is turned off and the QOD pin is left floating, much larger than 50kΩ. How are you testing the output impedance of the device? The test method can make a difference in the results obtained.

Thanks,

Alek Kaknevicius

0 Steve Clynes over 6 years ago in reply to Aleksandras_Kaknevicius

TI__Mastermind 43875 points

In my design the output is effectively connected to a 36K pull up to 3.3V but with the TPS output connected the voltage drops to about 1.9V

So...

Pin 1 = 5V
Pin 2 = GND
Pin 3 = 0V
Pin 4 = no connection
Pin 5 = no connection
Pin 6 = 36K pull up to 3.3V

Pin 6 measures 1.9V but I expect close to 3.3V

I will try replacing the device to see if it is somehow damaged.

BR,

Steve

0 Steve Clynes over 6 years ago in reply to Steve Clynes

TI__Mastermind 43875 points

Replacing the device gave the same result.

Can you see anything obvious I might be doing wrong?

When I enable the output it correctly goes to 5V.

BR,

Steve

0 Shreyas Dmello over 6 years ago in reply to Steve Clynes

TI__Mastermind 32650 points

Hi Steve,

We are looking into this. We measured the resistance at the out pin and we saw a value in the MegaOhm range.

We will test some more and have more information tomorrow.

Thanks,

Shreyas

0 Steve Clynes over 6 years ago in reply to Shreyas Dmello

TI__Mastermind 43875 points

It is absolutely possible I am doing something funky, but I think I have reduced it to just about as simple as I can.

BR,

Steve

0 Alpha H over 6 years ago in reply to Steve Clynes

TI__Genius 10855 points

Hi Steve,

I wanted to follow up on this thread, have you been able to resolve the issue?

Thanks,

Arthur Huang

0 Steve Clynes over 6 years ago in reply to Alpha H

TI__Mastermind 43875 points

Arthur,

I worked a little directly with the switch apps team and verified that there is some strange behavior when there is an external pull up.

They were able to duplicate the issue by applying a 36K pull up to 3.3V on the output and saw a similar (and unexpected) pull down resulting in a much lower voltage than expected (i.e. not 3.3V).

This is under further investigation by the switch team.

Kind regards,

Steve

0 Shreyas Dmello over 6 years ago in reply to Steve Clynes

TI__Mastermind 32650 points

Hi Steve,

I am going to close this thread but we are still waiting on some information. We can take this offline through email or meetings.

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TPS22810: TPS22810 VOut load resistance when switch disabled