TPS2115A: OUT is Hi-Z, when IN2 > IN1

Hello, 

I am not able to see your schematic clearly; could you send a higher resolution image or pdf?

Best Regards, 

Elizabeth 

Hi Elizabeth,

Sorry for the inconvenience.

PFA., Our Power Mux Circuit.pdf

Thanks & Regards,

Balaji G.

Hi Balaji, 

If you are hoping to accomplish autoswitching to connect OUT to the higher of IN1 and IN2, I would recommend setting D0 equal to logic 1 and D1 equal to logic 0 rather than keeping D0 floating. This will allow you to operate in this section of the TPS2115 truth table:

If you tie D0 to a voltage greater than 2V, do you still see this issue?

Best Regards, 

Elizabeth

Hi Elizabeth,

Thanks for the response.

Should the D0 be connected to a continuous voltage or for a period of time (if so, what is the time period)?  

I just want to clarify this because the reference circuit in the datasheet also mentions that D0 as' NC'.

Please provide your valuable inputs.

Thanks & Regards,

Balaji G.

Hi Balaji, 

Apologies on the miscommunication, the D0 can be floating since there is an internal pullup on the pin. 

To route out your issue, could you provide scope shots of VIN1, VIN2, Vout, and Iout during the switchover when you are seeing 1.68V on the output?

It is possible the device is either hitting the current limit or due to the high current limit close to the maximum output current capability of the device, the device could be hitting thermal shutdown and turning off and on. If you are hitting thermal shutdown, if you were to take the average value of the output rather than the transient values, it would make sense that you are seeing around 1.68V on average. 

A few more questions:

• Is this 1.68V DC over a long period of time?
• What is the total load at the output of the device?

I would recommend removing the feedback resistor R156 as it is not needed.

Best Regards, 

Elizabeth 

Hi Elizabeth,

1.68V is the output voltage that we observed continuously whenever IN2 > IN1. Our maximum load rating is 5.5V, 1.5A.

I will share the scope shots, but before that, I would like to clarify another thing.

Please find the below document.

Components-on-Input-side-of-PMUX.pdf

As mentioned, D16 is 'DNP', Q4 and D18 are used. No other components are available on the power supply lines of SYSTEM_PWR & VBUS.

Can it be the reason for the under voltage or priority failure of PMUX?

By the way, thanks for your response to my other question.

Thanks & Regards,

Balaji G.

Hi Balaji, 

Without seeing the scope shot of how IN1, IN2, Vout, and Iout are acting during the switchover when you are seeing 1.68V on the output, it is difficult to comment on what could be the route cause. 

Is there a possibility IN2 is simply at 1.68V?

Are there any other connections in the schematic to the SYSTEM_PWR node?

Best Regards, 

Elizabeth 

Hi Balaji, 

Just checking in, do you have an update here?

Best Regards, 

Elizabeth 

Hi Elizabeth,

Sorry for the belated response.

Due to the sudden unavailability of equipment, I couldn't share scope shots right now.

But I would like to share some important points. When 3.6V, 50mA input supply are applied to IN2, and IN1 is 0V, the OUT from the PMUX is 3.6V.

When 3.6V, ~15mA input supply is applied to IN2, whereas IN1 is 0V, OUT from PMUX is <=1.6V.

BQ25616JRTWR provides an input supply (SYSTEM_PWR) for PMUX.

If you want scope shots immediately, I may need more time. If you agree, I will close this case and create it again once I can share the scope shots.

Please share your convenience. Also, please share your inputs on my observations mentioned above.

Thanks & Regards,

Balaji G.