Original question:
Hi Team,
My customer is looking at the TPS2121 to use as Power MUX. They want to understand the operation of seamless switch between inputs of TPS2121. How the TPS2121 avoid collisions between two inputs? The TPS2121 has spec of tFSW (fast switchover time) 5us (typ). Is this fast switchover time fixed inside TPS2121, and is it like as break-before-make time that both IN1 and IN2 switches are off during switching between inputs?
Thank you.
Best Regards,
Koshi Ninomiya
Hi Koshi,
Welcome to E2E!
In order to achieve the seamless switchover with the TPS2121 there must be a voltage greater than Vref(1.06V) applied to the PR1 and CP2 pins of the device. This can be done with voltage divider configurations going from VIN1 and VIN2 to PR1 and CP2 respectively. We denote this fats switchover mode of operation as XCOMP/XREF mode in the datasheet. The TPS2121 will compare both voltages and will output VIN1 if PR1>CP2 or VIN2 if PR1<CP2. For an example of the switchover lets assume PR1 is greater than CP2 and VIN1 is the output. At the point PR1 drops lower than CP2, the TPS2121 will start the switchover between VIN1 to VIN2. The switchover in this mode is 5us typical. As you mentioned, the switchover has a break-before-make functionality, so during the 5us switchover neither channel will be conducting to the output.
Examples and more details on the XCOMP/XREF configurations can be found in the TPS2121 datasheet on section "10 Application and Implementation". Below is a truth table found in the datasheet in which i highlight the mode of operation to achieve the 5us typical switchover and an example schematic of the XCOMP mode found in the datasheet.
Let me know if you have any questions.
Best regards,
Andy Robles
