TPS65951 Configuration Questions (VBAT Turn-on, Hands-Free Speaker mix to mono, Unused LDO cap)

Hi,

1) 3.1V is fixed and cannot be changed. This values is harcoded.

2) I dont know th ereason for such a question, you cant mix it in the device. If you have any means of external mix then you cna try. Howeevr, I have never seen such use case. You may use only one channel output if you want to have mono. Dont know if this is what you can use.

3?Inputs need to be connected to supply, so yes, on the inputs you will need caps. Outputs if not used can be left flaoyting, make sure that software doesnt turn these resources ON.

Hi Gandhar,

Thanks very much for the answers to the questions that Jeff posted for me, this is helpful.

If I could ask for clarification on question 1) I am not sure I asked it correctly.

For our board we would prefer if the PMIC does not attempt to power up the system until the battery has enough charge to run without crashing. Right now the PMIC seems to default to 3.1V but we need this to be higher, like 3.5V, so we can have enough reserve power from the Lithium Ion battery to assure that we can boot safely. I am not sure if the VMBCH parameter is the one that describes the minimum turn-on voltage threshold. Is there a way in software or hardware to prevent the PMIC from powering up the OMAP when the battery is below some user-defined voltage level other than 3.1V?

Thanks for your help.

Paul

Hi Paul,

The way this is typically done is to actually let OMAP boot and have U-boot go into a charging mode where the system blinks an LED or provides some other end user notification/indication that battery charging is occuring.  The OMAP remains in a very low power state.  You can then charge until 3.5V and then release u-boot to boot the kernel.

Jeff

Hi Jeff,

Thanks for the reply.

When USB is not present and we are booting from the battery are we still restricted to a 3.1V turn on voltage? This seems too low to safely boot the processor if USB power is not being provided.

Thanks again.

Paul

Hi Gandhar,

Just posting the question we discussed earlier, which I know you are working on, but just to have it on the forum:

The default TPS65951 design will power up the OMAP if the battery voltage measures 3.1V or higher. We would like to raise this voltage threshold if possible by dividing down the voltage going into the VBAT pin using a high impedance resistor divider or similar circuit. Would this be possible?

Thanks,

Paul

Paul, Jeff,

VMBCH is set in hardware and hence cannot be modified. As discussed earlier (on the call as well) this level does have a threshold/hysteresis, the power-up level is 3.1V but the device can be active till ~2.7V. 

I guess this window is sufficient for powering up the device. We have customers who have used this part without any issues with this threshold levels. I do not see any need for a voltage divider to trick the PMIC for a higher than 3.1V level. 

Please let me know if the threshold mentioned above is sufficient. If you really need to have a higher threshold using a voltage divider then please let me know, I will have to check some more details. I am not sure if using a voltage divider will be a good idea.

Hi Gandhar,

Thanks for your reply. In the case where we have USB charging available I think we will be okay with 3.1V. In the case where we are booting without a USB connection we feel there is some risk that for battery voltages just above 3.1V the system could crash before the software has time to detect the low battery level and shut down gracefully. But as long as the nand flash does not get corrupted from the crash this should be okay. And since it has the hysteresis hopefully we can shut down without crashing before the battery reaches 2.7V.

Regards,

Paul

Hello,

I am working on DM3730  based project in which we are using PMIC TPS65951.

We are using audio codec of PMIC.

In our design we are planning to implement :

1. On board mic and speaker.
2. Headset mic and speaker.