TWL6030 NRESPWRON

Hi, this output is a push-pull so this is not recommended.

Best regards, Alain.

Hi Alain,

We will add a 22R series resistor. By this, the voltage on the NRESPWRON will drop to 0,25V. 
Do you think this should be OK to protect the output of the TWL6030? We measure a peak current consumption of about 10mA when the reset button is pushed.

Best regards,
Jens

Hi jens, on which side of the resistor do you see 0.25V: TWL6030 or OMAP? I guess it is on PMIC side which is not very good I think. By the way this may cause some logic side effect as well as this signal is used internally by the logic during reset stage. Why not using a bigger resistor value in this case?

Best regards, Alain.

Hi Alain,

Our setup is as in the schematic below. If the resistor value becomes higher, then the voltage level at the OMAP when the reset button is pressed will go higher as well. When this voltage level becomes too high, the OMAP will not see the reset.

Is there a risk in damaging the TWL6030 output when implementing this way?

Hi Jens, I thought you have implemented something like this:

This would prevent short-circuiting TWL6030 output and avoid a possible partial reset inside PMIC logic.

Best regards, Alain.

Hello Alain,

Thank you for your reply!

Can you indicate what resister value you would suggest in the circuit you included in your previous post?

Please note that my question is about the cold reset ouput pin of the TWL6030: NRESPWRON, not the warm reset input pin of the TWL6030.

Our implemention is shown in the image below. Despite from the pin name indicated in your drawing, the setup seems quite similar. Differences are:

1. NRESPWRON is an input pin of the OMAP, and will not influence the NRESPWRON signal. The different location of the resistor will only have an impact on the voltage level of the signal at the OMAP. As long as the voltage level is within the range specified by the OMAP, the funcctionality should still work.

2. When the push button is used, the push-pull output of the TWL6030 will be connected to GND via a resistor in your and in my drawing. You indicated in an earlier posting that a small series resistor should be sufficient in order not to damage the NRESPWRON output pin of the TWL6030. What value would you recommend?

Looking forward to your feedback!

Best regards,

Jens

Hi Jens, sorry I meant writing NRESPWRON instead of NRESWARM in my schematic. 1Kohms resistor or above should be fine. Your implementation is not correct as it may cause a partial reset in TWL6030 logic because even though it is an output to the device this signal is re-used internally to control some gates. Depending on its levevl I'm concerned that logic may misbehave. In addition 10mA is significant for a buffer which is designed to deliver up to 2mA only.

So overall I would not recommend it and I'd suggest my proposal instead (using NRESPWRON signal, not NRESWARM).

Best regards, Alain,

Hi Jens, the 1K resistor should be placed in serial like shown in my schematic, not in parallel. In this case OMAP will see the low level set by the switch, not NRESPWRON

When NRESPWRON pin is loaded by 22 Ohms I think the internal LDO supplying it may enter in drop zone so current is limited. Anyway 22 Ohms is way too much load for this output buffer.

NRESWARM cannot be programmed to initiate a cold reset unfortunately.

Best regards, Alain.

Hi Jens, according to your experiments it looks ok then but I cannot guarantee it as this is not part of the normal usage of the PMIC.

Best regards, Alain.