TS5A3166: Analog switch between RTC CLK and Microcontroller

HARI T O1

Part Number: TS5A3166
Other Parts Discussed in Thread: TS5A3167, TMUX1511

Tool/software:

Dear Team,

I am facing an issue and it is described here.

When Microcontroller is off the RTC clock is still on and draining the RTC battery via microcontrollers protection diodes.

I decided to keep an analog switch in between RTC CLK OUT and Microcontroller.

I have two options to power the Switch.

Option 1:

Provide the Microcontroller power rail to switch also.

Once the controller is off Switch also will be off.

My question is will RTC super capacitor discharge via I/O pin of the Switch.

Option 2:

Power switch using RTC super capacitor so that both will be in same power domain.

So that the discharge via i/o protection diodes can be eliminated

Option 3:

May I know you have any better ideas

Can I use a signal relay instead of switch.

Regards

HARI

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316510 points

Most switches have clamping diodes on their I/O pins, so the switch should stay powered.

If you want to power down the switch, you need one with the "powered-off protection" feature, e.g., TS5A3167.

The I²C pins must be high when idle, and need pull-up resistors, so take care what power supply you use for those. It's likely that you also must disconnect the I²C lines.

0 HARI T O1 over 1 year ago in reply to Clemens Ladisch

Expert 1645 points

Clemens Ladisch said:
you need one with the "powered-off protection" feature, e.g., TS5A3167.

May I know in that case will the RTC discharge through the clamping diodes of the I/O pins TS5A3167

0 Clemens Ladisch over 1 year ago in reply to HARI T O1

Guru 316510 points

The TS5A3167 does not have a current path through such clamping diodes when powered off.

0 HARI T O1 over 1 year ago in reply to Clemens Ladisch

Expert 1645 points

Thanks Clemens

This will work

0 HARI T O1 over 1 year ago in reply to HARI T O1

Expert 1645 points

Hi Clemens,

May I know can I keep a signal relay b/w RTC CLK and Controller GPIO

0 Clemens Ladisch over 1 year ago in reply to HARI T O1

Guru 316510 points

Do you mean a mechanical relay? Yes; but why would you want to do that?

0 HARI T O1 over 1 year ago in reply to Clemens Ladisch

Expert 1645 points

If I used relay I don't have any leakage issue

0 HARI T O1 over 1 year ago in reply to Clemens Ladisch

Expert 1645 points

Clemens Ladisch said:
The I²C pins must be high when idle, and need pull-up resistors, so take care what power supply you use for those. It's likely that you also must disconnect the I²C lines.

Currently I2C is pulled to Microcontroller supply and that will be off when the system is off

+1 Clemens Ladisch over 1 year ago in reply to HARI T O1

Guru 316510 points

With a switch with powered-off protection, you will not have a leakage issue either. For more channels, use the TMUX1511.

0 Kameron Hill over 1 year ago in reply to Clemens Ladisch

TI__Mastermind 24440 points

Hello I agree with Clemens on this topic

In addition here is a app note that talks about the comparison between using a relay vs analog switch

Please let us know if you have any further questions

Regards,

Kameron

Switches & multiplexers

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TS5A3166: Analog switch between RTC CLK and Microcontroller