TCA39306: Switch Enable Control by directly pull-down

Tamio Yokokura

Expert 3640 points

Part Number: TCA39306

TCA39305 support team

Figure 9-2 is recommended for controlling SW enable.

Is it possible to directly connect VREF2 and EN terminal to GND for SW control as shown below?

If NO, why is it?

Thanks

Tamio

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 271800 points

Yes, you can pull EN low with a switch or with an open-drain/open-collector output.

0 Tamio Yokokura over 1 year ago in reply to Clemens Ladisch

TI__Expert 3640 points

Hi, Ladisch,

Do you mean that EN and VREF2 can be pulled down directly to GND without a resistor?

Isn't there any leakage current from VREF1 to VREF2?

Thanks

Tamio

0 Clemens Ladisch over 1 year ago in reply to Tamio Yokokura

Guru 271800 points

EN is connected to the gates of all transistors. So when EN is low, there is no connection between V_REF1 and V_REF2.

0 Jack Guan over 1 year ago in reply to Tamio Yokokura

TI__Mastermind 23391 points

Hey Tamio,

To further add on to Clemens' response- the I/O ports are also put into high impedance when the EN pin is driven low as well. As for the connection from the EN pin to GND, you can use an open drain driver as shown in a similar device here @0:55 mark.

Regards,

Jack

0 Tamio Yokokura over 1 year ago in reply to Jack Guan

TI__Expert 3640 points

Hi, Ladisch, and Guan

I understood that SW can be disable by connecting EN pin to GND directly. And also, at the same time, can VREF2 connect to GND directly?

I think that VREF2 can connect to GND because I/O pin become Hi-Z at EN=LOW. Is my thought correct?

Thanks

0 Clemens Ladisch over 1 year ago in reply to Tamio Yokokura

Guru 271800 points

V_REF2 is connected to EN. In this situation, it indeed is connected to GND.

0 Tamio Yokokura over 1 year ago in reply to Clemens Ladisch

TI__Expert 3640 points

Hi, Ladisch

I understood that there are no issue even if VREF2 and EN was directly connected to GND during VREF1=1.8V. "No issue" I say means no leakage current and no damage IC. So customer can use it for SW control.

Thanks

0 Clemens Ladisch over 1 year ago in reply to Tamio Yokokura

Guru 271800 points

Correct.

0 Tamio Yokokura over 1 year ago in reply to Clemens Ladisch

TI__Expert 3640 points

Hi, Ladisch,

I could completely understand.

Thanks!

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TCA39306: Switch Enable Control by directly pull-down