PCA9306: power-on/off sequence

takahiro higuchi

Prodigy 170 points

Part Number: PCA9306

Tool/software:

Hi team,

When VREF1=3.3V and VREF2=5.0V, is there a power-on/off sequence specified?

Best regards,

6 months ago

+1 Clemens Ladisch 6 months ago

Guru 316690 points

The switches are active only when EN is above zero, and all output voltages are clamped at VREF1. So it does not matter which VREF is powered up first.

Please note that a small current flows into VREF2 and out of VREF1; this might raise the VREF1 voltage when VREF2 is powered up first.

0 takahiro higuchi 6 months ago in reply to Clemens Ladisch

Prodigy 170 points

Hi team,

Thank you for your response.

How much does the VREF1 voltage increase when VREF2 is first powered on?

Best regards,.

0 Clemens Ladisch 6 months ago in reply to takahiro higuchi

Guru 316690 points

The current through VREF2/1 is limited by the resistor. How the VREF1 voltage behaves depends on the power supply, the decoupling capacitor, and any other devices connected to it.

0 takahiro higuchi 6 months ago in reply to Clemens Ladisch

Prodigy 170 points

Is it correct to assume that if the current flowing through VREF2/1 is low, the VREF1 voltage will be low?
Example: Current = 1.5 to 2.5mA

+1 Clemens Ladisch 6 months ago in reply to takahiro higuchi

Guru 316690 points

The current will be about (VREF2 − VREF1 − 0.6 V) / 200 kΩ, i.e., a few µA.

In general, this does not matter if power up does not take too long. But if you want to power down one side for a long time, the only way to isolate the sides is by forcing EN low.

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PCA9306: power-on/off sequence