# ADG1409 for switching power supply

Hi all,

I want to switch two power supply (+5V and +12V) with an ADG1409 mux to 4 differents outputs. Please see attached image.

I use U15 to select the power supply. With A0_1 == A1_1 == 0 in DA pin I will have +5V, and with  A0_1 == 0 nad A1_1 == 1, I'll have +12V in the DA pin.

The U10 is for switch the 5V or 12V to another output. With A0_0 == A1_0 == 0 the selected power supply will mux in the +EXC1 signal, A0_0 == 0 and A1_0 == 1, +EXC2, etc.

The +12V is used for supply both mux and for the each +EXC signals. The voltage of logical signal control of both MUX is +3.3V.

The problem is that I haven't any voltage in DA pin of U15 when control pins are selected. For example, when EN = 3.3V, A0_1 = 3.3V and A1_1 = 0V, the DA output is 0V.

I have checked:

1. hi and lo voltage in control pins, they are ok.

2. the +5V and 12V are present on S1A and S2A of U15.

• Hi Joaquim,

With EN=1, A0=0, A1=0 S1A will be on, so you should see 5V on DA

With EN=1, A0=1, A1=0 S2A will be on, so you should see 12V on DA

I cannot see why this is not working once you have verified your logic and supply voltages are correct.  3.3V is sufficient for Logic Hi.

Is U10 working correctly for you?

Have you tried any of the other channels?

Is there any chance the U15 part has been damaged?

What current level are you switching?  Refer to table 5, page 8 of datasheet for continious current carrying capability of this part.

Rgds,

Theresa.

• Hi Theresa,

Is U10 working correctly for you?

answer: I have take off U15 and I have connected directly +5V and then +12V to the DA pin of U10 and it works ok.

Have you tried any of the other channels?

Is there any chance the U15 part has been damaged?

answer: I have changed 3 parts.

What current level are you switching?  Refer to table 5, page 8 of datasheet for continious current carrying capability of this part.

answer: the +5V are from an opamp output, and the +12V are from a step up limited at 50mA. The step up is working well.

With U10 and U15 connected only for +5V the mux is working well. The power supply for U15 is the same power signal (same voltage) at pin S2A, is this a problem?

thanks.

• Hi Theresa,

It's necessary that the voltage at pin S2A is lower than the Vcc for correct operation? in the my configuration both voltage are the same (+12V). Can the mux operate properly with this configuration?

thanks

• Hi Joaquim,

The ADG1409 is a rail to rail mux so the part should have no issue working correctly when Vdd = S1A = 12V

We would commonly use the same Vdd supply voltage as inputs to mux when doing checks in lab with no issues.

Rgds,

Theresa.

• Hi Theresa,

I have changed both mux ADG1409 by two mux ADG1609. I have the same problem. Must I insert a resistance between DA pins? I don't understand the problem...

I have a doubt with ABSOLUTE MAX RATINGS and CONTINOUS CURRENT PER CHANNEL, S or D. In abs max ratings the datasheet specifies a max of 30mA for analog/digital inputs but the continous current specifies 120mA for 25ºC and +12V single supply. What current is correct?

Thank you very much