Hi everybody!!!

I have this switch that are powered with +/- 15 V gived by a dc/dc converter (Traco TMA0515D).

Two of the four input are connected to two voltage divider and one to a resistor while the last is disconntected.

The first two input are voltage signals, while the third input it's a current signal ( 0 - 20 mA) that goes inside the resistor and create a voltage that crossing the switching.

The problem that i have it's that when switch to the current input, after a while, the switch it's breaks ( short circuit between Vdd and Vss). This event happened with 3 switch, and always with the current input and never with the two voltage input!!

The value of the resistor that i have it's 160 ohm ( to limit the max voltage about to 3,2 V ), while the value of the voltage divider it's 200 K about ( always to limit the max voltage to 3,2V).

• Hi harry!

The 1404 have four input: of this input two are voltage input, one it's current input and the last it's disconnected.

The voltage for the two voltage input it's for two kind of voltage: 0-10V and 0-5V ( from two different kind of sensors ) and then the voltage it's limited to 3.2V because goes to an adc input with range 0-3.2V.

The current input have a range 0-20mA and it's converted in a voltage input with the ADC dynamic (0-3.2V).

The 1404 it's powered with +/-15V and then the input signal it's always lower then power (+/-15V).

The input selection are gived by an aduc836 (that works correctly).

When the are selected the voltage input the switch works correctly, but when it's selected the current input, the 1404 works for a while, and then it's broke......

The resistance value used for the current conversion it's 160 ohm....  i think that the problem it's the resistance value and i need to insert a buffer to adapt the current input ....but i m not sure.....

• Hi tntsei,

I have the similar problem to switch current input.

In my case, when the input is broken (for example: S0 for current input), S0 and Vss are shorted.

But the other inputs S1, S2, S3 work fine.

Did you solve this problem?

If yes, could you share your solution to me?

Thank you.

Abby

• Hi Abby,

If S0 and Vss are shorted, it sounds like the max ratings of the ADG1404 are getting exceeded somehow,

What value are you using for your current sense resistor? can you measure the voltage at the input to the ADG1404?

Regards,

David

• Hi David,

Current: 4 to 20 mA

The device is SCT-10S-30A

www.deree.com.tw/sct-10s-split-core-current-transformer.html

Resistor: 470 ohm