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I am looking at using the ADuM5210 for voltage and communication isolation.

On page 4 of the datasheet, it says that the Logic High Input Threshold is .7 Viso, .7 VDD1.

Is this listed because the input signals could be from either the left or right sides?

Looking at page 14, it says that Vdd1 is the power supply for Side 1 of the logic circuits and is independent from Vddp. If we are looking to use the 5210 package, will we also need voltage on Vdd2 to produce an output, and does Vdd2 need to be isolated if we require an isolated output communication

In addition, I am looking to have VDDP set to 5 Volts such that VISO is 5 Volts, if I understand correctly Vdd1 and Vdd2 could use lower voltage levels? Looking at page 19 for the schematic, is it recommended not to have Vdd1 and Vdd2 connected together? If Vdd2 does require a voltage, I am looking to power both Vdd1 and Vdd2 from the same supply.

Just trying to understand the device a bit better.

Best Regards.

• My responses below:

1. Logic High Input Threshold is 0.7*Viso, 0.7*VDD1. This is listed because the input signals can be from the VDD1 for the ADuM5210, but could also be from the VISO side for the ADuM5211.

2. will we also need voltage on Vdd2 to produce an output, and does Vdd2 need to be isolated if we require an isolated output communication?  For isolated output communication, VDD2 should be connected to VISO to obtain an isolated voltage from VISO.

3. In your application, it looks like you want VDDP set to 5 Volts and you want to set VISO to 5 Volts, using the resistors R1 & R2 shown in the datasheet Figure 25. In most applications, VDD1 should be connected to VDDP, VDD2 should be connected to VISO.

4. You want the supply and GND pins on side 1 separate from the supply and GND pins on side 2, so that you have power isolation between the 2 sides.  This is needed for functional or safety reasons, depending on your application - what is your application?

Regards, Brian

• Thank you Brian,

The application is to operate a gate driver for a half bridge configuration that needs both voltage and communication isolation. (I need a specific gate driver, and need it to be isolated)

So, if I understand correctly Vdd2 needs to have an applied voltage to produce an isolated output? If you only have voltage on Vdd1 and not Vdd2, you would not have an isolated output?

My problem is that my microprocessor is providing a 3.3 Volt signal (high) which would not reach the 3.5 Volt threshold needed having 5 Volts on Vdd1.

What I would like to do is put 5 Volts on Vddp to get 5Volts on Viso. Have Viso connected to Vdd2 (so 5 volts) but have 3.5 volts on Vdd1 such that the communication signal would meet the threshold. is this feasible?

The grounds of either side will be connected for isolation.

Best,
~Joe

• Joe: It can work much like the way you described:

1. VDDP = 5V supply and the isolated supply VISO should be set for 5V output.

2. VDD1 = 3.3V supply will power side 1 of the ADuM5210 digital isolator which will accept 0 to 3.3V inputs.

3. The VDD2 = 5V = VISO supply will power the VDD2 side of the digital isolator and produce a 0 to 5V on the outputs. These 0 to 5V outputs can be used with the inputs of the gate driver to operate a half bridge.  The 5V VISO can provide up to 30mA of average current for the gate driver, the peak currents would need to come from the bypass capacitors for the gate driver.

Regards, Brian

• HI Brian,

I would like to reconfirm that this setup could configure?

VDD1= 3.3, VDDP = 5V,  VDD2 = VISO = 5V