I am using a wide input dc/dc converter chip with a Vin Gnd and a Vout Gnd.
On the input side of the dc/dc Vin is a 12V battery and on the output side is a 5V micro.
I would like the micro on the Vout side of the dc/dc to read the battery voltage level on Vin, but I have stumbled across a problem that they share different grounds. I have selected the ADUM3190 isolated amp to overcome this problem.
OK so far so good, I have decided to use figure 29 example circuit on page 13 of the datasheet, but I have a couple of questions.
1) I was hoping I could make VDD1 = 5V(micro side) and VDD2 = 12V(battery side), but looking hard at the datasheet at the top of page 3 just below specifications it quotes "VDD1 = VDD2 = 5 V, unless otherwise noted" Does this mean I cannot make VDD2 a different voltage to VDD1?
2) To measure the battery voltage I have dropped the voltage down using a resistor network (see below), and I am feeding this voltage directly into pin 12 (+IN) on figure 29 example. The output of figure 29 pin 7 (EA Out) I am feeding straight into the ADC pin on the 5V micro.
Vin (9V - 14.4V) ------ 9k3 Res ------- Vout (3V - 4.8V) ------- 4k7 Res ------ GND
3) I am using exactly the Figure 29 circuit with ROD being 5k (1mA = 5V/5K). Am I correct in thinking the output (EA Out) swings between 0.4 V and 2.4 V, when my input (+IN) swings between 3V and 4.8V.
4) If you see any errors in my design, components missed, please let me know?
Look forward to your reply.