FAQ

### Q

1.:What is the difference between the AD7745 and the AD7747? Is it only the
different resolution and accuracy and the input range?
2.:What is the difference between the models for the AD7746: ARUZ / REEL / REEL
7 ?
3.:If the resolution of the…

### Q

The datasheet states that the max. common-mode cap for a AD7745 is 17pF. Is it
possible to connect 50pF?
Maybe with a voltage devider at EXCx?

### A

1) Connect a known fixed capacitor in series with the sensor. That would work
by equation C = C1 x…

### Q

Is it possible to extend the range of measured capacitances above 4 pF by
decreasing excitation signal e.g. to a value of VDD/4 ?

### A

1) Connect a known fixed capacitor in series with the sensor. That would work
by equation C = C1 x C2 / (C1 + C2…

### Q

They make humidiysensors with a capacitive output. Therefor, they have
interests in CDC as AD7745. But the nominal capacitance of their sensors is
180pF with a max. change of +-50pF, which is higher than the AD7745 can handle.

### A

1) Connect a known…

### Q

Are there some protection circuit in front of the AD7745 to limit the input
voltage and current while not affecting the capacitance measurement.

### A

the AD7745 has no over voltage protection please refer to the absolute maximum
ratings in the datasheet…

• ### RE: Analog switch for AD7745

I forgot to update this post, but it works very well. I connected the ADG1208 directly to the AD7746 and I have good performances.

### Q

How to start a conversion in single conversion mode?

### A

How to start a conversion in single conversion mode:
It is the operation of writing "010" to the mode bits MD2-MD0 in the
configuration register which starts the conversion.
There…

### Q

The absolute maximum ratings for AD7745 state  the following;

I expect this device to be able to tolerate the Pb free solder temperature of
260C , Is AD7745 able to withstand up to 260C during Pb free soldering process?

### A

Our parts are qualified…