ADXRS150 ref voltage fluctuations

The gyro uses the same reference, so variations should be transparent. Why is the supply rail changing so dramatically? How are you measuring the variations? What does your summing circuit actually look like?

RL

The Ref supply rejection is stated at 1mV/V which is 60dB and that's only a typical value. No max is given.

I built a fairly sensitive device with one of those and that 2.5v ref gave me fits. It's very high impedance and almost everything I connected to that pin (including a plain old ceramic cap) was worse than nothing. In later gyros they got rid of the REF output in favor of other output formats.

i measured the variation using oscilloscope (Textronics TDS2024). The summing (or difference) ckt is built with opamp OP27AZ.with 4.7k resistors at both the input terminals and 47k in the feedback (required gain was 10). the rate out of gyro is connected to +ve i/p and the ref 2.5v is connected at -ve i/p

-CCD

I'd load the 2.5V reference pin with ~ 50uA to ground (47k), and bypass it locally.

I'd increase R1 to a minimum of 100K (adjusting other diff gain elements to suit).

This ensures that the reference always sees a load to ground, in spite of biasing requirements of the ICs and gain network, and is never overloaded.

I'd also stick a resistor in series with the comparator's inputs, because I just don't like bare analog IC input pins.

RL

Hi, thanx for the suggestions, i'm operating on the limits of the current from ref. I think the biasing suggested by Legg will sort out the problem, I'll check out wiht my ckt. Thankx guys.

Ok, but check the sink capability of that node. It might not have any.