3-phase BLDC current sensing questions

[secad]

Hi folks. Has current monitoring on 3-phase BLDC servo drivers been discussed on this forum? The sort of issues I am thinking of are ADC conversion timing, bandwidth of current sense circuit, opamp overload by the leading Rsns*Isns voltage spike, reverse current sensing, etc.
I am using the Freescale MCF51AC256 (2 PWM timer modules) to control 2 tightly coupled motors with sinusoidal 3-phase drive through International Rectifier IRAM136-3023B (150V 30A) inverter drive modules.
The problem is noisy, unreliable current readings interfering with attempts at torque limit control.
Any thought?

[nhatson.elec]

you can use shunt senses, for opto sense you can use HCPL-7800 or lem sensor

b.r

[secad]

Thanks nhatson.elec, the HCPL-7800 looks really nice. I had a much less elegant arrangement with linearized optocouplers & op amps.
This looks suitable for direct measurement of each motor lead phase current. I was hoping to derive this from the current sense resistor in the IRAM module, but the sense voltage is only present for a short time period (a few uSecs) if the BAT+ voltage is high and the motor RPM is low (low back emf).
This makes it hard to reliably trigger the ADC within the pulse period but while avoiding the leading edge spike.
Is there some cct configuration that can get around this?
I have the sneaking feeling that the HCPL-7800's in the motor phase leads are the way to go, & just leave the module's internal Isense resistor to do its job of protecting the module.
With the HCPL-7800's, if my understanding is right, I should be able to take ADC readings of phase current any time I want, as it should be relatively constant due to motor inductance. Does this sound right-ish?