Analog Devices uses six designations to inform our customers where a semiconductor product is in its life cycle. From emerging innovations to products which have been in production for twenty years, we understand that insight into life cycle status is important. Device life cycles are tracked on their individual product pages on analog.com, and should always be consulted before making any design decisions.
This particular articl/edocument/design has been retired or deprecated, which means it is no longer maintained or actively updated, even though the devices themselves may be Recommended for New Designs or in Production. This page is here for historical/reference purposes only.
The motor control system allows the measurement of the Ia(phase A current), Ib(phase B current) and It(total current) as well as the measurement of Vbus using signal chains which involve components from both the controller and low voltage driver boards.
The Ia and Ib currents are sensed using 6mΩ shunt resistors. There are two possible measurement paths showing measurement techniques for the case where the ADC can be placed close to the shunt resistor and for the case where the ADC cannot be placed in the proximity of the shunt resistor. Both techniques aim to get the best measurement accuracy.
Case 1: The ADC is placed in the proximity of the shunt resistor
where
Case 2: The ADC is not placed in the proximity of the shunt resistor
where
The Ia and Ib XADC measurement chain utilizes the entire path of the regular measurement chain and adds on the controller board after the AD7401 isolated ΣΔ modulator a Sallen Key analog reconstruction filter implemented using AD8646 operational amplifiers. The combination between the isolated ΣΔ modulator and the analog reconstruction filter provides a convenient and cheap way to achieve analog isolation of the XADC input signals. This analog isolation technique is described in this paper.
The It current is sensed using a 5mΩ shunt resistor. There are two possible measurement paths showing measurement techniques for the case where the ADC can be placed close to the shunt resistor and for the case where the ADC cannot be placed in the proximity of the shunt resistor. Both techniques aim to get the best measurement accuracy.
Case 1: The ADC is placed in the proximity of the shunt resistor
where
Case 2: The ADC is not placed in the proximity of the shunt resistor
where
The It XADC measurement chain utilizes the entire path of the regular measurement chain and adds on the controller board after the AD7401 isolated ΣΔ modulator a Sallen Key analog reconstruction filter implemented using AD8646 operational amplifiers. The combination between the isolated ΣΔ modulator and the analog reconstruction filter provides a convenient and cheap way to achieve analog isolation of the XADC input signals. This analog isolation technique is described in this paper.
Vbus sensing is done on the drive board using a resistive divider and an attenuation circuit implemented with the AD8207 operational amplifier. The total gain of this stage is 0.83 giving an output range of 0..5V. The analog signals go through the connector to the controller board. On the controller board the analog signals coming from the drive board are transferred from the 0..5V input range to a 0..250mV range suited for the AD7401 ΣΔ modulator. The attenuation is done using the ADA4084-2 amplifier.
The Vbus XADC measurement chain utilizes the entire path of the regular measurement chain and adds on the controller board after the AD7401 isolated ΣΔ modulator a Sallen Key analog reconstruction filter implemented using AD8646 operational amplifiers. The combination between the isolated ΣΔ modulator and the analog reconstruction filter provides a convenient and cheap way to achieve analog isolation of the XADC input signals. This analog isolation technique is described in this paper.