Isolated convertor measures motor currents

A new optically isolated, programmable A/D convertor is optimised for measuring motor-phase currents in variable-speed motor-drive control systems.

A new optically isolated, programmable analogue-to-digital (A/D) convertor is optimised for measuring motor-phase currents in variable-speed motor-drive control systems.

The new A/D convertor is designed for general-purpose applications such as conveyors, fans and blowers.

The two-chip (HCPL-7560 and HCPL-0872) optically isolated A/D convertor is designed specifically for interfacing directly to microcontroller/DSP-based motor-drive systems.

The HCPL-7560 isolated sigma-delta modulator allows direct measurement of current by means of a current-sensing resistor.

The HCPL-0872 digital interface IC is programmable to allow tradeoffs between resolution and speed.

The Agilent two-chip solution accelerates time-to-market by eliminating the need to design a complex and costly ASIC.

The HCPL-7560 isolated modulator provides isolation-mode transient immunity of 15 kV/us and a high noise margin by means of a sigma-delta oversampling A/D modulator that converts a low-bandwidth analogue input into a high-speed, digital data stream.

By choosing an appropriate current-sensing resistor, any range of current can be monitored from less than 1A to more than 100A.

The HCPL-0872 digital interface IC converts the single-bit data stream from the isolated modulator into 15bit output words and provides a serial output interface that is compatible with SPI, QSPI or Microwire synchronous bus protocols for direct microcontroller interface.

Resolution and conversion-time tradeoffs are achieved by programming the HCPL-0872 to one of five available conversion modes.

Additional programmable features include a pretrigger circuit that can reduce conversion time to 200ns, a fast over-range detector for quickly detecting short circuits within 3us, an offset calibration to eliminate initial offset and an adjustable threshold detector for detecting non-short-circuit overload conditions.

To assure performance, safety and reliability in industrial environments, both ICs are specified for operation over the -40 to +85C temperature range.

The HCPL-7560 features a 3750V RMS dielectric withstand voltage rating, and has received the following regulatory approvals: UL1577, CSA and IEC/EN/DIN EN60747-5-2.

The HCPL-7560 isolated modulator is supplied in a standard 8-pin, plastic dual-inline package (PDIP) or a gullwing, surface-mount, 8-pin PDIP.

The HCPL-0872 digital interface IC is supplied in a surface-mount, 16-pin, 300mil-wide SOIC package, with tape-and-reel form available.

The Agilent HCPL-7560 and HCPL-0872 are available now through Agilent's direct sales channel and worldwide distribution partners.

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