They also provide several types of digital outputs, including 2-wire CMOS with a single bit output (with or without clock), RS422 Manchester or LVDS Manchester, which minimizes the required connections, or 4-wire outputs according to LVDS or RS422 standards (with or without clock). The digital output allows the user to choose the filter used in the bit stream to optimize the combination of resolution and response time, depending on the application. The digital outputs are also inherently immune to noise in harsh environments.
In a typical transfer function, the average bit current density is 50% for zero current on the primary and 10% or 90% for maximum currents in the negative or positive directions.
In the HLSR-PW models, in one operating mode, the clock is obtained from the sensor at 10 MHz, and both the clock and data are single-ended signals with CMOS levels. Alternatively, the output can be Manchester-encoded on 2 pins, thus complying with the RS422 standard. These sensors are the same size as the analog HLSR.
The HO-NPW, HO-PW, and HO-SW models can be single-terminated and support Manchester modes, like the HLSR-PW models, but they add two more pins so that the clock and data can be differential signals that comply with RS422 and LVDS standards. Furthermore, the transducer clock can be configured as an input in the 5–12.5 MHz range to use a single clock throughout the system.
The new transducers can use a 5V power supply, and the operating temperature range is -40°C to +105°C.
Different filters can be used on a given bit stream. An example for a “current control loop” function: if a sinc3 filter with an over-sampling ratio (OSR) of 512 is used, the effective resolution of a 150A sensor is 12 bits and the bandwidth is 5 kHz.
Alternatively, for an “out-of-range detection” function, a sinc2 filter with an OSR of 16 would offer a response time of 5.2 µs from the same bit current, but the resolution would be reduced to 6 bits.
The HO family transducers also incorporate an over-current detection (OCD) function that measures the current level before the A/D converter. The OCD response time is 2 µs.
- Details
- Category: Integrated Circuits
Open-loop Hall effect current transducers with digital outputs for drive applications
LEM has expanded its range of HO and HLSR open-loop Hall effect current transducers with digital output, featuring A/D conversion via a built-in sigma-delta modulator. This provides a 1-bit serial output. These new components are designed to measure nominal currents of 16, 32, 40, 50, 80, 100, 120, 150, 200, and 250 ARMS in four different mechanical configurations (printed circuit board and panel mount) and offer up to 12-bit resolution with a bandwidth of 20 kHz.
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