Maxim releases analogue-output signal conditioners

Maxim Integrated Products has introduced the Max15500 and Max15501 industrial analogue-output signal conditioners.

The company claims that these devices offer higher functionality, enhanced integration and smaller total solution size than some competitive devices.

They feature: a programmable voltage-output amplifier and a current-output amplifier; +/-10V and 4-20mA outputs operating directly from a 24V field supply; +/-35V circuit protection; an error reporting capability; and daisy-chain flexibility.

The Max15500 and the Max15501 save board space and design time in 4-20mA and/or bipolar/unipolar voltage-output applications.

They are suitable for programmable logic controller (PLC) analogue outputs, distributed input/output (I/O), embedded systems and industrial control and automation.

Their high integration adds flexibility for designs, according to Maxim.

A single device is used for channel-isolated applications and multiple devices are used for group-isolated applications.

The Max15500 and the Max15501 simplify the design of PLC modules.

The devices' integrated voltage amplifiers and voltage-to-current converters eliminate the need for additional resistors, thus saving board space.

Only the current gain-setting resistor is external to the device.

They offer fault detection, including open-circuit load in current mode, short-circuit load in voltage mode, over-temperature and supply brownout.

Both intermittent and permanent load faults can be detected.

If a fault occurs, the open-drain fault-interrupt pin will be pulled low.

The status of the fault bits is available through the SPI interface.

The new analogue output conditioners give +5 per cent and +20 per cent over range, providing a programmable current of up to +/-24mA or voltage up to +/-12V proportional to a control-voltage signal, as required by PLC manufacturers.

The control voltage is typically supplied by an external DAC with an output voltage range of 0V to 4.096V for the Max15500 and 0V to 2.5V for the Max15501.

The output current and voltage are selectable as either unipolar or bipolar.

A Hart signal may be added to the input signal.

Many industrial-control systems require error detection and error handling.

Competitive devices use three times the number of interrupt flags for error detection, thus requiring more pins and potentially more optoisolators.

None of these fault pins are latched, so more microcontroller interrupts are needed to detect intermittent errors.

The company also claims that competitive devices monitor fewer sources of error and none of them offer power-supply monitoring.

The Max15500 and the Max15501 have error handling and reporting capabilities.

Instead of using separate interrupt pins, the devices report the status of short-circuit, open-circuit, brownout and over-temperature conditions through an SPI interface and an additional open-drain interrupt output.

This fault detection scheme is claimed to reduce the I/O pin count and software loading required by the host processor.

For error tracking and troubleshooting systems, an error register stores the error source.

The Max15500 and the Max15501 include an analogue output to monitor the load.

Jeremy Tole, Maxim's director of business development for data converters, said: 'Designers can now operate their output conditioners directly from a +/-24V field power supply.' The Max15500 and the Max15501 have a standard field supply of +/-24V and +/-20 per cent.

With a +/-24V supply voltage, the Maxim devices can handle a typical load of 750ohms in current mode.

With +/-32.5V supplies, this increases to 1,000ohms.

Voltage protection will save money and board space as the additional protection circuitry typically required in other solutions is not necessary.

The Max15500 and the Max15501 outputs, power-supply inputs and sense inputs are protected against over-current conditions, a short to ground or supply voltages up to +/-35V.

The devices are programmed through a three-wire SPI-/QSPI-/Microwire-/DSP-compatible serial interface with daisy-chain capability.

This interface saves board space and reduces the complexity of optically isolated and transformer-isolated applications.

A device-ready logic output and two device-select inputs facilitate a daisy-chain arrangement for multiple device applications.

A chain of Max15500 and Max15501 devices can be terminated with any standard SPI-compatible single device.

The Max15500/Max15501 portion of the chain continues to display timing parameters comparable to a single device.

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