The MAX14001/MAX14002 are isolated, single-channel analog-to-digital converters (ADCs) with programmable voltage comparators and inrush current control optimized for configurable binary input applications. 3.75kVRMS of integrated isolation is provided between the binary input side (field-side) and the comparator output/SPI-side (logic-side) of the MAX14001/MAX14002. An integrated, isolated, DC-DC converter powers all field-side circuitry, and this allows running field-side diagnostics even when no input signal is present. The 20-pin SSOP package provides 5.5mm of creepage and clearance with group II CTI rating.
These devices continually digitize the input voltage on the field-side of an isolation barrier and transmit the data across the isolation barrier to the logic-side of the device where the magnitude of the input voltage is compared to programmable thresholds. The binary comparator output pin is high when the input voltage is above the upper threshold and low when it is below the lower threshold. Response time of the comparator to an input change is less than 150μs with filtering disabled. With filtering enabled, the comparator uses the moving average of the last 2, 4, or 8 ADC readings. Both filtered and unfiltered ADC readings are available through the 5MHz SPI port, which is also used to set comparator thresholds and other device configuration.
The MAX14001/MAX14002 control the current of a binary input through an external, high-voltage FET. This current cleans relay contacts and attenuates input noise. An inrush comparator monitoring the ADC readings triggers the inrush current, or wetting pulse. The inrush trigger threshold, current magnitude, and current duration are all programmable in the MAX14001 but are fixed in the MAX14002. When the high-voltage FET is not providing inrush current, it switches to bias mode. Bias mode places a small current load on the binary input to attenuate capacitively coupled noise. The level of bias current is programmable between 50μA and 3.75mA in both the MAX14001 and MAX14002. This allows optimization of the tradeoff between noise attenuation and power dissipation.
Design Solution: Isolated ADC with Integrated DC-DC Converter Simplifies Field-Side Circuitry ›
Applications
- Distribution Automation
- High-Voltage Binary Input (12V–300V)
- Industrial Control, Multi-Range, Digital Input Modules with Individually Isolated Inputs
- Substation Automation
