LTC2410 24-Bit No Latency ∆ΣTM ADC with Differential Input and ...

LTC2410APPLICATIO S I FORATIOU W U UThe error associated with the 10V excitation would be–80ppm. Hence, overall reference error could be as highas 130ppm, the average of the two.Figure 53 shows a similar scheme to provide excitationusing resistor arrays to produce precise gain. The circuitis configured to provide 10V and –5V excitation to thebridge, producing a common mode voltage at the input tothe LTC2410 of 2.5V, maximizing the AC input range forapplications where induced 60Hz could reach amplitudesup to 2V RMS .The last two example circuits could be used where multiplebridge circuits are involved and bridge output can bemultiplexed onto a single LTC2410, via an inexpensivemultiplexer such as the 74HC4052.Figure 54 shows the use of an LTC2410 with a differentialmultiplexer. This is an inexpensive multiplexer that willcontribute some error due to leakage if used directly withthe output from the bridge, or if resistors are inserted asa protection mechanism from overvoltage. Although thebridge output may be within the input range of the A/D andmultiplexer in normal operation, some thought should begiven to fault conditions that could result in full excitationvoltage at the inputs to the multiplexer or ADC. The use ofamplification prior to the multiplexer will largely eliminateerrors associated with channel leakage developing errorvoltages in the source impedance.V S2.7V TO 5.5VR125.5k0.1%342V CCREF +REF –LTC2410PLATINUM100ΩRTD56IN +IN –GND1, 7, 8, 9,10, 15, 162410 F50Figure 50. Remote Half Bridge Interface5VR210k0.1%R110k, 5%R310k5%1µF+–5VLTC1050560Ω342V CCREF +REF –LTC2410PLATINUM100ΩRTD10k10k56IN +IN –GND1, 7, 8, 9,10, 15, 162410 F5140Figure 51. Remote Half Bridge Sensing with Noise Suppression on Reference