1N752A
Generic
A 5.6V Zener diode, D1, provides a sufficient bias because the V – pin draws very little current.
Design DocumentAnalog
A Single Supply RS232 Interface for Bipolar A to D Converters
Design guide for a single-supply 5V RS232 interface for bipolar ADCs using the LT1180 transceiver to provide power for the LTC1094 converter and LT1021 reference.
Overview
This design document describes a method for operating bipolar analog-to-digital converters from a single 5V supply. It utilizes the LT1180 RS232 transceiver's internal charge pump to generate the necessary positive and negative voltage rails for the LTC1094 serial ADC and an LT1021-5 precision voltage reference. The circuit supports a +/-5V input range with a total quiescent current of 37mA. It includes details on generating the chip select signal using a peak detector, managing ground noise for 12-bit accuracy, and adapting the design for the LTC1294 12-bit ADC.
Use Cases
- RS232 data acquisition systems
- Single-supply bipolar signal processing
- Battery-powered industrial instrumentation
- Remote sensor monitoring interfaces
Topics
LT1180
LTC1094
LT1021-5
RS232 transceiver
bipolar ADC
single supply
charge pump
1N752A
2N3906
LTC1294
LTC1093
serial A/D converter
Referenced Parts
LT1021-5
Linear Technology
These design problems are solved with an LT1021 precision reference, which delivers a stable, low noise, 5V signal from the LT1180’s V+ output.
LT1180
Linear Technology
The LT1180 RS232 transceiver includes a charge pump which produces low ripple supplies
LTC1094
Linear Technology
The LTC1094 serial A to D converter requires both a low noise supply and reference voltage for accurate operation.
LTC1294
Linear Technology
Note 3: The LTC1094 in Figure 1 was directly replaced with an LTC1294, with no changes to the circuit.
2N3906
Generic
peak detector, constructed with a single PNP transistor. ... Figure 1 shows 2N3906.
LTC1093
Linear Technology
Figure 2. LTC1093/4 Operating Sequence Example
| 1N752A | Generic | A 5.6V Zener diode, D1, provides a sufficient bias because the V – pin draws very little current. |
| LT1021-5 | Linear Technology | These design problems are solved with an LT1021 precision reference, which delivers a stable, low noise, 5V signal from the LT1180’s V+ output. |
| LT1180 | Linear Technology | The LT1180 RS232 transceiver includes a charge pump which produces low ripple supplies |
| LTC1094 | Linear Technology | The LTC1094 serial A to D converter requires both a low noise supply and reference voltage for accurate operation. |
| LTC1294 | Linear Technology | Note 3: The LTC1094 in Figure 1 was directly replaced with an LTC1294, with no changes to the circuit. |
| 2N3906 | Generic | peak detector, constructed with a single PNP transistor. ... Figure 1 shows 2N3906. |
| LTC1093 | Linear Technology | Figure 2. LTC1093/4 Operating Sequence Example |