SLAA869A December   2018  – September 2024 DAC80501 , DAC8560 , DAC8830

 

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  3.   Trademarks

Design Goals

DAC Supply VoltageAmplifier Supply VoltageDAC VoltageOutput VoltageError
5V±15V0V–2.5V±10V<0.25% FSR

Design Description

The unipolar to bipolar output voltage circuit converts the voltage from a unipolar DAC into a bipolar voltage span. The circuit consists of a DAC, op amp, voltage reference, and three resistors to set the scale and span of the bipolar output voltage. This circuit is commonly used in Analog output module, Field Transmitters, and other applications requiring a programmable bipolar voltage.

Design Notes

  1. Choose a DAC with low gain error, offset error, drift, and INL. Use a high-voltage op amp with low offset voltage and low offset voltage drift.
  2. Use precision 0.1% or better tolerance resistors with low temperature drift.
  3. Use a DAC with integrated reference to minimize solution size.

Design Steps

1. The voltage output based on DAC voltage, reference voltage, and resistors is given by:

2. Set the DAC voltage to zero to calculate ratio of RFB and RG1 to create the desired negative full-scale output. Select standard resistor values to produce this gain.

3. Calculate RG2 based on the full-scale range required, in this case 20V to produce ±10V range.

4. The output error can be approximated based on DAC TUE, amplifier offset voltage, resistor tolerance, and reference initial accuracy using root sum square (RSS) analysis.

DC Transfer Characteristic

Small Signal Step Response

Devices

DeviceKey FeaturesLinkOther Possible Devices
DACs
DAC856016-bit resolution, single channel, internal reference, low power, 4 LSB INL, SPI, 2V to 5.5V supply16-bit, single-channel, low-power, ultra-low glitch, voltage output DAC with 2.5V, 2ppm/°C referencePrecision DACs (≤10 MSPS)
DAC8050116-bit resolution, 1LSB INL, Single-Channel, Voltage Output DAC with 5ppm Internal ReferenceTrue 16-bit, 1-ch, SPI/I2C, voltage-output DAC in WSON package with precision internal referencePrecision DACs (≤10 MSPS)
DAC883016-bit resolution, single channel, ultra-low power, unbuffered output, 1 LSB INL, SPI, 2.7V to 5.5V supply16-bit, single-channel, ultra-low power, voltage output DACPrecision DACs (≤10 MSPS)
Amplifiers
OPA188Low-Noise, Low Offset Voltage, RRO, Zero-Drift, ±2V to ±18V supplyPrecision, Low-Noise, Rail-to-Rail Output, 36V Zero-Drift Operational AmplifierOperational amplifiers (op amps)
OPA196Low-Power, Low Offset Voltage, RRIO, ±2V to ±18V supplyOne-channel, 1MHz, rail-to-rail input and output 1.8V to 5.5V operational amplifierOperational amplifiers (op amps)
TLV170Cost Sensitive, Rail-to-Rail Output, ±1.35V to ±18V supplyLow Offset, Rail-to-Rail I/O Operational AmplifierOperational amplifiers (op amps)

Links to Key Files:

Texas Instruments, Bipolar ±10V Output from a Unipolar DAC for Industrial Voltage Drivers, TIPD125 tool