SLAA868A December   2018  – September 2024 DAC60501 , DAC80501 , DAC8830

 

  1.   1
  2.   2
  3.   Trademarks

Design Goals

VCC DAC Output Voltage Output Current Error Maximum Resistive Load
5V 0mV – 510mV 0mA – 100mA <0.25% FSR 44.9Ω

Design Description

The programmable low-side current sink sets the current through a load based on the DAC output voltage. The current is sensed through RSET and the op amp biases a transistor regulate the current through the load. Components CF, RISO, and RFB provide compensation to verify the stability of the circuit.

Design Notes

  1. Choose a DAC with low offset error, gain error, and drift. Use RRIO op amps to reduce error near the rails and maximize resistive load drive. Choose an op amp with low offset voltage to minimize error.
  2. Use a high-precision, low-drift resistor for RSET for accurate current regulation.
  3. RSET should be minimized for efficiency and power dissipation. Most of the power dissipation should occur through RLOAD
  4. To drive large RLOAD, use a separate high voltage supply for driving the current to the load.

Design Steps

  1. Calculate the RSET value for the maximum DAC output voltage and desired maximum output current.
  2. The maximum resistive load is given by:
  3. Verify that Q1 is rated for the power dissipation at maximum current.
  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

AC Loop Gain Analysis

Devices

Device Key Features Link Other Possible Devices
DACs
DAC60501 12-bit resolution, 1LSB INL, Single-Channel, Voltage Output DAC with 5ppm/°C Internal Reference True 12-bit, 1-ch, SPI/I2C, voltage-output DAC in WSON package with precision internal reference Precision DACs (≤10 MSPS)
DAC80501 16-bit resolution, 1LSB INL, Single-Channel, Voltage Output DAC with 5ppm/°C Internal Reference True 16-bit, 1-ch, SPI/I2C, voltage-output DAC in WSON package with precision internal reference Precision DACs (≤10 MSPS)
DAC8830 16-bit resolution, single channel, ultra-low power, unbuffered output, 1 LSB INL, SPI, 2.7V to 5.5V supply 16-bit, single-channel, ultra-low power, voltage output DAC Precision DACs (≤10 MSPS)
Amplifiers
TLV9061 Ultra-Small, 0.3-mV Offset, Rail-to-Rail I/O, 1.8V to 5.5V supply Single, 5.5V, 10MHz, RRIO operational amplifier for cost-optimized applications Operational amplifiers (op amps)
OPA317 Zero-Drift, Low-Offset, Rail-to-Rail I/O, 35-µA supply current max, 2.5V to 5.5V supply Low Offset, Rail-to-Rail I/O Operational Amplifier Operational amplifiers (op amps)
OPA388 Precision, Zero-Drift, Zero-Crossover, Low Noise Rail-to-Rail I/O, 2.5V to 5.5V supply Single, 10MHz, CMOS, zero-drift, zero-crossover, true RRIO precision operational amplifier Operational amplifiers (op amps)