Contents
What is the offset error on a DAC?
The deviation from the ideal code 0 voltage is the offset error. Offset errors are normally bipolar and often expressed in a DAC data sheet in terms of millivolts. The gain of a DAC is the slope of the output characteristic.
Do you have to calibrate a precision calc system?
Systems must either be designed to perform with the required gain and offset errors without calibration, or they must be calibrated. High-accuracy systems most often require calibration, which can be done in the analog domain, the digital domain, or a combination of both.
How are offset and gain errors measured in INL?
INL is a measure of how far the characteristic deviates from the ideal. It is measured in two ways: end to end, and best fit. To measure INL, the offset and gain errors are first removed. Figure 3.
What is the gain error in DAC calc?
So, initially the calibrated DAC code follows the input code, until the gain error results in -0.5 LSB of error. At this point one code is missed and the output jumps to +0.5 LSB of error. This can be repeated as many times as necessary to calibrate the gain error.
How is the offset and gain of the DAC calculated?
If offset error is the y-intercept (b) in the transfer function equation (y = m x + b), then gain error is the m, for slope. Gain error shows up as a deviation from the slope of the ideal transfer function for the DAC. The amount of gain error is measured in Least Significant Bits (LSBs) or as “percent full-scale range” (%FSR) of the DAC.
What is the offset voltage of a 16 bit DAC?
A 16-bit DAC has 216 = 65536 possible codes. If the offset voltage is measured at – 10mV, then the offset value is 10mV, and the offset voltage is equivalent to 54 LSB because 10mV/.184mV = 54 LSB. Writing 54 LSB to the DAC yields an output of zero volts. To compensate, you will add 54 LSB to the input of the DAC.
Is the current output of a DAC always at ground potential?
The current-output node is often connected to an op amp configured as a current-to-voltage converter. For matching reasons, the op-amp feedback resistor is usually included on the DAC chip. The switches are always at ground potential, and their voltage rating does not affect the reference voltage rating.