Difference between revisions of "ADC and DAC linearity in Readout Card"
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====Test Results==== | ====Test Results==== | ||
| − | + | A 200kHz 0mV-offset 250mV-pk-pk triangular wave is applied to the input of the preamp chain (JP1) through a 26dB attenuator. | |
On a Rev D card, We ran <code>rc_dnl_test</code> script and the calculated DNLs are: | On a Rev D card, We ran <code>rc_dnl_test</code> script and the calculated DNLs are: | ||
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ch7: 0.149 LSB SRC-213_1262987653 | ch7: 0.149 LSB SRC-213_1262987653 | ||
The ramp is slightly clipped on both sides, check 1262991813_raw | The ramp is slightly clipped on both sides, check 1262991813_raw | ||
| − | |||
=== INL or Integral non-linearity error=== | === INL or Integral non-linearity error=== | ||
This is typicall of less importance in imaging systems. INL is the deviation of the ADC code transfer function from the stright line. | This is typicall of less importance in imaging systems. INL is the deviation of the ADC code transfer function from the stright line. | ||
Listed in the datasheet, INL for ADC9252 is 1.5bits and for AD6644 is | Listed in the datasheet, INL for ADC9252 is 1.5bits and for AD6644 is | ||
Revision as of 15:12, 20 October 2014
Contents
ADC Linearity
RevB uses AD6644 and RevE uses AD9252
In general, ADC non-linearity can be broken down to offset-error, gain-error, DNL error and INL error.
DNL or Differential Non-linearity error
DNL is the difference between an actual analog-step-width and the ideal value corresponding to 1 lsb. For an ideal ADC, DNL is zero and all transition values are spaced exactly 1 lsb apart. Listed in the datasheet, DNL for AD9252 is +-0.4LSB (typical) and for AD6644 is +-0.25LSB (typical). AD9252 datasheet includes a DNL plot for fin=2.3MHz.
Test Results
A 200kHz 0mV-offset 250mV-pk-pk triangular wave is applied to the input of the preamp chain (JP1) through a 26dB attenuator.
On a Rev D card, We ran rc_dnl_test script and the calculated DNLs are:
>rc_dnl_test -a SRC-213 ch0: 0.177 LSB SRC-213_1262987653 (with no R37, input at R19) ch2: 0.432 LSB(50-Ohm termination card plugged in) ch3: 0.421 LSB (50-Ohm termination card plugged in) ch4: 0.147 LSB SRC-213_1262987653 ch5: 0.181 LSB SRC-213_1262987653 ch6: 0.149 LSB SRC-213_1262987653 ch7: 0.149 LSB SRC-213_1262987653
The ramp is slightly clipped on both sides, check 1262991813_raw
INL or Integral non-linearity error
This is typicall of less importance in imaging systems. INL is the deviation of the ADC code transfer function from the stright line. Listed in the datasheet, INL for ADC9252 is 1.5bits and for AD6644 is
