17-11-2012, 04:01 PM
Analog-to-Digital Converters
1Analog-to-Digital.pdf (Size: 969.3 KB / Downloads: 72)
Integrating ADC(or Dual-Slope ADC)
• A popular approach for realizing high-accuracy data
conversion on very slow-moving signals
• Very low offset error
Very low gain error
Highly linear
Small amount of circuitry required
• Simplified diagram
–From the above equations , the digital output does not
depend on the time constant, R1C1.
R1 and C1 should be chosen such that a reasonable
large peak value of Vx is obtained without clipping to
reduce noise effects.
–For a single-slope conversion, gain error occurs and is
a function of R1C1
Resistor-Capacitor Hybrid ADC
2) Successive-approximation conversion is performed
to find the two adjacent resistor nodes that have
voltages larger and smaller than Vin. One bus will be
connected to one node while the other is connected
to the other node.
3) A SA using the capacitor-array network is then done.
Charge-Redistribution with Error Correction
‧Calibration
– calculating the correction terms required,
and then storing in a data register as DVei.
–During a regular SA operation, whenever a
particular capacitor is used, its error is
cancelled by adding the value stored in
the data register to that stored in an
accumulator register, which contains the
sum of the correction terms for all of the
other capacitors currently connected to Vref.