Datasheet AD7740 (Analog Devices) - 6

AD7740 TERMINOLOGY POWER SUPPLY REJECTION RATIO (PSRR) INTEGRAL NONLINEARITY
This indicates how the apparent input voltage of the VFC is For the VFC, Integral Nonlinearity (INL) is a measure of the maxi- affected by changes in the supply voltage. The input voltage is mum deviation from a straight line passing through the actual kept constant at 2 V, VREF is 2.5 V and the VDD supply is varied endpoints of the VFC transfer function. The error is expressed in ⫾10% at 3.3 V and ±5% at 5 V. The ratio of the apparent change % of the actual frequency span: in input voltage to the change in VDD is measured in dBs. Frequency Span = FOUT(max) – FOUT(min)
OUTPUT FREQUENCY OFFSET ERROR FOUT
Ideally, the output frequency for 0 V input voltage is 10% of
0.9 fCLKIN
f
GAIN ERROR
CLKIN in unbuffered mode. The deviation from this value referred to the input is the offset error at BUF = 0. In buffered mode the minimum output frequency (corresponding to 0.10 V minimum input voltage) is 13.2% of fCLKIN at VREF = 2.5 V. The deviation
IDEAL
from this value referred to the input is the offset error at BUF = 1.
WITH OFFSET ERROR ONLY
Offset error is expressed in mV.
WITH OFFSET ERROR AND GAIN ERROR GAIN ERROR 0.1
This is a measure of the span error of the VFC. The gain is the
fCLKIN INPUT
scale factor that relates the input VIN to the output FOUT.
VOLTAGE 0
The gain error is the deviation in slope of the actual VFC transfer
OFFSET REFIN VIN ERROR
characteristic from the ideal expressed as a percentage of the full- scale span. See Figure 2. Figure 2. Offset and Gain
OFFSET ERROR DRIFT
This is a measure of the change in Offset Error with changes in temperature. It is expressed in µV/°C.
GAIN ERROR DRIFT
This is a measure of the change in Gain Error with changes in temperature. It is expressed in (ppm of span)/°C. REV. C – 5 –