REV. C

–8–

AD7713

Pin

Mnemonic

Function

21

DRDY

Logic output. A falling edge indicates that a new output word is available for transmission. The DRDY pin

will return high upon completion of transmission of a full output word. DRDY is also used to indicate

when the AD7713 has completed its on-chip calibration sequence.

22

SDATA

Serial Data. Input/Output with serial data being written to either the control register or the calibration

registers and serial data being accessed from the control register, calibration registers or the data register.

During an output data read operation, serial data becomes active after RFS goes low (provided DRDY is

low). During a write operation, valid serial data is expected on the rising edges of SCLK when TFS is low.

The output data coding is natural binary for unipolar inputs and offset binary for bipolar inputs.

23

24

DGND

Ground reference point for digital circuitry.

TERMINOLOGY

INTEGRAL NONLINEARITY

This is the maximum deviation of any code from a straight line

passing through the endpoints of the transfer function. The end-

points of the transfer function are zero scale (not to be confused

with bipolar zero), a point 0.5 LSB below the first code transi-

tion (000 . . . 000 to 000 . . . 001) and full scale, a point 0.5 LSB

above the last code transition (111 . . . 110 to 111 . . . 111). The

error is expressed as a percentage of full scale.

POSITIVE FULL-SCALE ERROR

Positive full-scale error is the deviation of the last code transi-

tion (111 . . . 110 to 111 . . . 111) from the ideal input full-scale

voltage. For AIN1(+) and AIN2(+), the ideal full-scale input

either AIN1(–) or AIN2(–) as appropriate; for AIN3, the ideal

full-scale voltage is +4

× V

scale error applies to both unipolar and bipolar analog input

ranges.

UNIPOLAR OFFSET ERROR

Unipolar offset error is the deviation of the first code transition

from the ideal voltage. For AIN1(+) and AIN2(+), the ideal

input voltage is (AIN1(–) + 0.5 LSB); for AIN3, the ideal input

is 0.5 LSB when operating in the Unipolar Mode.

BIPOLAR ZERO ERROR

This is the deviation of the midscale transition (0111 ...111

to 1000 . . . 000) from the ideal input voltage. For AIN1(+) and

AIN2(+), the ideal input voltage is (AIN1(–) – 0.5 LSB); AIN3

can only accommodate unipolar input ranges.

BIPOLAR NEGATIVE FULL-SCALE ERROR

This is the deviation of the first code transition from the ideal

input voltage. For AIN1(+) and AIN2(+), the ideal input volt-

commodate unipolar input ranges.

POSITIVE FULL-SCALE OVERRANGE

Positive full-scale overrange is the amount of overhead available

to handle input voltages on AIN1(+) and AIN2(+) inputs

than +4

× V

ages due to system gain errors in system calibration routines)

without introducing errors due to overloading the analog modu-

lator or to overflowing the digital filter.

NEGATIVE FULL-SCALE OVERRANGE

This is the amount of overhead available to handle voltages on

overloading the analog modulator or overflowing the digital filter.

OFFSET CALIBRATION RANGE

In the system calibration modes, the AD7713 calibrates its offset

with respect to the analog input. The offset calibration range

specification defines the range of voltages that the AD7713 can

accept and still calibrate offset accurately.

FULL-SCALE CALIBRATION RANGE

This is the range of voltages that the AD7713 can accept in the

system calibration mode and still calibrate full scale correctly.

INPUT SPAN

In system calibration schemes, two voltages applied in sequence

to the AD7713’s analog input define the analog input range.

The input span specification defines the minimum and maxi-

mum input voltages from zero to full scale that the AD7713 can

accept and still calibrate gain accurately.