REV. F

–8–

AD7710

Pin

Mnemonic

Function

19

TFS

Transmit Frame Synchronization. Active low logic input used to write serial data to the device with serial data

expected after the falling edge of this pulse. In the self-clocking mode, the serial clock becomes active after

TFS goes low. In the external clocking mode, TFS must go low before the first bit of the data word is written

to the part.

20

RFS

Receive Frame Synchronization. Active low logic input used to access serial data from the device. In the

self-clocking mode, the SCLK and SDATA lines both become active after

RFS goes low. In the external

clocking mode, the SDATA line becomes active after

RFS goes low.

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 AD7710 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 regis-

ters 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

endpoints of the transfer function are zero scale (not to be con-

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

transition (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 AIN(+) voltage

and bipolar analog input ranges.

UNIPOLAR OFFSET ERROR

Unipolar Offset Error is the deviation of the first code transition

from the ideal AIN(+) voltage (AIN(–) + 0.5 LSB) when oper-

ating in the unipolar mode.

BIPOLAR ZERO ERROR

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

1000 . . . 000) from the ideal AIN(+) voltage (AIN(–) – 0.5 LSB)

when operating in the bipolar mode.

BIPOLAR NEGATIVE FULL-SCALE ERROR

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

ing in the bipolar mode.

POSITIVE FULL-SCALE OVERRANGE

Positive Full-Scale Overrange is the amount of overhead avail-

able to handle input voltages on AIN(+) input greater than

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

analog modulator or overflowing the digital filter. Note that the

analog input will accept negative voltage peaks even in the uni-

polar mode provided that AIN(+) is greater than AIN(–) and

OFFSET CALIBRATION RANGE

In the system calibration modes, the AD7710 calibrates its offset

with respect to the analog input. The Offset Calibration Range

specification defines the range of voltages that the AD7710 can

accept and still calibrate offset accurately.

FULL-SCALE CALIBRATION RANGE

This is the range of voltages that the AD7710 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 AD7710’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 AD7710 can

accept and still calibrate gain accurately.