THS0842

DUAL-INPUT, 8-BIT, 40 MSPS LOW-POWER ANALOG-TO-DIGITAL CONVERTER

WITH SINGLE OR DUAL PARALLEL BUS OUTPUT

SLAS246 – DECEMBER 1999

7

POST OFFICE BOX 655303

(unless otherwise noted) (continued)

dc accuracy

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Integral nonlinearity (INL), best-fit

See Note 1

TA = –40°C to 85°C

–2.2

±1.5

2.2

LSB

Differential nonlinearity (DNL)

See Note 2

TA = –40°C to 85°C

–1

±0.7

2

LSB

Offset error

TA =40°Cto85°C (see Note 3)

±0.1

5

%FS

Gain error

TA = –40°C to 85°C, (see Note 3)

±7.1

%FS

Offset match

TA = –40°C to 85°C, (see Note 4)

–1

±0.1

1

LSB

Gain match

TA = –40°C to 85°C, (see Note 5)

–5

1

LSB

Missing codes – no missing codes assured

NOTES:

1. Integral nonlinearity refers to the deviation of each individual code from a line drawn from zero to full scale. The point used as zero

occurs 1/2 LSB before the first code transition. The full–scale point is defined as a level 1/2 LSB beyond the last code transition.

The deviation is measured from the center of each particular code to the best fit line between these two endpoints.

2. An ideal ADC exhibits code transitions that are exactly 1 LSB apart. DNL is the deviation from this ideal value. Therefore this measure

indicates how uniform the transfer function step sizes are. The ideal step size is defined here as the step size for the device under

test (i.e., (last transition level – first transition level)

÷ (2n – 2)). Using this definition for DNL separates the effects of gain and offset

error. A minimum DNL better than –1 LSB ensures no missing codes.

3. Offset error is defined as the difference in analog input voltage – between the ideal voltage and the actual voltage – that will switch

the ADC output from code 0 to code 1. The ideal voltage level is determined by adding the voltage corresponding to 1/2 LSB to the

bottom reference level. The voltage corresponding to 1 LSB is found from the difference of top and bottom references divided by

the number of ADC output levels (256).

Gain error is defined as the difference in analog input voltage – between the ideal voltage and the actual voltage – that will switch

the ADC output from code 254 to code 255. The ideal voltage level is determined by subtracting the voltage corresponding to 1.5

LSB from the top reference level. The voltage corresponding to 1 LSB is found from the difference of top and bottom references

divided by the number of ADC output levels (256).

4. Offset match is the change in offset error between I and Q channels.

5. Gain match is the change in gain error between I and Q channels.

analog input

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

CI

Input capacitance

4

pF

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Rref

Reference input resistance

200

Ω

Iref

Reference input current

5

mA

reference outputs

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

V(REFT)

Reference top voltage

AVDD =3V

2 + [(AVDD – 3)/2]

V

V(REFB)

Reference bottom voltage

AVDD = 3 V

1 + [(AVDD – 3)/2]

V

VREFB–VREFB

Absolute min/max values valid

and tested for AVDD = 3 V

0.9

1

1.3

V