ISL26310 datasheet(13/23 Pages) RENESAS

13 / 23 page

ISL26320, ISL26321, ISL26322, ISL26323, ISL26324, ISL26325, ISL26329

FN8273 Rev 1.00

Page 13 of 23

September 5, 2013

Analog Inputs

Some members of the ISL26320, ISL26321, ISL26322,

ISL26323, ISL26324, ISL26325 and ISL26329 family feature a

fully differential input with a nominal full-scale range equal to

twice the applied VREF voltage. Those devices with differential

inputs have a nominal full scale range equal to twice the applied

VREF voltage. Each input swings VREF volts (peak-to-peak), 180°

out of phase from one another for a total differential input of

2*VREF (refer to Figures 23 and 24).

Differential signaling offers several benefits over a single-ended

input, such as:

• Doubling of the full-scale input range (and therefore the

dynamic range)

• Improved even order harmonic distortion

• Better noise immunity due to common mode rejection

Figure 24 shows the relationship between the reference voltage

and the full-scale differential input range for two different values

of VREF. Note that the common-mode input voltage must be

maintained within ±200mV of VREF/2 for differential inputs.

Those devices with singled-ended inputs have a ground-referenced

peak-to-peak input voltage span equal to the reference voltage.

FIGURE 21. IDEAL TRANSFER CHARACTERISTICS, DIFFERENTIAL INPUT

FIGURE 22. IDEAL TRANSFER CHARACTERISTICS, SINGLE-ENDED INPUT

1LSB = 2•VREF/4096

100...000

100...001

100...010

111...111

000...000

000...001

011...110

011...111

ANALOG INPUT

AIN+ – (AIN–)

–VREF

+ ½LSB

+VREF

– 1½LSB

+VREF

– 1LSB

1LSB = VREF/4096

000...000

000...001

000...010

011...111

100...000

100...001

111...110

111...111

ANALOG INPUT

0 = + ½LSB

FS = +VREF-1LSB

FIGURE 23. DIFFERENTIAL INPUT SIGNALING

ISL2631X/32X

VCM

VREF (P-P)

AIN+

AIN-

FIGURE 24. RELATIONSHIP BETWEEN VREF AND FULL-SCALE

RANGE FOR DIFFERENTIAL INPUTS

3.0

5.0

2.0

1.0

4.0

AIN+

AIN–

2.5Vp-p

VREF = 2.5V

3.0

5.0

2.0

1.0

4.0

AIN+

AIN–

VCM

5Vp-p

VREF = 5V

ALLOWABLE VCM RANGE

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