AND8090 datasheet(7/20 Pages) ONSEMI

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AND8090/D

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DIFFERENTIAL CHARACTERISTICS

Section Note − This section explains concepts that only

apply for differential inputs and/or outputs. Differential

inputs and outputs have true and inverted pins, and are often

referred to as “complimentary” inputs and outputs. An

example of a differential input is a true data input (D), and

an inverted data input (D).

Differential Input Application – True and inverted input

signals must be applied in order to obtain accurate

differential test measurements for differential input devices.

The true output of the pulse generator is connected to the true

input of the DUT, and the inverted output of the pulse

generator is connected to the inverted input of the DUT.

Unused Output Termination – An unused output of a

differential pair must be terminated in the same manner as

the used output in order to obtain accurate measurements.

Differential Crosspoint – Differential crosspoints are

used as a measurement point for differential input and

differential output signals. A differential crosspoint (Xpt) is

located where the true and inverted inputs or outputs

intersect as shown in Figure 11.

Figure 11. Differential Input/Output Crosspoint

D or Q

Xpt

Input Voltage Swing – The minimum input voltage

swing (VPPmin) is found by decreasing the swing between

the true and inverted inputs until the device no longer

performs its specified function. The maximum input voltage

swing (VPPmax) is determined by the internal circuitry of a

specific device. The differential input voltage swing is

defined by the following equations and Figure 12.

Figure 12. Differential Input Voltage Swing

Xpt

VPP = | VIN(true) − VIN(inverted) |

VPP(min) v VPP v VPP(max)

VPP(min)

VPP(max)

Test Input Swing – The typical AC test input swing for

differential inputs is shown below:

VPP (AC Test) + |VIN (true) * VIN (inverted) | + 750 mV

Common Mode Range – The most positive of the true

and inverted input voltages (i.e., the HIGH level) must be

within the differential HIGH input common mode range

(VIHCMR) for proper operation. To restate, the common

mode range places an upper and lower boundary on the

differential HIGH input level. The HIGH input common

mode range is specified in relation to the input voltage swing

(VPP). The relationship is determined by the device type, so

refer to the device data sheet for specific information. The

differential HIGH input common mode range is defined by

the following equations.

VIHCMR(min) v VIH v VIHCMR(max)

VIHCMR(max) varies 1 : 1 with VCC

VIHCMR(min) varies 1:1withVEE

The example shown in Figure 13 is typical, and specifies

the common mode range with respect to the entire VPP

range.

Figure 13. Common Mode Range

VIHCMR(max)

VIH for all VPP

VIHCMR(min)

The MC100LVEL14 example shown in Figure 14

specifies the common mode range with respect to two VPP

ranges.

Figure 14. MC100LVEL14 Common Mode Range

1.2 V

2.9 V

VIH for VPP < 0.5 V

VIHCMR(max)

VIHCMR(min)

VIHCMR(max)

VIH for VPP w 0.5 V

VIHCMR(min)

2.9 V

1.4 V

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