ADA4177-2ARMZ-R7 datasheet(28/33 Pages) AD

28 / 33 page

ADA4177-1/ADA4177-2/ADA4177-4

Data Sheet

Rev. E | Page 28 of 33

EMI PROTECTION

The ADA4177-1/ADA4177-2/ADA4177-4 inputs are also

protected from high frequency EMI. In an op amp with no EMI

protection, signals not within the bandwidth of the op amp

couple into sensitive amplifier inputs and become rectified as

they travel through the amplifier, eventually appearing as ac

feedthrough on top of a dc offset. When an input filter is not

provided, these offsets can be quite large. These offsets are

referred to as the electromagnetic interference rejection ratio

(EMIRR). The amplifier EMIRR is defined as













ΔV

EMIRR

100

log

where:

100 mV is generally the peak-to-peak input used for the test.

ΔVOS is the change in the op amp offset as a result of the input

signal.

Figure 92 shows the input EMI protection of the ADA4177-1/

ADA4177-2/ADA4177-4.

120

100

FREQUENCY (MHz)

1000

100

INPUT +IN

VSY = ±15V

RF POWER = –16dBm (50mV p-p)

Figure 92. EMI Rejection Ratio Peak Voltage vs. Frequency

SELF HEATING

During an overvoltage condition, the ADA4177-1/ADA4177-2/

ADA4177-4 dissipate heat according to the thermal resistance

(θJA) of the package it is in, which, in turn, heats up the die. Ensure

that the specified operating junction temperature does not exceed

150°C for device protection. Extended overtemperature exposure

can cause some operating specifications to shift outside of their

guaranteed limits.

As shown in Figure 88, the ADA4177-1/ADA4177-2/ADA4177-4

inputs sink by approximately 8 mA at 15 V overvoltage. In that

condition, the ADA4177-1/ADA4177-2/ADA4177-4 dissipate

120 mW of power. If the package has a θJA of 100°C/W, the

junction temperature rises by approximately 12°C over the

ambient temperature of the package and junction. In such a case,

derate the ambient operating temperature by 12°C (125°C

minus 12°C) for an absolute maximum operating temperature

of 113°C.

When the junction temperature exceeds the absolute maximum

junction temperature of 150°C, add an additional series resistance

to the inputs to further decrease the overvoltage current. Figure 93

shows the maximum operating temperature vs. the continuous

overvoltage at θJA = 150°C/W.

140

120

100

CONTINUOUS OVERVOLTAGE (V)

WITH TWO INPUTS IN OVERVOLTAGE

WITH ONE INPUT IN OVERVOLTAGE

Figure 93. Maximum Operating Temperature vs. Continuous Overvoltage for

One Input and Two Inputs (θJA = 150°C/W)

USING THE ADA4177-1/ADA4177-2/ADA4177-4

AS A COMPARATOR

The ADA4177-1/ADA4177-2/ADA4177-4 can be used as a

comparator as long as relatively small input impedance can be

tolerated. That is, the input differential pair is diode clamped

but the overvoltage protection circuitry limits the differential.

Figure 94 shows the input current vs. the input differential voltage

with ±15 V supplies.

–8

–6

–4

–2

INPUT DIFFERENTIAL (V)

–20

–5

–10

–15

Figure 94. Input Current vs. Input Differential with ±15 V Supplies

ADA4177-2ARMZ-R7 Folha de dados(PDF) 28 Page - Analog Devices

ADA4177-2ARMZ-R7 Folha de dados(HTML) 28 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

Folha de dados Download

Ligação URL