ADA4091-2ARZ-R7 Analog Devices Inc, ADA4091-2ARZ-R7 Datasheet - Page 15

• Manufacturer Part Number: ADA4091-2ARZ-R7
• Description: 36V Micropower Single-Supply R/R OPAMP
• Manufacturer: Analog Devices Inc

Specifications of ADA4091-2ARZ-R7

• Design Resources: 30 V Low Cost DAC Using AD5292 Digital Potentiometer (CN0111)
• Amplifier Type: General Purpose
• Number Of Circuits: 2
• Output Type: Rail-to-Rail
• Slew Rate: 0.46 V/µs
• Gain Bandwidth Product: 1.27MHz
• Current - Input Bias: 50nA
• Voltage - Input Offset: 35µV
• Current - Supply: 200µA
• Current - Output / Channel: 20mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 36 V, ±1.35 V ~ 18 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

INPUT OVERVOLTAGE PROTECTION
The ADA4091-2 has two different ESD circuits for enhanced
protection, as shown in Figure 45.
One circuit is a series resistor of 5 kΩ to the internal inputs and
diodes (D1 and D2 or D5 and D6) from the internal inputs to
the supply rails. The other protection circuit is a circuit with
two DIACs (D3 and D4 or D7 and D8) to the supply rails. A
DIAC can be considered a bidirectional Zener diode with a
transfer characteristic, as shown in Figure 46.
–1
–2
–3
5
4
3
2
1
0
–50
–40
Figure 45. Complete Input Protection Network
D7 R2
Figure 46. DIAC Transfer Characteristic
–30
D8
D6
–20
D5
D3
–10
VOLTAGE (V)
R1
D4
D2
0
D1
10
V+
V–
20
30
40
50
Rev. A | Page 15 of 16
For a worst-case design analysis, consider two cases. The
ADA4091-2 has a normal ESD structure from the internal op
amp inputs to the supply rails. In addition, it has 42 V DIACs
from the external inputs to the rails, as shown in Figure 44.
Therefore, two conditions have to be considered to determine
which one is the limiting factor.
•
•
Additional resistance can be added externally in series with
each input to protect against higher peak voltages; however, the
additional thermal noise of the resistors must be considered.
The flatband voltage noise of the ADA4091-2 is approximately
24 nV/√Hz, and a 5 kΩ resistor has a noise of 9 nV/√Hz. Adding
an additional 5 kΩ resistor increases the total noise by less than
15% root-sum-square (rss). Therefore, maintain resistor values
below this value when overall noise performance is critical.
Note that this represents input protection under abnormal con-
ditions only. The correct amplifier operation input voltage range
(IVR) is specified in Table 2, Table 3, and Table 4 of this data sheet.
Condition 1. Consider, for example, that when operating
on ±15 V, the inputs can go +42 V above the negative
supply rail. With the −V pin equal to −15 V, +42 V above
this supply (the negative supply) is +27 V.
Condition 2. There is also a restriction on the input current
of 5 mA through a 5 kΩ resistor to the ESD structure to
the positive rail. In Condition 1, +27 V through the 5 kΩ
resistor to +15 V gives a current of 2.4 mA. Thus, the DIAC
is the limiting factor. If the ADA4091-2 supply voltages are
changed to ±5 V, then −5 V + 42 V = 37 V. However, +5 V
+ (5 kΩ × 5 mA) = 30 V. Thus, the normal resistor diode
structure is the limitation when running on lower supply
voltages.
ADA4091-2