ADA4941-1YRZ Analog Devices Inc, ADA4941-1YRZ Datasheet - Page 15

• Manufacturer Part Number: ADA4941-1YRZ
• Description: IC DIFF ADC DVR 18BIT 8-SOIC
• Manufacturer: Analog Devices Inc
• Type: ADC Driverr

Specifications of ADA4941-1YRZ

• Design Resources: Converting a Single-Ended Signal with AD7982 Differential PulSAR ADC (CN0032) Converting a Single-Ended Signal with AD7984 Differential PulSAR ADC (CN0033)
• Applications: Data Acquisition
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Number Of Channels: 1
• Number Of Elements: 2
• Power Supply Requirement: Single
• Common Mode Rejection Ratio: 84dB
• Voltage Gain Db: 6.06dB
• Unity Gain Bandwidth Product (typ): 31MHz
• Input Resistance: 24@5VMohm
• Input Offset Voltage: 0.4@5VmV
• Input Bias Current: 4.5@5VnA
• Single Supply Voltage (typ): 3/5/9V
• Dual Supply Voltage (typ): Not RequiredV
• Power Supply Rejection Ratio: 87dB
• Rail/rail I/o Type: Rail to Rail Output
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 12V
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: SOIC N
• No. Of Amplifiers: 1
• Bandwidth: 31MHz
• Slew Rate: 22V/µs
• Supply Voltage Range: 2.7V To 12V
• Supply Current: 2.2mA
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

THEORY OF OPERATION
The ADA4941-1 is a low power, single-ended input, differential
output amplifier optimized for driving high resolution ADCs.
Figure 47 illustrates how the ADA4941-1 is typically connected.
The amplifier is composed of an uncommitted amplifier, A1,
driving a precision inverter, A2. The negative input of A1 is
brought out to Pin 1 (FB), allowing for user-programmable
gain. The inverting op amp, A2, provides accurate inversion of
the output of A1, VOP, producing the output signal VON.
The voltage applied to the REF pin appears as the output
common-mode voltage. Note that the voltage applied to the
REF pin does not affect the voltage at the OUT+ pin. Because of
this, a differential offset can exist between the outputs, while the
desired output common-mode voltage is present. For example,
when VOP = 3.5 V and VON = 1.5 V, the output common-
mode voltage is equal to 2.5 V, just as it is when both outputs
are at 2.5 V. In the first case, the differential voltage (or offset) is
2.0 V, and in the latter case, the differential voltage is 0 V. When
calculating output voltages, both differential and common-mode
voltages must be considered at the same time to avoid undesired
differential offsets.
BASIC OPERATION
In Figure 47, R
VG and VREF are externally applied voltages. V
as the output common-mode voltage and V
the differential-mode output voltage. The following equations
can be derived from Figure 47:
VOP
VON
R
VG
G
Figure 47. Basic Connections (Power Supplies Not Shown)
=
=
VIN
−
VIN
G
R
VIN
F
and R
⎛
⎜
⎜
⎝
1
8
|| R
1
⎛
⎜
⎜
⎝
+
FB
IN
G
1
+
R
R
F
R
G
F
form the external gain-setting network.
F
R
R
A1
⎞
⎟
⎟
⎠
G
F
−
⎞
⎟
⎟
⎠
VG
2
+
VG
REF
⎛
⎜
⎜
⎝
VREF
R
R
⎛
⎜
⎜
⎝
500Ω
1kΩ
G
F
R
R
⎞
⎟
⎟
⎠
G
F
⎞
⎟
⎟
⎠
+
1kΩ
( 2
A2
O
VREF
, dm is defined as
O
, cm is defined
OUT+
OUT–
)
VOP
VON
+
–
+
–
4
5
Rev. B | Page 15 of 24
(1)
(2)
When R
following:
Figure 48 shows an example of a dual-supply connection. In this
example, VG and VREF are set to 0 V, and the external R
R
example takes full advantage of the rail-to-rail output stage.
The gain equation is
The in-series, 825 Ω resistor combined with Pin 8 compensates
for the voltage error generated by the input offset current of A1.
The linear output range of both A1 and A2 extends to within
200 mV of each supply rail, which allows a peak-to-peak
differential output voltage of 19.2 V on ±5 V supplies.
Figure 49 shows a single 5 V supply connection with A1 used as
a unity gain follower. The 2.5 V at the REF pin sets the output
common-mode voltage to 2.5 V. The transfer function is then
G
Figure 49. Single +5V Supply, G=2 Single-Ended-to-Differential Amplifier
Figure 48. Dual Supply, G = 2.4, Single-Ended-to-Differential Amplifier
network provides a noninverting gain of 1.2 in A1. This
V
VOP − VON = 2.4( VIN )
VOP − VON = 2( VIN ) − 5 V
V
VOP
V
4.99kΩ
O
O
O
, dm = 2( VIN ) − 2( VREF )
VIN
,
,
F
dm
cm
= 0 and R
−
VON
=
=
⎛
⎜
⎝
825Ω
VOP
VIN
1
8
1
8
=
G
FB
IN
( 2
FB
IN
is removed, Equation 3 simplifies to the
+
2
VIN
1kΩ
6
VON
3
A1
6
–5V
3
A1
V
V
V
V
)
+5V
S+
S–
+5V
⎛
⎜
⎜
⎝
S+
S–
1
2
2
⎞
⎟
⎠
+
=
REF
REF
R
R
VREF
+2.5V
G
F
500Ω
500Ω
1kΩ
1kΩ
⎞
⎟
⎟
⎠
−
2
VG
1kΩ
A2
1kΩ
⎛
⎜
⎜
⎝
A2
R
R
G
F
ADA4941-1
⎞
⎟
⎟
⎠
−
OUT+
OUT–
OUT+
OUT–
( 2
VREF
VOP
VON
VON
VOP
+
–
+
–
+
–
+
–
4
5
4
5
F
and
)
(3)
(4)
(5)
(6)
(7)