AD8370AREZ Analog Devices Inc, AD8370AREZ Datasheet - Page 18

• Manufacturer Part Number: AD8370AREZ
• Description: IC AMP VGA DIFF LN 16TSSOP
• Manufacturer: Analog Devices Inc
• Type: Var Gain Ampr

Specifications of AD8370AREZ

• Amplifier Type: Variable Gain
• Number Of Circuits: 1
• Output Type: Differential
• Slew Rate: 5750 V/ns
• -3db Bandwidth: 750MHz
• Current - Input Bias: 400pA
• Current - Supply: 79mA
• Voltage - Supply, Single/dual (±): 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
• No. Of Amplifiers: 1
• Bandwidth: 750MHz
• No. Of Channels: 1
• Supply Voltage Range: 3V To 5.5V
• Amplifier Case Style: TSSOP
• No. Of Pins: 16
• Operating Temperature Range: -40°C To +85°C
• Number Of Channels: 1
• Number Of Elements: 2
• Power Supply Requirement: Single
• Common Mode Rejection Ratio: 77dB
• Voltage Gain Db: 34dB
• Input Resistance: 0.0002@5VMohm
• Input Bias Current: 0.9@5VnA
• Single Supply Voltage (typ): 5V
• Dual Supply Voltage (typ): Not RequiredV
• Power Dissipation: 575mW
• Rail/rail I/o Type: No
• Single Supply Voltage (min): 3V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 16
• Package Type: TSSOP EP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output / Channel: -
• Gain Bandwidth Product: -
• Voltage - Input Offset: -
• Lead Free Status / Rohs Status: Compliant

AD8370
If the amplifier is driven in single-ended mode, the input
impedance varies depending on the value of the resistor used to
terminate the other input as
where R
input.
DC-COUPLED OPERATION
REFERENCED
Figure 51. DC Coupling the AD8370. Dual supplies are used to set the input
–100
–40
–50
–60
–70
–80
–90
GROUND
SERIAL CONTROL
INTERFACE
SOURCE
Rin
SINGLE-
ENDED
0
TERM
SE
Figure 50. Harmonic Distortion of the Circuit in Figure 47
= Rin
HD3
R
S
is the termination resistor connected to the other
32
LOW GAIN MODE
and output common-mode levels to 0 V.
HD2
DIFF
–2.5V
R
T
64
+ R
0.1μF
TERM
16
1
AD8370
96
GAIN CODE
15
2
14
3
0
0.1μF
13
HD3
4
32
HIGH GAIN MODE
12
5
HD2
–2.5V
11
6
64
10
7
1nF
1nF
9
8
96
+2.5V
128
R
0V
0V
L
Rev. A | Page 18 of 28
The AD8370 is also a dc accurate VGA. The common-mode dc
voltage present at the output pins is internally set to midsupply
using what is essentially a buffered resistive divider network
connected between the positive supply rail and the common
(ground) pins. The input pins are at a slightly higher dc
potential, typically 250 mV to 550 mV above the output pins,
depending on gain setting. In a typical single-supply
application, it is necessary to raise the common-mode reference
level of the source and load to roughly midsupply to maintain
symmetric swing and to avoid sinking or sourcing strong bias
currents from the input and output pins. It is possible to use
balanced dual supplies to allow ground referenced source and
load, as shown in Figure 51. By connecting the VOCM pin and
unused input to ground, the input and output common-mode
potentials are forced to virtual ground. This allows direct
coupling of ground referenced source and loads. The initial
differential input offset is typically only a few 100 μV. Over
temperature, the input offset could be as high as a few tens of
mVs. If precise dc accuracy is needed over temperature and time,
it may be necessary to periodically measure the input offset and
to apply the necessary opposing offset to the unused differential
input, canceling the resulting output offset.
To address situations where dual supplies are not convenient, a
second option is presented in Figure 52. The AD8138 differential
amplifier is used to translate the common-mode level of the
driving source to midsupply, which allows dc accurate
performance with a ground-referenced source without the need
for dual supplies. The bandwidth of the solution in Figure 52 is
limited by the gain-bandwidth product of the AD8138. The
normalized frequency response of both implementations is shown
in Figure 53.
SINGLE-ENDED GROUND
REFERENCED SOURCE
Figure 52. DC Coupling the AD8370. The AD8138 is used as a unity-gain level
shifting amplifier to lift the common-mode level of the source to midsupply.
R
S
R
T
499Ω
499Ω
R
2
T
SERIAL CONTROL
INTERFACE
499Ω
499Ω
AD8138
+5V
100Ω
100Ω
16
1
AD8370
15
2
14
3
0.1μF
1nF
13
4
12
5
11
6
10
7
1nF
9
8
+5V
V
V
R
OCM
OCM
L