AD8260 Datasheet, PDF (1/32 Pages) Analog Devices – High Current Driver Amplifier and Digital VGA/Preamplifier with 3 dB Steps

High Current Driver Amplifier and
Digital VGA/Preamplifier with 3 dB Steps
AD8260
FEATURES
High current driver
Differential input—direct drive from DAC
Preset gain: 1.5×
−3 dB bandwidth: 195 MHz
Large output drive: >±300 mA
VGA/preamplifier
Low noise
Voltage noise: 2.4 nV/√Hz
Current noise: 5 pA/√Hz
−3 dB bandwidth: 230 MHz
Gain range: 30 dB in 3 dB steps
−6 dB to +24 dB (for preamplifier gain of 6 dB)
Single-ended preamplifier input and differential VGA
output
Supplies: 3.3 V to 10 V (with VMID enabled)
±3.3 V to ±5 V (with VMID disabled)
Power: 93 mW with 3.3 V supplies
Power-down for VGA, driver amplifier, and system
APPLICATIONS
Digital AGC systems
Tx/Rx signal processing
Power line transceivers
GENERAL DESCRIPTION
The AD8260 includes a high current driver, usable as a
transmitter, and a low noise digitally programmable variable
gain amplifier (DGA), useable as a receiver.
The receiver section consists of a single-ended input preampli-
fier, and linear-in-dB, differential-output DGA. The receiver has
a small signal –3 dB bandwidth of 230 MHz; the driver small
signal bandwidth is 195 MHz. The driver delivers ±300 mA,
well suited for driving low impedance loads, even when
connected to a 3.3 V supply.
The AD8260 DGA is ideal for trim applications and has a gain
span of 30 dB, in 3 dB steps. Excellent bandwidth uniformity is
maintained across the entire frequency range. The low output-
referred noise of the DGA is advantageous in driving high
speed ADCs. The differential output facilitates the interface to
modern low voltage high speed ADCs.
Single-supply and dual-supply operation makes the part versatile
and enables gain control of negative-going pulses, such as those
generated by photodiodes or photo-multiplier tubes, as well as
processing band-pass signals on a single supply. For maximum
FUNCTIONAL BLOCK DIAGRAM
VOCM INPP INRP INRN INPN TXFB VNEG VNEG
32
31
30
29
28
27
26
25
1.5kΩ 1kΩ
1kΩ 1.5kΩ
VMDO 1
TXEN 2
VMDI 3
VNCM 4
VPSB 5
ENBL 6
VGAP 7
VGAN 8
VMID
+
–
GM
×1
HIGH CURRENT DRIVER
AD8260
BIAS
VGA/PREAMPLIFIER
ATTENUATOR
GM STAGES
LOGIC
24 TXOP
23 TXOP
22 VPOS
21 VPOS
20 VPSR
19 VMDO
18 PRAI
17 FDBK
9
10
11
12
13
14
15
16
VNGR VPSR GNS3 GNS2 GNS1 GNS0 PRAO VNGR
Figure 1. Functional Block Diagram
dynamic range, it is essential that the part be ac-coupled when
operating on a single supply.
The AD8260 preamplifier (PrA) is configured with external
resistors for gains greater than 6 dB and can be inverting or
noninverting. The DGA is characterized with a noninverting
preamplifier gain of 2×. The attenuator has a range of 30 dB and
the output amplifier has a gain of 8× (18.06 dB). The lowest
noninverting gain range is −6 dB to +24 dB and shifts up with
increased preamplifier gain. The gain is controlled via a parallel
port (Pin GNS0 to Pin GNS3) with 10 gain steps of 3 dB per
code. The preamplifier and DGA are disabled for any code that
is not assigned a gain step.
The AD8260 can operate with single or dual supplies from 3.3 V
to ±5 V. An internal buffer normally provides a split supply
reference for single-supply operation; an external reference
can also be used when the VMID buffer is shut down.
The operating temperature range is −40°C to +105°C. The
AD8260 is available in a 5 mm × 5 mm, 32-lead LFCSP.
Rev. 0
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