ADA4350 Datasheet, PDF (1/38 Pages) Analog Devices – FET Input Analog Front End with ADC Driver

Data Sheet
FET Input Analog Front End
with ADC Driver
ADA4350
FEATURES
GENERAL DESCRIPTION
Low noise, low input bias current FET input amplifier
Very low input bias current: ±0.25 pA typical at 25°C
Low input voltage noise
92 nV/√Hz typical at 10 Hz at 5 V
5 nV/√Hz typical at 100 kHz at ±5 V
Gain bandwidth product: 175 MHz
Input capacitance
3 pF typical, differential mode
2 pF typical, common mode
Integrated gain switching
Sampling and feedback switch off leakage: ±0.5 pA typical
Worst case tON/tOFF times: 105 ns typical/65 ns typical
The ADA4350 is an analog front end for photodetectors or other
sensors whose output produces a current proportional to the
sensed parameter or voltage input applications where the system
requires the user to select between very precise gain levels to
maximize the dynamic range.
The ADA4350 integrates a FET input amplifier, a switching network,
and an ADC driver with all functions controllable via a serial
peripheral interface (SPI) or parallel control logic into a single
IC. The FET input amplifier has very low voltage noise and current
noise making it an excellent choice to work with a wide range of
photodetectors, sensors, or precision data acquisition systems.
Integrated analog-to-digital converter (ADC) driver
Its switching network allows the user individual selection of up
Differential mode and single-ended mode
Adjustable output common-mode voltage
−5 V to +3.8 V typical for ±5 V supply
Wide output voltage swing: ±4.8 V minimum for ±5 V supply
Linear output current: 18 mA rms typical for ±5 V supply
SPI or parallel switch control of all functions
Wide operating range: 3.3 V to 12 V
Quiescent current: 8.5 mA typical (±5 V full system)
APPLICATIONS
Current to voltage (I to V) conversions
Photodiode preamplifiers
Chemical analyzers
Mass spectrometry
Molecular spectroscopy
to six different, externally configurable feedback networks; by
using external components for the feedback network, the user
can more easily match the system to their desired photodetector or
sensor capacitance. This feature also allows the use of low thermal
drift resistors, if required.
The design of the switches minimizes error sources so that they
add virtually no error in the signal path. The output driver can
be used in either single-ended or a differential mode and is
ideal for driving the input of an ADC.
The ADA4350 can operate from a single +3.3 V supply or a dual
±5 V supply, offering user flexibility when choosing the polarity of
the detector. It is available in a Pb-free, 28-lead TSSOP package and
is specified to operate over the −40°C to +85°C temperature range.
Laser/LED receivers
Multifunction pin names may be referenced by their relevant
Data acquisition systems
function only.
FUNCTIONAL BLOCK DIAGRAM
ADA4350
987654
27 1
S0
S6
IN-N 10
S1
S7
IN-P 11
S2
S8
S3
S9
S4
S10
S5
S11
SPI INTERFACE
12 13
16 17 19 20 21 22 23
28 2
P1
M1
25
3 VOUT1
26 VOUT2
FET AMP
SWITCHING NETWORK
Figure 1.
ADC DRIVER
Rev. B
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