Datasheet ADA4350 (Analog Devices)

FET Input Analog Front End with ADC Driver Data Sheet ADA4350 FEATURES GENERAL DESCRIPTION Low noise, low input bias current FET input amplifier
The ADA4350 is an analog front end for photodetectors or other
Very low input bias current: ±0.25 pA typical at 25°C
sensors whose output produces a current proportional to the
Low input voltage noise
sensed parameter or voltage input applications where the system
92 nV/√Hz typical at 10 Hz at 5 V
requires the user to select between very precise gain levels to
5 nV/√Hz typical at 100 kHz at ±5 V
maximize the dynamic range.
Gain bandwidth product: 175 MHz Input capacitance
The ADA4350 integrates a FET input amplifier, a switching network,
3 pF typical, differential mode
and an ADC driver with al functions controllable via a serial
2 pF typical, common mode
peripheral interface (SPI) or paral el control logic into a single
Integrated gain switching
IC. The FET input amplifier has very low voltage noise and current
Sampling and feedback switch off leakage: ±0.5 pA typical
noise making it an excel ent choice to work with a wide range of
Worst case t
photodetectors, sensors, or precision data acquisition systems.
ON/tOFF times: 105 ns typical/65 ns typical Integrated analog-to-digital converter (ADC) driver
Its switching network al ows the user individual selection of up
Differential mode and single-ended mode
to six different, external y configurable feedback networks; by
Adjustable output common-mode voltage
using external components for the feedback network, the user
−5 V to +3.8 V typical for ±5 V supply
can more easily match the system to their desired photodetector or
Wide output voltage swing: ±4.8 V minimum for ±5 V supply
sensor capacitance. This feature also allows the use of low thermal
Linear output current: 18 mA rms typical for ±5 V supply
drift resistors, if required.
SPI or parallel switch control of all functions
The design of the switches minimizes error sources so that they
Wide operating range: 3.3 V to 12 V
add virtually no error in the signal path. The output driver can
Quiescent current: 8.5 mA typical (±5 V full system)
be used in either single-ended or a differential mode and is
APPLICATIONS
ideal for driving the input of an ADC.
Current to voltage (I to V) conversions
The ADA4350 can operate from a single +3.3 V supply or a dual
Photodiode preamplifiers
±5 V supply, offering user flexibility when choosing the polarity of
Chemical analyzers
the detector. It is available in a Pb-free, 28-lead TSSOP package and
Mass spectrometry Molecular spectroscopy
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 UT UT A_O B_O 1 B0 B1 B2 B3 B4 B5 W W IN1 F F F F F F S S V RF 9 8 7 6 5 4 27 1 28 2 ADA4350 P1 3 VOUT1 S0 S6 IN-N 10 S1 S7 IN-P 11 S2 S8 S3 S9 S4 S10 S5 S11 M1 26 VOUT2 SPI INTERFACE 12 13 16 17 19 20 21 22 23 25 N N 0 1 F EN DE P P /P2 P4 B_I O I/P3 S/ RE A_I K/ O W M CH/ W SD C S T CL S SD A S L
001
FET AMP SWITCHING NETWORK ADC DRIVER
12417- Figure 1.
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Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM REVISION HISTORY SPECIFICATIONS ±5 V FULL SYSTEM ±5 V FET INPUT AMPLIFIER ±5 V INTERNAL SWITCHING NETWORK AND DIGITAL PINS ±5 V ADC DRIVER 5 V FULL SYSTEM 5 V FET INPUT AMPLIFIER 5 V INTERNAL SWITCHING NETWORK AND DIGITAL PINS 5 V ADC DRIVER TIMING SPECIFICATIONS Timing Diagrams for Serial Mode ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE MAXIMUM POWER DISSIPATION ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISITICS FULL SYSTEM FET INPUT AMPLIFIER ADC DRIVER TEST CIRCUITS THEORY OF OPERATION KELVIN SWITCHING TECHNIQUES APPLICATIONS INFORMATION CONFIGURING THE ADA4350 SELECTING THE TRANSIMPEDANCE GAIN PATHS MANUALLY OR THROUGH THE PARALLEL INTERFACE SELECTING THE TRANSIMPEDANCE GAIN PATHS THROUGH THE SPI INTERFACE (SERIAL MODE) SPICE MODEL TRANSIMPEDANCE AMPLIFIER DESIGN THEORY TRANSIMPEDANCE GAIN AMPLIFIER PERFORMANCE THE EFFECT OF LOW FEEDBACK RESISTOR RFx USING THE T NETWORK TO IMPLEMENT LARGE FEEDBACK RESISTOR VALUES OUTLINE DIMENSIONS ORDERING GUIDE