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Integration and
Collaboration at
the Heart of a High
Performance Image
Sensor Reference Design
Scott Hunt , System Applications Engineer
Image sensing in dispersive spectroscopy applications requires a linear
array image sensor with very low noise and a high bit rate for high sensitiv-
ity and high speed measurements. In order to reduce the detector dark noise
and further increase the sensitivity of the measurement, a thermoelectric
cooler
(
TEC
)
is required. These requirements also demand high performance
electronics to interface with the sensor. The sensor readout requires low
noise and fast settling amplifiers and a low noise, precision analog-to-digital
converter
(
ADC
)
. The TEC requires precision current control and voltage
limiting in order to precisely control the temperature. Power management
electronics must be capable of delivering the high power required by the
TEC, as well as the low noise required by the readout circuitry. Finally, a good
printed circuit board layout is critical to avoid magnetically or conductively
coupled interference of the high power switching signals with the precision
readout electronics.
Designing a system with discrete electronic components to interface with
these complex and high performance sensors has been a challenge in the past,
requiring careful trade off of size and complexity vs. performance. Hamamatsu
Photonics, Inc. and Analog Devices, Inc. saw this as an opportunity to combine
their expertise to create a reference design for the Hamamatsu G920x InGaAs
linear image sensor family, where Hamamatsu provided the sensor and
system components and Analog Devices designed the analog front-end
(
AFE
)
board. This reference design allows modular evaluation by interfacing to FPGA
carrier cards via an FMC connector. Analog Devices’ µModule
®
regulators
are used to provide a compact, optimal layout for the most challenging layout
portions of the design. For example, the LTM8053 µModule buck regulator inte-
grates the magnetic components with an internal layout that greatly reduces
electromagnetic noise. By providing a compact and optimized layout and
reducing the component count, these highly integrated products also enable a
smaller solution without trading off performance.
Hamamatsu G920x
InGaAs Photodiode Array
High Speed
Analog Outputs
Sensor
TEC
ADA4807-1
ADA4807-1
ADR4550
ADAQ7980
LTM8053
Silent Switcher
µModule Regulator
ADN8835
3 A TEC Controller
9 V AC Adapter
FMC Connection
5 V, 3.5 A
5 V, ±1.8 A
ADG719
Figure 1. Simplified block diagram of image sensor reference design.
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