Motorola SE4710, Integration Manual

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2 - 2 SE4710 Integration Guide
Environment
The engine and decoder must be sufficiently enclosed to prevent dust from gathering on the pattern forming
element, optical lens, and illumination system LEDs. Dust and other external contaminants eventually degrade
engine performance. Motorola does not guarantee performance of the SE4710 when used in an exposed
application.
Power Supply Noise
For reliable operation a low-noise power supply is required. Pay proper attention to power supply quality and
testing to ensure the best possible performance from the SE4710. In bar code applications, up to 100 mV
peak-to-peak noise is acceptable on all three power input pins (10 Hz to 100 kHz). For image capture applications,
power supply noise for VCC must be limited to 30 mV (peak-to-peak), across the same frequency range.
Thermal Considerations
The SE4710 engine includes several high-power components (e.g., microcontroller, sensor, LEDs) that dissipate
heat during operation. The engine temperature can reach as high as 72°C when the engine is running at 30 frames
per second with full image resolution, full illumination, and aiming on. These extreme conditions can increase
sensor noise, degrade image quality, and impact the scan engine's longevity. Use care when designing the
SE4710 for integration into the target application.
As a protective measure for the scan engine, at extreme temperatures the SE4710 first shuts off the aiming LED
and then dims the illumination LED (at 68°C engine temperature). Illumination shuts off at 72°C. As the engine
temperature returns to normal levels the aiming and illumination power returns to nominal values.
In a thermal chamber with zero air flow and no heat sink attached, the thermal dissipation of the SE4710 engine
can be simplified as the lumped capacitance thermal model shown in
Figure 2-1 . The parameters are listed below.
•
P
engine
: The total power consumption of the SE4710 engine (W)
•
T
engine_chassis
: The SE4710 engine chassis temperature (K)
•
T
ambient
: The ambient temperature (K)
•
R
t_conv
: The thermal resistance between the SE4710 engine and the ambient through natural convection
(reference: 50 K/W)
•
C
engine
: The thermal capacity of the SE4710 engine (reference: 5.4 Joule/K)
•
T
thermal_constant
: The thermal time constant of SE4710 engine (reference: 270 sec),
which equals R
t_conv
* C
engine
Figure 2-1
Lumped Capacitance Thermal Model of SE4710 Scan Engine