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USB Powered Host and USB Interface Design Recommendations
The OEM decoder features some basic ESD protection and a controlled soft
start during power up sequence, with a peak surge current below 130 mA
(about 400us width) during input voltage ramp-up. Additional peaks are
present during boot phase (see figure 11 for boot time), with a maximum
peak below 250 mA (about 800us width). Carefully consider the OEM
decoder consumption when integrating it on a USB powered system. If
deemed necessary, the host may provide additional soft start circuitry in
order to limit surge current. This might increase the power up time, of a
value depending on the host circuitry design. OEM decoder is USB compliant,
also when connected using its micro-USB connector.
Moreover, if USB communication interface is being used, additional standard
USB protection for electrical immunity and adaptation might be applied to
USB D+ and D- lanes on Host PCB, if needed. Carefully investigate such the-
matics when designing the host electronics.
Already on OEM decoder USB D+ and D- lines: 10 Ohm series resistor, com-
mon mode choke and TVS array; please consider this when designing USB
transmission line on Host.
OEM Decoder Operation
The OEM decoder features three power states (working modes) that are
reachable using the control interface by sending commands through it.
Table 8 - Power States (Working Modes)
Mode
LOW POWER
IDLE
OPERATING
Default Operation: The decoder in IDLE state starts the acquisition and
decoding phase (entering OPERATING mode) when the level of the TRIG_C-
TRL signal goes from low to high (or issuing a DESP "Start" command
through the communication interface). If an image is decoded,
GOOD_READ_LED goes high and BEEPER_CTRL outputs a PWM and the
decoder returns to IDLE state.
When UART interface is selected: The decoder can be put in LOW POWER
mode by sending the DESP command "Suspend" through the UART interface.
While in Low power, be sure to keep AIM_CTRL signal low and UART_RX sig-
nal High for correct low power operation.
Integration Guide
Description
Mode for energy saving: the decoder is in a state of sleep and
most of the internal circuitry is disabled.
T
is required for wake up. Lowest on power consumption.
w
The decoder is waiting for commands, all systems ready for
operations. The connected scan engine is in low power mode.
Moderate power consumption.
The connected scan engine is in Running mode with illumi-
nation and AIM turned on; the scan engine is continuously
acquiring images to the decoder, that provides decoded data
as soon as ready. All systems working, full power consump-
tion.
OEM Decoder Operation
15
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