Metrologic Instruments IS4921 - Manual (Page 42)

36
Current Waveforms
Figure 29 - Figure 31 show typical current signature for the decode engine (USB version) in various operating
modes.
Note: The next three waveforms are shown with VIN = 3.3V and the output signals nBeeper and nGoodRead
are pulled high externally through 10K resistors. Thus, these waveforms only account for the current
drawn by the IS4920 circuitry and does not show additional current required for driving the LED or
Beeper.
The IS4920 series engines do not have current limiting fuses. Care must be taken on the host side to prevent
against over current conditions that could potential damage the host system.
Figure 29. Single Image Decode Current Waveform (from Idle Mode)
Figure 30. Continuous Image Decode Current Waveform (I_ave = 204mA)