Specifications

A – Power Control
Page 40 Airborne Wireless LAN Node Module Data Book 100-8004-102G
Quatech, Inc. Confidential
Figure 15. Inrush Current Characteristics
Since the Module’s peak operating current is approximately 450 mA, the power budget for the
Module is approximately the same. This is satisfactory for an always-on system. For an
operating system, however, rapidly switching on the Module and its corresponding inrush
requirement can cause system problems.
Figure 16 shows the inrush problem on a 5 V system with a current-limited supply. The lower
trace is the system +5 V supply and the upper trace is the Module’s +3.3 V supply. With the
supply current limited at approximately 500 mA, the power supply falls to 4.16 V. In most
systems, this causes a power-fail situation in which the system-supervisor device forces the
Host system into reset.
Figure 16. Voltage Droop with Current-Limited Supply