Sierra Wireless MC5725 Hardware Integration Manual page 25

Figure 2-5: Inrush model - MC87xx
50m
Note: In some circumstances,
depending on temperature and
the components in use, two or
more regulators may switch on
at the same time. The host
power system must be designed
to handle this possibility.
Rev 1.9.1 Feb.09
In the event of a discrepancy in values between this guide and the Product Specification Document (PSD), the PSD takes precedence.
4.5m
ESR
50m
47uF
0.1m
Inrush current via application of host power supply
This event occurs when the host's supply is enabled, charging
the input capacitors on the Mini Card power rail. The switch
shown in Figure 2‐4 and Figure 2‐5 is open (typically) when
this event occurs.
To limit the inrush current and stabilize the supply of power to
the module, sufficient capacitance must be added to the host
power rail. The recommended capacitance range is
470 μF ‐ 1000 μF.
Peak current (IPEAK) is calculated using:
IPEAK =
RSERIES = (impedance from power source (+ive) through to
Inrush current via floating W_Disable#
The second event type occurs when the host leaves the
W_Disable
module. The switch shown in Figure 2‐4 and Figure 2‐5 is
closed when this event occurs. This enables the power
management system of the module, charging several internal
regulator output capacitors.
When
W_Disable
current is less than 500 mA (with a 30 μs rise time).
Proprietary and Confidential
2 ohm
ON/OFF
VCC / RSERIES
the Regulator output capacitor)
+ (impedance from power source (-ive) through to
GND pins of the EM regulator)
# signal floating (high impedance) to power up the
# is left floating (high impedance), the peak
Power Interface
MC87xx
30m
10uF
25