Huawei MU509 Series Hardware Manual page 36

HUAWEI MU509 Series HSDPA LGA Module
Hardware Guide
Blinking Twice Each Time
Figure 3-10 Status when the indictor blinks twice each time
Light on
Light off
External Circuits
Figure 3-11 shows the recommended circuits of the LED_MODE and LED_STATUS
pins. According to LED feature, you can adjust the LED brightness by adjusting the
impedance of resistor R.
Figure 3-11 Driving circuit
For resistance of R placed on user board, choose the value such that it satisfies the
following equation:
I *R+V
F
V : Forward voltage
F
I : Forward current
F
Take a LED as an example, Figure 3-12 shows its I
the desired current through the LED I
according to I
(3.8-1.5)/0.003 = 767 Ω.
The brightness of the LED depends on the current value, and for most of the indicator
lights the current from 2 mA to 5 mA is already enough.
Issue 09 (2014-03-06)
100ms 100ms 100ms
Module
(DCE)
LED_MODE
LED_STATUS
= VBAT
F
- V curves, and the corresponding value for resistance of R is
F F
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Copyright © Huawei Technologies Co., Ltd.
Description of the Application Interfaces
1 cycle: 3s
R
V
F
R
V
F
- V
F
is 3 mA, then the voltage of the LED V
F
VBAT
I
F
I
F
curves. If VBAT is 3.8 V and
F
F
is 1.5 V
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