HUAWEI MC509 Series CDMA LGA Module
Hardware Guide
Description of the Application Interfaces
Issue 02 (2013-05-06)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
32
Figure 3-11
Driving circuit
For resistance of R placed on user board, choose the value such that it satisfies the
following equation:
I
F
*R+V
F
= VBAT
V
F
: Forward Voltage
I
F
: Forward current
Take the LED 19-213/GVC-AMNB/3T as an example (its manufacturer is Everlight
Electronics., Ltd. And the website is
). Figure 3-12 shows its
I
F
- V
F
curves. If VBAT is 3.8 V and the desired current through the LED I
F
is 3 mA,
then the voltage of the LED V
F
is 1.5 V according to I
F
-V
F
curves, and the
corresponding value for resistance of R is (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.
Module
(DCE)
LED_STATUS
LED_MODE
VBAT
R
D201
1
2
1
2
D202
LED
V
F
I
F
LED
V
F
I
F
R