LTE-A Module Series
EM121R-GL Hardware Design
EM121R-GL Hardware Design 51 / 80
4.5.3. WWAN_LED#
The WWAN_LED# signal is used to indicate RF status of the module, and its sink current is up to 10 mA.
To reduce current consumption of the LED, a current-limited resistor must be placed in series with the
LED, as illustrated in the figure below. The LED is ON when the WWAN_LED# signal is at low level.
Module
WWAN_LED#
PMU
10
VCC (Typ. 3.7 V)
R1
330
Ω
LED1
2, 4
70, 72, 74
VCC
Figure 29: WWAN_LED# Reference Circuit
The following table shows the RF status indicated by WWAN_LED#.
Table 24: Network Status Indications of WWAN_LED#
4.5.4. WAKE_ON_WAN#*
The WAKE_ON_WAN# is an open drain pin, which requires a pull-up resistor on the host. When a URC
returns, a 1 s low level pulse signal will be outputted to wake up the host. The module operation status
indicated by WAKE_ON_WAN# is shown below.
WWAN_LED# Level
Description
Low Level (LED On)
RF function is turned on
High Level (LED Off)
RF function is turned off if any of the following occurs:
⚫
The (U)SIM card is not powered.
⚫
W_DISABLE1# is at low level (airplane mode enabled).
⚫
AT+CFUN=4
(RF function disabled).