CM-42 Technical Description
PAGE 29 OF 38
SEM/CX-02:0076/DES A
2.3.8.4.2
Creating an analog reference voltage (BIAS)
The BIAS reference should be generated from the analog supply voltage (VANA) and be referenced to the analog
ground. This reference shall be used to bias all analog circuitry in the application.
Figure 13: BIAS reference Diagram
The bias can be tapped directly from the resistor voltage divider, but the amplifier will make the bias more stable
and less susceptible to noise.
2.3.8.4.3
Analog ground vs. AGND
The AGND signal output from the module is not a ground. It is an analog reference, which is connected to the main
ground used by the module in one place inside the module. It should not under any circumstances be used as a
ground or connected to a ground in the application.
AGND must be treated as a signal. Together with ATMS and AFMS it creates a semi differential interface.
The analog ground shall be used as ground plane for the analog circuitry of the application. It should not be
connected to the AGND signal output from the phone module.
-
+
0
100k
100k
VANA
BIAS
