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MANUAL
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3.1.6.3 Creating an analog ground
An analog ground plane can be created in the application if there is any risk of noise. The analog ground plane
should connect to the main GND in one point so that high frequency digital current is not floating through the analog
ground. Connecting the analog ground in only one point avoids ground currents from power supplies and other
high current circuitry from creating noise in the analog circuitry. This common point should preferably be located
where the analog supply voltage (VANA) is generated (at filter (A), or regulator (B) depending on implementation).
Figure 27: Analog Ground Plane Recommendation
3.1.6.4 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 (not AGND). This reference shall be used to bias all analog circuitry in the application.
Figure 28: BIAS reference Recommendation
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.
3.1.6.5 Analog Ground vs. AGND
The AGND signal output from the module is not a ground.
The AGND signal is an analog reference, which is connected to the main ground used by the module in one place
inside the module. It should under no 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.
The Analog Ground is a ground-plane created in the application. It connects to the application GND-plane at one
point, preferably close to where the analog supply voltage is created.
Vsupply
VANA
Vsupply
VANA
Regulator
B
A
