Novatel HS 3001, Integration Manual

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Even the best layout will have some impedance from the source to the cellular module;
therefore, sufficient bulk decoupling capacitance is required at the Vbat input to the cellular
module. If necessary, you may use up to two 1000
µ
F, low ESR, tantalum capacitors to provide
the desired decoupling. If used, the capacitors should be located very close to the cellular
interface connector V
BAT
pins. Any thermal relief used on these capacitors should comply with
the information given above to provide the lowest possible impedance. The grounding of
these capacitors is critical. Therefore, it should be a low impedance and should use multiple
vias to the internal ground plane close to the capacitor.
It is highly recommended to have the battery voltage be set at 3.8 Volts (the approximate
midpoint between 3.4 Volt and 4 .4 Volt) to avoid any negative side effects related to
transmit power of the radio module caused by high voltage drops due to high current draw
on the Vbat line.
Figure 4-5 Example of GOOD V
BAT
layout
Audio Reference Design
The audio quality is dependent on the circuit design and layout. As an aid to obtaining good
audio quality, we included a reference design below.