Specifications

LEON-G100/G200 - System Integration Manual
GSM.G1-HW-09002-C Preliminary Design-In
Page 56 of 75
SPK_P / SPK_N are high level balanced output. They are DC coupled and must be used with a speaker
connected in bridge configuration.
Route SPK_P / SPK_N as differential pair, to reduce differential noise pick-up. The balanced configuration
will help reject the common mode noise
If audio output is directly connected to speaker transducer, given the low load impedance of its load, then
consider enlarging PCB lines to reduce series resistive losses
HS_P is single ended analog audio referenced to GND. Reduce coupling with noisy lines as this Audio
output line does not benefit from common mode noise rejection of SPK_P / SPK_N
Use twisted pair cable for balanced audio usage, shielded cable for unbalanced connection to speaker
If DC decoupling is required, a large capacitor needs to be used, typically in the µF range, depending on the
load impedance, in order not to increase the lower cut-off frequency due to its High-Pass RC filter response
2.2.1.4 Module grounding
Good connection of the module with application board solid ground layer is required for correct RF
performance. It significantly reduces EMC issues and provides a thermal heat sink for the module.
Connect each GND pin with application board solid GND layer. It is strongly recommended that each GND
pad surrounding VCC and ANT pins have one or more dedicated via down to application board solid ground
layer. The same applies to GND pins on the opposite side close to Charger pins
If Application board is a multilayer PCB, then it is required to tight together each GND area with complete
via stack down to main board ground layer
It is recommended to implement one layer of the application board as ground plane
Good grounding of GND pads will also ensure thermal heat sink. This is critical during call connection, when
the real network commands the module to transmit at maximum power: proper grounding helps prevent
module overheating.
2.2.1.5 Charger Layout
If battery charger is implemented, V_CHARGE must withstand the charge current (typically in the order of
several hundred mA) continuous current sink. Voltage drop is not as critical as for VCC, but dimension the line
width adequately to support the charge current without excessive loss that may lead to increase in PCB
temperature.
CHARGE_SENSE senses the charger voltage: it sinks a few µA. Therefore its line width is not critical. Since it is
an analog input, it must be connected to V_CHARGE away from noisy sources.
2.2.1.6 Other Sensitive pins
A few other pins on the LEON-G100/G200 require careful layout.
Backup battery (V_BCKP): avoid injecting noise on this voltage domain as it may affect the stability of
sleep oscillator
Analog-to-Digital Converter (ADC1): it is a high impedance analog input; the conversion accuracy will be
degraded if noise injected. Low-pass filter may be used to improve noise rejection; typically L-C tuned for RF
rejection gives better results;
Power On (PWR_ON): is the digital input for power-on of the LEON-G100/G200. It is implemented as high
impedance input. Ensure that the voltage level is well defined during operation and no transient noise is
coupled on this line, otherwise the module may detect a spurious power-on request