d15 Modem Integration and Application Developers Guide version draft 0.53 Page 26 of 181
CHAPTER 3 Design Considerations
When integrating a wireless modem, internal connections and placements are critical to a successful implementation.
Specific attention must be paid to the following support mechanisms:
•
DC power
•
Audio considerations.
•
Serial interface and control
•
SIM card considerations
•
ESD considerations
•
Antenna Considerations
•
Mechanical mounting
•
Differences between D10 to D15
•
Desense control (see “Desense” on Annex G)
•
How to connect a 3788 handset to D15
•
GPS Considerations.
3.1 Power supply consideration.
3.1.1 Power Supply losses.
The D15 is specified to operate from 3.0V to 6.0V on the D15 input (after the flat cable losses). In
order to be able to work in the lowest battery values it is important to verify the losses in the
power supplies lines, Flat cable and in the user PCB.
The D15 is a GSM phone that transmits in pulses of about 0.5mS every 4.6mS. The Peak current
is about 1.5A.
The VCC line will drop down in the TX periods:
Figure 8 – The VCC signal during TX periods
In order to minimise the
∆
it is recommended to use a short Flat cable as possible and to put a
1000uF capacitor (or maximum possible) in the D15 VCC input.
TX
TX
TX
Transmit
Periods
VCC
