LISA-C2 series and FW75-C200 - System Integration Manual
UBX-13000620 - R21
Early Production Information
System description
Page 14 of 103
When designing the power supply for the application, pay specific attention to power losses and transients.
The DC power supply must be able to provide a voltage profile to the VCC pins with the following
characteristics:
•
Voltage drop during transmission must be lower than 250 mV
Any degradation in power supply performance (due to losses, noise or transients) will directly affect the RF
performance of the module since the single external DC power source indirectly supplies all the digital and
analog interfaces, and also directly supplies the RF power amplifier (PA).
1.5.2.1
Handling sudden momentary power loss
If the host application board should be susceptible to sudden momentary power loss, then it should ensure
either one of the following during such an event:
•
The supply to LISA-C200 VCC pin remains stable as described in section 1.5.2 to keep module powered-on.
•
If the host supply cannot sustain the VCC requirements to keep the module powered on during the sudden
momentary power loss, then the supply to the LISA-200 VCC pin should go to 0V to power down the
module. In addition, the falling voltage on the VCC pin must have a minimal of a 2 sec duration timed
during the downward segment between 2.6V to 0V. This will allow the module to reach power-off state.
The module will then be ready to power-up again provided is meets the criteria described in section 1.6.1.
Failure to handle sudden momentary power loss as outlined in section 1.5.2.1 can result in
unpredictable behavior and possible memory corruption within the modem.
1.5.3
VCC application circuits
LISA-C200 and FW75-C200 modules must be supplied through the
VCC
pins by one (and only one) proper DC
power supply that must be one of the following:
•
Switching regulator
•
Low Drop-Out (LDO) linear regulator
•
Rechargeable Li-Ion battery
•
Primary (disposable) battery
Main Supply
Available?
Battery
Li-Ion 3.7 V
Linear LDO
Regulator
Main Supply
Voltage
>5 V?
Switching
Step-Down
Regulator
No, portable device
No, less than 5 V
Yes, greater than 5 V
Yes, always available
Figure 3: VCC supply concept selection
The switching step-down regulator is the typical choice when the available primary supply source has a nominal
voltage much higher (e.g. greater than 5 V) than the LISA-C200 and FW75-C200 modules operating supply