Telit Wireless Solutions GM862-GPS Manuel D’Utilisation

 
 
 
 

 
 

 

 1vv0300728 Rev. 0 - 27/04/06  

  

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page 13 of 55 

 

 

3.2.1.2   + 12V input Source Power Supply Design Guidelines 

 
•  The desired output for the power supply is 3.8V, hence due to the big difference between the input 

source and the desired output, a linear regulator is not suited and shall not be used. A switching 
power supply will be preferable because of its better efficiency especially with the 2A peak current 
load represented by the GM862-GPS. 

•  When using a switching regulator, a 500Khz switching frequency regulator is preferable because 

of its smaller inductor size and its faster transient response. This allows the regulator to respond 
quickly to the current peaks absorption.  

•  For car PB battery the input voltage can rise up to 15,8V and this should be kept in mind when 

choosing components: all components in the power supply must withstand this voltage. 

•  A Bypass low ESR capacitor of adequate capacity must be provided in order to cut the current 

absorption peaks, a 100μF tantalum capacitor is usually suited. 

•  Make sure the low ESR capacitor on the power supply output (usually a tantalum one) is rated at 

least 10V. 

•  For Car applications a spike protection diode should be inserted close to the power input, in order 

to clean the supply from spikes.  

•  A protection diode should be inserted close to the power input, in order to save the GM862-GPS 

from power polarity inversion. This can be the same diode as for spike protection.