GE863-PRO3 Hardware User Guide
1vv0300773a Rev. 0 - 24/01/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 25 of 64
The suggested circuit is:
The quoted current intensity are without VBATT power supply for the module.
The S-817A19A Seiko LDO has a value of 1.2μA Typ for the quiescent current. Without VBATT power
supply voltage, the VRTC Reverse Current is 7- 8 μA Typ. (depending on OSCSEL pin status)
At ambient temperature 20°C, the BR2032 coin type (Panasonic 190 mAh) should be sufficient for 2-3
years with typical current intensity. The CR2032 coin type Panasonic 220 mAh) has an improved
behaviour at low and high temperatures.
When the VBATT voltage is present, the VRTC voltage exceeds the S-817 output voltage, so the
current from the Lithium Primary Battery is only 1.2μA Typ (or less).
NOTE: the 2-3 years are given considering the worst case (VBATT always off)
The principal guidelines for the Power Supply Design embrace three different design steps:
• the electrical design
• the thermal design
• the PCB layout
5.4.1 Electrical design Guidelines
The electrical design of the power supply depends strongly from the power source where this power is
drained. We will distinguish them into three categories:
• +5V input (typically PC internal regulator output)
• +12V input (typically automotive)
• Battery
GE863-PRO
3
VRTC
S-817A19A
Seiko
10K
Ω
1
μ F
ceramic
1.2μΑ
3V
Lithium
primary
battery
1μ F
ceramic