User's Manual
Table Of Contents
- GC864 Hardware User Guide
- APPLICABILITY TABLE
- 1. Introduction
- 2. Overview
- 3. GC864 Mechanical Dimensions
- 4. GC864-QUAD/PY Module Connections
- 5. Hardware Commands
- 6. Power Supply
- 7. Antenna
- 8. Logic Level Specifications
- 9. Serial Ports
- 10. Audio Section Overview
- 11. General Purpose I/O
- 11.1. GPIO Logic Levels
- 11.2. Using a GPIO Pad as INPUT
- 11.3. Using a GPIO Pad as OUTPUT
- 11.4. Using the RF Transmission Control GPIO4
- 11.5. Using the RFTXMON Output GPIO5
- 11.6. Using the Alarm Output GPIO6
- 11.7. Using the Buzzer Output GPIO7
- 11.8. Magnetic Buzzer Concepts
- 11.9. Using the Temperature Monitor Function
- 11.10. Indication of Network Service Availability
- 11.11. RTC Bypass Out
- 11.12. VAUX1 Power Output
- 12. DAC and ADC Section
- 13. Mounting the GC864-QUAD/PY on the Board
- 14. Packing System
- Conformity Assessment Issues
GC864 Hardware User Guide
1vv0300733 Rev.12 – 2009-06-04
6.2.1.3. Battery Source Power Supply Design Guidelines
The desired nominal output for the power supply is 3.8V and the maximum voltage
allowed is 4.2V (4.5 if using SW release 7.03.x00 or newer). A single 3.7V Li-Ion cell
battery type is suited for supplying the power to the Telit GC864-QUAD/PY module.
CAUTION:
The three cells Ni/Cd or Ni/MH 3,6 V Nom. Battery types or 4V PB types MUST NOT
BE USED DIRECTLY since their maximum voltage can rise over the absolute
maximum voltage for the GC864-QUAD/PY and damage it.
CAUTION:
DO NOT USE any Ni-Cd, Ni-MH, and Pb battery types directly connected with GC864-
QUAD/PY. Their use can lead to overvoltage on the GC864-QUAD/PY and damage it.
USE ONLY Li-Ion battery types.
A Bypass low ESR capacitor of adequate capacity must be provided, in order to cut
the current absorption peaks. A 100F tantalum capacitor is typically used.
Make sure the low ESR capacitor (usually a tantalum one) is rated at least 10V.
A protection diode must be inserted close to the power input, in order to save the
GC864-QUAD/PY from power polarity inversion. Otherwise the battery connector
must be done in a way to avoid polarity inversions when connecting the battery.
The battery capacity must be at least 500mAh in order to withstand the current peaks
of 2A; the suggested capacity is from 500mAh to 1000mAh.
6.2.1.4. Battery Charge Control Circuitry Design Guidelines
The charging process for Li-Ion Batteries can be divided into 4 phases:
• Qualification and trickle charging
• Fast charge 1 – constant current
• Final charge – constant voltage or pulsed charging
• Maintenance charge
The qualification process consists in a battery voltage measure, indicating roughly its
charge status. If the battery is deeply discharged, then its voltage is lower than the
trickle charging threshold and the charge must start slowly, possibly with a current
limited pre-charging process where the current is kept very low with respect to the
fast charge value, aka the trickle charging.
During the trickle charging, the voltage across the battery terminals rises; when it
reaches the fast charge threshold level the charging process goes into fast charge
phase.
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