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
6.2.1.2. +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 GC864-QUAD/PY.
• When using a switching regulator, a 500kHz (or more) 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.
• In any case the frequency and switching design selection is related to the
application to be developed, due to the fact that the switching frequency
could also generate EMC interferences.
• As far as car PB battery, the input voltage can rise up to 15.8V. This must
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 100F tantalum capacitor is
typically used.
• Make sure the low ESR capacitor on the power supply output (usually a
tantalum one) is rated at least 10V.
• As far as car applications, a spike protection diode must be inserted close
to the power input, in order to clean the supply from spikes.
• A protection diode must be inserted close to the power input, in order to
save the GC864-QUAD/PY from power polarity inversion. This can be the
same diode used for spike protection.
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