User's Manual

GE864- QUAD Har dwar e User Guide
1vv0300872 Rev.1 2010-04-02
- All Rights Reserved. Page 27 of 77
6.2. General Design Rules
The principal guidelines for the Power Supply Design embrace thr ee different design
steps:
the electr ical design
the thermal design
the PCB layout.
6.2.1. Electrical Design Guidelines
The electr ical design of the power supply depends strongly fr om the power sour ce
wher e this power is dr ained. We will distinguish them into three categories:
+5V input (typically PC internal regulator output)
+12V input (typically automotive)
Battery
6.2.1.1. +5V input Sour ce Power Suppl y Design Guidel ines
The desired output for the power supply is 3.8V, hence there is not a big
difference between the input source and the desir ed output and a linear
regulator can be used. A switching power supply will not be suited
because of the low drop out requirements.
When using a linear regulator, a proper heat sink shall be provided in
order to dissipate the power generated.
A Bypass low ESR capacitor of adequate capacity must be provided in
order to cut the cur rent absor ption peaks close to the GE864-QUAD, a
100μF tantalum capacitor is usually suited.
Make sur e the low ESR capacitor on the power supply output (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 GE864-QUAD fr om power polarity inver sion.