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The Roadrunner IC is designed to support the needs of portable iDEN cellular telephone products. It
provides the necessary control, audio, and regulator functions. The following functions are
provided:
•
Turn on control signals to properly activate the unit
•
Turn off control signals to turn off the unit if an error is detected
•
Audio amplification for the speaker
•
Audio amplification for the alert
•
Audio amplification for the external audio
•
Audio amplification of the microphone
•
13-bit, linear audio CODEC
•
Band-gap reference voltage
•
Linear regulation of DC voltages
•
Two switching regulators (BUCK/BOOST)
•
Operational amplifiers for use in the battery charger
•
Internal D/A conversion for the battery charger
•
14-channel, 10-bit A/D conversion
•
PA high-end regulation
•
Real-time clock
1.5
Audio Section
Audio components for the i897 consist primarily of the audio amplifiers, a coder/decoder
(CODEC), and acoustic transducers such as microphones and speakers. Other components include
active RC filters, digital filters, software controlled amplifiers and attenuators, an analog-to-digital
converter (ADC), and two digital-to-analog converters (DACs).
1.5.1 Acoustic Transducers
The i897 uses the following acoustic input and output transducers:
•
Active internal and external microphones requiring a DC bias
•
A dynamic 32-ohm earpiece speaker
•
A pair of dynamic high audio 8-ohm speakers
1.5.2 Audio Amplifiers
The i897 uses seven audio amplifiers, five from the Roadrunner and 2 from an external class D
amplifier, as shown and further described in the Figure 1-6, Figure 1-7 and Figure 1-1.
6880401P59-O
OVERVIEW: iDEN Digital Modulation Technology
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