OVERVIEW: iDEN Digital Modulation Technology
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.
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