Simplified Block Diagram
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The power management subsystem includes an AC adapter/USB dual input linear charger that is designed with a special CC, CV, and die temperature regulation algorithm. The MOSFET, reverse current blocking diode, and current sense resistor are integrated to minimize total solution size and improve reliability. The AC adapter input can withstand peak voltages as high as 28V, further enhancing system reliability. Four high efficiency buck regulators provide core, memory and IO power. Nineteen LDOs power RF, baseband processor, applications processor, and accessories are provided, each with 60dB PSRR, less than 67µV of output noise, and an input voltage range down to 1.7V.
The real-time clock/calendar (RTC) provides 32.768kHz buffered output, seconds, minutes, hours, day, date, month, and year information as well as two time/date-programmable alarms. Also included are a 32kHz sleep clock, backup battery charger, SIM level translator, full-speed USB transceiver, reset output, power on/off control logic, and TCXO buffer. The MAX8906 provides complete power conversion and signal level shifting circuits to interface with 1.8V or 3.0V SIMs and USB. An I²C serial interface provides complete control over regulator output voltages and on/off states.
The MAX8906 audio subsystem includes a high-efficiency Class D mono audio power amplifier with low-power bypass mode, a stereo DirectDrive® headphone amplifier, differential analog audio input, four single ended analog audio inputs, and two headset detection comparators. The Class D amplifier features Maxim’s 3rd generation filterless active emissions limiting Class D technology, rendering the traditional Class D output filter unnecessary in handheld audio applications. The MAX8906 also offers a spread-spectrum modulation (SSM) mode that further reduces EMI radiated emissions. The stereo headphone amplifier use Maxim's patented DirectDrive architecture that produces a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors, saving cost, space and component height. The device utilizes a user-defined input architecture, two channel input Mixer + MUX, volume control, comprehensive click-and-pop suppression, internal gain, and I²C control. Integrated SPST switches allow the integrated speaker amplifier to be bypassed. This allows an external amplifier to power the same speaker that is connected to the Class D amplifier without requiring external switches.
The MAX8906 is available in a 5.85mm x 5.7mm x 0.7mm, 0.4mm pitch, 13 x 14 array, wafer-level package (WLP).