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Class D amps claim 'lowest' solution cost

Posted: 29 Apr 2008 ?? ?Print Version ?Bookmark and Share

Keywords:Class D speaker amplifiers? filterless modulation? lowest solution cost?

Maxim Integrated Products has introduced the MAX9736A/B, a family of versatile single-supply, filterless Class D speaker amplifiers, which provide high-performance, thermally efficient amplifier solutions at the lowest solution cost. These amplifiers are especially targeted for all-in-one PCs, LCD/PDP/CRT monitors and TVs, conference phones, MP3 docking stations, notebook PCs, and PC speakers.

Filterless modulation
As IC costs continue to trend downwards, the number of external components becomes increasingly important in determining total solution cost. The MAX9736A/B feature a spread-spectrum, filterless modulation design that minimizes external components and keeps costs low. The devices pass CE EMI limits with 1m cables by using only a low-cost ferrite bead and a capacitor on each output.

The MAX9736A/B do not require any external Schottky diodes, which add cost to competing solutions. The devices save further space by eliminating both output LC (inductor-capacitor) filters and input-filter operational amplifiers.

Feature set
Several integrated features make these amplifiers more versatile than competing devices.

The MAX9736A/B provide 2次 to 8次 (or higher) load drive capability. The MAX9736A delivers 2 x 15W into 8次 loads, or 1 x 30W into a 4次 load; the MAX9736B delivers 2 x 6W into 8次 loads or 1 x 12W into a 4次 load. With a pin-selectable stereo/mono mode, the MAX9736A/B can drive a 4次 stereo or 2次 mono load with supply voltages up to 12V.

The devices are pin compatible, so a single audio design will work across a broad range of platforms. Design efforts are thus simplified and PCB inventory reduced.

Available as mid- (MAX9736B) and high-power (MAX9736A) devices, the MAX9736A/B operate from a wide, single-supply 8V to 28V power supply that allows direct battery operation in portable applications. The high 67dB PSRR eliminates the need for a costly, regulated power supply. High efficiency (up to 88 percent at 12V supply) eliminates the need for a heatsink.

Comprehensive click-and-pop reduction circuitry eliminates noise coming into and out of shutdown or mute.

Filtering and mixing operational amplifiers are integrated. The input op amps allow the user to create summing amplifiers, lowpass or highpass filters, and select the optimal amplifier gain. For even more design flexibility, in mono mode the right input op amp is available as a spare device.

Excellent clipping recovery eliminates audible Class D overload artifacts. Thermal and short-circuit protection assures robust operation. The MAX9736A/B are fully specified over the -40∼C to 85∼C extended temperature range. The devices are available in a small 7mm x 7mm, 32-pin TQFN package. Prices start at $1.49 (1,000-up).

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