MAX9715 Ver la hoja de datos (PDF) - Maxim Integrated

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MAX9715

2.8W, Low-EMI, Stereo, Filterless Class D Audio Amplifier

Maxim Integrated 

2.8W, Low-EMI, Stereo, Filterless Class D

Audio Amplifier

Supply Bypassing, Layout,

and Grounding

Proper layout and grounding are essential for optimum

performance. Use large traces for the power-supply

inputs and amplifier outputs to minimize losses due to

parasitic trace resistance. Large traces also aid in moving

heat away from the package. Proper grounding improves

audio performance, minimizes crosstalk between chan-

nels, and prevents any switching noise from coupling into

the audio signal. Route ground return paths that carry

switching transients to power ground (PGND). Keep high-

current return paths that connect to PGND short and

route them away from analog ground (GND) and any

traces or components in the audio input signal path. Use

a star connection to connect GND and PGND together at

one point on the PC board.

Bypass each PVDD with a 0.1μF capacitor to PGND.

Bypass VDD to GND with a 0.1μF capacitor. Place a bulk

capacitor between VDD and PGND. Place the bypass

capacitors as close to the MAX9715 as possible.

Use large, low-resistance output traces. Current drawn

from the output increases as load impedance decreases.

High-output-trace resistance decreases the power deliv-

ered to the load. For example, when compared to a 0Ω

trace, a 100mΩ trace reduces the power delivered to a

4Ω load from 2.1W to 2.0W. Large output, supply, and

GND traces decrease the thermal impedance of the cir-

cuit and allow more heat to be radiated from the MAX9715

to the air.

The MAX9715 thin QFN-EP package features an

exposed thermal pad on its underside. This pad lowers

the package’s thermal impedance by providing a direct-

heat conduction path from the die to the PC board.

Connect the exposed thermal pad to an electrically iso-

lated pad of copper. A bigger pad area provides better

thermal performance. Connect EP to GND if PC board

layout rules do not allow for isolated pads of copper. If

EP is connected to GND, ensure that high-current return

paths do not flow through EP.

Biamp Configuration

The Typical Application Circuit shows the MAX9715

configured as a mid-/high-frequency amplifier and the

MAX9713 is configured as a mono bass amplifier.

Capacitors C1 and C2 set the highpass cutoff frequen-

cy according to the following equation:

f=

1

2π × RIN × C1

where RIN is the input resistance of the MAX9715 and

C1 = C2. The 10μF capacitors on the output of the

MAX9715 ensure a two-pole roll-off with the 5Ω load

shown.

The stereo signal is summed to a mono signal and then

sent to a two-pole lowpass filter. The filtered signal is

then amplified by the MAX9713. The passband gain of

the lowpass filter, for coherent left and right signals is

(-2 x R3) / R1, where R1 = R2. The cutoff frequency of

the lowpass filter is set by the following equation:

f= 1 ×

1

2π C3 × C4 × R3 × R4

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