MP7752 – 18V, 2X15W STEREO FIX FREQUENCY INDUCTORLESS BTL CLASS D AUDIO AMPLIFIER

MP7752 Rev. 1.01

www.MonolithicPower.com

17

5/27/2016

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APPLICATION INFORMATION

COMPONENT SELECTION

Delay time for input signal absence report

The Recovery time is defined as follows.

 





8

delay

R

T1.6 10

C sec

Choosing the Output EMI Filter

The magnetic bead-capacitor filter converts the

pulses at SW to the output voltage that drives

the speaker. Both PVCC line and output current

flow needed magnetic beads to prevent large

radiation from high slew-rate pulse. The larger

impedance of the magnetic bead, the better

EMI performance can be approach.

Input Coupling Capacitor

The input coupling capacitor transmits the AC

signal from the source to the MP7752 while

blocking the DC voltage. Choose an input

coupling capacitor such that the corner

frequency. The corner frequency is calculated

as:

IN

IN

IN

C

R

2

1

f











The impedance of the input resister is different

with the different gain setting. At the same gain

setting, the input impedance from part-to-part

may shift by ±20% due to shifts in the actual

resistance of the input resistors. But please

note that the gain variation from part-to-part is

small.

For design purposes, the input network should

be designed assuming an input impedance of

16 kΩ, which is the absolute minimum input

impedance of the MP7752. At the lower gain

settings, the input impedance could increase as

high as 90 kΩ.

Power Source

For maximum output power, the amplifier circuit

requires a regulated external power source. A

high power-supply voltage can deliver more

power to a given load resistance, but a power-

source voltage exceeding the maximum voltage

of 18V can damage the MP7752. The

MP7752’s power supply rejection is excellent,

though power-supply noise can pass to the

output, so care must be taken to minimize

power supply noise within the pass-band

frequencies. Bypass the power supply with a

large capacitor (typically aluminum electrolytic)

along with two smaller 1μF and 1nF ceramic

capacitors at the MP7752 VCC supply pins.

PCB Layout

Circuit layout is critical for optimal performance,

low output distortion, and noise. Duplicate the

EVB layout for best results. For layout changes,

follow these guidelines.

1) Place the following components as close to

the MP7752 as possible:

Bootstrap Capacitors

pin as possible.

Power Supply Bypass Capacitors

power stage. To avoid overstressing the

MP7752 and excessive output noise, place

2) The magnetic bead-Capacitor filter converts

the pulse train at SW to the output voltage that

drives the speaker. Please keep the filter

capacitor close to the magnetic bead.

3) Make sure that any traces carrying the switch

node (SW) voltages are routed far from any

input signal traces. If the trace must run near

the SW trace near the input, shield the input

with a ground plane between the traces.

Physically separate each channel to prevent

crosstalk.

Route each power supply from the source to

each channel individually, not serially. This

prevents channel-to-channel coupling through

the power supply input.