MP7722 MPS, MP7722 Datasheet - Page 6

• Manufacturer Part Number: MP7722
• Description: 2 x 20W Class D Stereo Single Ended Audio Amplifer
• Manufacturer: MPS

OPERATION
The MP7722 uses Monolithic Power Systems’
patented Analog Adaptive Modulation
convert the audio input signal into pulses of
power that, when filtered through an external
inductor-capacitor filter, reproduce the amplified
signal across the load. Because of the
switching
dissipation in the amplifier is drastically reduced
when compared to Class A, B or A/B amplifiers
while providing high fidelity and low distortion.
The voltage gain is set by the combination of
the input resistor R
R
Where for Channel 1: R
and for Channel 2: R
The
MOSFETS wherein for each channel the output
driver stage uses two 180mΩ N-Channel
MOSFETs to deliver the pulses to the LC output
filter that in turn drives the load. To fully
enhance the high-side MOSFET, the gate is
driven to a voltage higher than V
bootstrap capacitor between SW and BS. While
the output is driven low, the bootstrap capacitor
is charged from V
MOSFET is driven high from the voltage at BS,
forcing the MOSFET gate to a voltage higher
than V
on, reducing power loss in the amplifier.
MP7722 Rev. 1.3
9/25/2006
FB
and is calculated by the equation:
DD
MP7722
and allowing the MOSFET to fully turn
Class
includes
DD
A
IN
D
V
. The gate of the high-side
FB
and the feedback resistor
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
=
=R
output
−
R
MP7722 – 2 x 20W CLASS D STEREO SINGLE ENDED AUDIO AMPLIFIER
R
FB2
FB
IN
FB
=R
and R
four
FB1
stage,
and R
IN
=R
high-power
DD
© 2006 MPS. All Rights Reserved.
IN2
by the
IN
.
TM
power
www.MonolithicPower.com
=R
IN1
to
Pop Elimination
The capacitors C
signal and pass only the AC signals to the load.
To insure that the amplifier passes low
frequency signals, the capacitor values need to
be chosen such that the time constant of C
R
need to be charged up to the DC operating
point, which is typically at ½ of V
MP7722 includes special integrated circuitry
that carefully controls the pre-charging of these
capacitors, eliminating the turn-on and turn-off
pop normally associated with the charging of
the AC coupling capacitors.
Short Circuit/Overload Protection
The MP7722 has internal overload and short
circuit protection. The currents in both the
high-side
measured and if the current exceeds the 5.0A
short circuit current limit, both MOSFETs are
turned off. The MP7722 then restarts with the
same power up sequence that is used for
normal starting to prevent a pop from occurring
after a short circuit condition is removed.
Mute/Enable Function
The MP7722 EN inputs are active high enable
controls. To enable the MP7722, drive EN with
a 2.0V or higher voltage. To disable the
amplifier, drive EN below 0.4V. While the
MP7722 is disabled, the V
is less than 10µA and the output driver
MOSFETs are turned off. The MP7722 requires
approximately 500ms from the time that EN is
asserted (driven high) to when the amplifier
begins normal operation.
LOAD
is long. During startup, these capacitors
and
OUT1
low-side
and C
DD
OUT2
operating current
MOSFETs
block the DC
DD
. The
OUT
are
x
6