max9727eept Maxim Integrated Products, Inc., max9727eept Datasheet - Page 8

• Manufacturer Part Number: max9727eept
• Description: Max9727 Quad Audio Line Driver With 3vrms Output
• Manufacturer: Maxim Integrated Products, Inc.

Quad Audio Line Driver with 3V
The MAX9727 is a quad audio line driver with an output
of 3V
single +3.3V supply. The device employs Maxim’s
patented DirectDrive architecture that produces a
ground-referenced output from a single supply, elimi-
nating the need for large DC-blocking capacitors. An
internal charge pump creates an internal negative sup-
ply voltage. This allows the amplifier outputs of the
MAX9727 to be biased at GND, almost doubling
dynamic range while operating from a single supply.
An active-low shutdown input disables the amplifiers
and reduces quiescent current consumption to less
than 100nA.
The MAX9727 also features click-and-pop suppression
circuitry that reduces audible clicks and pops during
startup and shutdown.
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage, allowing
the MAX9727 outputs to be biased about ground. This
allows for a symmetrical output biased around 0V. The
MAX9727’s charge pump requires two small ceramic
capacitors, conserving board space, reducing cost,
and improving the frequency response of the ampli-
fiers. See the Charge-Pump Output Voltage vs. Output
Current graphs in the Typical Operating Characteristics
for details of the possible capacitor sizes. There is a
low DC voltage on the amplifier outputs due to amplifier
offset. However, the offsets of the MAX9727 are typical-
ly 500µV, which, when combined with a 1kΩ load,
results in less than 500nA of DC current flow to the line-
in device.
The MAX9727 features a low-noise charge pump. The
300kHz switching frequency is well beyond the audio
range and does not interfere with audio signals. The
switch drivers feature a controlled switching speed that
minimizes noise generated by turn-on and turn-off tran-
sients. The di/dt noise caused by the parasitic bond
wire and trace inductance is minimized by limiting the
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RMS
from a single +5V supply and 2V
Detailed Description
DirectDrive
Charge Pump
RMS
from a
switching speed of the charge pump. Although not typ-
ically required, additional high-frequency noise attenu-
ation can be achieved by increasing the value of C2
(see the Functional Diagram / Typical Operating Circuit ).
Figure 1. Conventional Driver Output Waveform vs. MAX9727
Output Waveform
V
GND
DD
GND
V
V
V
DD
DD
DD
/2
V
V
OUT
OUT
CONVENTIONAL DRIVER BIASING SCHEME
DirectDrive BIASING SCHEME
RMS
Output
2V
V
DD
DD