max9722beue Maxim Integrated Products, Inc., max9722beue Datasheet - Page 13

• Manufacturer Part Number: max9722beue
• Description: 5v, Differential Input, Directdrive, 130mw Stereo Headphone Amplifiers With Shutdown Products
• Manufacturer: Maxim Integrated Products, Inc.

Figure 8. Common-Mode Sense Input Eliminates Ground-Loop
Noise
Figure 9. Common-Mode Noise Rejection
AUDIO
AUDIO
INPUT
RIGHT
INPUT
LEFT
Stereo Headphone Amplifiers with Shutdown
SHDN
5V, Differential Input, DirectDrive, 130mW
______________________________________________________________________________________
MAX9722A
EXAMPLE CONNECTION:
IMPROVEMENT FROM
ADDING MAX9722 WITH
SERIES RESISTANCE
V
AUDIO
V
AUDIO
R
2
R
1
RESISTOR IS
INSERTED
BETWEEN THE
JACK SLEEVE
AND
GND = 9.8Ω
MAX9722A
9.8Ω
•
•
•
9.8Ω RESISTOR ADDS TO HP CROSSTALK, BUT DIFFERENTIAL
SENSING AT THE JACK SLEEVE CORRECTS FOR THIS (ONE CHANNEL
ONLY SHOWN).
CURRENT FLOW (IN SIGNAL CABLE SCREEN) DUE TO V
IS GREATLY REDUCED.
NOISE COMPONENT IN THE RECEIVER OUTPUT IS REDUCED BY 34dB
OVER THE PREVIOUS EXAMPLE WITH THE VALUES SHOWN.
•
•
•
V
0.10Ω RESISTANCE FROM CABLE SCREEN.
0.10Ω RESISTANCE DUE TO GND CABLING AT RECEIVER.
V
THE TWO GNDS.
V
0.1Ω
0.1Ω
NOISE
NOISE
NOISE
When the headphone jack is used as a line out to inter-
face between other equipment (notebooks, desktops,
and stereo receivers), potential differences between
the equipment grounds can create ground loops and
excessive ground-current flow. The MAX9722A’s INR+
and INL+ inputs are connected together to form a com-
mon-mode input that senses and corrects for the differ-
ence between the headphone return and device
ground (see Figure 8). Connect INR+ and INL+ through
a resistive voltage-divider between the headphone jack
return and SGND of the device. For optimum common-
mode rejection, use the same value resistors for R
R
and R
capacitor between SGND and R
Application Circuit ). If ground sensing is not required,
connect INR+ and INL+ directly to SGND.
Figure 9 shows a theoretical connection between two
devices, for example, a notebook computer (transmit-
ter, on the left) and an amplifier (receiver, on the right),
REPRESENTS THE POTENTIAL DIFFERENCE BETWEEN
IN
, and R
F
0.1Ω
0.1Ω
= 30kΩ. Improve DC CMRR by adding a
2
V
V
V
V
REF_IN
REF_IN
IN
IN
and R
= V
= V
Common-Mode Noise Rejection
GND NOISE COMPONENT IN
OUTPUT = V
GND NOISE COMPONENT IN
OUTPUT = V
AUDIO
AUDIO
= V
= (V
NOISE
NOISE
+ (V
F
. For the MAX9722B, R
/2
NOISE
x 0.99)
NOISE
NOISE
x 0.98)
/2
/100
NOISE
Common-Mode Sense
2
(see the Typical
IN
= 15kΩ
1
and
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