max9770euit Maxim Integrated Products, Inc., max9770euit Datasheet - Page 16

• Manufacturer Part Number: max9770euit
• Description: 1.2w Low-emi, Filterless, Mono Class D Amplifier With Stereo Directdrive Headphone Amplifiers
• Manufacturer: Maxim Integrated Products, Inc.

The MAX9770/MAX9772 feature internally generated,
power-supply independent, common-mode bias voltages
referenced to GND. BIAS provides both click-and-pop
suppression and sets the DC bias level for the amplifiers.
Choose the value of the bypass capacitor as described in
the BIAS Capacitor section. No external load should be
applied to BIAS. Any load lowers the BIAS voltage, affect-
ing the overall performance of the device.
The MAX9770/MAX9772 feature logic-selectable, inter-
nally set gains. GAIN1 and GAIN2 set the gain of the
MAX9770/MAX9772 speaker and headphone amplifiers
as shown in Table 4.
The MAX9770/MAX9772 can be configured to automat-
ically switch between two gain settings depending on
whether the device is in speaker or headphone mode.
By driving one or both gain inputs with HPS, the gain of
the device changes when a headphone is inserted or
removed. For example, the block diagram shows HPS
1.2W, Low-EMI, Filterless, Mono Class D Amplifier
with Stereo DirectDrive Headphone Amplifiers
Table 4. Gain Selection
Table 5. Gain Settings with HPS
Connection
16
G A I N 1 G A I N 2
GAIN1
HPS
HPS
HPS
0
1
0
0
1
1
0
0
1
1
______________________________________________________________________________________
HPS
HPS
HPS
GAIN2
0
1
0
1
0
1
0
1
0
1
MODE GAIN
SPEAKER
MAX9770
(HPS = 0)
SPEAKER
MAX9770
(dB)
GAIN
(dB)
6
3
6
9
6
6
3
9
0
6
3
9
0
MODE GAIN
SPEAKER
MAX9772
(HPS = 0)
SPEAKER
MAX9772
(dB)
15.6
15.6
15.6
15.6
GAIN
(dB)
15.6
12
20
12
20
6
12
20
6
Gain Selection
HEADPHONE
HEADPHONE
MODE GAIN
(HPS = 1)
GAIN
(dB)
(dB)
-2
-2
-2
1
4
1
1
7
4
1
7
4
1
BIAS
connected to GAIN2, while GAIN1 is connected to V
In this configuration, the gain in speaker mode is 9dB,
while the gain in headphone mode is 1dB. The gain
settings with the HPS connection are shown in Table 5.
The MAX9770/MAX9772 feature a 0.1µA, low-power
shutdown mode that reduces quiescent current con-
sumption and extends battery life. Drive SHDN low to
disable the drive amplifiers, bias circuitry, and charge
pump. Bias is driven to GND and the headphone ampli-
fier output impedance is 10kΩ in shutdown. Connect
SHDN to V
The MAX9770/MAX9772 speaker amplifiers feature
comprehensive click-and-pop suppression that elimi-
nates audible transients on startup and shutdown. While
in shutdown, the H-bridge is in a high-impedance state.
During startup or power-up, the input amplifiers are
muted and an internal loop sets the modulator bias volt-
ages to the correct levels, preventing clicks and pops
when the H-bridge is subsequently enabled. A soft-start
function unmutes the input amplifiers 30ms after startup.
In conventional single-supply headphone drivers, the
output-coupling capacitor is a major contributor of
audible clicks and pops. Upon startup, the driver
charges the coupling capacitor to its bias voltage, typi-
cally half the supply. Likewise, during shutdown, the
capacitor is discharged to GND. This results in a DC
shift across the capacitor, which in turn, appears as an
audible transient at the speaker. Since the
MAX9770/MAX9772 headphone amplifiers do not
require output-coupling capacitors, this does not arise.
Additionally, the MAX9770/MAX9772 feature extensive
click-and-pop suppression that eliminates any audible
transient sources internal to the device. The Exiting
Shutdown (Headphone Mode) and Entering Shutdown
(Headphone Mode) graphs in the Typical Operating
Characteristics shows that there are minimal spectral
components in the audible range at the output upon
startup or shutdown.
In most applications, the output of the preamplifier dri-
ving the MAX9770/MAX9772 has a DC bias of typically
half the supply. During startup, the input-coupling
capacitor is charged to the preamplifier’s DC bias volt-
age through the R
in a DC shift across the capacitor and an audible click-
and-pop. An internal delay of 50ms eliminates the click-
and-pop caused by the input filter.
DD
for normal operation.
F
of the MAX9770/MAX9772, resulting
Click-and-Pop Suppression
Headphone Amplifier
Speaker Amplifier
Shutdown
DD
.