MAX9888EWY+T Maxim Integrated Products, MAX9888EWY+T Datasheet - Page 96

• Manufacturer Part Number: MAX9888EWY+T
• Description: IC CODEC AUDIO FLEXSOUND 63WLP
• Manufacturer: Maxim Integrated Products
• Series: DirectDrive®, FLEXSOUND™r
• Type: Class Dr

Specifications of MAX9888EWY+T

• Output Type: 3-Channel with Stereo Headphones
• Max Output Power X Channels @ Load: 1.37W x 2 @ 8 Ohm; 40mW x 2 @ 16 Ohm
• Voltage - Supply: 2.8 V ~ 5.5 V
• Features: Depop, Differential Inputs, I²S, Microphone, Mute, Shutdown
• Mounting Type: Surface Mount
• Package / Case: 63-WLP
• For Use With: MAX9888EVKIT+ - KIT EVALUATION FOR MAX9888
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Stereo Audio CODEC
with FLEXSOUND Technology
Alternative approaches to eliminating the output-cou-
pling capacitors involve biasing the headphone return
(sleeve) to the DC bias voltage of the headphone ampli-
fiers. This method raises some issues:
U The sleeve is typically grounded to the chassis. Using
U During an ESD strike, the amplifier’s ESD structures
U When using the headphone jack as a line out to other
The IC features a low-noise charge pump to generate
a negative supply for the headphone amplifier. The
nominal switching frequency is well beyond the audio
range, and thus does not interfere with audio signals.
96
Figure 29. Traditional Amplifier Output vs. DirectDrive Output
the midrail biasing approach, the sleeve must be
isolated from system ground, complicating product
design.
are the only path to system ground. Thus, the ampli-
fier must be able to withstand the full energy from an
ESD strike.
equipment, the bias voltage on the sleeve may con-
flict with the ground potential from other equipment,
resulting in possible damage to the amplifiers.
DirectDrive AMPLIFIER BIASING SCHEME
CONVENTIONAL AMPLIFIER BIASING SCHEME
GND
+V
GND
V
V
-V
(V
DD
DD
DD
SS
DD
/2
)
The switch drivers feature a controlled switching speed
that minimizes noise generated by turn-on and turn-off
transients. By limiting the switching speed of the charge
pump, the di/dt noise caused by the parasitic trace
inductance is minimized. The charge pump is active only
in headphone modes.
To reduce audible noise at the outputs, the IC’s head-
phone amplifier includes headphone ground sensing.
Connect the sense line (HPSNS) to the ground terminal
of the device’s headphone jack. Any noise present at
the headphone ground is then added to the headphone
output. The result is elimination of this noise from the
audible output. If ground sensing is not required, con-
nect HPSNS directly to ground. Figure 30 shows a block
diagram of the headphone output section including the
headphone sense function.
The IC’s headphone amplifier accepts input from the
stereo DAC and the line inputs. The output of the left and
right DAC cannot be mixed at the headphone mixer. Use
MIXDAL/MIXDAR to mix the left and right audio channels
before conversion.
Figure 30. Headphone Amplifier Block Diagram
PGAOUT1:
0dB TO -23dB
PGAOUT2:
0dB TO -23dB
PREOUT1
PREOUT2
DALEN
DAREN
DACL
DACR
+9dB
+9dB
Headphone Output Mixers
MIXHPL
MIXHPR
MIX
MIX
HPVOLL:
+3dB TO -67dB
HPLEN
HPREN
HPVOLR:
+3dB TO -67dB
HPSNS
HPR
HPL