MAX9888EWY+T Maxim Integrated Products, MAX9888EWY+T Datasheet - Page 95

• 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

Table 27. Distortion Limiter Registers
The IC’s headphone amplifier integrates Maxim’s
DirectDrive architecture to eliminate the need for large
DC-blocking capacitors. Traditional single-supply head-
phone amplifiers have outputs biased at a nominal
DC voltage (typically half the supply). Large coupling
capacitors are needed to block this DC bias from the
headphone. Without these capacitors, a significant
amount of DC current flows to the headphone, resulting
in unnecessary power dissipation and possible damage
to both the headphone and headphone amplifier.
The DirectDrive architecture uses a charge pump to
create an internal negative supply voltage. This allows
the IC’s headphone outputs to be biased at GND while
operating from a single supply (Figure 29). Without a DC
component, there is no need for the large DC-blocking
capacitors. Instead of two large (220FF, typ) capaci-
tors, the IC charge pump requires two small ceramic
capacitors, conserving board space, reducing cost, and
REGISTER
0x44
BIT
7
6
5
4
2
1
0
THDCLP
THDT1
NAME
Headphone Amplifier
Distortion Limit
Measured in % THD+N.
Distortion Limiter Release Time Constant
Duration of time required for the speaker amplifier’s output gain to adjust back to the
nominal level after a large signal has passed.
000 = 6.2s
001 = 3.1s
010 = 1.6s
011 = 815ms
100 = 419ms
101 = 223ms
110 = 116ms
111 = 76ms
with FLEXSOUND Technology
VALUE
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
THD+N LIMIT (%)
Limiter disabled
improving the frequency response of the headphone
amplifier. There is a low DC voltage on the amplifier out-
puts due to amplifier offset. However, the offset of the IC
is typically Q0.2mV, which, when combined with a 32I
load, results in less than 6FA of DC current flow to the
headphones.
In addition to the cost and size disadvantages of
the DC-blocking capacitors required by conventional
headphone amplifiers, these capacitors limit the ampli-
fier’s low-frequency response and can distort the audio
signal. The DC-blocking capacitor not only blocks DC,
but also low-frequency audio. Improving the low-fre-
quency response of a conventional headphone amplifier
requires increasing the capacitor size, further adding
to the cost and size of the solution. Due to the voltage
coefficient of the capacitors used for DC blocking, they
introduce significant distortion near the corner frequency
of the highpass filter they create. This distortion further
degrades the low-frequency audio quality.
< 1
Stereo Audio CODEC
10
1
2
4
6
8
DESCRIPTION
VALUE
0xA
0xB
0xC
0xD
0x8
0x9
0xE
0xF
THD+N LIMIT (%)
12
14
16
18
20
21
22
24
95