MAX9850ETI+T Maxim Integrated Products, MAX9850ETI+T Datasheet - Page 15

• Manufacturer Part Number: MAX9850ETI+T
• Description: IC AMP AUDIO .095W STER 28TQFN
• Manufacturer: Maxim Integrated Products
• Series: DirectDrive™r
• Type: Class ABr

Specifications of MAX9850ETI+T

• Output Type: Headphones, 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 95mW x 2 @ 16 Ohm
• Voltage - Supply: 1.8 V ~ 3.6 V
• Features: DAC, Depop, Digital Inputs, I²C, I²S, Line Level Inputs & Outputs, Mute, Shutdown, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 28-WQFN Exposed Pad, 28-HWQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 1. Headphone Amplifier Attenuation Profile
requires only two small ceramic capacitors (0.47µF and
2.2µF), conserving board space, reducing cost,
improving the frequency response, and THD of the
headphone amplifier. In addition to the cost and size
disadvantages, the DC-blocking capacitors required by
conventional headphone amplifiers limit low-frequency
response and decrease PSRR performance. Some
dielectrics can significantly distort the audio signal.
Program VOL(5:0) in the volume register (register 0x2,
bits B5–B0) to set the volume attenuation of the head-
phone amplifiers. Program VOL(5:0) to 0x00 for full vol-
ume. Minimum volume occurs at VOL(5:0) greater than
or equal to 0x28. VMN in the status A register (register
0x0, bit B3) sets to 1 when the MAX9850 output is pro-
grammed to and reaches volume step 0x3F. Figure 1
shows the attenuation profile for each VOL(5:0) value.
Set SLEW = 1 in the volume register (register 0x2, bit
B6) to enable the volume slew circuit. When SLEW = 1
headphone amplifier volume changes will slew
between programmed levels smoothly. Set the volume
slew rate with SR(1:0) in the charge-pump register
(register 0x7, bits B7 and B6). Table 1 lists the volume
slew-rate settings for each value of SR(1:0).
Set ZDEN = 1 in the general-purpose register (register
0x3, bit B0) to force volume changes and headphone
amplifier muting to occur when the audio signal is at its
zero crossing. For optimal performance, set SR(1:0) to
01. This zero-crossing detection reduces audible
clicks/pops caused when transitioning or slewing
between volume levels.
Volume Slew, Zero-Crossing Detect, and Mute
-100
-110
-120
-10
-20
-30
-40
-50
-60
-70
-80
-90
10
0
0
______________________________________________________________________________________
8
16
VOL(5:0) CODE
24
32
Stereo Audio DAC with DirectDrive
40
48
Volume Control
56
64
Set MUTE = 1 in the volume register (register 0x2, bit
B7) to mute the headphone amplifiers. The mute func-
tion is independent of the volume control. The pro-
grammed volume settings are not reset when mute is
enabled. With the zero-crossing detection and volume
slew enabled, the Mute command mutes the output
after the first zero crossing or after a 200ms timeout
(SR = 01).
Set MONO = 1 in the general-purpose register (register
0x3, bit B2) to enable mono mode. In mono mode, HPR
is disabled, the left and right audio channels are
summed and output on HPL. The 6dB attenuation
ensures that the summed signal amplitude does not
overdrive headphone amplifiers. SMONO in the status B
register (register 0x1, bit B4) sets to 1 when the
MAX9850 is in mono mode.
Set HPEN and LNOEN in the enable register (register
0x5, bits B3 and B2) equal to 1 to enable the head-
phone outputs (HPR and HPL). Set HPEN or LNOEN =
0 to disable the headphone outputs.
The headphone amplifier inputs are driven from the out-
puts of the line amplifier. Disabling the line out by setting
LNOEN = 0 in the enable register (register 0x5, bit B2),
deprives the headphone amplifiers of an input signal and
disables the headphone outputs (HPR and HPL).
The internal charge pump must be enabled to operate
the headphone and line outputs. Enable the charge
pump by programming CPEN(1:0) = 11 in the enable
register (register 0x5, bits B5 and B4). See the Charge
Pump section for more details.
The headphone sense input (HPS) monitors the head-
phone jack, and automatically disables the headphone
amplifiers based upon the voltage applied at HPS. For
automatic headphone detection, connect HPS to the
Table 1. Slew-Rate Settings
SR1
0
0
1
1
Headphone Amplifier
Configuring the Headphone and Line Outputs
SR0
0
1
0
1
VOLUME TO MUTE
Headphone Sense Input (HPS)
FROM FULL
TYPICAL VOLUME SLEW RATE
125ms
63ms
42ms
63µs
VMN = 1 (ms)
VOLUME TO
FROM FULL
Mono Mode
200
100
0.1
67
15