MAX9850ETI+T Maxim Integrated Products, MAX9850ETI+T Datasheet - Page 14

• 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

The MAX9850 audio digital-to-analog converter (DAC)
with a stereo DirectDrive headphone amplifier is a com-
plete digital audio playback solution. The sigma-delta
DAC has 90dB of dynamic range and accepts stereo
audio data at sampling frequencies ranging from 8kHz to
48kHz. Headphone output volume level, muting, and
device configuration are programmed through the
I
are available. Both basic modes of operation, integer and
noninteger, provide full dynamic range performance and
allow maximum flexibility when choosing the MAX9850’s
master clock (MCLK) frequency. Integer mode operation
requires that MCLK is an integer multiple of 16 times the
sample rate, and provides maximum full-scale SNR per-
formance. Noninteger mode allows maximum flexibility
when choosing an MCLK frequency, as the MCLK may
be any frequency in the acceptable range.
Audio data is sent to the MAX9850 through a 3-wire
digital audio data bus that supports numerous input for-
mats. LRCLK and BCLK signals are generated by the
MAX9850 when configured in master mode. The
MAX9850 can also be configured as a slave device,
accepting LRCLK and BCLK signals from an external
digital audio master. External LRCLK and BCLK signals
may be either synchronous or asynchronous with MCLK
when the MAX9850 is configured as a slave device.
Maxim’s DirectDrive architecture employs an internal
charge pump to create a negative voltage supply to
power the headphone amplifier outputs. The internal
negative supply allows the analog output signals to be
biased at ground, eliminating the need for an output-
coupling capacitor, reducing system cost and size.
The MAX9850’s stereo line inputs allow mixing of ana-
log audio with digital audio. The summed audio signal
is sent directly to the line and headphone outputs. The
line inputs/outputs can be activated even when the
DAC is disabled and MCLK is not present.
The headphone sense input (HPS) detects when a
headphone is connected to the MAX9850. The HPS cir-
cuit shuts down the headphone amplifier outputs when
no headphones are connected. The headphone ampli-
fiers can be automatically enabled when HPS detects
the presence of headphones.
The MAX9850 uses a sigma-delta DAC to achieve up to
91dB of SNR. The DAC receives a stereo digital input
signal sampled at f
to an 8 times f
Stereo Audio DAC with DirectDrive
Headphone Amplifier
14
2
C-compatible interface. Three selectable I
______________________________________________________________________________________
LRCLK
LRCLK
frequency, and digitally filters the
Detailed Description
, interpolates the signal data
Sigma-Delta DAC
2
C device IDs
samples. The resulting oversampled digital signal is
then converted using a multibit sigma-delta modulator
followed by an analog smoothing filter that greatly
attenuates high-frequency quantization noise typical
with oversampling converters. Flexible clocking modes
allow the MAX9850 to be used effectively in applica-
tions normally not well suited for oversampling convert-
ers all without the need for expensive sample rate
converters.
Set DACEN = 0 in the enable register (register 0x5, bit B0)
to disable the DAC. Set DACEN = 1 to enable the DAC.
The MAX9850 features line inputs (INR, INL) and line
outputs (OUTR, OUTL). The line inputs allow a line level
signal to be mixed with the DAC output, see the
Functional Diagram/Typical Operating Circuit. Set
LNIEN = 1 in the enable register (register 0x5, bit B1) to
enable the line inputs. The line inputs are biased at
AGND and can be directly coupled or AC-coupled to
INR and INL, depending on the signal source.
Stereo DirectDrive line outputs (OUTR and OUTL) can
be used to drive line-level loads. Line outputs internally
drive the inputs of the headphone amplifier. Set LNOEN
= 1 in the enable register (register 0x5, bit B2) to
enable the line outputs. Disabling the line outputs will
also disable the headphone outputs.
The internal charge pump must be enabled to operate
the line outputs. Enable the charge pump by configuring
CPEN(1:0) = 11 in the enable register (register 0x5, bit
B5 and B4). See the Charge Pump section.
Unlike the MAX9850, traditional single-supply head-
phone amplifiers have their outputs biased about a
nominal DC voltage, typically half the supply, for maxi-
mum dynamic range. Large coupling capacitors are
typically needed to block this DC bias from the head-
phone. Without these capacitors, a significant amount
of DC current flows to the headphone, resulting in
unnecessary power dissipation and possible damage
to both headphone and headphone amplifier.
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage. This
allows the MAX9850 headphone and line outputs to be
biased about ground, almost doubling the dynamic
range while operating from a single supply. With no
DC component, there is no need for the large DC-
blocking capacitors. Instead of two large (33µF to
330µF) capacitors, the MAX9850 charge pump
DirectDrive Headphone and
Line Outputs/Inputs
Line Amplifiers