MAX9726BETP+ Maxim Integrated Products, MAX9726BETP+ Datasheet - Page 10

• Manufacturer Part Number: MAX9726BETP+
• Description: IC AMP AUDIO .124W STER 20TQFN
• Manufacturer: Maxim Integrated Products
• Series: DirectDrive™r
• Type: Class ABr

Specifications of MAX9726BETP+

• Output Type: Headphones, 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 124mW x 2 @ 16 Ohm
• Voltage - Supply: 2.7 V ~ 5.5 V
• Features: Bass Boost, Depop, I²C, Mute, Short-Circuit and Thermal Protection, Shutdown, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 20-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DirectDrive, Headphone Amplifier with
BassMax, I
The MAX9726 stereo headphone amplifier features
Maxim’s DirectDrive architecture, eliminating the large
output-coupling capacitors required by conventional
single-supply headphone amplifiers. The MAX9726 con-
sists of two 105mW Class AB headphone amplifiers, two
adjustable gain preamplifiers, hardware/software shut-
down control, inverting charge pump, integrated 64-
level volume control, BassMax feature, comprehensive
click-and-pop suppression circuitry, and an I
/SMBus-compatible interface (see the Functional
Diagram/Typical Operating Circuit ). A negative power
supply (PV
tive supply (V
PV
almost twice that of other single-supply amplifiers,
increasing the total available output power. High PSRR
topologies eliminate the need for an external voltage
regulator.
An I
munication between the MAX9726 and a microcon-
troller. The internal command register controls the
shutdown status of the MAX9726, enables the BassMax
circuitry, and sets the volume level (see the Volume
Control section). The MAX9726’s BassMax circuitry
improves audio reproduction by boosting the bass
response of the amplifier, compensating for any low-
frequency attenuation introduced by the headphone.
External components set the MAX9726’s overall gain
allowing for custom gain settings (see the Gain-Setting
Components section). Amplifier volume is digitally pro-
grammable to any one of 64 levels.
Traditional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage, typi-
cally half the supply, for maximum dynamic range.
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 head-
phone, resulting in unnecessary power dissipation and
possible damage to both the headphone and head-
phone amplifier. In addition to the cost and size disad-
vantages, the DC-blocking capacitors required by
conventional headphone amplifiers limit low-frequency
response and can distort the audio signal.
10
SS
2
______________________________________________________________________________________
C-/SMBus-compatible interface allows serial com-
increases the dynamic range of the amplifiers to
SS
) is created internally by inverting the posi-
DD
). Powering the amplifiers from V
Detailed Description
2
C, Volume and Gain Control
DirectDrive
DD
and
2
C-
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage. This
allows the MAX9726 headphone amplifier outputs to be
biased about ground, almost doubling the dynamic
range while operating from a single supply (see Figure
1). With no DC component, there is no need for the
large DC-blocking capacitors. Instead of two large (up
to 220µF) tantalum capacitors, the MAX9726 charge
pump requires only two small 1µF ceramic capacitors,
conserving board space, reducing cost, and improving
the frequency response of the headphone amplifier.
See the Output Power vs. Charge-Pump Capacitance
and Load Resistance graphs in the Typical Operating
Characteristics for details of the possible capacitor
sizes.
Figure 1. Traditional Amplifier Output vs. MAX9726 DirectDrive
Output
V
-V
V
DD
GND
*
GND
V
DD
DD
V
AND TO LIMIT POWER DISSIPATION.
DD
/2
DD
V
V
*
*
OUT
OUT
IS INTERNALLY LIMITED TO ±2.5V DUE TO ABSOLUTE MAXIMUM RATINGS
CONVENTIONAL DRIVER-BIASING SCHEME
DirectDrive BIASING SCHEME
2V
V
DD
DD
*