MAX97220CETE+ Maxim Integrated, MAX97220CETE+ Datasheet - Page 13

• Manufacturer Part Number: MAX97220CETE+
• Description: Audio Amplifiers DirectDrive LDriver Headphone Amplifier
• Manufacturer: Maxim Integrated

Specifications of MAX97220CETE+

• Rohs: yes
• Product: Class-AB
• Output Type: 2-Channel Headphone
• Output Power: 125 mW x 2 at 32 Ohms
• Thd Plus Noise: 0.0035 %
• Operating Supply Voltage: 2.5 V to 5.5 V
• Supply Current: 5 mA
• Maximum Power Dissipation: 1.667 W
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TQFN-16
• Common Mode Rejection Ratio (min): 45 dB
• Minimum Operating Temperature: - 40 C

Figure 3. Pseudo-Differential Input Configuration
Conventional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage (typically
half the supply) for maximum dynamic range. Large cou-
pling 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 the headphone amplifier.
Maxim’s patented DirectDrive architecture uses a charge
pump to create an internal negative supply voltage,
allowing the IC's outputs to be biased about PGND.
With no DC component, there is no need for the large
DC-blocking capacitors. Instead of two large (220FF,
typ) tantalum capacitors, the IC charge pump requires
two small ceramic capacitors, conserving board space,
reducing cost, and improving the frequency response of
the headphone amplifier.
In addition to the cost and size disadvantages of
DC-blocking capacitors required by conventional head-
phone amplifiers, these capacitors limit the amplifier’s
low-frequency response and can distort the audio signal.
If input capacitors are used, input capacitor C
junction with internal input resistor R
Maxim Integrated
CODEC
AUDIO
GND
OUT
R
*R
IN1
IN1
= R
AND R
IN2
, R
F1
F1
ARE INTERNAL FOR MAX97220C/MAX97220D
IN+
IN-
= R
F2
R
R
IN1*
IN2
Line Drivers/Headphone Amplifiers
R
F2
IN
, forms a highpass
R
F1*
DirectDrive
Input Filter
Differential Input DirectDrive
IN
, in con-
OUT
MAX97220A–MAX97220E
filter that removes the DC bias from an incoming signal.
The AC-coupling capacitor allows the amplifier to bias
the signal to an optimum DC level. Assuming zero-
source impedance, the -3dB point of the highpass filter
is given by:
Setting f
of the amplifier. Use capacitors with adequately low volt-
age coefficients, such as X7R ceramic capacitors with a
high voltage rating. Capacitors with higher voltage coef-
ficients result in increased distortion at low frequencies.
Bypass BIAS with a 0.1FF capacitor to PGND. Do not
connect external loads to BIAS.
The MAX97220_ features a low-noise charge pump. The
500kHz switching frequency is well beyond the audio
range and, thus, does not interfere with the audio sig-
nals. 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
bond wire and trace inductance is minimized. The IC
requires a 1FF flying capacitor between C
and a 1FF hold capacitor from PVSS to PGND.
The IC features Maxim’s industry-leading click-and-pop
suppression circuitry. When entering shutdown, the
amplifier outputs are high impedance to ground. This
scheme minimizes the energy present in the audio band.
The IC features a 1FA low-power shutdown mode
that reduces power consumption. When the active-low
shutdown mode is entered, the device’s internal bias
circuitry is disabled, the amplifier outputs go high imped-
ance, and BIAS is driven to PGND. The MAX97220A/
MAX97220B/MAX97220E inputs are driven to PGND.
-3dB
too high affects the low-frequency response
f
-3dB
Click-and-Pop Suppression
=
2 R C
π
IN IN
1
BIAS Capacitor
Charge Pump
Shutdown
1P
and C
1N
13