MAX9787ETI+T Maxim Integrated Products, MAX9787ETI+T Datasheet - Page 7

• Manufacturer Part Number: MAX9787ETI+T
• Description: IC AMP AUDIO PWR 2.2W AB 28TQFN
• Manufacturer: Maxim Integrated Products
• Type: Class ABr

Specifications of MAX9787ETI+T

• Output Type: 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 2.2W x 2 @ 3 Ohm
• Voltage - Supply: 4.5 V ~ 5.5 V
• Features: Depop, Short-Circuit and Thermal Protection, Shutdown, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX9787 combines a 2.2W bridge-tied load speak-
er amplifier and an analog volume control, BEEP input,
and four-level gain control. The MAX9787 features high
90dB, low 0.01% THD+N, industry-leading click-pop
performance, and a low-power shutdown mode.
Each signal path consists of an input amplifier that sets
the gain of the signal path, and feeds the speaker
amplifier (Figure 1). The speaker amplifier uses a BTL
architecture, doubling the voltage drive to the speakers
and eliminating the need for DC-blocking capacitors.
The output consists of two signals, identical in magni-
tude, but 180
An analog volume control varies the gain of the ampli-
fiers based on the DC voltage applied at VOL. An under-
voltage lockout prevents operation from an insufficient
power supply. Click-and-pop suppression eliminates
audible transients on startup and shutdown. The ampli-
fiers include thermal-overload and short-circuit protec-
tion. An additional feature of the speaker amplifiers is
that there is no phase inversion from input to output.
The MAX9787 features a low-noise charge pump. The
550kHz switching frequency is well beyond the audio
range, and does not interfere with the audio signals.
The switch drivers feature a controlled switching speed
that minimizes noise generated by turn-on and turn-off
transients. Limiting the switching speed of the charge
pump minimizes the di/dt noise caused by the parasitic
bond wire and trace inductance. Although not typically
Figure 1. MAX9787 Signal Path
VOL
IN_
BIAS
CONTROL
VOLUME
o
out of phase.
_______________________________________________________________________________________
Detailed Description
BIAS
BIAS
2.2W Stereo Audio Power Amplifier
Charge Pump
OUT_+
OUT_
with Analog Volume Control
required, additional high-frequency ripple attenuation
can be achieved by increasing the size of C2 (see the
Typical Operating Circuit).
The MAX9787 features an internally generated, power-
supply independent, common-mode bias voltage of 1.8V
referenced to GND. BIAS provides both click-and-pop
suppression and sets the DC bias level for the amplifiers.
Choose the value of the bypass capacitor as described
in the BIAS Capacitor section. No external load should
be applied to BIAS. Any load lowers the BIAS voltage,
affecting the overall performance of the device.
The GAIN1 and GAIN2 inputs set the maximum gain of
the speaker and amplifiers (Table 1). The gain of the
device can vary based upon the voltage at VOL (see
the Analog Volume Control (VOL) section). However,
the maximum gain cannot be exceeded.
An analog volume control varies the gain of the device
in 31 discrete steps based upon the DC voltage
applied to VOL. The input range of V
volume) to 0.858 x PV
sizes shown in Table 2. Connect the reference of the
device driving VOL (Figure 2) to PV
ume control ADC is ratiometric to PV
Table 1. Gain Settings
Figure 2. Volume Control Circuit
GAIN2
0
0
1
1
V
REF
DAC
Analog Volume Control (VOL)
DD
GAIN1
0
1
0
1
(full mute), with example step
PV
VOL
DD
MAX9787
DD
Gain Selection
DD
SPEAKER MODE
VOL
, any changes in
. Since the vol-
GAIN (dB)
is from 0 (full
10.5
7.5
6
9
BIAS
7