PAM8902A Datasheet, PDF (7/12 Pages) Diodes Incorporated – 30 VPP MONO CLASS-D AUDIO AMPLIFIER FOR PIEZO/CERAMIC SPEAKERS WITH ANTI-SATURATION

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Diodes Incorporated
PAM8902A
Application Information
Select Boost Converter Output Voltage
The V_SET pin sets the boost converter output voltage to 8V, 12V or 17.5V. V_SET pin configuration table as below:
V_SET Pin Configuration
High
Floating
Low
Min
AVDD – 0.5
1V
GND
Max
AVDD
AVDD – 1V
0.5V
PVCC Voltage
17.5V
12V
8V
Audio Amplifier
Maximum Output Voltage
11 V_RMS (V_PP = 31.1V)
8 V_RMS (V_PP = 22.6V)
5 V_RMS (V_PP = 14.1V)
Gain Setting and Input Resistance (R_I)
Gain setting function is only available in disable condition (ENA = low) and need to follow the sequence as pull ENA to low (disable the IC) first,
and change the GSET voltage between high, floating, low, then pull ENA to high (enable the IC).
The input resistors (R_I = R_IN + R_EX) set the gain of the amplifier according to Equation 1 when anti-saturation is inactive.
G = 20 Log [12.8*R_F/ (R_IN + R_EX)] (dB)
G_SET
R_IN
R_FB
High
77.4kΩ
122.6kΩ
Floating
100kΩ
100kΩ
Low
122.6kΩ
77.4kΩ
Where R_IN is a 77.4KΩ internal resistor, R_EX is the external input resistor, R_F is a 122.6KΩ internal resistor. Resistor matching is very important
in fully differential amplifiers. The balance of the output on the reference voltage depends on matched ratios of the resistors. CMRR, PSRR, and
cancellation of the second harmonic distortion diminish if resistor mismatch occurs. Therefore, it is recommended to use 1% tolerance resistors
or better to keep the performance optimized. Matching is more important than overall tolerance. Resistor arrays with 1% matching can be used
with a tolerance greater than 1%.
Place the input resistors very close to the PAM8902A to limit noise injection on the high-impedance nodes. For optimal performance the gain
should be set to lower. Lower gain allows the PAM8902A to operate at its best, and keeps a high voltage at the input making the inputs less
susceptible to noise. In addition to these features, higher value of R_I minimizes pop noise.
Anti-Saturation/Clipping Function
The anti-saturation circuitry detects the duty cycle of the PWM output. When the output starts to exhibit clipping, the gain is automatically
decreased with an attack time of 100µs per step a release time of 186ms per step. The following table describes the operation:
Variable
Gain
Description
The original gain of the device when the Anti-saturation is
inactive.
Attenuation Range The gain control range when anti-saturation is active.
Step Size
Attack Time
Release Time
Gain adjust step size.
The minimum time between two gain decrements.
The minimum time between two gain increments.
Value
26dB (G_SET = High)
22dB (G_SET = Floating)
18dB (G_SET = Low)
-26dB (G_SET = High)
-22dB (G_SET = Floating)
-18dB (G_SET = Low)
0.25dB/Step
100µs
186ms
PAM8902A
Document number: DSxxxxx Rev. 1 - 3
7 of 12
www.diodes.com
February 2013
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