PAM8902H Datasheet, PDF (7/12 Pages) Diodes Incorporated – 30 VPP MONO CLASS-D AUDIO AMPLIFIER FOR PIEZO/CERAMIC SPEAKERS

A Product Line of
Diodes Incorporated
PAM8902H
Application Information
Select Boost Convertor Output Voltage
Customer can use V_SET pin to set boost converor output voltage between 8V, 12V and 17.5V. V_SET pin configuration table as below:
V_SET Pin
Configuration
Connect to AVDD
Floating
Connect to GND
Min
AVDD – 0.5V
1V
GND
Max
AVDD
AVDD – 1V
0.5V
PVCC Voltage
17.5V
12V
8V
Audio Amplifier Maximum
Output Voltage
11V_RMS (V_PP = 31.1V)
5V_RMS (V_PP = 22.6V)
5V_RMS (V_PP = 14.1V)
Input Resistance (R_I)
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+_REX)] (dB)
G_SET
G_SET = V_DD
G_SET = Floating
G_SET = GND
R_IN
36.5kΩ
59kΩ
82kΩ
R_F
122.6kΩ
100kΩ
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 PAM8902H to limit noise injection on the high-impedance nodes. For optimal performance the gain
should be set to lower. Lower gain allows the PAM8902H 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.
Input Capacitors (C_I)
In the typical application, an input capacitor, C_I, is required to allow the amplifier to bias the input signal to the proper DC level for optimum
operation. In this case, C_I and the minimum input impedance R_I form is a high-pass filter with the corner frequency determined in the follow
equation:
f_C
=
1
2πR_{I CI}
It is important to consider the value of C_I as it directl y affects the low frequency performance of the circuit. For example, when R_I is 150kΩ and
the specification calls for a flat bass response are down to 150Hz. Equation is reconfigured as followed:
C_I
=
1
2πR_IFC
When input resistance variation is considered, the C_I is 7nF, so one would likely choose a value of 10nF. A further consideration for this
capacitor is the leakage path from the input source through the input network (C_I, R_I + R_F) to the load. This leakage current creates a DC offset
voltage at the input to the amplifier that reduces useful headroom, especially in high gain applications. For this reason, a low-leakage tantalum or
ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor should face the amplifier input in
most applications as the DC level is held at V_DD/2, which is likely higher than the source DC level. Please note that it is important to confirm the
capacitor polarity in the application.
PAM8902H
Document number: DSxxxxx Rev. 1 - 0
7 of 12
www.diodes.com
December 2012
© Diodes Incorporated