PAM8620 Datasheet, PDF (12/15 Pages) Power Analog Micoelectronics – 15W Stereo Class-D Audio Power Amplifier with Power Limit

PAM8620
15W Stereo Class-D Audio Power Amplifier with Power Limit
Differential Input
The differential input stage of the amplifier
eliminates noises that appear on the two input
lines of the channel. To use the PAM8620 with a
differential source, connect the positive lead of
the audio source to the INP input and the negative
lead from the audio source to the INN input. To
use the PAM8620 with a single-ended source, ac-
ground the INP input through a capacitor equal in
value to the input capacitor on INN and apply the
audio source to the INN input. In a single-ended
input application, the INP input should be ac-
grounded at the audio source other than at the
device input for best noise performance.
Using low-ESR Capacitors
Low-ESR capacitors are recommended
throughout this application section. A real (with
respect to ideal) capacitor can be modeled simply
as a resistor in series with an ideal capacitor. The
voltage drop across this resistor minimizes the
beneficial effects of the capacitor in the circuit.
The lower the equivalent value of this resistance
the more the real capacitor behaves as an ideal
capacitor.
Short-circuit Protection
The PAM8620 has short circuit protection circuitry
on the outputs to prevent damage to the device
when output-to-output shorts, output-to-GND
shorts, or output-to-VCCshorts occur. Once a
short-circuit is detected on the outputs, the output
drive is immediately disabled. This is a latched
fault and must be reset by cycling the voltage on
the SD pin to a logic low and back to the logic high
state for normal operation. This will clear the
short-circuit flag and allow for normal operation if
the short was removed. If the short was not
removed, the protection circuitry will again
activate.
Thermal Protection
Thermal protection on the PAM8620 prevents
damage to the device when the internal die
temperature exceeds 160°C. There is a ±15
degree tolerance on this trip point from device to
device. Once the die temperature exceeds the set
thermal point, the device enters into the shutdown
state and the outputs are disabled. This is not a
latched fault. The thermal fault is cleared once the
temperature of the die is reduced by 50°C. The
device begins normal operation at this point
without external system intervention.
Power Limit
The voltage at PL pin can used to limit the power
to levels below that which is possible based on
the supply rail. Add a resistor from PL to ground to
set the voltage at the PLIMIT pin. An external
reference may also be used if tighter tolerance is
required. Also add a 1uF capacitor fromPL pin to
ground. The PLIMIT circuit sets a limit on the
output peak-to-peak voltage. The gain of class D
amplifier will automatic reduced if the output
power higher than setting value to make output
power less than limited value and also provide
good sound quality.
The output power vs PL pin resistor value as
below.
VCC=24V,Rload=8Ω
R(Ω) PL (V) PL(W) R(Ω) PL (V) PL(W)
56K 0.62 3.2 110K 1.08 9.6
62K 0.68 3.8 120K 1.15 11.0
68K 0.73 4.4 130K 1.23 12.4
75K 0.79 5.2 150K 1.36 15.5
82K 0.86 6.1 160K 1.43 17.0
91K 0.93 7.1 180K 1.55 19.9
100K 1.00 8.2 200K 1.66 22.9
R(Ω)
56K
62K
68K
75K
82K
91K
VCC=12V,Rload=8Ω
PL (V) PL(W) R(Ω) PL (V)
0.61 3.1 100K 0.99
0.67 3.7 110K 1.07
0.73 4.3 120K 1.15
0.79 5.1 130K 1.22
0.85 6.0 140K 1.36
0.92 7.0
PL(W)
8.1
9.0
9.6
10.0
10.7
Soft Clip
PAM Plimit
Hard Clip
Power Analog Microelectronics,Inc
www.poweranalog.com
12
10/2012 Rev1.0