ETC PAM8302

PAM8302
Tiny Package 2 Watt Class-D Audio Amplifiers With Enable
FEATURES
DESCRIPTION
The PAM8302 is a 2 Watt, 8-pin, class D audio
amplifier with Enable function, it offers low THD+N
(0.10%), allowing it to produce high-quality sound
reproduction.
2 Watts @ 10% THD output into a 4 load at 5V
Support speakers or earphone (4 to 32 ).
With Enable function.
Superior low noise without input.
Supply voltage from 2.5V to 5.5V.
85% efficiency above.
Short Circuit Protection.
Less output capacitor and inductor to save the
space and cost.
Low THD+N
Low quiescent current < 10 mA
The PAM8302 runs off of a 5 Volt supply at much
higher efficiencies than their class AB cousins,
making it ideal for many portable applications.
The PAM8302 only requires very few external
components (as few as two tiny capacitors), results
in significant cost and board space savings.
The PAM8302 is available in a SOP8 package.
APPLICATIONS
Notebook Computers.
PDAs/ GPS Navigator/ e-Dictionary
Portable DVD Players, Game Machines.
Cellular Phones, VoIP Phones, Screen Phones
MP3 or PMP Players.
Portable Speaker System, Portable Amplifier
LCD monitor / TV.
Bluetooth Car-Kit
TYPICAL APPLICATION CIRCUIT
Vdd
33 H
VDD
0.47 F
10K
0.47 F
+OUT
Input
IN
Speaker
33 H
Enable
-OUT
GND
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0.47 F
1
PAM8302 data sheet, Rev. 0.1
PAM8302
Tiny Package 2 Watt Class-D Audio Amplifiers With Enable
TOP MARKING & PIN CONFIGURATION
8
7
6
Absolute Maximum Ratings:
Supply voltage: *6V
Input voltage: -0.3V to VDD +0.3V
Operation Temperature range: 40OC to 85OC
Operation junction temperature: -40OC to 125OC
Storage Temperature: -65OC to 150OC
Maximum Junction Temperature: 150OC
Soldering temperature: 250 OC, 10 secretary
5
A Y WW
AYWW
1
2
3
Weekly
Year
4
Assembly Location
Recommended operating Conditions:
SOP8
Supply voltage Range: 2.5V to 5.5V
Operation Temperature Range: -40OC to 85OC
Junction Temperature Range: -40OC to 125OC
Pin Description
Thermal Information:
Pin No.
Pin Name
Description
1
IN_R
Right channel audio input.
2
VDD
Supply voltage, need a 1uF ceramic
decouple capacitor very close bet
ween this pin to GND pin.
3
EN
Chip enable, high active.
*Note: Without input signal.
4
GND
GNDChip ground.
5
NC
Not connected
ORDERING INFORMATION
6
GND
Chip ground.
7
+OUT
Non-inverted output
8
-OUT
Inverted output
Thermal Resistance (
SOP8:
JC):
90 OC/W
JA
O
DIP8
C/W
Ordering
Number
Package
PAM8302S8R SOP-8
Shipping
2,500 Units/ Reel
ELECTRONIC SPECIFICATIONS
PARAMETER
CONDITION
Vdd Range
MIN
TYP
MAX
UNITS
2.5
5
5.5
V
10
mA
Vdd Quiescent current
Each channel
SW On Resistance
VDD = 5V
0.4
SW Frequency
No Input Signal
500
kHz
PSRR
VDD = 2.5V to 5.5V
-45
dB
Gain
VDD = 2.5V to 5.5V, 0 input resistor
10
V/V
SNR
VDD = 5V, Po = 1.5W, 8
60
dB
Load
Input impedance
100
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K
2
PAM8302
Tiny Package 2 Watt Class-D Audio Amplifiers With Enable
BLOCK DIAGRAM
Vdd
C1
Input Signal
1
1 F
Enable
Bit
Speaker
Controller
Over Current
TEST CIRCUIT FOR GRAPHS
PAM8302 Demo Board
+OUT
Load
Input
AP System One
Generator
GND
-OUT
AP
Low Pass
Filter
AUX-0025
AP System One
Analyzer
VDD
Power Supply
Notes:
1.The AP AUX-0025 low pass filter is necessary for every class D amplifier measurement done by AP analyzer.
2.A 33 H inductor is used in series with load resistor to emulate the small speaker for efficiency measurement.
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3
PAM8302
Tiny Package 2 Watt Class-D Audio Amplifiers With Enable
(%)
100
50
THD+N vs. Output Power
8 , 1kHz, VDD = 5V
(W)
2
3
1
500m
200m
50m
100m
20m
10m
5m
1
2m
0.02
0.01
(W)
2
3
0.02
0.01
500m
0.05
200m
0.05
100m
0.2
0.1
50m
0.2
0.1
20m
2
1
0.5
10m
2
1
0.5
5m
5
2m
5
1m
20
10
600u
20
10
Ap
1m
Ap
600u
(%)
100
50
THD+N vs. Output Power
4 , 1kHz, VDD = 5V
(%)
100
50
Efficiency VS Output Power
100%
Ap
20
10
Efficiency
80%
5
2
1
0.5
60%
40%
0.2
0.1
20%
0.02
0.01
20
50
100 200
500
1k
2k
5k
1
0.05
10k
(Hz)
20k
0%
0
2
3
Power
Power Dissipation vs. Output Power
4 , 1kHz, VDD = 5V
THD+N vs. Frequency
8 , 500mW output, VDD = 5V
1.4
(dBr)
1.2
Power Dissipation -W
1
1.0
0.8
0.6
0.4
0.2
0.0
0
0.5
1
1.5
2
Output Power -W
+0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
20
(Hz)
50
100
Power Dissipation vs. Output Power
4 , 1kHz, VDD = 5V
Class AB = Blue line
PAM8202 = Magenta line
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200
500
1k
2k
5k
10k 20k
FFT Noise Floor
(16k FFT)
4
PAM8302
Tiny Package 2 Watt Class-D Audio Amplifiers With Enable
OPERATION INFORMATION
Calculating Output Power of BTL amplifier
Output power is related to supply voltage and the saturation
Vsupply
Vsat
voltage (Vsat). The Maximum peak-to-peak output voltage
on one side of BTL amplifier output is
Vp-p = ( Vsupply - 2 X Vsat )
Vpk-pk
Vrms =
Vsat
Vsupply
Vp-p
2 2
One side
Maximum output power of a BTL amplifier with 1% THD is
Pout (1%) = 4 X Vrms2/ Rload
Maximum output power of a BTL amplifier with 10% THD is
Pout (10%) = Pout (1%) X 1.25
Output Power vs. Vp-p
BTL Output Power
Output Power @THD 10%
5.0
4.0
4
3.0
2.0
8
1.0
0.0
0
1
2
3
4
Vdd - Vsat (V)
5
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6
5
PAM8302
Tiny Package 2 Watt Class-D Audio Amplifiers With Enable
Vdd
C1
C2
33 H
0.47 F
VDD
10K
0.47 F
+OUT
Input
IN
Speaker
33 H
-OUT
Enable
GND
0.47 F
Fig. 1
Setting Amplifier voltage gain
It is very important to know the maximum output level (0dB) of the signal source connected to a power amplifier in
order to prevent hard clipping during operation.
Gain (max) = Vsupply/ Vin (p-p)
Insufficient voltage gain will cause low output level and maybe not enough to drive speaker properly. On the
other hand, the distortion will be very high if the voltage gain is too high in an audio system.
There is a 10k input resistor integrated in side IN (input) node, and since the integrated feedback resistor is 100k ,
so the maximum voltage gain of PAM8302 is limited at 10V/V (100k/10k, one output). With an external input resistor
(Rin) placed between signal source & input node, the voltage gain will be
Gain = 100k/ (10k + Rin) = Vsupply/ Vin (p-p)
Actual voltage gain is two times of this calculation because of BTL connection.
Decouple capacitor
PAM8302 is a high performance, high speed class D amplifier, and it requires a 1 F, X7R ceramic decouple
capacitor (C1) placed very close between VDD & GND pins to ensure the total harmonic distortion plus noise
(THD+N) performance is as designed. This is also very important for efficiency and lowering noise floor. Another
100 F to 1000 F main decouple capacitor (C2) should be placed close to supply pin for low frequency
Ecoupling.
Input capacitor
Input capacitor (Cin) blocks the DC voltage between signal source & amplifier to ensure the DC balancing will not
be broken between two systems. It also form a high-pass-filter (HPF) with input resistors (Rin + 10k), the lower corner
frequency (FCL) is determine by equation below.
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6
PAM8302
Tiny Package 2 Watt Class-D Audio Amplifiers With Enable
FCL = 1/ [2
X Cin X (Rin + 10k)]
FCL is the lower corner on frequency response curve.
Cin is very important consider to the lower frequency performance. The Cin should not be too large with small
speakers as the load, because such small speakers usually can not response with lower frequency, delivering too
much low frequency energy into a small speaker which usually got resonant frequency (Fs) around 150Hz is
meaningless and dangerous. This will easily over drive the small speakers. The movement of speaker cone will be
too much under such condition and this also creates unnecessary distortion on mid-to high frequency range
because the speaker is now operating in non-linear area. Speakers can only generate heat but not low frequency
sound when it is over driven, the will cause speaker or amplifier failure in some cases.
Cin should have 10% tolerance or less because the tolerance can cause the input impedance mismatch at FCL
and below.
Output filter
The L and C on each output node of PAM8302 form the low-pass-filter (LPF), the higher corner frequency (FCH) is
determine by equation below.
FCH = 1/ [2
X sqr (L X C)]
FCH is the higher corner on frequency response curve.
Important Notice
The L-C filters (-12dB/Oct) gives twice much attenuation and lower impedance (means lower insertion loss)
compare to those R-C filters (-6dB), but remember, the FCH above is also the resonant frequency of this LC
network. The quality factor (Q) of this resonant network can be very high, depended on the Q of L and C. The high
resonant Q which is usually caused by open-load can generate a very high voltage on speaker terminal, and the
impedance of the L-C network can be very low, thus induces large amount of current flows from output stage of
PAM8302. This always causes part failure. So Do Not test open-load on any class D amplifier with output filters.
LC filter calculator with output load impedance and cut-off frequency
1
1
f=
2
LC
, XL= 2 fL , XC=
2 fC
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7
PAM8302
Tiny Package 2 Watt Class-D Audio Amplifiers With Enable
OUTLINE DIMENSION
SOP8
5.80 - 6.20
0.35 - 0.49
1.27 TYP.
3.80 - 4.00
4.80 - 5.00
45
1.35 - 1.75
0.19 - 0.25
0 ~8
0 - 0.15
0.40 - 0.90
Note: Package outline exclusive of mold flash and metal burr.
Power Analog Microelectronics, Inc.
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