DESCRIPTION
The PT2303 is a power amplifier utilizing CMOS Technology specially designed for audio purpose. It can deliver 2W × 2 power output to the 5V power voltage. The power consumption is very low in stand-by. Total harmonic distortion is lower than 0.03%. The output mode can be switched between the SE (Single-Ended) or BTL (Bridge-Tied Load) mode. Built-in over-temperature protection, package size is not occupies PCB space. It is suitable for small or portable products.
FEATURES
• CMOS Technology
• Stereo input
•Output power 2W × 2 (4Ω)
•Low harmonics distortion (0.03%)
•SE and BTL modes operation
•Suppress the pop and click noise when mode changed
•Shutdown function, turn on can into save mode (Icc<0.5µA)
•Built-in overheat protect
APPLICATIONS
•LCD monitor (for TV)
• Portable audio
• Multimedia speakers
•Other audio applications
BLOCK DIAGRAM
Power Block
-I 1N +I 1
N Shutdown
VDD Vref GND
+
--OUT1
+
-+OUT1
HP-IN
SE/BTL
-I 2N +I 2
N +
--OUT2
+
-
+OUT2
AMP1N
AMP2N
AMP1P
AMP2P
PIN CONFIGURATION
Shutdown
GND +OUT1VDD -OUT1
-I 1N GND +I 1
N HP-IN GND +OUT2VDD -OUT2-I 2N Vref +I 2
N 12345678
9
10111213141516P 2303
T Shutdown
GND +OUT1VDD -OUT1
-I 1N GND +I 1N +I 2N NC NC
1234567811
12131415
16
1718P 2303
T NC NC
910
1920HP-IN GND +OUT2VDD -OUT2-I 2N Vref
PIN DESCRIPTION
Pin No. Pin Name I/O
Description
16 Pins 20 Pins Shutdown I
Shutdown pin 。Entire IC into the shutdown mode
when this pin connected to the Vcc.
1 1 GND - Ground
2    2 +OUT1 O Channel 1 output (+)
3    3 VDD - Supply voltage input
4    4 -OUT1 O Channel 1 output (-)
5    5 -IN1 I Channel 1 input (-)    6
6
GND - Ground 7 7 +IN1 I Channel 1 input (+) 8 8 +IN2 I Channel 2 input (+) 9 13 Vref I Bias reference bypassing 10 14 -IN2 I Channel 2 input (-) 11 15 -OUT2 O Channel 2 output (-) 12 16 VDD - Supply voltage input 13 17 +OUT2 O Channel 2 output (+) 14
18
GND - Ground
15 19 HP-IN I
Output mode select, connected to the VDD for SE
mode or GND for BTL mode
16 20vimax
NC - No Connect -
9 ~ 12
FUNCTION DESCRIPTION
POWER SUPPLY
The operating voltage of PT2303 is from 3V to 5V, In general operation 5V is recommended, it can deliver higher power output. When the supply voltage less then 3V the IC can work properly, but the distortion will rise. After the supply voltage exceed 6V the temperature of package outside will rising quickly due to higher stand-by current consumption.
SHUTDOWN
When the supply still powered the chip, pull-up the shutdown pin to VDD level will take chip into the shutdown mode. After the shutdown mode is active, the total current consumption is less than 0.5µA and  the all of input or output pins no voltage output. When shutdown pin set to GND, the IC is back to the normal operation.
Shutdown Pin Output State
ON
VDD Shutdown
GND Normal
VOLTAGE GAIN ADJUST
The output stage structure of the PT2303 is Bridge Tied Loaded (BTL), the close loop voltage gain can be get from following formula.
Gain = 20log ( Rf  ÷ Ri ) + 6dB
The close loop gain can be adjusted by external resistance, in general purpose the 6dB gain setting is recommended, please reference to the application circuit. If the amplitude of input voltage in lower level (ex. < 2Vpp), it can raise the voltage gain to get enough power output. Recommended of the minimum series resistance (Ri) is 10KΩ to ensure IC have appropriate input impedance. Please refer to following table.
External Resistance Gain= 0dB Gain= 6dB Gain=12dB
Ri 20KΩ 20KΩ 10KΩ
Rf 10KΩ 20KΩ 20KΩ
If the amplitude of input signal exceed the VDD-GND range, or voltage gain setup too high, the input stage is very easy overload and distorted. Please make sure the amplitude of audio source (Vin) and setting the best gain value, in general use the gain setup to +6dB is recommended. Please refer to following table.
Operating Voltage Gain= 0dB Gain= 6dB Gain=12dB
VDD=3V Vin <5Vpp Vin <2.5Vpp Vin <1.25Vpp
VDD =5V Vin
<8Vpp Vin<4Vpp Vin<2Vpp
SE/BTL MODE SWITCHING
PT2303 have two output modes, SE (Single-Ended) or BTL (Bridge-Tied Load). When driving a 4Ωspeaker load suggestion set to the BTL mode for get the more power output. And driving a 32Ωheadphone load, it can be set to SE mode and turn-off the un-work amplifier to decrease stand-by
power consumption. Switching between the SE/BTL modes is controlled by the HP-IN pin, please refer to following table:
HP-IN Output Mode
VDD SE
GND BTL
OVER TEMPERATURE PROTECTION
The PT2303 has a built-in over temperature protection circuit, it will turn off all output  when the chip temperature over 130,
℃the chip will return to normal operation automatically after the temperature cool down to 100℃.
POP AND CLICK SURPRESS
A power amplifier uses single supply voltage may almost have inrush noise on output in the power-on/off period. It is because of the output DC potential needs time to stable on 1/2VDD, the period relative with the capacitance (CB) on the Vref pin. Larger C
B value will extend the stable time, and also can suppress the noise happened in power-on. In supply voltage=5V and CB=2.2µF, stable time is about 300mS. The value of CB also relative with the value of the D
C blocking capacitor connected in input terminal. In general condition the time constant of DC blocking capacitor should be less than CB stable time. The recommended value of DC blocking capacitor is 1µF, and the capacitor of output terminal connected to 32Ω headphone is 220µF. Smaller capacitance can shorten the charge time to suppress the pop noise, both the input and output capacitance will limited the low frequency extend range.

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