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FUNCTION DESCRIPTION 
POWER SUPPLY 
The operating voltage of PT2309 is from 3V to 5V, In general operation 5V is recommended.  
It should connect a modest bias capacitor nearby the power source terminal. It can improve IC stability 
and decrease the noise output. Suggestion value of capacitor is from 0.1μF to 10μF. 
POP AND CLICK SUPPRESS 
For normal operation, the Input/Output port of a power amplifier powered by a single supply voltage 
must have a stable DC bias. Each time turn on the Vcc the input/output pins will present 1/2 Vcc DC 
bias voltage. For blocking the DC bias flowing to another circuit, each input/output port should have a 
DC blocking capacitor, it will charge/discharge when power on or off, the capacitance is relative with 
the pop noise. In general condition to prevent the pop noise, the time constant of bypass cap (CB) on 
the bypass pin will be set to maximum. Higher CB value will extend the stable time, and also can 
suppress the noise heard when power-on. In supply voltage=5V and CB=10μF, stable time is approx 
1s. The value of CB also relative with the value of the DC blocking capacitor connected in input 
terminal. In general condition the time constant of DC blocking capacitor should be less than CB stable 
time. Recommend parts values please refer to application circuit. 
INPUT CAPACITOR 
Input capacitor decide the bandwidth and charge time constant, due to there is a 50K
 impedance, so 
input terminal charge period  constant is:  
Tin= (2
π
 × 50K
 × Cin) 
If Cin=1μF, Tin=0.3s, Low frequency lower limit is 3Hz. This capacitor can use a non-polarity SMD 
capacitor
。
OUTPUT CAPACITOR 
The headphone driver is designed to drive 32
 headphone load, it needs a larger capacitance to 
extending the lower frequency cut off point. If driving a small headphone a 100μF capacitor is a good 
choice and the low frequency limit is around 50Hz; for better low frequency performance a 220μF 
capacitor is recommended and it’s low frequency can extend to 22Hz. Due to charge/discharge time 
constant is shorter than CB stable time, so it will not have pop and click noise. 
PT2309 V1.2 
- 4 - 
August, 2006
Headphone Driver IC 
PT2309