PT2309 查看數據表（PDF） - Princeton Technology

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PT2309

Headphone Driver IC

Princeton Technology 

PT2309

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 50KΩ impedance, so input terminal

charge period constant is:

Tin= (2π × 50KΩ × 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 32Ω 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.

MUTE

When the mute pin is connected to the GND, all of outputs signal will be muted immediately. Connecting the external

R/C components on here could prevent the power–on “POP” noises, the mute function also can be active by the external

DC voltage. Due to the built-in pull down resistor (150KΩ), a larger value series resistor connecting to the mute pin may

causes mute malfunction because of mute voltage divided by the resistor network. For the detailed connection

description please refer to the application circuit. The attenuation of mute is relation with CB, we suggest CB must be

higher then 10µF, the recommend value is 47µF. Higher CB will have better mute characteristic.

V1.3

4

December 2009

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