TS4909 datasheet(28/32 Pages) STMICROELECTRONICS

部件名	TS4909

功能描述	Dual mode low power 150mW stereo headphone amplifier with capacitor-less and single-ended outputs

PDF	32 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

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28 / 32 page

Application information

TS4909

28/32

Example calculation:

With Rin =20kΩ and FCL = 20Hz, -3db low cut-off frequency, Cin = 398nF. So, Cin = 390nF

with standard value which gives a lower cut-off frequency equal to 20.4Hz.

In this case,

τ in = Rin xCin =7.8ms

This value is sufficient with regards to the previous formula, so we can state that the pop will

be imperceptible.

Connecting the headphones

Generally headphones are connected using a jack connector. To prevent pop in the

headphones while plugging in the jack, a pulldown resistor should be connected in parallel

with each headphone output. This allows the capacitors Cout to be charged even when no

headphones are plugged in.

A resistor of 1 k

Ω is high enough to be a negligible load, and low enough to charge the

capacitors Cout in less than one second.

4.8

Standby mode

When the TS4909 is in standby mode, the time required to put the output stages (Vout1,

Vout2 and Vout3) into a high impedance state with reference to ground, and the internal

circuitry in standby mode, is a few microseconds.

Figure 83.

Internal equivalent circuit schematics of the TS4909 in standby mode

25K

Vin1

BYPASS

Vin2

Vout1

Vout2

GND

Vout3

TS4909 数据表(PDF) 28 Page - STMicroelectronics