TS487-1 datasheet(27/31 Pages) STMICROELECTRONICS

27 / 31 page

TS486-TS487

27/31

APPLICATION NOTE:

TS486/487 GENERAL DESCRIPTION

TS486/487 is a family of dual audio amplifiers able

to drive 16

Ω or 32Ω headsets. Working in the 2V to

5.5V supply voltage range, they deliver 100mW at

5V and 12mW at 2V in a 16

Ω load. An internal

output current limitation, offers protection against

short-circuits at the output over a limited time

period.

Fixed gain versions of the TS486 and TS487

including the feedback resistor and the input

resistors are also proposed to reduce the number

of external parts.

The TS486 and TS487 exhibit a low quiescent

current of typically 1.8mA, allowing usage in

portable applications.

The

standby

mode

selected

using

the

SHUTDOWN input. For TS486 (respectively

TS487), the device is in sleep mode when PIN 5 is

connected at GND (resp. VCC).

GAIN SETTING

The gain of each inverter amplifier of the TS486

and TS487 is set by the resistors RIN and RFEED.

GainLINEAR = -(RFEED/RIN)

GaindB = 20 Log(RFEED/RIN)

Fixed

gain

versions

TS486-n

and

TS487-n

including RIN and RFEED are proposed to reduce

external parts.

LOW FREQUENCY ROLL-OFF WITH INPUT

CAPACITORS

The low roll-off frequency of the headphone

amplifiers depends on the input capacitors CIN1

and CIN2 and the input resistors RIN1 and RIN2.

The CIN capacitor in series with the input resistor

RIN of the amplifier is equivalent to a first order

high pass filter.

Assuming that Fmin is the lowest frequency to be

amplified (with a 3dB attenuation), the minimum

value of CIN is:

CIN > 1 / (2*π*Fmin*RIN )

The

following

curve

gives

directly

the

low

frequency roll-off versus the input capacitor CIN

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