TS486 Datasheet, PDF (27/31 Pages) STMicroelectronics – 100mW STEREO HEADPHONE AMPLIFIER WITH STANDBY MODE

APPLICATION NOTE:
TS486-TS487
TS486/487 GENERAL DESCRIPTION
TS486/487 is a family of dual audio amplifiers able
to drive 16Ω or 32Ω headsets. Working in the 2V to
5.5V supply voltage range, they deliver 100mW at
5V and 12mW at 2V in a 16Ω 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 is selected using the
SHUTDOWN input. For TS486 (respectively
TS487), the device is in sleep mode when PIN 5 is
connected at GND (resp. V_CC).
GAIN SETTING
The gain of each inverter amplifier of the TS486
and TS487 is set by the resistors R_IN and R_FEED.
Gain_LINEAR = -(R_FEED/R_IN)
Gain_dB = 20 Log(R_FEED/R_IN)
Fixed gain versions TS486-n and TS487-n
including R_IN and R_FEED 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 C_IN1
and C_IN2 and the input resistors R_IN1 and R_IN2.
The C_IN capacitor in series with the input resistor
R_IN of the amplifier is equivalent to a first order
high pass filter.
Assuming that F_min is the lowest frequency to be
amplified (with a 3dB attenuation), the minimum
value of C_IN is:
C_IN > 1 / (2*π*F_min*R_IN )
The following curve gives directly the low
frequency roll-off versus the input capacitor C_IN
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