LM49150 datasheet(20/28 Pages) NSC

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TABLE 8. Volume Control Table

Volume Step

(1) xG4

xG3

xG2

xG1

xG0

(2) Gain (dB)

–80.00

–46.50

–40.50

–34.50

–30.00

–27.00

–24.00

–21.00

–18.00

–15.00

–13.50

–12.00

–10.50

–9.00

–7.50

–6.00

–4.50

–3.00

–1.50

0.00

1.50

3.00

4.50

6.00

7.50

9.00

10.50

12.00

13.50

15.00

16.50

18.00

(1.) x = M, L and R

(2.) Gain / Attenuation is from input to output

SHUTDOWN FUNCTION

The LM49150 features the following shutdown controls.

Bit B4 (GAMP_SD) of the SHUTDOWN CONTROL register

controls the gain amplifiers. When GAMP_SD = 1, it disables

the gain amplifiers that are not in use. For example, in Modes

1, 4 and 5, the Mono inputs are in use, so the Left and Right

input gain amplifiers are disabled, causing the I

DD to be min-

imized.

Bit B0 (PWR_On) of the SHUTDOWN CONTROL register is

the global shutdown control for the entire device. Set

PWR_On = 0 for normal operation. PWR_On = 1 overrides

any other shutdown control bit.

OUTPUT MODE CONTROL

In the LM49150 OUTPUT MODE CONTROL register (Table

4), Bit B5 (EP Bypass) controls the operation of the Earpiece

Bypass path. If EP Bypass = 0, it would act under normal out-

put mode operation set by bits B3, B2, B1, and B0. If EP

Bypass = 1, it overrides the B3, B2, B1, and B0 Bits and en-

ables the Receiver Bypass path, a class AB amplifier, to the

speaker output.

Bit B4 (HPR_SD) of the OUPUT MODE CONTROL register

controls the right headphone shutdown. If HPR_SD = 1, the

right headphone output is disabled.

DIFFERENTIAL AMPLIFIER EXPLANATION

The LM49150 features a differential input stage, which offers

improved noise rejection compared to a single-ended input

amplifier. Because a differential input amplifier amplifies the

difference between the two input signals, any component

common to both signals is cancelled. An additional benefit of

the differential input structure is the possible elimination of the

DC input blocking capacitors. Since the DC component is

common to both inputs, and thus cancelled by the amplifier,

the LM49150 can be used without input coupling capacitors

when configured with a differential input signal.

LM49150 Datasheet(PDF) 20 Page - National Semiconductor (TI)

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