LM4875 datasheet(11/37 Pages) NSC

11 / 37 page

External Components Description

Components

Functional Description

This is the input coupling capacitor. It blocks the DC voltage and couples the input signal to the

amplifier’s input terminals. C

IN also creates a highpass filter with the internal resistor Ri (Input

Impedance) at f

c = 1/(2

πR

iCIN).

This is the supply bypass capacitor. It filters the supply voltage applied to the V

DD pin and helps

reduce the noise at the V

DD pin.

This is the BYPASS pin capacitor. It filters the V

DD / 2 voltage and helps maintain the LM4857’s

PSRR.

OUT

This is the output coupling capacitor. It blocks the DC voltage and couples the output signal to the

speaker load R

L.COUT also creates a high pass filter with RL at fO = 1/(2

πR

LCOUT).

This resistor sets the gain of the National 3D effect. Please refer to the National 3D Enhancement

section for information on selecting the value of R

3D.

This capacitor sets the frequency at which the National 3D effect starts to occur. Please refer to the

National 3D Enhancement section for information on selecting the value of C

3D.

Typical Performance Characteristics (Note 11)

LM4857SP THD+N vs Frequency

20079755

DD = 5V; LLS, RLS; PO = 400mW;

L =4

Ω; Mode 7; 0dB Gain

20079756

DD = 3V; LLS, RLS; PO = 200mW;

L =4

Ω; Mode 7; 0dB Gain

LM4875 Datenblatt(PDF) 11 Page - National Semiconductor (TI)