LM4875 datasheet(10/13 Pages) NSC

10 / 13 page

Application Information (Continued)

an external 1k

Ω -5kΩ resistor can be placed in parallel with

the internal 20k

Ω resistor. The tradeoff for using this resistor

is increased quiescent current.

RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT

Figure 4 through Figure 6 show the recommended two-layer

PC board layout that is optimized for the SO-8 packaged

LM4875 and associated external components. Figure 7

through Figure 9 show the recommended two-layer PC

board layout for the MSOP packaged LM4875. Both layouts

are designed for use with an external 5V supply, 8

Ω speak-

ers, and 8

Ω -32Ω headphones. The schematic for both

recommended PC board layouts is Figure 1.

Both circuit boards are easy to use. Apply a 5V supply

voltage and ground to the board’s V

DD and GND pads,

respectively. Connect a speaker with an 8

Ω minimum imped-

ance between the board’s -OUT and +OUT pads. For head-

phone use, the layout has provisions for a headphone jack,

J1. When a jack is connected as shown, inserting a head-

phone plug automatically switches off the external speaker.

10104238

FIGURE 4. Recommended SO PC board layout:

component side silkscreen

10104239

FIGURE 5. Recommended SO PC board layout:

component side layout

10104240

FIGURE 6. Recommended SO PC board layout:

bottom side layout

LM4875 Fiches technique(PDF) 10 Page - National Semiconductor (TI)