Datasheet

Exposed DAP

LM4917

www.ti.com

SNAS238G –AUGUST 2004–REVISED MAY 2013

LM4917 Reference Design Boards

Bill Of Materials

Part Description Qty Ref Designator

LM4917 Mono Reference Design Board 1

LM4917 Audio AMP 1 U1

Tantalum Cap 1µF 16V 10 1 Cs

Ceramic Cap 0.39µF 50V Z50 20 2 Ci

Resistor 20kΩ 1/10W 5 4 Ri, Rf

Resistor 100kΩ 1/10W 5 1 Rpu

Jumper Header Vertical Mount 2X1, 0.100 1 J1

PCB Layout Guidelines

This section provides practical guidelines for mixed signal PCB layout that involves various digital/analog power

and ground traces. Designers should note that these are only "rule-of-thumb" recommendations and the actual

results will depend heavily on the final layout.

Avoiding Shorts on the Charge Pump Outputs

For the LM4917SD package, the exposed dap is connected to the substrate of the device. Because LM4917’s

charge pump is powered by both a negative and positive supply the exposed dap must be left floating. This will

avoid shorting the charge pump outputs.

Figure 30. Bottom View of LM4917SD Package

Minimization of THD

PCB trace impedance on the power, ground, and all output traces should be minimized to achieve optimal THD

performance. Therefore, use PCB traces that are as wide as possible for these connections. As the gain of the

amplifier is increased, the trace impedance will have an ever increasing adverse affect on THD performance. At

unity-gain (0dB) the parasitic trace impedance effect on THD performance is reduced but still a negative factor in

the THD performance of the LM4917 in a given application.

General Mixed Signal Layout Recommendation

Power and Ground Circuits

For two layer mixed signal design, it is important to isolate the digital power and ground trace paths from the

analog power and ground trace paths. Star trace routing techniques (bringing individual traces back to a central

point rather than daisy chaining traces together in a serial manner) can greatly enhance low level signal

performance. Star trace routing refers to using individual traces to feed power and ground to each circuit or even

device. This technique will require a greater amount of design time, but will not increase the final price of the

board. The only extra parts required may be some jumpers.

Product Folder Links: LM4917