LM4937

SNAS369J – OCTOBER 2006 – REVISED MAY 2013

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Cap-Coupled (CD_6 = 0)

–

S1 = OFF

–

S2 = OFF

–

S3 = OFF

–

S4 = ON

PLL FILTER CONFIGURATION

The LM4937 demo board comes with a simple filter setup by connecting jumpers S5 and S6. Removing these

and connecting jumpers S7 and S8 will allow for an alternate PLL filter configuration to be used at R2 and C23.

ON-BOARD SPDIF RECEIVER

The SPDIF receiver present on the LM4937 demo board allows quick demonstration of the capabilities of the

LM4937 by using the common SPDIF output found on most CD/DVD players today. There are some limitations in

its useage, as the receiver will not work with digital supplies of less than 3.0V and analog supplies of less than

4V. This means low analog supply voltage testing of the LM4937 must be done on the external digital bus.

The choice of using on-board or external digital bus is made usign jumpers S23, S24, S26, and S27 as described

above.

S25 selects whether the Toslink or Coaxial SPDIF input is used. The top two pins connects the toslink, the

bottom two connect the coaxial input.

Power on the digital side is routed through S20 (connecting to the other digital supplies), while on the analog side

it is interrupted by S21. Both jumpers must be in place for the receiver to function. The part is already configured

for I2S standard outputs. Jumper S28 allows the DATA output to be pulled either high or low. Default is high

(jumper on right two pins).

It may be necessary to quickly toggle S29 to reset the receiver and start it working upon initial power up.. A quick

short across S29 should clear this condition.

Convenient graphical user interface software is available for demonstration purposes of the LM4937. It allows for

include all mode and output settings, volume controls, PLL and DAC setup, FIR setting and on-the-fly adjustment

by an easy to use graphical interface. An advanced option is also present to allow direct, register-level

commands. Software is available from www.ti.com and is compatible with Windows operating systems of

Windows 98 or more (with USB support) with the latest .NET updates from Microsoft.

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