lm4934rlx National Semiconductor Corporation, lm4934rlx Datasheet - Page 36

• Manufacturer Part Number: lm4934rlx
• Description: 3d Audio Sub-system With Stereo Speaker, Ocl/se Stereo Headphone, Earpiece And Mono Line Level Outputs
• Manufacturer: National Semiconductor Corporation

Application Information
(Continued)
MISCELLANEOUS
I2S BUS SELECT
S23, S24, S26, S27 – I2S Bus select. Toggles between on-board and external I2S (whether on-board SPDIF receiver is used).
All jumpers must be set the same. Jumpers on top two pins selects external bus (JP19). Jumpers on bottom two pins selects
on-board SPDIF receiver output.
HEADPHONE OUTPUT CONFIGURATION
Jumpers S1, S2, S3, and S4 are used to configure the headphone outputs for either cap-coupled outputs or output capacitorless
(OCL) mode in addition to the register control internal to the LM4934 for this feature. Jumpers S1 and S3 bypass the output DC
blocking capacitors when OCL mode is required. S2 connects the center amplifer HPCOUT to the headphone ring when in OCL
mode. S4 connects the center ring to GND when cap-coupled mode is desired. S4 must be removed for OCL mode to function
properly. Jumper settings for each mode:
OCL
S1 = ON
S2 = ON
S3 = ON
S4 = OFF
Cap-Coupled
S1 = OFF
S2 = OFF
S3 = OFF
S4 = ON
PLL FILTER CONFIGURATION
The LM4934 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 LM4934 demo board allows quick demonstration of the capabilities of the LM4934 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 3V and analog supplies of less than 4V. This means low analog supply voltage testing
of the LM4934 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.
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LM4934 I
C/SPI INTERFACE SOFTWARE
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Convenient graphical user interface software is available for demonstration purposes of the LM4934. It allows for either SPI or I
C
control via either USB or parallel port connections to a Windows computer. Control options 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.national.com and is compatible
with Windows operating systems of Windows 98 or more (with USB support) with the latest .NET updates from Microsoft.
www.national.com
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