LM4543 Datasheet, PDF (9/16 Pages) National Semiconductor (TI) – AC ’97 Codec with National 3D Sound

Pin Description (Continued)
Digital I/O and Clocking
Name
Pin
XTL_IN
2
XTL_OUT
3
SDATA_OUT
5
BIT_CLK
6
SDATA_IN
8
SYNC
10
RESET#
11
I/O
I
O
I
O
O
I
I
Functional Description
24.576 MHz crystal input. Use a fundamental-mode type crystal. When operating from a
crystal, a 1MΩ resistor must be connected across pins 2 and 3.
24.576 MHz crystal output. When operating from a crystal, a 1MΩ resistor must be
connected across pins 2 and 3.
This data stream contains both control data and DAC audio data. This input is sampled by
the LM4543 on the falling edge of BIT_CLK.
12.288 MHz clock which is derived (divide by two) from the 24.576MHz crystal input
(XTL_IN).
This data stream contains both control data and ADC audio data. This output is clocked out
by the LM4543 on the rising edge of BIT_CLK.
48kHz sync pulse which signifies the beginning of both the SDATA_IN and SDATA_OUT
serial streams. SYNC must be synchronous to BIT_CLK.
This active low signal causes a hardware reset which returns the control registers to their
default conditions.
Power Supplies and References
Name
AVDD
AVSS
DVDD
DVSS
VREF
VREFOUT
AFILT1
AFILT2
3DP,3DN
Pin
25,38
26,42
1,9
4,7
27
28
29
30
31,32
I/O
I
I
I
I
O
O
O
O
O
Functional Description
Analog supply pins.
Analog ground pins.
Digital supply pins.
Digital ground pins.
Nominal 2.2V reference output. Not intended to sink or source current. Bypassing of this pin
should be done with short traces to maximize performance.
Nominal 2.2V reference output. Can source up to 5mA of current and can be used to bias a
microphone. Do not connect any external capacitance to this pin.
This pin is not used and should be left open (NC). However, a capacitor to ground on this
pin is permitted as it will not affect performance.
This pin is not used and should be left open (NC). However, a capacitor to ground on this
pin is permitted as it will not affect performance.
These pins are used to complete the National 3D Sound circuit. Connect a 0.022µF
capacitor between pins 3DP and 3DN. The National 3D Sound can be turned on and off via
control register 20h. This is a fixed-depth type stereo enhance circuit, thus writing to register
22h has no effect. If National 3D Sound is not desired, then these pins should be left as no
connect (NC).
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