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參數(shù)資料
| 型號： | LM4550VHX/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 消費家電 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PQFP48 |
| 封裝： | 7 X 7 X 1.40 MM, LQFP-48 |
| 文件頁數(shù)： | 5/30頁 |
| 文件大?。?/td> | 611K |
| 代理商： | LM4550VHX/NOPB |
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Pin Descriptions (Continued)
DIGITAL I/O AND CLOCKING (Continued)
Name
Pin
I / O
Functional Description
SYNC
10
I
AC Link frame marker and Warm Reset
This input defines the boundaries of AC Link frames. Each frame lasts 256 periods of
BIT_CLK. In normal operation SYNC is a 48 kHz positive pulse with a duty cycle of 6.25%
(16/256). SYNC is sampled on the rising edge of BIT_CLK and the codec takes the first
positive sample of SYNC as defining the start of a new AC Link frame. If a subsequent SYNC
pulse occurs within 255 BIT_CLK periods of the frame start it will be ignored.
SYNC is also used as an active high input to perform an (asynchronous) Warm Reset. Warm
Reset is used to clear a power down state on the codec AC Link interface.
RESET#
11
I
Cold Reset
This active low signal causes a hardware reset which returns the control registers and all
internal circuits to their default conditions. RESET# must be used to initialize the LM4550
after Power On when the supplies have stabilized. Cold Reset also clears the codec from
both ATE and Vendor test modes. In addition, while active, it switches the PC_BEEP mono
input directly to both channels of the LINE_OUT stereo output.
ID0#
45
I
Codec Identity
ID1# and ID0# determine the Codec Identity for multiple codec use. The Codec Identity
configures the codec in either Primary or one of three Secondary Codec modes. These
Identity pins are of inverted polarity relative to the Codec Identity bits ID1, ID0 (bits D15, D14)
in the read-only Extended Audio ID register, 28h. If the ID0# pin (pin 45) is connected to
ground then the ID0 bit (D14, reg 28h) will be set to “1”. Similarly, connection to DV
DD will set
the ID0 bit to “0”. If left open (NC), ID0# is pulled high by an internal pull-up resistor. The
Codec Identity bits are also used in the Chain-In Control register, 74h. See the register
description and the CIN pin description for details.
ID1#
46
I
Codec Identity
ID1# and ID0# determine the codec address for multiple codec use. The Codec Identity
configures the codec in either Primary or one of three Secondary Codec modes. These
Identity pins are of inverted polarity relative to the Codec Identity bits ID1, ID0 (bits D15, D14)
in the read-only Extended Audio ID register, 28h. If the ID1# pin (pin 46) is connected to
ground then the ID1 bit (D15, reg 28h) will be set to “1”. Similarly, connection to DV
DD will set
the ID1 bit to “0”. If left open (NC), ID1# is pulled high by an internal pull-up resistor. The
Codec Identity bits are also used in the Chain-In Control register, 74h. See the register
description and the CIN pin description for details.
EAPD
47
O
External Amplifier Power Down control signal
This output is set by the EAPD bit (bit D15) in the Powerdown Control/Status register, 26h. As
with the other logic outputs, the output voltage is set by DV
DD. This pin is intended to be
connected to the shutdown pin on an external power amplifier. For normal operation the
default value of EAPD=0 will enable the external amplifier allowing an input on PC_BEEP to
be heard during Cold Reset.
CIN
48
I
Chain In
The codec can be instructed to disconnect its own SDATA_IN signal and instead pass the
signal on CIN through to the SDATA_IN output pin. This is achieved by changing the value of
the two LSBs of the Chain-In Control register (74h) so that they differ from the Codec Identity
bits ID1, ID0. Those two LSBs default to the value of the Codec Identity bits following Cold
Reset thereby disabling the Chain In feature. Chain In can also be disabled by reading the
Codec Identity from the Extended Audio ID register (28h) and writing the value back into
register 74h LSBs. The Codec Identity bits are determined by the input pins ID1#, ID0#.
CIN can be left open (NC) provided that the chain feature is disabled. When the chain feature
is used, CIN should always be driven. Either connect the SDATA_IN pin from another codec
or else ground CIN to prevent the possibility of floating the SDATA_IN signal at the controller.
LM4550
www.national.com
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