LM49450SQ/NOPB National Semiconductor, LM49450SQ/NOPB Datasheet - Page 27

• Manufacturer Part Number: LM49450SQ/NOPB
• Description: IC AUDIO SUBSYSTEM 2.5W D 32LLP
• Manufacturer: National Semiconductor
• Series: Boomer®r
• Type: Class Dr

Specifications of LM49450SQ/NOPB

• Output Type: 2-Channel (Stereo) with Stereo Headphones
• Max Output Power X Channels @ Load: 2.5W x 2 @ 4 Ohm
• Voltage - Supply: 2.7 V ~ 5.5 V
• Features: 3D, DAC, Depop, I²C, I²S, Mute, Short-Circuit and Thermal Protection, Shutdown, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 32-LLP
• Amplifier Class: D
• No. Of Channels: 2
• Output Power: 1.2W
• Supply Voltage Range: 2.7V To 5.5V
• Load Impedance: 8ohm
• Operating Temperature Range: -40°C To +85°C
• Amplifier Case Style: LLP
• Rohs Compliant: Yes
• For Use With: LM49450SQEVAL - BOARD EVAL FOR LM49450
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM49450SQ; LM49450SQ; LM49450SQTR

CLK NETWORK
LM49450 Clock Structure
The MCLK input is first divided by the R divider to product the
clock at point B; this is then decoded according to the
DAC_MODE to produce a signal which goes to both the DAC
digital and the I2S interface, and a signal which goes to the
DAC analog.
Common Clock Settings for the DAC
In DAC_MODE 0, the DAC has an oversampling rate (OSR)
of 125 but requires a 250xfs clock at point B. This allows a
simple clocking solution as it will work from 12.000MHz (com-
mon in most systems with Bluetooth or USB) at 48kHz exact-
Sample Rate
DAC MODE
11.025
22.05
176.4
44.1
88.2
192
00
01
10
11
12
16
24
32
48
96
8
TABLE 4. Relationship between clocks for each of the four DAC modes
(OSR = 125fs, Clock
DAC MODE = 2b00
Required = 250fs)
2.75625
5.5125
11.025
OSR
125
128
64
32
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2
3
4
6
8
TABLE 5. Common DAC Clock Frequencies
DAC MODE = 2b01 (OSR
= 128fs, Clock Required =
CLK Network Diagram
CLK at B
11.2896
2.8224
5.6448
12.288
256fs)
2.084
3.072
4.096
6.144
8.192
250fs
256fs
128fs
128fs
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Clock Required at B (MHz)
27
This table describes the relationship between the clocks, for
each of the four possible DAC modes in terms of audio input
sampling frequency fs.
ly. In the other DAC modes, the DAC requires a conventional
2^Nxfs clock for conversation. The following table describes
the clock required at point B for various clock sample rates in
the different DAC modes:
Description
DAC MODE = 2b10
(OSR = 64fs, Clock
Required = 128fs)
DAC Digital CLK
11.2896
12.288
250fs
128fs
128fs
128fs
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DAC MODE = 2b11
(OSR = 32fs, Clock
Required = 128fs)
DAC Analog CLK
30045559
22.5792
24.576
125fs
128fs
64fs
32fs
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