ACS422A68TAGZBX8 IDT, ACS422A68TAGZBX8 Datasheet - Page 25

• Manufacturer Part Number: ACS422A68TAGZBX8
• Description: Interface - CODECs
• Manufacturer: IDT

Specifications of ACS422A68TAGZBX8

• Rohs: yes
• Part # Aliases: IDTACS422A68TAGZBX8

ACS422x68
LOW-POWER, HIGH-FIDELITY, INTEGRATED CODEC
©2011 INTEGRATED DEVICE TECHNOLOGY, INC.
thresholds. The compressor recalculates the target gain value every block, typically every
10ms.
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The required attenuation is: 9db or a gain coefficient of 0.1259.
Translating this calculation from log space to linear yields the formula:
The resulting attenuation required is 8db or a gain value of 0.1585.
The linear equation for calculating the gain is:
Atten(in db) = (1-1/ratio)(threshold(in db) – level(in db);
Gain =(level/threshold)
Gain =(level/threshold)
The gain calculation operates in 3 regions:
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Compression region gain calculation: In the compression region, the gain calculation is:
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Expansion region gain calculation: In the expansion region, the attenuation calculation is:
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State Transitions: In addition to calculating the new gain for the compressor, the gain calcu-
lation block will also select the filter coefficient for the attack/release filter. The rules for
selecting the coefficient are as follows:
Atten(in db) = (1 - ratio)(threshold-level);
Linear region – If the level is higher than the expander threshold and lower than the
compression threshold, then the gain is 1.0
Compression region – When the level is higher than the compressor threshold, then the
comp/limiter is in the compression region. The gain is a function of the compressor ratio
and the signal level.
Expansion region – When the signal is lower than the expansion threshold, the
comp/limiter is in the expansion region. In this region, the gain is a function of the signal
level and the expansion ratio.
For example,
For example,
• Ratio = 4:1 compression
• Threshold = -16db
• Level = -4 db
• Ratio = 3:1
• Threshold = -40db
• Level = -44 db
1/ratio
ratio
25
*(threshold/level)
*(threshold/level)
ACS422X68
V1.6 01/13