ssm2602 Analog Devices, Inc., ssm2602 Datasheet - Page 10

• Manufacturer Part Number: ssm2602
• Description: Low Power Audio Codec
• Manufacturer: Analog Devices, Inc.

SSM2602
THEORY OF OPERATION
ADC HIGH-PASS FILTER
DC offset can be removed by using the SSM2602 adjustable
digital high-pass filter (see Table 3 for characteristics).
Digital Filter Characteristics
The ADC and DAC employ separate digital filters.
AUTOMATIC LEVEL CONTROL (ALC)
Codec has an automatic level control that aims to keep a constant
recording volume irrespective of the input signal level. This is
achieved by continuously adjusting the PGA gain so that the
signal level at the ADC input remains constant. A digital peak
detector monitors the ADC output and changes the PGA gain if
necessary.
INPUT SIGNAL
SIGNAL
AFTER
PGA
ALC
Figure 13. PGA and ALC Decay Time and Attack Time Definitions
DECAY TIME
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Decay (Gain Ramp-Up) Time
This is the time for the PGA gain to ramp up through 90% of its
range. The time for the recording level to return to its target value
therefore depends on both the decay time and the gain adjustment
required. If the gain adjustment is small, the time to return to
the target value will be less than the decay time.
Attack (Gain Ramp-Down) Time
This is the time for the PGA gain to ramp down through 90% of
its range. The time for the recording level to return to its target
value therefore depends on both the attack time and the gain
adjustment required. If the gain adjustment is small, the time
to return to the target value will be less than the attack time.
ATTACK TIME
Preliminary Technical Data
ALC TARGET
VALUE