max9758etjt Maxim Integrated Products, Inc., max9758etjt Datasheet - Page 15

• Manufacturer Part Number: max9758etjt
• Description: 2.3w Stereo Speaker Amplifiers And Directdrive Headphone Amplifiers With Automatic Level Control
• Manufacturer: Maxim Integrated Products, Inc.

The attack time is the time it takes to reduce the gain
after the input signal has exceeded the threshold level.
Suggested attack time range is from 150µs to 50ms.
The gain attenuation in attack is exponential and the
attack time is defined as one time constant. The time
constant of the attack is given by 15,000 x C
onds (where C
• Use a short attack time for the ALC to react quickly
• Use a longer attack time to allow the ALC to ignore
Figure 4. Attack, Hold, and Release Time
Table 1. Attack and Release Time
Headphone Amplifiers with Automatic Level Control
TIMING CAPACITOR
to transient signals, such as snare drum beats
(music) or gun shots (DVD). Fast attack times can
lead to gain “pumping” where rapid ALC action can
be heard reacting to dynamic material.
short-duration peaks and only reduce the gain when
a noticeable increase in loudness occurs. Short-dura-
tion peaks are not reduced, but louder passages are.
100nF
330nF
(C
2.2µF
3.3µF
33nF
10nF
1µF
2.3W Stereo Speaker Amplifiers and DirectDrive
CT
)
CT
is the external timing capacitor).
______________________________________________________________________________________
10ms/div
ATTACK TIME
DR = ‘X’
4.95ms
49.5ms
495µs
150µs
1.5ms
15ms
33ms
CT
1V/div
Attack Time
OUTPUT
2V/div
CT
sec-
DR = V
300ms
990ms
99ms
30ms
6.6s
10s
3s
Hold time is the delay after the signal falls below the
threshold level before the release phase is initiated.
Hold time is internally set to 50ms and nonadjustable.
The hold time is cancelled by any signal exceeding the
set threshold level and attack is reinitiated.
The release time is how long it takes for the gain to
return to its normal level after the input signal has fallen
below the threshold level and 50ms hold time has
expired. Release time is defined as release from a 6dB
gain compression to 10% of the nominal gain setting
after the input signal has fallen below PREF threshold
and the 50ms hold time has expired. Release time is
adjustable between 95ms and 10s. The release time is
set by picking an attack time using C
attack to release time ratio by configuring DR as shown
in
inversely proportional to the magnitude of gain com-
pression:
• Use a small ratio to maximize the speed of the ALC.
• Use a large ratio to maximize the sound quality and
Release and attack times are set by selecting the
capacitance value between CT and GND, and by set-
ting the logic state of DR (Table 1). DR is a tristate logic
input that sets the attack-to-release time ratio. A fixed
hold time of 50ms is internally added to the release time.
DD
This allows the louder passages to be reduced in vol-
ume, thereby maximizing output dynamic range.
Having the attack time too long can possibly result in
some damage to the loudspeaker under harsh condi-
tions.
Table 2. Release time is linear in dB with time and is
prevent repeated excursions above the threshold
from being independently adjusted by the ALC.
RELEASE TIME
DR = V
313ms
950ms
95ms
3.1s
9.5s
—
—
BIAS
CT
DR = GND
and setting the
Release Time
990ms
300ms
9.9s
3s
—
—
—
Hold Time
15