max9758etjt Maxim Integrated Products, Inc., max9758etjt Datasheet - Page 16

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

The release/attack time ratio that can be achieved by
programming DR is listed in
To set the threshold at which speaker output is
clamped, an external resistor must be connected from
PREF to ground. The suggested external resistor range
is from 100kΩ to 200kΩ (for best results use a 1% resis-
tor). Leaving PREF unconnected disables the ALC
function. A constant current of 12µA is sourced at
PREF, so that a 180kΩ resistor results in 1.2W clamp
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Table 2. Release to Attack Ratio
Figure 5. Recommended Output Power Threshold, Attack, and
Release Time Components
Table 3. Maximum Gain Settings
16
VALUES SHOWN FOR AN OUTPUT POWER THRESHOLD OF 1.2W WITH AN
R
GAIN3
L
______________________________________________________________________________________
= 8Ω ATTACK TIME OF 495µs AND A RELEASE TIME OF 990ms
0
0
0
0
1
1
1
1
V
GND
V
DR
BIAS
DD
GAIN2
0
0
1
1
0
0
1
1
MAX9757
MAX9756
V
5V
DD
RELEASE/ATTACK RATIO
Table 2.
Output Power Threshold
PREF
GAIN1
DR
CT
0
1
0
1
0
1
0
1
2000
200
633
180kΩ
33nF
SPEAKER MODE GAIN (dB)
+16.5
+19.5
+22.5
+25.5
+15
+18
+21
+24
limit on an 8Ω load and a 200kΩ resistor results in a
1.5W clamp limit on an 8Ω load (Figure 6).
Use the following equation to choose the value for
R
based on a sine wave input:
The MAX9756/MAX9757/MAX9758 feature an internally
set, selectable gain. The GAIN1, GAIN2, and GAIN3
inputs set the maximum gain for the speaker and head-
phone amplifiers (Table 3). The gain of the device can
vary based upon the voltage at VOL but does not
exceed the maximum gain listed below (see the Analog
Volume (VOL) Control section).
Figure 6. Output Power Threshold vs. R PREF
PREF
for the desired maximum output power level
R
3.0
2.5
2.0
1.5
1.0
0.5
PREF
0
100
110
=
OUTPUT POWER THRESHOLD
180
120
k
130
Ω
HEADPHONE MODE GAIN (dB)
⎛
⎜ ⎜
⎝
140
vs. R
⎛
⎜
⎝
R
PREF
150
1 166
P
PREF
R
OUT
.
(kΩ)
L
R
160
= 4Ω
L
= 8Ω
170
⎞
⎟ ×
⎠
Gain Selection
+3
+3
+3
+3
0
0
0
0
180
⎛
⎜
⎝
190
R
8
L
200
⎞
⎟
⎠
⎞
⎟ ⎟
⎠