ISL22102 Datasheet, PDF (8/11 Pages) Intersil Corporation – 32 Tap, Push-button, Dual Audio Logarithmic Potentiometer with Buffer Amplifiers and Audio Detection

ISL22102
V_TH
This terminal allows to set up the threshold level of audio
input to be detected. When audio input to either Left or Right
channel is below this threshold - the FLAG output is Low;
when audio input is above this threshold - the FLAG output
is High. The threshold level is maintained over an external
resistor R_TH placed between V_TH pin, which is a source of
±10µA current, and VB pin. To calculate the actual threshold
we need to multiply 10µA by a resistor value and divide the
result by 1000. For example, a 100kΩ resistor is a subject of
1mV audio detection threshold, e.g. 10µA*100k/1000 = 1mV.
Note, the V_TH threshold multiplied by 1000 should not exceed
1/2 of AVCC. The maximum resistor value for detection
threshold can be found in Table 2.
TABLE 2. R_TH vs AVCC
AVCC (V)
MAX R_TH (kΩ)
5.5
188
5.25
177
5.0
167
4.75
156
4.5
146
4.25
135
4.0
125
3.75
115
3.5
104
3.25
94
3.0
83
2.75
73
Device Operation
There are four sections in the ISL22102: the input control,
counter and decode section, two resistor arrays with
buffered wiper outputs, reference voltage generator of VB
output, and audio detection block with programmable delay
FLAG output. The input control section operates just like an
up/down counter. The output of this counter is decoded to
turn on a single electronic switch, connecting a point on the
resistor array to the wiper output. Each resistor array is
comprised of 31 individual resistors connected in series and
its wiper output pass an attenuated audio input to the power
amplifier. Both resistor arrays have logarithmic taper with
-72dB dynamic range as shown in Table 2.
The ISL22102 is designed to interface directly to two
push-button switches for effectively moving the wipers up or
down. The UP and DN inputs increment or decrement 5-bit
counters respectively. The output of these counters are
decoded to select one of the thirty-two wiper positions along
the resistive array. The wiper increment input, UP, and the
wiper decrement input, DN, are both connected to an
internal pull-up so that they normally remain High. When
pulled Low by an external push button switch or a logic Low
level input, the wipers will be switched to the next adjacent
tap position.
Internal debounce circuitry prevents inadvertent switching of
the wipers position if UP or DN remain Low for less than
15ms, typical. Each of the buttons can be pushed either
once for a single increment/decrement or continuously for a
multiple increments/decrements. When making a continuous
push, after the first second, the device is going to auto
increment/decrement mode. If the button is held for longer
than 1s, the wiper position will be auto
incremented/decremented with a rate of 4Hz for 4s, and with
a rate of 8Hz after that. As soon as the button is released,
the ISL22102 will return to a low power standby condition.
Each wiper acts like its mechanical equivalent and does not
move beyond the last position. That is, the counter does not
wrap around when clocked to either extreme.
Table 3 contains information about attenuation level for each
tap position.
TABLE 3. WIPER TAP POSITION vs ATTENUATION
TAP POSITION
ATTENUATION
0
0
1
-2dB
2
-4dB
3
-6dB
4
-8dB
5
-10dB
6
-12dB
7
-14dB
8
-16dB
9
-18dB
10
-20dB
11
-22dB
12
-24dB
13
-26dB
14
-28dB
15
-30dB
16
-32dB
17
-34dB
18
-36dB
19
-38dB
20
-40dB
21
-42dB
22
-44dB
23
-46dB
24
-48dB
8
FN6788.1
January 14, 2010