Tel:886-2-66296288
Fax:886-2-29174598
URL:http://www.princeton.com.tw
Electronic Volume Controller IC
PT2256V
DESCRIPTION
PT2256V is an electronic volume controller IC utilizing CMOS Technology specially designed for use
on audio equipment. It has 2 built-in channels making it ideally suitable for mono and stereo sound
applications. PT2256V provides the Loudness Function, a wide frequency response range and a very
low total harmonic distortion, thereby guaranteeing a highly effective and reliable performance. It is
housed in 16-pin DIP or SOP and is functionally compatible with TC9235P. Pin assignments and
application circuit are optimized for low cost advantages and easy PCB Layout.
FEATURES
•
•
•
•
•
•
•
•
•
•
•
CMOS Technology
Low Power Consumption
Wide Operation Voltage Range: VDD=4.5
~
11V
Least External Components
2 Channels in the same chip
0dB to -78dB Attenuation can be controlled by UP and Down Pin
20dB Tap for Loudness Circuit
Built-in DC Output Circuit (8 levels) for Volume Level Metering
Wide Frequency Response Range
Low Total Harmonic Distortion
Available in 16 pins DIP or SOP
APPLICATION
•
Audio Equipment Volume Control
PT2256V V1.2
-1-
August, 2006
Tel:886-2-66296288
Fax:886-2-29174598
URL:http://www.princeton.com.tw
Electronic Volume Controller IC
PT2256V
BLOCK DIAGRAM
VS S
OUT1
IN 1
LT 1
AG N D
VD D
OUT2
IN 2
LT 2
AG N D
D e co d e r
/U P
/D N
O SC
U p /D o w n
C o u n te r
C o n tr o l
D/A Con ve rte r
DCO
/I N H
/R ST
PT2256V V1.2
-2-
August, 2006
Tel:886-2-66296288
Fax:886-2-29174598
URL:http://www.princeton.com.tw
Electronic Volume Controller IC
PT2256V
PIN CONFIGURATION
VSS
OUT1
IN1
LT1
AGND
/UP
/DN
OSC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VDD
OUT2
IN2
LT2
AGND
DCO
/INH
/RST
PT2256V
PIN DESCRIPTION
Pin Number
VSS
OUT1
IN1
LT1
AGND
UP
I/O
-
O
I
O
-
I
Description
Negative Power Supply
Volume Output Pin 1
Volume Input Pin 1
Tap Output Pin 1 for Loudness Function
Analog Ground Pins 1
Volume UP Control Input Pin. The
1 step/1 push volume is controlled by pressing the UP Key. If
the key has been pushed continuously increase. Built-in
Pull-up Resistor.
Volume DOWN Control Input Pin. The
1 step/1 push volume is controlled by pressing the DOWN
Key. If the key is continuously pressed, the volume control will
continuously decrease. Built-in Pull-up Resistor.
Oscillation Pin.
The oscillation circuit of a resistor and capacitor connection.
Oscillator is activated when the key is pressed.
Reset Pin.
This pin sets the initial volume level. The volume level is set to
-46dB by “L” Input. Built-in Pull-up Resistor Low Active
Backup Mode Input Pin
DC Output Pin for Volume Level Meter
Tap Output Pin 2 for Loudness Function
Volume Input Pin 2
Volume Output Pin 2
Positive Power Supply
-3-
Pin No.
1
2
3
4
5, 12
6
DN
I
7
OSC
RST
/INH
DCO
LT2
IN2
OUT2
VDD
PT2256V V1.2
I/O
I
I
O
O
I
O
-
8
9
10
11
13
14
15
16
August, 2006
Tel:886-2-66296288
Fax:886-2-29174598
URL:http://www.princeton.com.tw
Electronic Volume Controller IC
PT2256V
FUNCTION DESCRIPTION
ATTENUATION
The PT2256V volume control circuit consists of ladder resistors and analog switches. The Tap for
loudness function is connected to the Step 10 (-20dB). When the (3.9KΩ) resistor is connected
between LT and AGND pins, the attenuation is given in table below.
The equivalent circuit is shown below:
Step
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Attenuation
(dB)
0
-2
-4
-6
-8
-10
-12
-14
-16
-18
-20
-22
-24
-26
-28
-30
Step
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Attenuation
(dB)
-32
-34
-36
-38
-40
-42
-46
-50
-54
-58
-62
-66
-70
-74
-78
∞
OUT
IN
Step 0
Step 1
Step 2
29KΩ
Step 9
LT
Step 10
Step 11
22KΩ
Step 30
AGND
Step 31
Note:
1. Step 22 has an initial value of -46dB.
PT2256V V1.2
-4-
August, 2006
Tel:886-2-66296288
Fax:886-2-29174598
URL:http://www.princeton.com.tw
Electronic Volume Controller IC
PT2256V
DC OUTPUT FOR VOLUME LEVEL
The DC Output for the Volume Level Meter is internally connected to the D/A Converter. PT2256V has
8 stages of output voltage with each stage corresponding to a particular volume level. Please refer to
the table below:
Step
0-3
4-7
8-11
12-15
16-19
20-23
24-27
28-31
Attenuation (dB)
0-6
8-14
16-22
24-30
32-38
40-50
54-66
70-∞
Output Voltage (V)
7/8 VDD
6/8 VDD
5/8 VDD
4/8 VDD
3/8 VDD
2/8 VDD
1/8 VDD
0
UP/DOWN VOLUME CONTROL
PT2256V features two Volume Control Pins, namely: UP and DN. UP is the control pin used to
increase volume level while the DN is the control pin used to decrease the volume level. Thus, volume
level may regulated using the Up or Down Keys. These keys are operated on a 1 step/1 push volume
level control when UP or DN keys are set to “L” Level. If the keys are continuously pressed (input
“Low”), then the volume level continuously steps up or down as the case maybe. Please refer to the
diagram below for the timing of the key input.
/UP, /DN Input
Volume Level
Control
t
T
a
Notes:
1. t= Preventive Time for Chattering (2.2 x 1/fosc )
2. T= Switching Time to Automatic Mode (10 x 1/fosc)
3. a=Up, Down Speed (2x1/fosc)
PT2256V V1.2
-5-
August, 2006
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