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DS1807E+
Addressable Dual Audio Taper Potentiometer
FEATURESOperates from 3V or 5V Power SuppliesUltra-low power consumptionTwo digitally controlled, 65-position
potentiometersLogarithmic resistor characteristics (1 dB per
step)Zero-crossing detection eliminates noise
caused by discrete wiper changesAddressable using 3-Chip Select InputsSerial/Synchronous Bus InputsOperating Temperature Range:
- Industrial: -40°C to +85°CStandard Resistance Value: 45 kΩ
PIN ASSIGNMENT
PIN DESCIPTIONL0, L1 -Low End of Resistor
H0, H1 - High End of Resistor
W0,W1 - Wiper Terminal of Resistor
VCC - 3V/5V Power Supply Input
A0..A2 - Chip Select Inputs
SDA - Serial Data I/O
SCL - Serial Clock Input
GND-Ground
AGND-Analog Ground-No connection
DESCRIPTIONThe DS1807 Addressable Dual Audio Taper Potentiometer is a dual audio taper potentiometer having a
logarithmic resistive characteristic. Each potentiometer has a total of 65 wiper positions including the
mute position. Adjacent wiper positions are separated by 1 dB giving a total attenuation range of 64 dB.
When the wipers are in the mute position, attenuation in excess of 90 dB is achieved. The DS1807 also
provides a zero-crossing detection capability. This capability eliminates noise caused by discrete wiper
position changes. The DS1807 is controlled via a two-input, serial synchronous interface that provides the
capability of addressing up to eight different DS1807s. Addressability is obtained via communication
protocol and three (3) address select inputs A0, A1, and A2. Communication protocol allows for the exact
positioning of the DS1807 wiper’s position. Additionally, communication protocol allows for
DS1807
Addressable Dual Audio Taper Potentiometer
www.dalsemi.com GND114VCC
A2213SCL
A1312SDA411AGND
W0 5 10H16 9L17 8W1
DS1807 14-Pin DIP (300-mil)
DS1807E 14-Pin TSSOP (173-mil)
GND116VCC215NC314SCL413SDA512AGND
W0611H1710L18 9W1
DS1807S 16-Pin SOIC (300-mil)
See mech. Drawings Section
DS1807
The DS1807 is available in 14-pin DIP, SOIC, and TSSOP packages. The DS1807 is offered in industrial
temperature grades. The standard resistance of the DS1807 is 45 kΩ.
DEVICE OPERATIONThe DS1807 is an addressable, digitally controlled device that has two 65-position potentiometers. The
DS1807 potentiometers are logarithmic tapers providing a resolution or step size of 1 dB per step from
positions 0 through 63. The 64th position is the mute position and provides attenuation in excess of 90 dB.
Moving the potentiometer’s wiper from position 63 (or 63 dB of attenuation) to position 64 will provide a
step size in excess of 30 dB. A functional block diagram of the part is shown in Figure 1.
As stated, each potentiometer is composed of a 65 position resistor array. Two 8-bit registers, each
assigned to a respective potentiometer, are used to set wiper position on the resistor array. The wiper
terminal is multiplexed to one of 65 positions on the resistor array based on its corresponding 8-bit
register value.
Because the DS1807 has 65 positions, only seven bits of data are needed to set a wiper’s position. Bits 0
through 5 of the register are used to set the position on the resistor array. Bit 6 is used to set the wiper
position to the mute position and bit 7 is a don’t care. If the value of bit 6 is set equal to 1, regardless of
all other bit values, the wiper position of the respective potentiometer will be set to the mute position. An
example diagram of the wiper register and associated bit function is provided in Figure 2.
The DS1807 is designed to operate as an attenuator. (see Figure 3) As such, wiper position values are set
with respect to the amount of attenuation desired. For example, if the user wishes to attenuate an
incoming signal by 6 dB, the wiper position register value(s) should be set to binary (0000 0110).
The H0 and H1 terminals of the DS1807 have wiper position values (binary) 0000 0000. These terminals
provide 0 dB of attenuation for the input signal. The L0 and L1 terminals provide the greatest attenuation
of the input signal. They represent the mute positions for the DS1807 and have wiper position values
(binary) 0100 0000 or greater.
On power-up, the serial port is stable and active within 10 microseconds. Additionally, DS1807 wiper
positions will be set to position 63 or (binary) 0011 1111, one position above mute. The user may then set
the wiper register to a desired value.
Communication with the DS1807 takes place over the 2-wire serial interface consisting of the bi-
directional data terminal, SDA, and the serial clock input, SCL. The 2-wire serial interface and chip
select inputs A0, A1, and A2 allow operation of up to eight devices in a bus topology; with A0, A1, and
A2 being the physical address of the device. Complete details of the 2-Wire interface are discussed in the
section entitled “2-Wire Serial Data Bus.”
DS1807
DS1807 BLOCK DIAGRAM Figure 1
WIPER REGISTER CONFIGURATION Figure 2
DS1807
DS1807 ATTENUATOR CONFIGURATION Figure 3
ZERO-CROSSING DETECTIONThe DS1807 provides many features for digitally controlled audio applications. Zero-crossing detection is
useful in eliminating “zipper noise,” which is commonly associated with digital potentiometers. Zipper
noise (because it sounds like a zipper) is caused by discrete wiper position changes on the resistor array.
These changes cause discontinuities in the audio output signal which are manifested as audible pops
heard at the output of the audio chain. If subsequent amplification follows the digital potentiometer, this
audible noise can be quite disturbing. The DS1807 minimizes zipper noise by allowing wiper position
changes only during zero-crossings of the input signal.
The zero-crossing detection feature can be enabled or disabled via software. The complete software
command for enabling or disabling zero-crossing is discussed in the section, “2-wire serial data bus.”
When enabled, the zero-crossing detection feature allows independent wiper changes within a 50
millisecond time window when the Hx and Lx (where x = 0 or 1) terminals have equal potentials. The 50
millisecond time window begins once the DS1807 has responded with an ACKNOWLEDGE after a
“write potentiometer “ command. The STOP condition is discussed in the following section.
If at 50 milliseconds the DS1807 has not detected a zero-crossing (Hx - Lx = 0), the wiper position of the
potentiometer(s) will change regardless of the state of the input signal.
When the zero-crossing detection feature is not activated, the DS1807 will allow movement to the new
wiper position as soon as the ACKNOWLEDGE condition has been issued by the master controlling
device.
The DS1807 is designed to provide the zero-crossing detection feature when initially powered. If this
feature is not to be used, it must be deactivated once the device has reached a fully powered condition.
2-WIRE SERIAL DATA BUSThe DS1807 supports a bi-directional 2-wire bus and data transmission protocol. A device that sends data
on the bus is defined as a transmitter, and a device receiving data as a receiver. The device that controls
the message is called a “master.” The devices that are controlled by the master are “slaves.” The bus must
be controlled by a master device which generates the serial clock (SCL), controls the bus access, and
generates the START and STOP conditions. The DS1807 operates as a slave on the 2-wire bus.
Connections to the bus are made via the open-drain I/O line, SDA, and the serial clock line, SCL.
The following bus protocol has been defined (See Figure 4).Data transfer may be initiated only when the bus is not busy.
DS1807
2-WIRE DATA TRANSFER OVERVIEW Figure 4Accordingly, the following bus conditions have been defined:
Bus not busy: Both data and clock lines remain HIGH.
Start data transfer: A change in the state of the data line, from HIGH to LOW, while the clock is
HIGH, defines a START condition.
Stop data transfer: A change in the state of the data line, from LOW to HIGH, while the clock line isHIGH, defines the STOP condition.
Data valid: The state of the data line represents valid data when, after a START condition, the data lineis stable for the duration of the HIGH period of the clock signal. The data on the line must be changed
during the LOW period of the clock signal. There is one clock pulse per bit of data. Figure 4 details how
data transfer is accomplished on the 2-wire bus. Depending upon the state of the R/W bit, two types of
data transfer are possible:
Each data transfer is initiated with a START condition and terminated with a STOP condition. The
number of data bytes transferred between START and STOP conditions is not limited, and is determined
by the master device. The information is transferred byte-wise and each receiver acknowledges with a 9th
bit.
Within the bus specifications a regular mode (100 kHz clock rate) and a fast mode (400 kHz clock rate)
are defined. The DS1807 works in both modes.
Acknowledge: Each receiving device, when addressed, is obliged to generate an acknowledge after the
reception of each byte. The master device must generate an extra clock pulse which is associated with this
acknowledge bit.
A device that acknowledges must pull down the SDA line during the acknowledge clock pulse in such a
way that the SDA line is stable LOW during the HIGH period of the acknowledge related clock pulse. Of
course, setup and hold times must be taken into account. A master must signal an end of data to the slave
DS1807
1.
Data transfer from a master transmitter to a slave receiver. The first byte transmitted by the
master is the control byte (or slave address). Next follows a number of data bytes. The slave returns
an acknowledge bit after each received. byte.
Data transfer from a slave transmitter to a master receiver. The first byte (the slave address) is
transmitted by the master. The slave then returns an acknowledge bit . Next follows a number of data
bytes transmitted by the slave to the master. The master returns an acknowledge bit after all received
bytes other than the last byte. At the end of the last received byte, a ‘not acknowledge’ is returned.
The master device generates all of the serial clock pulses and the START and STOP conditions. A
transfer is ended with a STOP condition or with a repeated START condition. Since a repeated START
condition is also the beginning of the next serial transfer, the bus will not be released.
The DS1807 may operate in the following two modes:
1.
Slave receiver mode: Serial data and clock are received through SDA and SCL. After each byte isreceived, an acknowledge bit is transmitted. START and STOP conditions are recognized as the
beginning and end of a serial transfer. Address recognition is performed by hardware after reception
of the slave address and direction bit.
Slave transmitter mode: The first byte is received and handled as in the slave receiver mode.
However, in this mode the direction bit will indicate that the transfer direction is reversed. Serial data
is transmitted on SDA by the DS1807 while the serial clock is input on SCL. START and STOP
conditions are recognized as the beginning and end of a serial transfer.
SLAVE ADDRESSA control byte is the first byte received following the START condition from the master device. The
control byte consists of a 4-bit control code. For the DS1807, this is set as 0101 binary for read/write
operations. The next 3 bits of the control byte are the device select bits (A2, A1, and A0). They are used
by the master device to select which of eight devices are to be accessed. The select bits are in effect the
three least significant bits of the slave address. The last bit of the control byte (R/W) defines the operation
to be performed. When set to a 1 a read operation is selected, and when set to a 0 a write operation is
selected. Figure 5 shows the control byte structure for the DS1807.
Following the START condition, the DS1807 monitors the SDA bus checking the device type identifier
being transmitted. Upon receiving the 0101 address code and appropriate device select bits, the slave
device outputs an acknowledge signal on the SDA line.
COMMAND AND PROTOCOLThe command and protocol structure of the DS1807 allows the user to read or write the potentiometer(s).
The command structures for the part are presented in Figures 6 and 7. Potentiometer data values and
control and command values are always transmitted most significant bit (MSB) first. During
communications, the receiving unit always generates the acknowledgement.
READING THE DS1807As shown in Figure 6, the DS1807 provides one read command operation. This operation allows the user
to read both potentiometers. Specifically, the R/W bit of the control byte is set equal to a 1 for a read
operation. Communication to read the DS1807 begins with a START condition which is issued by the
master device. The control byte from the master device will follow the START condition. Once the
DS1807
When the master has received the ACKNOWLEDGE from the DS1807, the master can then begin to
receive potentiometer wiper data. The value of the potentiometer-0 wiper position will be the first
returned from the DS1807. Once the 8 bits of the potentiometer-0 wiper position have been transmitted,
the master will need to issue an ACKNOWLEDGE, unless it is the only byte to be read, in which case the
master issues a NOT ACKNOWLEDGE. If desired the master may stop the communication transfer at
this point by issuing the STOP condition. However, if the value of the potentiometer-1 wiper position
value is needed communication transfer can continue by clocking the remaining eight bits of the
potentiometer-1 value, followed by a NOT ACKNOWLEDGE. Final communication transfer is
terminated by issuing the STOP command. Again the flow of the read operation is presented in Figure 6.
WRITING THE DS1807A data flow diagram for writing the DS1807 is shown in Figure 7. The DS1807 has three commands
which are used to change the position(s) of the wiper. These include write pot-0, write pot-1, and write
pot-0/1. The write pot-0 command allows the user to write the value of potentiometer-0 and as an option
the value of potentiometer-1. The write-1 command allows the user to write the value of potentiometer-1
only. The last write command, write-0/1, allows the user to write both potentiometers to the same value
with one command and one data value being issued.
All the write operations begin with a START condition. Following the START condition, the master
device will issue the control byte. The read/write bit of the control byte will be set to 0 for writing the
DS1807. Once the control byte has been issued and the master receives the acknowledgment from the
DS1807, the command byte is transmitted to the DS1807. As mentioned above, there exist three write
operations that can be used with the DS1807. The binary value of each write command is shown in Figure
7 and also in Table 1.
2-WIRE WRITE COMMAND WORDS Table 1 ÁÁÁÁÁÁÁ
COMMANDCOMMAND VALUEWrite Potentiometer-0101010 01
Write Potentiometer-1101010 10
Write Both Pots101011 11
Once the DS1807 has received the command byte, it will responds with an ACKNOWLEDGE. The
master can then write the corresponding data-byte associated with the command byte. When the DS1807
has received the data byte(s), it will respond with an acknowledgement. At this point the master device
should respond with the STOP condition.
ZERO-CROSSING DETECTION COMMAND WORDZero-crossing detection was described under the operation section of this document. As stated earlier,
zero-crossing detection must be deactivated or activated under software control. The command words
used to activate or deactivate the zero-crossing detection feature is shown in Table 2.
ZERO-CROSSING DETECTION COMMAND WORDS Table 2
COMMANDCOMMAND VALUEActivate Zero-Crossing101111 01
