DS1844SN-010 [MAXIM]

Digital Potentiometer, 4 Func, 10000ohm, 2-wire Serial Control Interface, 64 Positions, PDSO20, 0.300 INCH, SOIC-20;
DS1844SN-010
型号: DS1844SN-010
厂家: MAXIM INTEGRATED PRODUCTS    MAXIM INTEGRATED PRODUCTS
描述:

Digital Potentiometer, 4 Func, 10000ohm, 2-wire Serial Control Interface, 64 Positions, PDSO20, 0.300 INCH, SOIC-20

光电二极管 转换器
文件: 总14页 (文件大小:289K)
中文:  中文翻译
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DS1844  
Quad Digital Potentiometer  
www.dalsemi.com  
FEATURES  
PIN ASSIGNMENT  
§ Four independent, digitally controlled 64-  
position potentiometers  
§ Two interface control options  
PS  
H2  
1
20  
19  
18  
17  
16  
15  
14  
13  
12  
11  
VCC  
2
H1  
H3  
3
H0  
-
-
5-wire serial  
2-wire addressable  
W3  
4
W0  
§ Standard resistance values  
L3  
5
L0  
-
-
-
DS1844-010 10 kW  
DS1844-050 50 kW  
DS1844-100 100 kW  
L2  
6
L1  
W2  
7
W1  
R/W, A0  
A2, RST  
GND  
8
SCL, CLK  
SDA, DIN  
A1, DOUT  
§ Mixed resistor value combinations (contact  
factory for availability)  
§ Operating Temperature Range  
- Industrial: -40°C to +85°C  
9
10  
20-Pin DIP (300-mil)  
20-Pin SOIC (300-mil)  
20-Pin TSSOP (173-mil)  
PIN DESCRIPTION  
VCC  
PS  
- 2.7V to 5.5V  
- Port Select  
A0, A1, A2 - Device Select Pins (2-Wire)  
SDA  
SCL  
- Serial Data I/O (2-Wire)  
- Serial Clock (2-Wire)  
R/  
- Read/Write enable (5-Wire)  
W
- Serial Port Reset Input (5-Wire)  
- Serial Port Data Input (5-Wire)  
- Serial Port Clock Input (5-Wire)  
- Cascade Data Output (5-Wire)  
- High-end Terminal of Pot  
- Low-end Terminal of Pot  
- Wiper Terminal of Pot  
RST  
DIN  
CLK  
DOUT  
H0-H3  
L0-L3  
W0-W3  
GND  
- Ground  
DESCRIPTION  
The DS1844 Quad Digital Potentiometer is a four-channel, digitally controlled linear potentiometer. Each  
potentiometer is comprised of 63 equi-resistive sections and has three terminals accessible to the user.  
These include the high side terminals, HX, the wiper terminals, WX, and the low-side terminals, LX. The  
wiper position on the resistor ladder is selected via an 8-bit register value. Communication and control of  
the device are supported by two types of serial interface. These include a 5-wire I/O shift register  
interface and a 2-wire addressable interface.  
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The DS1844 is available in standard 10 kW, 50 kW, and 100 kW versions. Mixed resistor combinations  
are also available through custom setups. The DS1844 is specified to operate over the industrial  
temperature range: -40°C to +85°C. Packages for the DS1844 include 20-pin DIPs, SOICs, and TSSOPs.  
OPERATION  
The DS1844 contains four 64-position potentiometers. Each potentiometer is independent and has three  
accessible terminals, which include HX, LX, and WX. Each potentiometer is comprised of 63 individual  
resistor elements. Between each resistor element is a tap-point that is multiplexed to the wiper terminal,  
WX. Additionally, the wiper terminal can be multiplexed directly to the end-terminals, HX and LX.  
The DS1844 supports two interface control options. Both options allow for the direct placement of the  
wiper position on the resistor ladder. Each wiper has an associated 6-bit register used to hold its positional  
value.  
The DS1844 is a volatile device and will always power-up with the wiper positions set to mid-tap  
(position 32-decimal). The end-terminal HX will have wiper position value 63-decimal and the LX terminal  
will have wiper position value 0-decimal. Because the DS1844 is a 64-position device only 6 bits of data  
are necessary to write a wiper’s value. However, communication with the DS1844 will require using a  
full 8 bits, with the remaining 2 bits specifying the potentiometer selected. A discussion of proper  
communication protocol is provided under the section entitled Serial Port Operation. A block diagram of  
the DS1844 is shown in Figure 1.  
SERIAL PORT OPERATION  
As stated, the DS1844 can support two types of serial interface control. This includes a 5-wire serial  
interface and a 2-wire addressable interface. The type interface supported during operation is selectable  
via the port select input pin, PS. Additionally, certain pins provide dual functionality dependent on the  
serial port selected. The pin description table lists pin functionality according to the interface selected.  
5-Wire Serial Port Control  
The 5-wire serial interface provides an 8-bit I/O shift register for loading and reading wiper data. The 5-  
wire serial interface control is selected when the port select input, PS, is in a low state. This interface is  
controlled by the signals RST , DIN, DOUT, CLK, and R/ W . Timing diagrams for the 5-wire serial port  
can be found in Figure 3. Timing information for the 5-wire serial port is provided in the AC Electrical  
Characteristics table for 5-wire serial communications.  
Data is loaded MSB first and in multiples of 8 bits. The 8-bit data to specify wiper position has the format  
or protocol as that shown in Figure 2. The 8-bit data is divided into potentiometer select data and wiper  
position value. The 6 least significant bits of data specify the wiper position value while the 2 most  
significant bits specify the potentiometer to be loaded. This allows the interface control logic/protocol to  
provide order independent potentiometer loading, as well as variable-length data loads.  
As stated earlier, the 5-wire serial port is selected when the PS input is in a low state. If the device will  
only be used in the 5-wire mode, the PS input can be tied directly to ground. Communication via the 5-  
wire interface is enabled when RST is in a high state. A low-to-high transition on the RST indicates the  
start of a communication transaction with the DS1844. While RST is high, data can be read or written to  
the part. Data will be read or written dependent on the state of the read-write enable input, R/ W . The  
state of R/ W must be stable before a low-to-high transition on RST . Once the RST input has begun a  
communication transaction, the serial port will ignore any transitions on the R/ W input.  
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When writing data, the R/ W input should be in a low state. Once RST has activated the port, a data bit is  
latched (or valid) on the low-to-high transition of the CLK signal. Once, eight low-to-high transitions  
have occurred on the CLK input, the associated 8-bit data block will be loaded as the wiper’s value on the  
falling edge of the eighth clock pulse. Potentiometer wiper values can be loaded in any order. Also,  
potentiometer wiper data can be loaded 1, 2, 3, or 4 bytes at a time. When  
low, the 5-wire port will be disabled.  
transitions from high to  
RST  
While RST is high and R/ W is low, (the write or load state) the cascade data output, DOUT will be  
inhibited; preventing the passing of data from DIN to DOUT . However, when RST is low data is passed  
directly from DIN to DOUT  
.
When reading data, the R/ W input should be in a high state. Once RST has enabled the port, data can be  
clocked out of the device and will appear on the DOUT terminal. A data bit will be valid on the falling  
edge of a clock pulse after a maximum time period of 20 ns (of that falling edge). Data will appear on  
DOUT most significant bit (MSB) first and starting with potentiometer-0, followed by potentiometer-1 and  
so forth.  
2-Wire Addressable Serial Port Control  
The 2-wire serial port interface supports a bi-directional data transmission protocol with device  
addressing. 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 DS1844 operates as  
a slave on the two-wire bus. Connections to the bus are made via the open-drain I/O lines SDA and SCL.  
The 2-wire serial port is selected when the port select input, PS, is in a high-state. The following I/O  
terminals control the 2-wire serial port: SDA, SCL, A0, A1, A2, PS=1. Timing diagrams for the 2-wire  
serial port can be found in Figures 4 through 8. Timing information for the 2-wire serial port is provided  
in the AC Electrical Characteristics table for 2-wire serial communications.  
The following bus protocol has been defined (See Figure 4).  
-
-
Data transfer may be initiated only when the bus is not busy.  
During data transfer, the data line must remain stable whenever the clock line is HIGH. Changes  
in the data line while the clock line is high will be interpreted as control signals.  
Accordingly, 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 is  
HIGH defines the STOP condition.  
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Data valid: The state of the data line represents valid data when, after a START condition, the data line  
is stable for the duration of the HIGH period of the clock signal. The data on the line can 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 two-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 DS1844 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  
by not generating an acknowledge bit on the last byte that has been clocked out of the slave. In this case,  
the slave must leave the data line HIGH to enable the master to generate the STOP condition.  
1.  
Data transfer from a master transmitter to a slave receiver. The first byte transmitted by the master  
is the command/control byte. Next follows a number of data bytes. The slave returns an  
acknowledge bit after each received byte.  
2.  
Data transfer from a slave transmitter to a master receiver. The 1st byte (the command/control  
byte) 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’ can be returned.  
The master device generates all 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 DS1844 may operate in the following two modes:  
1.  
2.  
Slave receiver mode: Serial data and clock are received through SDA and SCL, respectively. After  
each byte is received, 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 (device) address and direction bit.  
Slave transmitter mode: The 1st 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 DS1844 while the serial clock is input on SCL. START and  
STOP conditions are recognized as the beginning and end of a serial transfer.  
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SLAVE ADDRESS  
A command/control byte is the 1st byte received following the START condition from the master device.  
The command/control byte consists of a 4-bit control code. For the DS1844, this is set as 0101 binary for  
read/write operations. The next 3 bits of the command/ control byte are the device select bits or slave  
address (A2, A1, A0). They are used by the master device to select which of eight devices is to be  
accessed. When reading or writing the DS1844, the device-select bits must match the device-select pins  
(A2, A1, A0). The last bit of the command/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 command/control byte structure for the DS1844.  
Following the START condition, the DS1844 monitors the SDA bus checking the device type identifier  
being transmitted. Upon receiving the 0101 control code, the appropriate device address bits, and the  
read/write bit, the slave device outputs an acknowledge signal on the SDA line.  
COMMAND AND PROTOCOL  
The command and protocol structure of the DS1844 allows the user to read or write the potentiometer(s).  
Additionally, the 2-wire command/protocol structure of the DS1844 will support eight different devices  
and a maximum of 32 channels that can be uniquely controlled. The command structures for the device  
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 DS1844  
As shown in Figure 6, the DS1844 provides one read command operation. This operation allows the user  
to read all potentiometers. Specifically, the R/W bit of the command/control byte is set equal to a 1 for a  
read operation. Communication to read the DS1844 begins with a START condition which is issued by  
the master device. The command/control byte from the master device will follow the START condition.  
Once the command/control byte has been received by the DS1844, the part will respond with an  
ACKNOWLEDGE. The read/write bit of the command/control byte, as stated, should be set equal to 1  
for reading the DS1844.  
When the master has received the ACKNOWLEDGE from the DS1844, 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 DS1844, followed by potentiometer-1 and so forth. 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 remaining potentiometers is needed, transfer can continue  
by clocking the 8 bits of the potentiometer-1 value, followed by an ACKNOWLEDGE, and so forth.  
Final communication transfer is terminated by issuing the STOP command. Again, the flow of the read  
operation is presented in Figure 6.  
Writing the DS1844  
A data flow diagram for writing the DS1844 is shown in Figure 7. The DS1844 has one write command  
that is used to change the position(s) of the wiper. The 2-wire serial interface write structure is similar to  
that of the 5-wire serial write. However, there are differences.  
All the write operations begin with a START condition. Following the START condition, the master  
device will issue the command/control byte. The read/write bit of the command/control byte will be set to  
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0 for writing the DS1844. Once the command/control byte has been issued and the master receives the  
acknowledgment from the DS1844, potentiometer wiper data is transmitted to the DS1844 by the master  
device.  
As in the case of the 5-wire serial protocol, a data byte for the DS1844 will contain potentiometer select  
data and wiper position value. The six least significant bits of data specify the wiper position value while  
the two most significant bits specify the potentiometer to be loaded. When the DS1844 has received the  
data byte, it will respond with an ACKNOWLEDGE. At this point, the new wiper value for the  
potentiometer selected will be updated in the DS1844. The master device, after the receipt of the  
ACKNOWLEDGE, can continue to transmit additional data bytes or if the transaction is complete  
respond with the STOP condition. Additionally, the DS1844 does not require a specific order for writing  
a particular potentiometer wiper's data. The 2-wire serial timing diagram is presented in Figure 8.  
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ABSOLUTE MAXIMUM RATINGS*  
Voltage on Any Pin Relative to Ground  
Operating Temperature  
-1.0V to +7.0V  
-40°C to +85°C  
Storage Temperature  
Soldering Temperature  
-55°C to +125°C  
260°C for 10 seconds  
* This is a stress rating only and functional operation of the device at these or any other conditions above  
those indicated in the operation sections of this specification is not implied. Exposure to absolute  
maximum rating conditions for extended periods of time may affect reliability.  
RECOMMENDED DC OPERATING CONDITIONS  
(-40°C to +85°C)  
PARAMETER  
Supply Voltage  
Resistor Inputs  
SYMBOL CONDITION MIN TYP MAX UNITS NOTES  
VCC  
+2.7  
+5.5  
V
V
1
L,H,W  
GND  
-0.5  
VCC  
1,12  
+0.5  
DC ELECTRICAL CHARACTERISTICS  
(-40°C to +85°C; VCC =2.7V to 5.5V)  
PARAMETER  
SYMBOL CONDITION  
MIN  
TYP MAX UNITS NOTES  
Supply Current Active  
Input Leakage  
ICC  
2
+1  
mA  
µA  
Ohms  
mA  
V
19  
ILI  
-1  
Wiper Resistance  
Wiper Current  
RW  
250  
500  
IW  
1
Input Logic 1  
VIH  
0.7VCC  
VCC+0.5  
0.3VCC  
VCC+0.5  
0.3VCC  
+10  
1,2  
1,2  
11  
GND-0.5  
Input Logic 0  
VIL  
V
Input Logic levels A0, A1,  
A2  
Input Logic 1  
0.7VCC  
V
GND-0.5  
Input Logic 0  
0.4<VI/O<0.9VDD  
Input Current each I/O pin  
-10  
µA  
µA  
Istby  
4
Standby Current  
15  
25  
40  
3V  
5V  
Low Level Output Voltage  
(SDA)  
VOL1  
VOL2  
CI/O  
tSP  
3 mA sink current  
6 mA sink current  
0.0  
0.0  
0.4  
0.6  
10  
V
V
I/O Capacitance  
pF  
ns  
Pulse width of spikes which  
must be suppressed by the  
input filter  
Fast Mode  
0
50  
22  
DOUT Output @ 2.4V  
DOUT Output @ 0.4V  
IOH  
IOL  
-1.0  
mA  
mA  
23,24  
23,24  
4
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ANALOG RESISTOR CHARACTERISTICS (-40°C to +85°C; VCC=2.7V to 5.5V)  
PARAMETER  
SYMBOL CONDITION  
MIN  
TYP MAX UNITS NOTES  
End-to-End Resistor  
Tolerance  
-20  
+20  
%
25  
Absolute Linearity  
-0.5  
+0.5  
LSB  
LSB  
16  
17  
13  
18  
Relative Linearity  
-0.25  
+0.25  
-3dB Cutoff frequency  
Temperature Coefficent  
fcutoff  
kHz  
750  
ppm/°C  
2-WIRE ADDRESSABLE INTERFACE  
AC ELECTRICAL CHARACTERISTICS  
(-40°C to +85°C; VCC=2.7V to 5.5V)  
PARAMETER  
SYMBOL CONDITION  
MIN  
TYP MAX UNITS NOTES  
Port Select Setup  
tSETUP  
fSCL  
30  
ns  
20,22  
SCL Clock Frequency  
0
0
400  
100  
kHz  
*,8  
**,22  
Bus Free Time Between  
STOP and START Condition  
tBUF  
tHD:STA  
tLOW  
tHIGH  
tHD:DAT  
tSU:DAT  
tR  
1.3  
4.7  
µs  
µs  
µs  
µs  
µs  
ns  
ns  
ns  
µs  
pF  
*,8  
**,22  
*,5,8  
**,22  
*,8  
Hold Time (repeated)  
START Condition  
0.6  
4.0  
Low Period of SCL Clock  
High Period of SCL Clock  
Data Hold Time  
1.3  
4.7  
**,22  
*,8  
0.6  
4.0  
**,22  
*,6,7,  
**,22  
*,8  
0
0
0.9  
Data Setup Time  
100  
250  
**,22  
*,9  
20+0.1CB  
Rise Time of Both SDA and  
SCL Signals  
300  
1000  
300  
**,22  
*,9  
20+0.1CB  
Fall Time of Both SDA and  
SCL Signals  
tF  
300  
**,22  
*,  
Setup Time for STOP  
Condition  
tSU:STO  
0.6  
4.0  
**,22  
9
Capacitive Load for each  
Bus Line  
CB  
400  
* fast mode  
** standard mode  
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5-WIRE SERIAL INTERFACE  
AC ELECTRICAL CHARACTERISTICS  
(-40°C to +85°C; VCC=2.7V to 5.5V)  
PARAMETER  
SYMBOL MIN  
TYP  
MAX  
UNITS  
NOTES  
Port Select Setup  
R/ Setup  
tSETUP  
tSETUP  
30  
30  
ns  
ns  
14, 21  
14, 21  
W
DC  
50  
30  
0
5
14, 15  
Clock Frequency  
Width of CLK Pulse  
Data Setup Time  
Data Hold Time  
fCLK  
tCH  
MHz  
ns  
14, 15  
14, 15  
14, 15  
14, 15  
tDC  
ns  
tCDH  
tDV  
ns  
Progapation Delay Time High to Low  
Level Clock to Output  
40  
50  
ns  
50  
50  
tCC  
tHLT  
tRLT  
tCR  
ns  
ns  
ns  
ns  
14, 15  
14, 15  
14, 15  
14, 15  
High to Clock Input High  
Low from Clock Input High  
Inactive  
RST  
RST  
RST  
125  
CLK Rise Time, CLK Fall Time  
NOTES:  
1.  
2.  
3.  
4.  
All voltages are referenced to ground.  
I/O pins of fast mode devices must not obstruct the SDA and SCL lines if VCC is switched off.  
ICC specified with SDA pin open.  
ISTBY specified with for VCC equal 3.0V and 5.0V and control port logic pins are driven to the  
appropriate logic levels. Appropriate logic levels specify that logic inputs are within a 0.5-volt of  
ground or VCC for the corresponding inactive state.  
5.  
6.  
After this period, the first clock pulse is generated.  
A device must internally provide a hold time of at least 300 ns for the SDA signal (referred to the  
VIH MIN of the SCL signal) in order to bridge the undefined region of the falling edge of SCL.  
7.  
8.  
The maximum tHD:DAT has only to be met if the device does not stretch the LOW period (tLOW ) of  
the SCL.  
A fast mode device can be used in a standard mode system, but the requirement tSU:DAT > 250 ns  
must then be met. This will automatically be the case if the device does not stretch the LOW  
period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must  
output the next data bit to the SDA line tRMAX + tSU:DAT = 1000+250=1250 ns before the SCL line  
is released.  
9.  
CB - total capacitance of one bus line in picofarads, timing referenced to (0.9)(VCC) and (0.1)  
(VCC).  
10.  
Typical values are for ta = 25°C and nominal supply voltage.  
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Address Inputs, A0, A1, and A2, should be tied to either VCC or GND depending on the desired  
address selections.  
11.  
12.  
13.  
Resistor inputs cannot go below GND by more than 0.5 volts or above VCC by more than 0.5  
volts.  
-3dB cutoff frequency characteristics for the DS1844 depend on potentiometer total resistance:  
DS1844-010; 1 MHz; DS1844-050; 200 kHz; DS1844-100; 100 kHz.  
14.  
15.  
See Figure 3, 5-wire timing diagram.  
For 5-wire control logic and VCC = 5V ±10%, maximum VIL = +0.8V. For VCC = 3.0V ±10%,VIL  
= +0.6V.  
16.  
Absolute linearity is used to measure expected wiper voltage versus measured wiper voltage as  
determined by wiper position. The DS1844 is specified to provide an absolute linearity of ± 0.5  
LSB.  
17.  
18.  
Relative linearity is used to determine the change in wiper voltage between two adjacent wiper  
positions. The DS1844 is specified to provide a relative linearity of ± 0.25 dB.  
When used as a rheostat or variable resistor the temperature coefficient applies: 650 ppm/°C.  
When used as a voltage divider or potentiometer, the effective temperature coefficient approaches  
30 ppm/°C.  
19.  
20.  
Maximum ICC active current is dependent on clock rates during serial port activity. Maximum  
ICC active current is specified for 5 MHz clock rates, and worse case input logic levels.  
tSETUP is the minimum time required for the port select input, PS, to be stable before any activity  
on SDA or SCL terminals.  
21.  
tSETUP is the minimum time required for the port select input, PS, and/or the R/  
input to be  
W
stable before  
becomes active (or goes to a high state).  
RST  
22.  
23.  
24.  
See Figure 8, 5-wire timing diagram.  
Measured with load as shown in Figure 9.  
Valid for VCC = 5V only.  
25.  
Valid at 25°C only.  
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DS1844 BLOCK DIAGRAM Figure 1  
WIPER REGISTER CONFIGURATION Figure 2  
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5-WIRE SERIAL TIMING DIAGRAM Figure 3 (A), (B)  
(A) WRITING DATA TO THE DS1844  
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DS1844  
2-WIRE DATA TRANSFER OVERVIEW Figure 4  
START  
COMMAND/CONTROL BYTE Figure 5  
2-WIRE READ PROTOCOL Figure 6  
2-WIRE WRITE PROTOCOLS Figure 7  
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2-WIRE TIMING DIAGRAM Figure 8  
DIGITAL OUTPUT LOAD Figure 9  
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