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DS1848B-050 |DS1848B050MAXIMN/a58avaiDual Temperature-Controlled NV Variable Resistor & Memory
DS1848E-010 |DS1848E010DALLASN/a15000avaiDual Temperature-Controlled NV Variable Resistor & Memory
DS1848E-010 |DS1848E010MAXIMN/a100avaiDual Temperature-Controlled NV Variable Resistor & Memory
DS1848E-050 |DS1848E050MAXIMN/a280avaiDual Temperature-Controlled NV Variable Resistor & Memory
DS1848E-050 |DS1848E050DALLSAN/a2270avaiDual Temperature-Controlled NV Variable Resistor & Memory


DS1848E-010 ,Dual Temperature-Controlled NV Variable Resistor & MemoryFEATURES Two linear taper, temperature-controlledvariable resistors SDA 1 14 Vcc DS184 ..
DS1848E-010 ,Dual Temperature-Controlled NV Variable Resistor & MemoryDS1848Dual Temperature-ControlledNV Variable Resistor & MemoryPIN ASSIGNMENT
DS1848E-010+ ,Dual Temperature-Controlled NV Variable Resistor & MemoryFEATURES Two linear taper, temperature-controlled variable resistors SDA 1 14 Vcc ..
DS1848E-010+T&R ,Dual Temperature-Controlled NV Variable Resistor & MemoryPIN DESCRIPTIONS Name TSSOP BGA Description V 14 A3 Power Supply Terminal. The DS1848 ..
DS1848E-050 ,Dual Temperature-Controlled NV Variable Resistor & MemoryPIN DESCRIPTIONSName TSSOP BGA DescriptionV 14 A3 Power Supply Terminal. The DS1848 wi ..
DS1848E-050 ,Dual Temperature-Controlled NV Variable Resistor & MemoryPIN DESCRIPTIONSName TSSOP BGA DescriptionV 14 A3 Power Supply Terminal. The DS1848 wi ..
DZ2J110 ,Zener DiodesAbsolute Maximum Ratings Ta = 25 C Panasonic SMini2-F5-BJEITA SC-90AParameter Symbol Rating UnitR ..
DZD9.1 ,0.2W Zener DiodesElectrical Characteristics at Ta = 25˚CZener voltage VZ will be subdivided into X, Y, Z at your req ..


DS1848B-050-DS1848E-010-DS1848E-050
Dual Temperature-Controlled NV Variable Resistor & Memory
FEATURESTwo linear taper, temperature-controlled
variable resistorsDS1848-050One 50k�, 256 positionOne 10k�, 256 positionDS1848-010Two 10k�, 256 positionResistor settings changeable every 2°CAccess to temperature data and devicecontrol via a 2-wire interfaceOperates from 3V or 5V suppliesPackaging: 14-pin TSSOP, 16-ball CSBGAOperating temperature: -40ºC to +95ºCProgramming temperature: 0ºC to +70ºC128 bytes of user EEPROM
PIN ASSIGNMENT
DESCRIPTION

The DS1848 Dual Temperature-Controlled Nonvolatile (NV) Variable Resistor consists of two 256-
position linear, variable resistors. The DS1848-050 consists of one 10k��and one 50k���while the
DS1848-010 consists of two 10k���resistors; both incorporate a direct-to-digital temperature sensor. The
device provides an ideal method for setting and temperature-compensating bias voltages and currents in
control applications using a minimum of circuitry.
The variable resistors settings are stored in EEPROM memory and can be accessed over the industrystandard 2-wire serial bus. The value of each variable resistor is determined by a temperature-addressed
look-up table, which can assign a unique value to each resistor for every 2°C increment over the -40°C to
+95°C range. The output of the digital temperature sensor is also available as a 13-bit, 2’s complement
value over the serial bus. The interface I/O pins consist of SDA and SCL.
DS1848
Dual Temperature-Controlled
NV Variable Resistor & Memory
DS1848
PIN DESCRIPTIONS
Name TSSOP BGADescriptionVCC
14 A3Power Supply Terminal. The DS1848 will support supply
voltages ranging from +3.0V to +5.5V.
GND
7 D1Ground Terminal.
SDA
1 B22-Wire Serial Data Interface. The serial data pin is for serial datatransfer to and from the DS1848. The pin is open drain and may
be wire-ORed with other open drain or open collector interfaces.
SCL
2 A22-Wire Serial Clock Input. The serial clock input is used to
clock data into the DS1848 on rising edges and clock data out on
falling edges.WP6 C1Write Protect Input. If open or set to logic 1, all memory, control
registers, and Look-up tables are write protected. If set to a logic 0, the
device is not write protected and can be written to. The WP pin is pulled
high internally.3 A1Address Input. Pins A0, A1, and A2 are used to specify theaddress of each DS1848 when used in a multi-dropped
configuration.4 B1Address Input.5 C2Address Input.13 A4High terminal of Resistor 0. For both resistors, it isnot required that the high terminal be connected to a potential
greater than the low terminal. Voltage applied to the high terminal
of each resistor cannot exceed VCC, or go below ground.11 B3High terminal of Resistor 1.8 D3Low terminal of Resistor 0. For both resistors, it isnot required that the low terminal be connected to a potential less
than the high terminal. Voltage applied to the low terminal of each
resistor cannot exceed VCC, or go below ground.10 C4Low terminal of Resistor 1.9 D4No Connect.NC12 B4No Connect. C3No Connect. D2No Connect.
DS1848
DS1848 BLOCK DIAGRAM Figure 1
SDA
SCL
Vcc
Gnd
0h
7Fh
47h
DS1848
DS1848
DS1848
PROGRAMMING THE LOOK-UP TABLE (LUT)

The following equation can be used to determine which resistor position setting, 00h – FFh, should be
written in the LUT to achieve a given resistance at a specific temperature.�����������������2251),,(CzCyxCRpos
DS1848-050
� = 3.78964 for the 50k� resistor
� = 19.74866 for the 10k� resistor
DS1848-010
� = 8.394533 for both 10k� resistors
R = resistance desired at the output terminal
C = temperature in degrees Celsius
u, v, w, x, y, and z are calibration constants programmed into each of the corresponding look-up tables.
Their addresses and LSB values are given in Table 1 below. Resistor 1 variables are found in Look-Up
table 1 of the EEPROM, and Resistor 2 variables are found in Look-Up Table 2. After these values areread, they should be overwritten with the appropriate temperature specific resistance settings. Copies of
these values can also be found in the User EEPROM memory.
LOOK-UP VARIABLE ADDRESSES Table1

When shipped from the factory, all other memory locations in the LUTs are programmed to FFh (except
bytes 00h-07h of Table 1 and 2 which may be factory programmed to values other than FFh).
Note: Memory locations 44h – 47h, which cover the temperature range (+96ºC to +102ºC), are outside

of the specified operating temperature range (-40ºC to +95ºC). However, the values stored in these
locations will act as valid resistance settings if the temperature exceeds +95ºC. Therefore, DallasSemiconductor recommends that the user program a resistance value into all LUT locations. Failure to do
so will result in the part being set to the default value.
DS1848
TEMPERATURE CONVERSION

The direct-to-digital temperature sensor measures temperature through the use of an on-chip temperature
measurement technique with an operating range from -40°C to +95°C. Temperature conversions are
initiated upon power-up, and the most recent result is stored in address locations E2h and E3h, which are
updated every 10ms. Temperature conversion will not occur during an active read or write to memory.
The value of each resistor is determined by the temperature-addressed look-up table that assigns a unique
value to each resistor for every 2°C increment with a 1°C hysteresis at a temperature transition over the
operating temperature range. This can be seen in Figure 2.
TEMPERATURE CONVERSION HYSTERESIS Figure 2
EXAMPLE TEMPERATURE READINGS Table 2

2 4 6 8 10 12
TEMPERATURE (C)
M6
MEMO
LO
CAT
DS1848
2-WIRE OPERATION
Clock and Data Transitions: The SDA pin is normally pulled high with an external resistor or device.

Data on the SDA pin may only change during SCL low time periods. Data changes during SCL high
periods will indicate a start or stop conditions depending on the conditions discussed below. Refer to the
timing diagram (Figure 4) for further details.
Start Condition: A high-to-low transition of SDA with SCL high is a start condition that must precede

any other command. Refer to the timing diagram (Figure 4) for further details.
Stop Condition:
A low-to-high transition of SDA with SCL high is a stop condition. After a readsequence, the stop command places the DS1848 into a low-power mode. Refer to the timing diagram
(Figure 4) for further details.
Acknowledge: All address and data byte are transmitted via a serial protocol. The DS1848 pulls the SDA

line low during the ninth clock pulse to acknowledge that it has received each word.
Standby Mode: The DS1848 features
a low-power mode that is automatically enabled after power-on,
after a stop command, and after the completion of all internal operations.
2-Wire Interface Reset: After any interruption in protocol, power loss, or system reset, the
followingsteps reset the DS1848.Clock up to nine cycles.Look for SDA high in each cycle while SCL is high.Create a START condition while SDA is high.
Device Addressing:
The DS1848 must receive an 8-bit device address word following a START
condition to enable a specific device for a read or write operation. The address word is clocked into the
DS1848 MSB to LSB. The address word consists of Ah (10106) followed by A2, A1, and A0 then the
R/W bit. If the R/W bit is high, a read operation is initiated. If the R/W is low, a write operation isinitiated. For a device to become active, the values of A2, A1 and A0 must be the same as the hard-wired
address pins on the DS1848. Upon a match of written and hard-wired addresses, the DS1848 will output a
zero for one clock cycle as an acknowledge. If the address does not match, the DS1848 returns to a low-
power mode.
Write Operations:
After receiving a matching address byte with the R/W bit set low, the device goes
into the write mode of operation. The master must transmit an 8-bit EEPROM memory address to the
device to define the address where the data is to be written. After byte has been received, the DS1848 will
transmit a zero for one clock cycle to acknowledge the receipt of the address. The master must then
transmit an 8-bit data word to be written into this address. The DS1848 will again transmit a zero for oneclock cycle to acknowledge the receipt of the data. At this point, the master must terminate the write
operation with a STOP condition. The DS1848 then enters an internally timed write process tw to the
EEPROM memory. All inputs are disabled during this byte write cycle.
The DS1848 is capable of an 8-byte page write. A page write is initiated the same way as a byte write, butthe master does not send a STOP condition after the first byte. Instead, after the slave acknowledges
receipt of the data byte, the master can send up to seven more bytes using the same nine-clock sequence.
DS1848
The master must terminate the write cycle with a STOP condition or the data clocked into the DS1848
will not be latched into permanent memory.
Acknowledge Polling: Once the internally-timed write has started and the DS1848 inputs are disabled,
acknowledge polling can be initiated. The process involves transmitting a START condition followed by
the device address. The R/W bit signifies the type of operation that is desired. The read or write sequence
will only be allowed to proceed if the internal write cycle has completed and the DS1848 responds with a
zero.
Read Operations: After receiving a matching address byte with the R/W bit set high, the device goes

into the read mode of operation. There are three read operations: current address read, random read, and
sequential address read.
CURRENT ADDRESS READ

The DS1848 has an internal address register that maintains the address used during the last read or write
operation, incremented by one. This data is maintained as long as VCC is valid. If the most recent addresswas the last byte in memory, then the register resets to the first address. This address stays valid between
operations as long as power is available.
Once the device address is clocked in and acknowledged by the DS1848 with the R/W bit set to high, the
current address data word is clocked out. The master does not respond with a zero, but does generate aSTOP condition afterwards.
RANDOM READ

A random read requires a dummy byte write sequence to load in the data word address. Once the device
and data address bytes are clocked in by the master and acknowledged by the DS1848, the master must
generate another START condition. The master now initiates a current address read by sending the deviceaddress with the read/write bit set high. The DS1848 will acknowledge the device address and serially
clocks out the data byte.
SEQUENTIAL ADDRESS READ

Sequential reads are initiated by either a current address read or a random address read. After the master
receives the first data byte, the master responds with an acknowledge. As long as the DS1848 receivesthis acknowledge after a byte is read, the master may clock out additional data words from the DS1848.
After reaching address FFh, it resets to address 00h.
The sequential read operation is terminated when the master initiates a stop condition. The master does
not respond with a zero.
For a more detailed description of 2-wire theory of operation, refer to the next section.
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