Dallas DS1847 Dual temperature-controlled nv variable resistor Datasheet

DS1847
Dual Temperature-Controlled
NV Variable Resistor
www.maxim-ic.com
FEATURES
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PIN ASSIGNMENT
Two linear taper, temperature-controlled
variable resistors
DS1847-050
- One 50kW, 256 position
- One 10kW, 256 position
DS1847-010
- Two 10kW, 256 position
Resistor settings changeable every 2°C
Access to temperature data and device
control via a 2-wire interface
Operates from 3V or 5V supplies
Packaging: 14-pin TSSOP, 16-ball CSBGA
Operating temperature: -40ºC to +95ºC
Programming temperature: 0ºC to +70ºC
SDA
1
14
Vcc
SCL
2
13
H0
A0
3
12
NC
A1
4
11
H1
A2
5
10
L1
WP
6
9
NC
GND
7
8
L0
14-Pin TSSOP (173-mil)
Top View
A
B
C
D
1
2
3
4
16-Ball CSBGA (4mm x 4mm)
DESCRIPTION
The DS1847 Dual Temperature-Controlled Nonvolatile (NV) Variable Resistor consists of two 256position linear, variable resistors. The DS1847-050 consists of one 10kW and one 50kW, while the
DS1847-010 consists of two 10kW 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 industry
standard 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.
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081502
DS1847
PIN DESCRIPTIONS
Name TSSOP BGA
VCC
14
A3
GND
SDA
7
1
D1
B2
SCL
2
A2
WP
6
C1
A0
3
A1
A1
A2
H0
4
5
13
B1
C2
A4
H1
L0
11
8
B3
D3
L1
NC
NC
NC
NC
10
9
12
C4
D4
B4
C3
D2
Description
Power Supply Terminal. The DS1847 will support supply
voltages ranging from +3.0V to +5.5V.
Ground Terminal.
2-Wire Serial Data Interface. The serial data pin is for serial data
transfer to and from the DS1847. The pin is open drain and may
be wire-ORed with other open drain or open collector interfaces.
2-Wire Serial Clock Input. The serial clock input is used to
clock data into the DS1847 on rising edges and clock data out on
falling edges.
Write 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.
Address Input. Pins A0, A1, and A2 are used to specify the
address of each DS1847 when used in a multi-dropped
configuration.
Address Input.
Address Input.
High terminal of Resistor 0. For both resistors, it is
not 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.
High terminal of Resistor 1.
Low terminal of Resistor 0. For both resistors, it is
not 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.
Low terminal of Resistor 1.
No Connect.
No Connect.
No Connect.
No Connect.
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DS1847
DS1847 BLOCK DIAGRAM Figure 1
WP
A0
A1
A2
SDA
0h
2-Wire
Interface
SCL
VCC
Gnd
Digital
Temperature
Sensor
47h
72x8 bit
EEPROM
Resistor 0
Look-up Table
(Table 1)
72x8 bit
EEPROM
Resistor 1
Look-up Table
(Table 2)
E0h
Table Select Byte
E1h
Configuration
Byte
E2h
Temperature
MSB Byte
E3h
Temperature
LSB Byte
E4h
Address Pointer
E5hE6h
User Memory
E7h
Internal Address
Select
E8hEFh
User Memory
F0h
Resistor 0 Setting
F1h
Resistor 1 setting
F2hFFh
User Memory
3 of 17
256 Position
DigitallyControlled
10kW or 50kW
Resistor 0
H0
256 Position
DigitallyControlled 10kW
Resistor 1
H1
L0
L1
DS1847
Memory
Location
00h to 47h
Name of Location
Function of Location
User Defined Look-Up Table
(LUT)
This block contains the user defined temperature
settings of the resistors. Values between 00h and
FFh can be written to either table to set the 256
position variable resistors. The first address
location, 00h, is used to set the resistor at -40°C.
Each successive memory location will contain the
resistor setting for the previous temperature +2°C.
For example, memory address 01h is the address
that will set the resistor in a –38°C environment.
(Table Select
Byte, E0h, must
be set to 01h or
02h to access the
Look-Up Tables)
E0h
Table Select Byte
E1h
Configuration Byte
For default memory settings and programming
the look-up table, refer to the Programming the
Look-Up Table (LUT) section of the datasheet.
Writing to this byte determines which of the two
72x8 EEPROM look-up tables is selected for
reading or writing.
01h (Look-Up Table 1 selected)
02h (Look-Up Table 2 selected)
TAU TEN AEN
TAU – Temperature/Address Update
TEN – Temperature Update Enable
AEN – Address Update Enable
Default setting is 03h, TAU = 1, TEN = 1 and
AEN = 1.
TAU becomes a 1 after a temperature and address
update has occurred as a result of a temperature
conversion. The user can write this bit to 0 and
check for a transition from 0 to 1 in order to
verify that a conversion has occurred.
If TEN = 0, the temperature conversion feature is
disabled. The user sets the resistor in “manual
mode” by writing to addresses F0h and
F1h to control resistors 0 and 1, respectively.
With AEN = 0 the user can operate in a test
mode. Address updates made from the
temperature sensor will cease. The user can load a
memory location into E4h and verify that the
values in locations F0h and F1h are the expected
user-defined values.
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DS1847
Memory
Location
E2h
Name of Location
Function of Location
Temperature MSB
This byte contains the MSB of the 13-bit 2s
complement temperature output from the
temperature sensor.
S 27 26 25 24 23 22 21
E3h
Temperature LSB
This byte contains the LSB of the 13-bit 2s
complement temperature output from the
temperature sensor.
20 2-1 2-2 2-3 2-4 X X X
E4h
Address Pointer
E5h to E6h
E7h
User Memory
Address Select
For example temperature readings, refer to Table
2.
Calculated, current resistor address (0h – 47h).
The user-defined resistor setting at this location in
the respective look-up table will be loaded into
F0h and F1h to set the two resistors.
General purpose user memory (SRAM)
Internal or external device address select. This
byte allows the user to use the external address
pins or an internal register location to determine
the device address.
A2 A1 A0 ENB
ENB = 0 and external A2, A1, A0 grounded,
device will use internal address bits (A2, A1, A0)
in this register
ENB = 1, external A2, A1, A0 = any setting,
device will use external address pins
E8h to EFh
User Memory
F0h
Resistor 0 Setting
F1h
Resistor 1 Setting
F2h to FFh
User memory
Default setting is 01h. The device uses external
pins to determine its address.
General purpose user memory (SRAM)
In the user-controlled setting mode, this block
contains the resistor 0 setting.
In the user-controlled setting mode, this block
contains the resistor 1 setting.
General purpose user memory (SRAM)
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DS1847
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.
pos (a , R , C ) =
[
R - u · 1 + v · (C - 25 ) + w · (C - 25 )
(x ) · [1 + y · (C - 25 ) + z · (C - 25 )
2
2
]
]-a
DS1847-050
a = 3.78964 for the 50kW resistor
a = 19.74866 for the 10kW resistor
DS1847-010
a = 8.394533 for both 10kW 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. 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 are read, they
should be overwritten with the appropriate temperature-specific resistance settings.
LOOK-UP VARIABLE ADDRESSES Table 1
Address in
LUT (HEX)
28 – 29
2A – 2B
2C – 2D
2E – 2F
30 – 31
32 – 33
Variable
LSB
u
v
w
x
y
z
2-8
10-6
10-9
2-8
10-7
10-10
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, Dallas
Semiconductor recommends that the user programs a resistance value into all LUT locations. Failure to
do so will result in the part being set to the default value.
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DS1847
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
M6
MEMORY LOCATION
M5
Increasing temp
Decreasing temp
M4
M3
M2
M1
2
4
6
8
10
TEMPERATURE (C)
12
EXAMPLE TEMPERATURE READINGS Table 2
TEMP
+95ºC
+25.0625ºC
-10.125ºC
-40ºC
BINARY DATA
0010 1111 1000 0000
0000 1100 1000 1000
1111 1010 1111 0000
1110 1100 0000 0000
HEX DATA
2F80h
0C88h
FAF0h
EC00h
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DS1847
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 read
sequence, the stop command places the DS1847 into a low-power mode. Refer to the timing diagram
(Figure 4) for further details.
Acknowledge Bit: All address and data byte are transmitted via a serial protocol. The DS1847 pulls the
SDA line low during the ninth clock pulse to acknowledge that it has received each word.
Standby Mode: The DS1847 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 following
steps reset the DS1847:
1. Clock up to nine cycles.
2. Look for SDA high in each cycle while SCL is high.
3. Create a START condition while SDA is high.
Device Addressing: The DS1847 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
DS1847 MSB to LSB. The address word consists of Ah (1010) followed by A2, A1, and A0 then the
R/W (READ/WRITE) bit. If the R/W bit is high, a read operation is initiated. If the R/W is low, a write
operation is initiated. 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 DS1847. Upon a match of written and hard-wired addresses, the DS1847
will output a zero for one clock cycle as an acknowledge. If the address does not match, the DS1847
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 this byte has been received, the DS1847
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 DS1847 will again transmit a zero for one
clock cycle to acknowledge the receipt of the data. At this point, the master must terminate the write
operation with a STOP condition. The DS1847 then enters an internally timed write process tw to the
EEPROM memory. All inputs are disabled during this byte write cycle.
The DS1847 is capable of an 8-byte page write. A page write is initiated the same way as a byte write, but
the 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.
8 of 17
DS1847
The master must terminate the write cycle with a STOP condition or the data clocked into the DS1847
will not be latched into permanent memory.
Acknowledge Polling: Once the internally-timed write has started and the DS1847 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 DS1847 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 DS1847 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 address
was 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 DS1847 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 a
STOP 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 DS1847, the master must
generate another START condition. The master now initiates a current address read by sending the device
address with the read/write bit set high. The DS1847 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 DS1847 receives
this acknowledge after a byte is read, the master may clock out additional data words from the DS1847.
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.
9 of 17
DS1847
2-WIRE SERIAL PORT OPERATION
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 that generates the serial clock
(SCL), controls the bus access, and generates the START and STOP conditions. The DS1847 operates as
a slave on the 2-wire bus. Connections to the bus are made via the open-drain I/O lines SDA and SCL.
The following I/O terminals control the 2-wire serial port: SDA, SCL, A0, A1, A2. Timing diagrams for
the 2-wire serial port can be found in Figures 3 and 4. 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:
§
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.
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. Figures 3 and 4 detail
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
ninth bit.
Within the bus specifications a regular mode (100kHz clock rate) and a fast mode (400kHz clock rate) are
defined. The DS1847 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 that 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 a 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
10 of 17
DS1847
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 master transmits the first byte (the
command/control byte) to the slave. 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 DS1847 may operate in the following two modes:
1. 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.
2. 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 DS1847, while the serial clock is input on SCL. START and STOP
conditions are recognized as the beginning and end of a serial transfer.
3. Slave Address: Command/control byte is the first byte received following the START condition from
the master device. The command/control byte consists of a 4-bit control code. For the DS1847, this is
set as 1010 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 DS1847, 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.
Following the START condition, the DS1847 monitors the SDA bus checking the device type identifier
being transmitted. Upon receiving the 1010 control code, the appropriate device address bits, and the
read/write bit, the slave device outputs an acknowledge signal on the SDA line.
WRITE PROTECT
The write-protect input pin (WP) protects all memory (including EEPROM), control registers, and lookup tables from alteration in an application. However, this does not interfere with internal
temperature/resistor updates. If set to a logic 0, the device is not write protected and can be written to via
the 2-wire interface. This pin has an internal pull-up resistor.
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DS1847
2-WIRE DATA TRANSFER PROTOCOL Figure 3
2-WIRE AC CHARACTERISTICS Figure 4
12 of 17
DS1847
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature
Programming Temperature
Storage Temperature
Soldering Temperature
-0.3V to +6.0V
-40°C to +95°C
0°C to +70°C
-55°C to +125°C
See J-STD-020A specification
* 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
PARAMETER
SYMBOL
Supply Voltage
Vcc
Resistor Inputs
L0, L1,
H0, H1
Resistor Current
IRESISTOR
CONDITION
SYMBOL
Supply Current
ICC
Input Leakage
(digital inputs)
IL
Input Leakage (H0,
H1, L0, and L1)
MAX
UNITS
NOTES
+3.0
5.5
V
1
GND-0.3
VCC+0.3
V
-1
-3
1
3
mA
DS1847-050
DS1847-010
DC ELECTRICAL CHARACTERISTICS
PARAMETER
MIN
(-40°C to +95°C)
TYP
(-40°C to +95°C; VCC = 3.0V to 5.5V)
TYP
MAX
UNITS
NOTES
0.5
1
mA
2
-1
+1
µA
IL
-100
+100
nA
Input Logic 1
VIH
0.7VCC
VCC+0.3
V
Input Logic 0
VIL
GND-0.3
0.3VCC
V
0.4<VI/O<0.9VCC
-10
+10
mA
Input Current each
I/O pin
CONDITION
MIN
Low Level Output
Voltage (SDA)
VOL1
3mA sink current
0.0
0.4
V
VOL2
6mA sink current
0.0
0.6
V
I/O Capacitance
CI/O
10
pF
WP Internal Pull Up
Resistance, Rwp
Rwp
100
kW
40
13 of 17
65
15
13
DS1847
ANALOG RESISTOR CHARACTERISTICS (-40°C to +95°C; VCC = 3.0V to 5.5V)
PARAMETER
Absolute Error
SYMBOL
CONDITION
using cal. values
Position FFh Resistance
DS1847-050
DS1847-050
DS1847-010
MIN
-4
(50k resistor)
(10k resistor)
(10k resistor)
Position 00h Resistance
DS1847-050
DS1847-050
DS1847-010
44.6
9.0
8.0
(50k resistor)
(10k resistor)
(10k resistor)
500
500
250
TYP
55.8
11.3
10.0
850
850
425
MAX
+4
67.0
13.6
12.0
1200
1200
600
UNITS NOTES
14
LSB
kW
3
W
3
Absolute Linearity
-2
+2
LSB
4
Relative Linearity
-1
+1
LSB
5
-4
+4
LSB
14
ppm/°C
12
Compensated Tempco
Error
using calibration
values
Uncompensated Tempco
850
DIGITAL THERMOMETER
PARAMETER
Thermometer Error
Conversion Time
SYMBOL
CONDITION
TERR
tCONVT
MAX
UNITS
-40°C to 95°C
±3.0
°C
12-bit conversion
10
ms
14 of 17
TYP
NOTES
DS1847
AC ELECTRICAL CHARACTERISTICS
PARAMETER
SCL clock frequency
SYMBOL
fSCL
Bus free time between
STOP and START
Hold time (repeated)
START condition
Low period of SCL clock
tBUF
t HD:STA
High period of SCL clock
tHIGH
tLOW
Data hold time
tHD:DAT
Data set-up time
tSU:DAT
Start set-up time
tSU:STA
Rise time of both SDA
and SCL signals
Fall time of both SDA
and SCL signals
Set-up time for STOP
condition
Capacitive load for each
bus line
EEPROM write time
tR
tF
tSU:STO
(-40°C to +95°C, VCC = 3.0V to 5.5V)
CONDITION
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
Fast Mode
Standard Mode
MIN
0
0
1.3
4.7
0.6
4.0
1.3
4.7
0.6
4.0
0
0
100
250
0.6
4.7
TYP
MAX
400
100
0.9
300
1000
300
300
20+0.1CB
20+0.1CB
0.6
4.0
NOTES
6
ms
6
ms
7, 6
ms
6
ms
6
ms
6, 8, 9
ns
6
ms
6
ns
10
ns
10
ms
CB
tW
UNITS
kHz
5
400
pF
10
20
ms
11
NONVOLATILE MEMORY CHARACTERISTICS
PARAMETER
Writes
SYMBOL
CONDITION
85°C
MIN
50,000
15 of 17
TYP
MAX
UNITS
DS1847
NOTES:
1.
2.
3.
4.
All voltages are referenced to ground.
Inputs SDA = SCL = WP = VCC. A0, A1, and A2, must be tied to VCC or GND.
Valid at 25°C only.
Absolute linearity is the difference of measured value from expected value at DAC position.
Expected value is a straight line from measured minimum position to measured maximum position.
5. Relative linearity is the deviation of an LSB DAC setting change vs. the expected LSB change.
Expected LSB change is the slope of the straight line from measured minimum position to measured
maximum position.
6. A fast mode device can be used in a standard mode system, but the requirement tSU:DAT > 250ns 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 = 1000ns + 250ns = 1250ns before the SCL line is released.
7. After this period, the first clock pulse is generated.
8. The maximum tHD:DAT has only to be met if the device does not stretch the LOW period (tLOW) of the
SCL signal.
9. A device must internally provide a hold time of at least 300ns for the SDA signal (referred to the
VIHMIN of the SCL signal) in order to bridge the undefined region of the falling edge of SCL.
10. CB – total capacitance of one bus line in picofarads, timing referenced to 0.9VCC and 0.1VCC.
11. EEPROM write begins after a STOP condition occurs.
12. The temperature coefficient varies with resistor position from 650ppm/°C at position FFh to
1000ppm/°C at 00h (for the 50k resistor), or 1500ppm/°C at 00h (for the 10k resistor). See the graphs
below. The tempco can be significantly reduced by using the resistor calibration values. When doing
so, the average tempco over the entire temperature range is between 200ppm°/C (for the lower
positions) and 10ppm/°C (higher positions). Refer to the Programming the Look-Up Table section of
the data sheet.
13. I/O pins of fast mode devices must not obstruct the SDA and SCL lines if VCC is switched off.
14. Refer to Programming the Look-Up Table section of the data sheet for calibration.
15. Address input A1 passes Latch-up per JEDEC 78 class I. All other pins pass class II.
TEMPCO vs. RESISTANCE
10K RESISTOR
TEMPCO vs. RESISTANCE
50K RESISTOR
1100
1500
1400
1000
1300
1200
900
PPM/°C
PPM/°C
1100
1000
800
900
700
800
700
600
600
500
500
0
2000
4000
6000
8000
RESISTANCE (OHMS)
10000
0
10000
20000
30000
RESISTANCE (OHMS)
16 of 17
40000
50000
DS1847
ORDERING INFORMATION
ORDERING
NUMBER
PACKAGE
OPERATING
TEMPERATURE
DS1847E-010
DS1847E-050
DS1847E-010/T&R
DS1847E-050/T&R
DS1847B-010
DS1847B-050
14-PIN TSSOP (173-MIL)
14-PIN TSSOP (173-MIL)
14-PIN TSSOP/TAPE & REEL
14-PIN TSSOP/TAPE & REEL
16-BALL CSBGA
16-BALL CSBGA
-40ºC TO +95ºC
-40ºC TO +95ºC
-40ºC TO +95ºC
-40ºC TO +95ºC
-40ºC TO +95ºC
-40ºC TO +95ºC
17 of 17
VERSION
Resistor 0
/Resistor 1
10kW/10kW
50kW/10kW
10kW/10kW
50kW/10kW
10kW/10kW
50kW/10kW