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DS1859B-050-DS1859E-050
Dual, Temperature-Controlled Resistors with Internally Calibrated Monitors
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
General DescriptionThe DS1859 dual, temperature-controlled, nonvolatile
(NV) variable resistors with three monitors consists of
two 50kΩor two 20kΩ, 256-position, linear, variable
resistors; three analog monitor inputs (MON1, MON2,
MON3); and a direct-to-digital temperature sensor. The
device provides an ideal method for setting and tem-
perature-compensating bias voltages and currents in
control applications using minimal circuitry. The vari-
able resistor settings are stored in EEPROM memory
and can be accessed over the 2-wire serial bus.
ApplicationsOptical Transceivers
Optical Transponders
Instrumentation and Industrial Controls
RF Power Amps
Diagnostic Monitoring
FeaturesSFF-8472 CompatibleFive Monitored Channels (Temperature, VCC,
MON1, MON2, MON3)Three External Analog Inputs (MON1, MON2, MON3)
That Support Internal and External CalibrationScalable Dynamic Range for External Analog InputsInternal Direct-to-Digital Temperature SensorAlarm and Warning Flags for All Monitored
ChannelsTwo 50kΩor Two 20kΩ, Linear, 256-Position,
Nonvolatile Temperature-Controlled Variable
ResistorsResistor Settings Changeable Every 2°CAccess to Monitoring and ID Information
Configurable with Separate Device Addresses2-Wire Serial InterfaceTwo Buffers with TTL/CMOS-Compatible Inputs and
Open-Drain OutputsOperates from a 3.3V or 5V SupplyOperating Temperature Range of -40°C to +95°C
Ordering InformationRev 1; 11/03
Pin Configurations
Typical Operating Circuit
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
ABSOLUTE MAXIMUM RATINGSStresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Voltage Range on VCCRelative to Ground...........-0.5V to +6.0V
Voltage Range on Inputs Relative
to Ground*................................................-0.5V to VCC+ 0.5V
Voltage Range on Resistor Inputs Relative
to Ground*................................................-0.5V to VCC+ 0.5V
Current into Resistors............................................................5mA
Operating Temperature Range...........................-40°C to +95°C
Programming Temperature Range.........................0°C to +70°C
Storage Temperature Range.............................-55°C to +125°C
Soldering Temperature.......................................See IPC/JEDEC
J-STD-020A
RECOMMENDED DC OPERATING CONDITIONS(TA= -40°C to +95°C, unless otherwise noted.)
DC ELECTRICAL CHARACTERISTICS*Not to exceed 6.0V.
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
DIGITAL THERMOMETER(VCC= 2.97V to 5.5V, TA= -40°C to +95°C, unless otherwise noted.)
NONVOLATILEMEMORYCHARACTERISTICS
ANALOG VOLTAGE MONITORING
ANALOGRESISTOR CHARACTERISTICS(VCC= 2.97V to 5.5V, TA= -40°C to +95°C, unless otherwise noted.)
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated MonitorsELECTRICAL CHARACTERISTICS
Note 1:All voltages are referenced to ground.
Note 2: I/O pins of fast-mode devices must not obstruct the SDA and SCL lines if VCCis switched off.
Note 3:SDA and SCL are connected to VCCand all other input signals are connected to well-defined logic levels.
Note 4: Full Scale is user programmable.The maximum voltage that the MON inputs read is approximately Full Scale, even if the volt-
age on the inputs is greater than Full Scale.
Note 5:This voltage defines the maximum range of the analog-to-digital converter voltage, not the maximum VCC voltage.
Note 6: Absolute linearity is the difference of measured value from expected value at DAC position. The expected value is a
straight line from measured minimum position to measured maximum position.
Note 7: Relative linearity is the deviation of an LSB DAC setting change vs. the expected LSB change. The expected LSB change
is the slope of the straight line from measured minimum position to measured maximum position.
Note 8: See the Typical Operating Characteristics.
Note 9: A fast-mode device can be used in a standard-mode system, but the requirement tSU:DAT> 250ns must then be met. This
is automatically the case if the device does not stretch the LOWperiod of the SCL signal. If such a device does stretch the
LOWperiod 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.
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
Note 10: After this period, the first clock pulse is generated.
Note 11: The maximum tHD:DATonly has to be met if the device does not stretch the LOWperiod (tLOW) of the SCL signal.
Note 12: A device must internally provide a hold time of at least 300ns for the SDA signal (see the VIH MIN of the SCL signal) to
bridge the undefined region of the falling edge of SCL.
Note 13: CB—total capacitance of one bus line, timing referenced to 0.9 x VCCand 0.1 x VCC.
Note 14: Guaranteed by design.
Typical Operating Characteristics(VCC= 5.0V, TA= +25°C, for both 50kΩand 20kΩversions, unless otherwise noted.)
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
Typical Operating Characteristics (continued)(VCC= 5.0V, TA= +25°C, for both 50kΩand 20kΩversions, unless otherwise noted.)
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
Typical Operating Characteristics (continued)(VCC= 5.0V, TA= +25°C, for both 50kΩand 20kΩversions, unless otherwise noted.)
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
Detailed DescriptionThe user can read the registers that monitor the VCC,
MON1, MON2, MON3, and temperature analog signals.
After each signal conversion, a corresponding bit is set
that can be monitored to verify that a conversion has
occurred. The signals also have alarm and warning flags
that notify the user when the signals go above or below
the user-defined value. Interrupts can also be set for
each signal.
The position values of each resistor can be indepen-
dently programmed. The user can assign a unique
value to each resistor for every 2°C increment over the
-40°C to +102°C range.
Two buffers are provided to convert logic-level inputs
into open-drain outputs. Typically, these buffers are
used to implement transmit (Tx) fault and loss-of-signal
(LOS) functionality. Additionally, OUT1 can be asserted
in the event that one or more of the monitored values
go beyond user-defined limits.
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
Monitored SignalsEach signal (VCC, MON1, MON2, MON3, and tempera-
ture) is available as a 16-bit value with 12-bit accuracy
(left-justified) over the serial bus. See Table1 for signal
scales and Table2 for signal format. The four LSBs
should be masked when calculating the value.
For the 20kΩversion, the 3 LSBs are internally masked
with 0s.
The signals are updated every frame rate (tframe) in a
round-robin fashion.
The comparison of all five signals with the high and low
user-defined values are done automatically. The corre-
sponding flags are set to 1 within a specified time of
the occurrence of an out-of-limit condition.
Calculating Signal ValuesThe LSB = 100µV for VCC, and the LSB = 38.147µV for
the MON signals when using factory default settings.
To calculate VCC, convert the unsigned 16-bit value to
decimal and multiply by 100µV.
To calculate MON1, MON2, or MON3, convert the
unsigned 16-bit value to decimal and multiply by
38.147µV.
To calculate the temperature, treat the two’s comple-
ment value binary number as an unsigned binary num-
ber, then convert to decimal and divide by 256. If the
result is greater than or equal to 128, subtract 256 from
the result.
Temperature: high byte: -128°C to +127°C signed; low
byte: 1/256°C.
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
Variable ResistorsThe value of each variable resistor is determined by
a temperature-addressed look-up table, which can
assign a unique value (00h to FFh) to each resistor for
every 2°C increment over the -40°C to +102°C range
(see Table3). See the Temperature Conversion section
for more information.
The variable resistors can also be used in manual
mode. If the TEN bit equals 0, the resistors are in manu-
al mode and the temperature indexing is disabled. The
user sets the resistors in manual mode by writing to
addresses 82h and 83h in Table 01 to control resistors
Memory DescriptionMain and auxiliary memories can be accessed by two
separate device addresses. The Main Device address
is A2h (or value in Table 01 byte 8Ch, when ADFIX = 1)
and the Auxiliary Device address is A0h. A user option
is provided to respond to one or two device addresses.
This feature can be used to save component count in
SFF applications (Main Device address can be used)
or other applications where both GBIC (Auxiliary
Device address can be used) and monitoring functions
are implemented and two device addresses are need-
ed. The memory blocks are enabled with the corre-
sponding device address. Memory space from 80h and
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitorsabove is accessible only through the Main Device
address. This memory is organized as three tables. The
desired tablecan be selected by the contents of mem-
ory location 7Fh, Main Device. The Auxiliary Device
address has no access to the tables, but the Auxiliary
Device address can be mapped into the Main Device’s
memory space as a fourth table. Device addresses are
programmable with two control bits in EEPROM.
ADEN configures memory access to respond to differ-
ent device addresses (see Tables4 and 5).
The default device address for EEPROM-generated
addresses is A2h.
If the ADEN bit is 1, additional 128 bytes of EEPROM
are accessible through the Main Device, selected as
Table00 (see Figure3). In this configuration, the
Auxiliary Device is not accessible. APEN controls the
protection of Table 00 regardless of ADEN’s setting.
ADFIX (address fixed) determines whether the Main
Device address is determined by an EEPROM byte
(Table01, byte 8Ch, when ADFIX = 1). There can be
up to 128 devices sharing a common 2-wire bus, with
each device having its own unique device address.
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
Register MapA description of the registers is below. The registers
are read only (R) or read/write (R/W). The R/W registers
are writable only if write protect has not been asserted
(see theMemory Descriptionsection).
Bytes designated as "Reserved" have been set aside
for added functionality in future revisions of this device.
DS1859
Dual, Temperature-Controlled Resistors with
Internally Calibrated Monitors
