Rev 1; 4/05
Dual, Temperature-Controlled Resistors with Inter-
nally Calibrated Monitors and Password Protection
General Description
Features
♦ SFF-8472 Compatible
The DS1856 dual, temperature-controlled, nonvolatile
(NV) variable resistors with three monitors consists of
two 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 temperature-compensating
bias voltages and currents in control applications using
minimal circuitry. The variable resistor settings are
stored in EEPROM memory and can be accessed over
the 2-wire serial bus.
♦ Five Monitored Channels (Temperature, V
,
CC
MON1, MON2, MON3)
♦ Three External Analog Inputs (MON1, MON2, MON3)
That Support Internal and External Calibration
♦ Scalable Dynamic Range for External Analog Inputs
♦ Internal Direct-to-Digital Temperature Sensor
♦ Alarm and Warning Flags for All Monitored
Channels
♦ Two Linear, 256-Position, Nonvolatile Temperature-
Controlled Variable Resistors
♦ Resistor Settings Changeable Every 2°C
♦ Three Levels of Security
♦ Access to Monitoring and ID Information
Configurable with Separate Device Addresses
♦ 2-Wire Serial Interface
♦ Two Buffers with TTL/CMOS-Compatible Inputs and
Open-Drain Outputs
♦ Operates from a 3.3V or 5V Supply
♦ -40°C to +95°C Operating Temperature Range
Relative to other members of the family, the DS1856 is
essentially a DS1859 with a DS1852-friendly memory
map. In particular, the DS1856 can be configured so
the 128 bytes of internal Auxiliary EEPROM memory is
mapped into Main Device Table 00h and Table 01h,
maintaining compatibility between both the
DS1858/DS1859 and the DS1852. The DS1856 also
features password protection equivalent to the DS1852,
further enhancing compatibility between the two.
Applications
Optical Transceivers
Ordering Information
Optical Transponders
Instrumentation and Industrial Controls
RF Power Amps
RES0/RES1
PART
RESISTANCE
PIN-PACKAGE
(kΩ)
Diagnostic Monitoring
DS1856E-050
50/50
50/50
50/50
16 TSSOP
DS1856E-050/T&R
DS1856B-050
16 TSSOP
16-Ball CSBGA
Typical Operating Circuit
Ordering Information continued at end of data sheet.
+Denotes lead free.
*Future product—contact factory for availability.
T&R denotes tape-and-reel.
V
CC
V
CC
= 3.3V
All parts operate at the -40°C to +95°C temperature range.
4.7kΩ
2-WIRE
4.7kΩ
DECOUPLING
CAPACITOR
0.1µF
Pin Configurations
16
1
V
CC
SDA
15
14
2
TO LASER BIAS
CONTROL
TOP VIEW
H1
L1
INTERFACE
SCL
OUT1
IN1
SDA
1
2
3
4
5
6
7
8
16 V
CC
3
4
A
B
C
D
V
IN1
SCL
SDA
IN2
H1
L1
CC
TO LASER
MODULATION
CONTROL
13
12
SCL
OUT1
IN1
15 H1
Tx-FAULT
H0
L0
14 L1
5
6
OUT2
H0
DS1856
OUT2
13 H0
LOS
DS1856
11
10
9
Rx POWER*
IN2
MON3
MON2
MON1
OUT2
IN2
12 L0
N.C.
OUT1
MON3
7
8
Tx POWER*
Tx BIAS*
DIAGNOSTIC
INPUTS
N.C.
GND
11 MON3
10 MON2
N.C.
GND
GND
1
L0
2
MON1
3
MON2
4
9
MON1
*SATISFIES SFF-8472 COMPATIBILITY
CSBGA (4mm x 4mm)
1.0mm PITCH
TSSOP
______________________________________________ Maxim Integrated Products
1
For pricing delivery, and ordering information please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.