DS1626/DS1726
www.maxim-ic.com
High-Precision 3-Wire Digital
Thermometer and Thermostat
PIN CONFIGURATION
DQ
CLK/
CNV
RST
GND
1
2
3
4
8
7
6
5
FEATURES
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Temperature Measurements Require No
External Components
Measure Temperatures from -55°C to +125°C
(-67°F to +257°F)
DS1626:
±0.5°C
Accuracy from 0°C to
+70°C
DS1726:
±1°C
Accuracy from -10°C to
+85°C
Output Resolution is User-Selectable to 9, 10,
11, or 12 Bits
Wide Power-Supply Range (2.7V to 5.5V)
Convert Temperature to Digital Word in
750ms (max)
Stand-Alone Thermostat Capability
Thermostatic Settings are User-Definable and
Nonvolatile (NV)
Data is Read/Written Through a 3-Wire Serial
Interface
Available in 8-Pin
mMAX/mSOP
Package
V
DD
T
HIGH
T
LOW
T
COM
mSOP
(DS1626U, DS1726U)
See Table 1 for Ordering Information
See Table 2 for Pin Descriptions
APPLICATIONS
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Thermostatic Controls
Industrial Controls
Consumer Products
Any Space-Constrained Thermally Sensitive
Application
DESCRIPTION
The DS1626 and DS1726 digital thermometers/thermostats provide temperature measurements and stand-
alone thermostat capability over a -55°C to +125°C range. The DS1626 offers ±0.5°C accuracy from 0°C to
+70°C and the DS1726 has ±1°C accuracy from -10°C to +85°C. The resolution of the measured
temperature is user-selectable from 9 to 12 bits. Communication with the DS1626 and DS1726 is achieved
through a 3-wire serial bus.
The DS1626 and DS1726 offer thermostatic functionality with three dedicated thermostat outputs (T
HIGH
,
T
LOW
, and T
COM
), and over-temperature (T
H
) and under-temperature (T
L
) user-programmable thresholds
stored in on-chip EEPROM. For stand-alone thermostat operation, T
H
and T
L
can be programmed prior to
installation, and the DS1626/DS1726 can be configured to automatically begin taking temperature
measurements at power-up.
Pin descriptions for the DS1626 and DS1726 are provided in Table 2 and user-accessible registers are
summarized in Table 3. A functional diagram is shown in Figure 1.
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06/10/03
DS1626/DS1726
ORDERING INFORMATION
PART
DS1626U
DS1626U/T&R
DS1726U
DS1726U/T&R
PIN
1
2
3
4
5
6
7
8
SYMBOL
DQ
CLK/CNV
RST
GND
T
COM
T
LOW
T
HIGH
V
DD
PACKAGE MARKING
D1626
D1626
D1726
D1726
DESCRIPTION
8-Pin
mSOP
8-Pin
mSOP,
3000-Piece Tape-and-Reel
8-Pin
mSOP
8-Pin
mSOP,
3000-Piece Tape-and-Reel
Table 2. DETAILED PIN DESCRIPTION
FUNCTION
Data Input/Output Pin
(Tri-State) for 3-Wire Serial Communication
Clock Input Pin
for 3-Wire Serial Communication. Controls temperature
measurements when the DS1626/DS1726 is configured as a stand-alone thermostat
Reset Input Pin
for 3-Wire Serial Communication
Ground Pin
Thermostat Output Pin
(Push-Pull) with Programmable Hysteresis
Thermostat Output Pin
(Push-Pull) with T
L
Trip Point
Thermostat Output Pin
(Push-Pull) with T
H
Trip Point
Supply Voltage.
+2.7V to +5.5V Input Power Pin
MEMORY
TYPE
SRAM
EEPROM
EEPROM
SRAM and
EEPROM
REGISTER CONTENTS
AND POWER-UP/POR STATE
Measured Temperature (Two’s Complement)
Power-Up/POR State: -60ºC (1100 0100 0000)
Upper Alarm Trip Point (Two’s Complement)
Power-Up/POR State: User-Defined.
Initial State from Factory: +15°C (0000 1111 0000)
Lower Alarm Trip Point (Two’s Complement)
Power-Up/POR State: User-Defined.
Initial State from Factory: +10°C (0000 1010 0000)
Configuration and Status Information (Unsigned)
4MSbs = SRAM and 4LSbs = EEPROM
Power-Up/POR State: 1000XXXX (XXXX = User-
Defined)
Table 3. DS1626/DS1726 REGISTER SUMMARY
REGISTER NAME
(USER ACCESS)
Temperature
(Read Only)
T
H
(Read/Write)
T
L
(Read/Write)
Configuration
(Various Bits are
Read/Write and Read
Only—See Table 5)
SIZE
12 Bits
12 Bits
12 Bits
1 Byte
Figure 1. DS1626/DS1726 FUNCTIONAL DIAGRAM
V
DD
GND
TEMPERATURE SENSOR AND
DS
ADC
ADDRESS
and
I/O CONTROL
CLK/
CNV
SDA
RST
TEMPERATURE REGISTER
T
H
REGISTER
T
L
REGISTER
2 of 13
T
COM
T
HIGH
T
LOW
CONFIGURATION REGISTER AND CONTROL LOGIC
DIGITAL
COMPARATOR/LOGIC
DS1626/DS1726
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature Range
Storage Temperature Range
Solder Dip Temperature (10s)
Reflow Oven Temperature
-0.5V
to +6.0V
-55°C to +125°C
-55°C to +125°C
+260°C
+220°C
*
These are stress ratings 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.
DC ELECTRICAL CHARACTERISTICS
(V
DD
= 2.7V to 5.5V; T
A
= -55°C to +125°C.)
PARAMETER
Supply Voltage
DS1626
Thermometer Error
(Note 2)
SYMBOL
V
DD
CONDITIONS
(Note 1)
0°C to +70°C,
3.0V
£
V
DD
£
5.5V
0°C to +70°C,
2.7V
£
V
DD
<
3.0V
-55°C to +125°C
-10°C to +85°C,
3.0V
£
V
DD
£
5.5V
-10°C to +85°C,
2.7V
£
V
DD
<
3.0V
-55°C to +125°C
(Note 1)
(Note 1)
0.4 < V
I/O
< 0.9 x V
DD
Temperature conversion
-55°C to +85°C
Temperature conversion
+85°C to +125°C
E
2
write
RST
to GND
DQ, CLK to V
DD
0°C to +70°C (Note 3)
1mA source current
4mA sink current
(Note 4)
±0.2
2.4
0.4
V
°C
MIN
2.7
TYP
MAX
5.5
±0.5
±1.25
±2
±1
±1.5
±2
-0.5
0.7 x V
DD
-10
0.3 x V
DD
V
DD
+ 0.3
+10
1
mA
1.25
400
1
1.5
µA
MW
µA
V
V
µA
°C
°C
UNITS
V
T
ERR
DS1726
Thermometer Error
(Note 2)
Low-Level Input
Voltage
High-Level Input
Voltage
Input Current each
Input Pin
Active Supply
Current (Note 3)
Input Resistance
Standby Supply
Current
THIGH, TLOW,
TCOM, DQ Output
Logic Voltages
(Note 1)
Thermal Drift
T
ERR
V
IL
V
IH
I
DD
R
I
I
STBY
V
OH
V
OL
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DS1626/DS1726
EEPROM AC ELECTRICAL CHARACTERISTICS
(V
DD
= 2.7V to 5.5V; T
A
= -55°C to +125°C.)
PARAMETER
EEPROM Write Cycle Time
EEPROM Writes
EEPROM Data Retention
SYMBOL CONDITIONS
t
wr
N
EEWR
-55°C to +55°C
t
EEDR
-55°C to +55°C
MIN
50k
10
TYP
4
MAX
10
UNITS
ms
Writes
Years
AC ELECTRICAL CHARACTERISTICS
(V
DD
= 2.7V to 5.5V; T
A
= -55°C to +125°C.)
PARAMETER
Temperature Conversion Time
Data In to Clock Setup
Clock to Data In Hold
Clock to Data Out Delay
Clock Low/High Time
Clock Frequency
Clock Rise/Fall Time
RST
to Clock Setup
Clock to
RST
Hold
RST
Inactive Time
Clock High to I/O Hi-Z
RST
Low to I/O Hi-Z
CNV
Pulse Width
I/O Capacitance
Input Capacitance
SYMBOL
t
TC
t
DC
t
CDH
t
CDD
t
CL
, t
CH
f
CLK
t
R
, t
F
t
RC
t
CRH
t
RI
t
CDZ
t
RDZ
t
CNV
C
I/O
C
I
CONDITIONS
9-bit
10-bit
11-bit
12-bit
(Note 5)
(Note 5)
(Notes 5, 6)
(Note 5)
(Note 5)
(Note 5)
(Note 5)
(Note 5)
(Note 7)
(Note 5)
(Note 5)
(Note 8)
MIN
TYP
MAX
93.75
187.5
375
750
150
285
0
100
40
125
250ns
10
5
50
50
500ms
1.75
500
UNITS
ms
ns
ns
ns
ns
MHz
ns
ns
ns
ns
ns
ns
pF
pF
35
40
NOTES:
1)
2)
3)
4)
5)
6)
7)
8)
All voltages are referenced to ground.
See Figure 2 for
TYPICAL OPERATING CURVES.
I
STBY
, I
DD
specified with DQ, CLK/CNV = V
DD
and
RST
= GND.
Drift data is based on a 1000hr stress test at +125°C with V
DD
= 5.5V.
See Timing Diagrams in Figure 3. All timing is referenced to 0.7 x V
DD
and 0.3 x V
DD
.
Load capacitance = 50pF.
t
RI
must be 10ms minimum following any write command that involves the E
2
memory.
250ns is the guaranteed minimum pulse width for a conversion to start, however, a smaller pulse
width may start a conversion.
4 of 13
DS1626/DS1726
Figure 2. TYPICAL OPERATING CURVES
DS1626
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
0
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
-10
DS1726
ERROR (°C)
+3s
ERROR °C
+3s
MEAN
-3s
10
20
30
40
50
60
70
MEAN
-3s
0
10
20
30
40
50
60
70
80
REFERENCE TEMPERATURE (°C)
REFERENCE TEMPERATURE (°C)
Figure 3. TIMING DIAGRAMS
a) Read Timing
t
CRH
t
RC
b) Write Timing
t
RI
t
RC
t
CRH
5 of 13
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