Rev 1; 3/08
Digital Thermometer and Thermostat
General Description
The DS7505 low-voltage (1.7V to 3.7V) digital ther-
mometer and thermostat provides 9-, 10-, 11-, or 12-bit
digital temperature readings over a -55°C to +125°C
range with
±0.5°C
accuracy over a -0°C to +70°C range.
A 9-bit resolution mode is software compatible with the
LM75. Communication with the DS7505 is achieved
through a simple 2-wire serial interface. Three address
pins allow up to eight DS7505 devices to operate on the
same 2-wire bus, which greatly simplifies distributed
temperature-sensing applications.
The DS7505 thermostat has a dedicated open-drain out-
put (O.S.) and programmable fault tolerance, which
allows the user to define the number of consecutive
error conditions that must occur before O.S. is activated.
There are two thermostatic operating modes that control
thermostat operation based on user-defined trip points
(T
OS
and T
HYST
) that are stored in EEPROM registers.
o
Operating Range from 1.7V to 3.7V
o
Temperature Measurements Require No External
Components
o
Measures Temperatures from -55°C to +125°C
(-67°F to +257°F)
o
±0.5°C Accuracy Over a 0°C to +70°C Range
o
Thermometer Resolution is User-Configurable
from 9 (Default) to 12 Bits (0.5°C to 0.0625°C
Resolution)
o
9-Bit Conversion Time is 25ms (max)
o
Thermostatic Settings are User-Definable and
Nonvolatile (NV)
o
Stand-Alone Thermostat Capability
o
Data Read/Write Occurs Through a 2-Wire Serial
Interface (SDA and SCL Pins)
o
Data Lines Filtered Internally for Noise Immunity
(50ns Deglitch)
o
Optional Bus Timeout Feature Prevents Lockup
Problems on 2-Wire Interface
o
Multidrop Capability Simplifies Distributed
Temperature-Sensing Applications
o
Pin/Software Compatible with the LM75
o
Available in 8-Pin SO and µMAX
®
Packages
TOP VIEW
Features
DS7505
Applications
Networking Equipment
Cellular Base Stations
Office Equipment
Medical Equipment
Any Thermally Sensitive System
Pin Configurations
Ordering Information
SDA
SCL
O.S.
GND
1
2
3
4
8
VDD
PART
DS7505
7
6
5
A0
A1
A2
TEMP RANGE
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
PIN-PACKAGE
8 SO (150 mils)
8 SO (150 mils),
2500-Piece T&R
8 µMAX
8 µMAX,
3000-Piece T&R
DS7505S+
DS7505S+T&R
DS7505U+
SO
DS7505U+T&R
8
7
VDD
A0
A1
A2
SDA
SCL
O.S.
GND
1
2
3
4
+Denotes
a lead-free package.
T&R = Tape and reel.
DS7505
6
5
Commands are capitalized for clarity.
µ
MAX
µMAX is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Digital Thermometer and Thermostat
DS7505
ABSOLUTE MAXIMUM RATINGS
Voltage Range on VDD Relative to Ground ..........-0.3V to +4.0V
Voltage Range on Any Other Pin
Relative to Ground.............................................-0.3V to +6.0V
Operating Temperature Range .........................-55°C to +125°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature...........................Refer to the IPC/JEDEC
J-STD-020 Specification.
Stresses 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.
DC ELECTRICAL CHARACTERISTICS
(1.7V
≤
V
DD
≤
3.7V, T
A
= -55°C to +125°C, unless otherwise noted.)
PARAMETER
Supply Voltage
Input Voltage Range (SDA, SCL,
O.S., A0, A1, A2)
Thermometer Error
(Note 2, 3)
Input Logic-High
Input Logic-Low
SDA Output Logic-Low Voltage
O.S. Saturation Voltage
Input Current Each I/O pin
I/O Capacitance
Standby Current
Active Current
(Notes 4, 5, 6)
C
I/O
I
DD1
I
DD
(Notes 4, 5, 6)
Active temp conversions
Communication only
E
2
Copy only
T
ERR
V
IH
V
IL
V
OL1
V
OL2
SYMBOL
V
DD
(Note 1)
0°C to +70°C
-55°C to +125°C
(Note 1)
(Note 1)
6mA sink current (Note 1)
4mA sink current (Notes 1, 2)
0.4V < V
I/O
< 0.9 x V
DD
-10
0
0.7 × V
DD
0.3 × V
DD
0.6
0.8
+10
10
2
750
100
500
µA
CONDITIONS
MIN
1.7
-0.3
MAX
3.7
+5.5
±
0.5
±
2.0
UNITS
V
V
°C
V
V
V
V
µA
pF
µA
AC ELECTRICAL CHARACTERISTICS
(1.7V
≤
V
DD
≤
3.7V, T
A
= -55°C to +125°C, unless otherwise noted.)
PARAMETER
Resolution
9-bit conversions
10-bit conversions
Temperature Conversion Time
t
CONVT
11-bit conversions
12-bit conversions
SCL Frequency
EEPROM Copy Time
EEPROM Copy Endurance
f
SCL
t
WR
N
EEWR
-40°C to +85°C
-40°C
T
A
+85°C (Note 7)
10k
40k
20k
Cycles
80k
T
A
= +25°C (Note 7)
SYMBOL
CONDITIONS
MIN
9
TYP
MAX
12
25
50
ms
100
200
400
10
kHz
ms
UNITS
Bits
2
_______________________________________________________________________________________
Digital Thermometer and Thermostat
AC ELECTRICAL CHARACTERISTICS (continued)
(1.7V
≤
V
DD
≤
3.7V, T
A
= -55°C to +125°C, unless otherwise noted.)
PARAMETER
EEPROM Data Retention
Bus Free Time Between a STOP
and START Condition
START and Repeated START
Hold Time from Falling SCL
Low Period of SCL
High Period of SCL
Repeated START Condition
Setup Time to Rising SCL
Data-Out Hold Time from Falling
SCL
Data-In Setup Time to Rising
Rise Time of SDA and SCL
(Receive)
Fall Time of SDA and SCL
(Receive)
Spike Suppression Filter Time
(Deglitch Filter)
STOP Setup Time to Rising SCL
Capacitive Load for Each Bus
Line
Input Capacitance
Serial Interface Reset Time
SYMBOL
t
EEDR
t
BUF
t
HD:STA
t
LOW
t
HIGH
t
SU:STA
t
HD:DAT
t
SU:DAT
t
R
t
F
t
SS
t
SU:STO
C
B
C
I
t
TIMEOUT
SDA time low (Note 13)
75
5
325
(Note 9)
CONDITIONS
-40°C to +125°C (Note 8)
(Note 9)
(Notes 9, 10)
(Note 9)
(Note 9)
(Note 9)
(Notes 9, 11)
(Note 9)
(Notes 9, 12)
(Notes 9, 12)
MIN
10
1.3
600
1.3
0.6
600
0
100
20 +
0.1C
B
20 +
0.1C
B
0
600
400
300
300
50
0.9
TYP
MAX
UNITS
Years
µs
ns
µs
µs
ns
µs
ns
ns
ns
ns
ns
pF
pF
ms
DS7505
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
All voltages are referenced to ground.
Internal heating caused by O.S. loading causes the DS7505 to read approximately 0.5°C higher if O.S. is sinking the
max-rated current.
Specified in 12-bit conversion mode. Quantization error must be considered when converting in lower resolutions.
I
DD
specified with O.S. pin open.
I
DD
specified with V
DD
at 3.0V and SDA, SCL = 3.0V, T
A
= -55°C to +85°C.
I
DD
specified with A0, A1, A2 = 0V or V
DD
.
V
DD
must be > 2.0V.
E
2
Copy occurs at +25°C.
See the timing diagram (Figure 1). All timing is referenced to 0.9 x V
DD
and 0.1 x V
DD
.
After this period, the first clock pulse is generated.
The DS7505 provides an internal hold time of at least 75ns on the SDA signal to bridge the undefined region of SCL’s
falling edge.
For example, if C
B
= 300pF, then t
R(MIN)
= t
F(MIN)
= 50ns.
This timeout applies only when the DS7505 is holding SDA low. Other devices can hold SDA low indefinitely and the
DS7505 does not reset.
_______________________________________________________________________________________
3
Digital Thermometer and Thermostat
DS7505
Pin Description
PIN
1
2
3
4
5
6
7
8
NAME
SDA
SCL
O.S.
GND
A2
A1
A0
VDD
FUNCTION
Data Input/Output. For 2-wire serial communication port. Open drain.
Clock Input. For 2-wire serial communication port.
Thermostat Output. Open drain.
Ground
Address Input
Address Input
Address Input
Supply Voltage. +1.7V to +3.7V supply pin.
SDA
t
F
t
SU:DAT
t
LOW
t
R
t
F
t
HD:STA
t
SP
t
R
t
BUF
SCL
t
HD:STA
t
HD:DAT
t
SU:STA
SR
t
SU:STO
P
S
Figure 1. Timing Diagram
PRECISION
REFERENCE
VDD
OVERSAMPLING
MODULATOR
DIGITAL
DECIMATOR
SCL
SDA
A0
A1
A2
ADDRESS
AND
I/O CONTROL
CONFIGURATION
REGISTER
R
F
O.S.
THERMOSTAT
COMPARATOR
TEMPERATURE
REGISTER
T
OS
AND T
HYST
REGISTERS
GND
DS7505
Figure 2. Block Diagram
4
_______________________________________________________________________________________
Digital Thermometer and Thermostat
OperationMeasuring
Temperature
The DS7505 measures temperature using a bandgap
temperature-sensing architecture. An on-board delta-
sigma analog-to-digital converter (ADC) converts the
measured temperature to a digital value that is calibrat-
ed in degrees Celsius; for Fahrenheit applications a
lookup table or conversion routine must be used. The
DS7505 is factory-calibrated and requires no external
components to measure temperature.
The DS7505 can be configured to power up either
automatically converting temperature or in a low-power
standby state. The preferred power-up mode can be
set using the SD bit in the configuration register as
explained in the
Configuration Register
section. The
resolution of the digital output data is user-configurable
to 9, 10, 11, or 12 bits, corresponding to temperature
increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C,
respectively. The factory default resolution at power-up
is 9 bits (R1 = 0, R0 = 0), however this can be pro-
grammed to 10, 11, or 12 bits using the R0 and R1 bits
in the configuration register as explained in the
Configuration Register
section. Note that the conver-
sion time doubles for each additional bit of resolution.
After each temperature measurement and analog-to-
digital (A/D) conversion, the DS7505 stores the temper-
ature as a 16-bit two’s complement number in the
2-byte temperature register (see Figure 3). The sign bit
(S) indicates if the temperature is positive or negative:
for positive numbers S = 0 and for negative numbers S
= 1. The most recently converted digital measurement
can be read from the temperature register at any time.
Since temperature conversions are performed in the
background, reading the temperature register does not
affect the operation in progress.
Bits 3 through 0 of the temperature register are hard-
wired to 0. When the DS7505 is configured for 12-bit
resolution, the 12 MSBs (bits 15 through 4) of the tem-
perature register contain temperature data. For 11-bit
resolution, the 11 MSBs (bits 15 through 5) of the tem-
perature register contain data, and bit 4 reads out as 0.
Likewise, for 10-bit resolution, the 10 MSBs (bits 15
through 6) contain data, and for 9-bit the 9 MSBs (bits
15 through 7) contain data and all unused LSBs con-
tains 0s. Table 1 gives examples of 12-bit resolution dig-
ital output data and the corresponding temperatures.
DS7505
Bit 15
MS Byte
LS Byte
S
Bit 7
2
-1
Bit 14
2
6
Bit 6
2
-2
Bit 13
2
5
Bit 5
2
-3
Bit 12
2
4
Bit 4
2
-4
Bit 11
2
3
Bit 3
0
Bit 10
2
2
Bit 2
0
Bit 9
2
1
Bit 1
0
Bit 8
2
0
Bit 0
0
Figure 3. Temperature, T
OS
, and T
HYST
Register Format
Table 1. 12-Bit Resolution Temperature/Data Relationship
TEMPERATURE (°C)
+125
+25.0625
+10.125
+0.5
0
-0.5
-10.125
-25.0625
-55
DIGITAL OUTPUT
(BINARY)
0111 1101 0000 0000
0001 1001 0001 0000
0000 1010 0010 0000
0000 0000 1000 0000
0000 0000 0000 0000
1111 1111 1000 0000
1111 0101 1110 0000
1110 0110 1111 0000
1100 1001 0000 0000
DIGITAL OUTPUT
(HEX)
7D00
1910
0A20
0080
0000
FF80
F5E0
E6F0
C900
_______________________________________________________________________________________
5
京公网安备 11010802033920号
EEWORLD
