DS1775
Digital Thermometer and Thermostat in SOT23
General Description
The DS1775 digital thermometer and thermostat
provides temperature readings that indicate the device’s
temperature. Thermostat settings and temperature
readings are all communicated to/from the DS1775 over
a simple 2-wire serial interface. No additional components
are required; the device is truly a “temperature-to-digital”
converter.
For applications that require greater temperature resolution,
the user can adjust the readout resolution from 9 to 12
bits. This is particularly useful in applications where
thermal runaway conditions must be detected quickly.
The open-drain thermal alarm output, O.S., becomes
active when the temperature of the device exceeds a
user-defined temperature TOS. The number of consecutive
faults required to set O.S. active is configurable by the
user. The device can also be configured in the interrupt or
comparator mode, to customize the method which clears
the fault condition.
As a digital thermometer, the DS1775 is software compatible
with the DS75 2-wire thermal watchdog. The DS1775 is
assembled in a compact 5-pin SOT23 package, allowing
for low-cost thermal monitoring/control in spaceconstrained applications. The low thermal mass allows for
time constants previously only possible with thermistors.
Applications
●●
●●
●●
●●
Personal Computers/Servers/Workstations
Cell Phones
Office Equipment
Any Thermally-Sensitive System
19-6687; Rev 1; 11/16
Benefits and Features
●● Temperature Measurements Require No External
Components
●● Measures Temperatures from -55°C to +125°C
(-67°F to +257°F)
●● ±2.0°C Thermometer Accuracy
●● Thermometer Resolution is Configurable from 9 Bits
to 12 Bits (0.5°C to 0.0625°C Resolution)
●● User-Definable Thermostat Settings
●● Data is Read From/Written to Through a
●● 2-Wire Serial Interface
●● 2.7V to 5.5V Wide Power-Supply Range
●● Software Compatible with DS75 2-Wire Thermal
Watchdog in Thermometer Mode
●● Space-Conscious 5-Pin SOT23 Package with Low
Thermal Time Constant
Ordering Information appears at end of data sheet.
DS1775
Digital Thermometer and Thermostat in SOT23
Absolute Maximum Ratings
Storage Temperature Range............................. -55°C to +125°C
Lead Temperature (soldering, 10s).................................. +300°C
Soldering Temperature (reflow)........................................ +260°C
(Voltages relative to ground.)
Voltage Range on VDD..........................................-0.3V to +7.0V
Voltage Range on Any Other Pin..........................-0.3V to +7.0V
Operating Temperature Range.......................... -55°C to +125°C
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
(2.7V ≤ VDD ≤ 5.5V, TA = -55°C to +125°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITION
MIN
TYP
MAX
UNITS
Supply Voltage
VDD
(Note 1)
2.7
5.5
V
Input Logic-High
VIH
(Note 1)
0.7 x
VDD
VDD+
0.5
V
Input Logic-Low
VIL
(Note 1)
-0.5
0.3 x
VDD
V
SDA Output Logic-Low Voltage
O.S. Saturation Voltage
VOL1
3mA sink current (Note 1)
0
0.4
VOL2
6mA sink current (Note 1)
0
0.6
VOL
4mA sink current (Notes 1, 9)
0.4 < VI/O < 0.9 x VDD (Note 2)
Input Current Each I/O Pin
I/O Capacitance
CI/O
Standby Current
IDD1
Active Current
IDD
-10
(Notes 3, 4)
V
0.8
V
+10
µA
10
pF
1
µA
Active temp conversions (Notes 3, 4)
1000
Communication only (Notes 3, 4)
100
µA
DIGITAL THERMOMETER
Thermometer Error
TERR
-10°C to +85°C (Notes 9, 10)
±0.5
±2.0
-55°C to +125°C (Notes 9, 10)
±1.0
±3.0
Resolution
Conversion Time
www.maximintegrated.com
9
tCONVT
12
9-bit conversion
125
187.5
10-bit conversion
250
375
11-bit conversion
500
750
12-bit conversion
1000
1500
°C
Bits
ms
Maxim Integrated │ 2
DS1775
Digital Thermometer and Thermostat in SOT23
AC Electrical Characteristics-2 Wire Interface
(VDD = 2.7V to 5.5V, TA = -55°C to +125°C, unless otherwise noted.) (Figure 5)
PARAMETER
SYMBOL
SCL Clock Frequency
fSCL
Bus Free Time Between a
STOP and START Condition
tBUF
Hold Time (Repeated) START
Condition
tHD:STA
Low Period of SCL
tLOW
High Period of SCL
tHIGH
Setup Time for a
Repeated START
tSU:STA
Data Hold Time
tHD:DAT
Data Setup Time
tSU:DAT
Rise Time of Both SDA and
SCL Signals
tR
Fall Time of Both SDA and SCL
Signals
tF
Setup Time for STOP
tSU:STO
Capacitive Load for Each Bus
Line
CB
Input Capacitance
CI
CONDITIONS
MIN
TYP
MAX
Fast mode
400
Standard mode
100
Fast mode
1.3
Standard mode
4.7
Fast mode (Note 5)
0.6
Standard mode (Note 5)
4.0
Fast mode
1.3
Standard mode
4.7
Fast mode
0.6
Standard mode
4.0
Fast mode
0.6
Standard mode
4.7
µs
µs
µs
µs
0
0.9
Standard mode (Note 6)
0
0.9
100
Standard mode (Note 7)
250
20 + 0.1CB
300
Standard mode (Note 8)
20 + 0.1CB
1000
Fast mode (Note 8)
20 + 0.1CB
300
Standard mode (Note 8)
20 + 0.1CB
300
0.6
Standard mode
4.0
µs
ns
Fast mode (Note 8)
Fast mode
kHz
µs
Fast mode (Note 6)
Fast mode (Note 7)
UNITS
ns
ns
µs
(Note 8)
400
5
pF
pF
Note
Note
Note
Note
Note
Note
Note
1: All voltages are referenced to ground.
2: I/O pins of fast mode devices must not obstruct the SDA and SCL lines if VDD is switched off.
3: IDD specified with O.S. pin open.
4: IDD specified with VDD at 5.0V and VSDA, VSCL = 5.0V, 0°C to +70°C.
5: After this period, the first clock pulse is generated.
6: The maximum tHD:DAT has only to be met if the device does not stretch the low period (tLOW) of the SCL signal.
7: 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 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 tR MAX + tSU:DAT = 1000 + 250 = 1250ns before the
SCL line is released.
Note 8: CB = Total capacitance of one bus line in pF.
Note 9: Internal heating caused by O.S. loading causes the DS1775 to read approximately 0.5°C higher if O.S. is sinking the max
rated current.
Note 10: Contact the factory for operation requiring temperature readings greater than +120°C.
www.maximintegrated.com
Maxim Integrated │ 3
DS1775
Digital Thermometer and Thermostat in SOT23
Pin Configuration
TOP VIEW
SCL 1
+
GND 2
5
SDA
4
VDD
DS1775
O.S. 3
SOT-23
GND
GROUND
SCL
2-WIRE SERIAL CLOCK
SDA
2-WIRE SERIAL DATA INPUT/OUTPUT
VDD
POWER-SUPPLY VOLTAGE
O.S.
THERMOSTAT OUTPUT SIGNAL
Pin Description
PIN
NAME
1
SCL
Clock Input/Output for 2-Wire Serial Communication Port. This input should be tied to GND for
stand-alone thermostat operation.
2
GND
Ground
3
O.S.
Thermostat Output. Open-drain output becomes active when temperature exceeds TOS.
Device configuration defines means to clear overtemperature state.
4
VDD
Supply Voltage 2.7V to 5.5V Input Power Pin
5
SDA
Data Input/Output for 2-Wire Serial Communication Port. In the stand-alone thermostat mode,
this input selects hysteresis.
www.maximintegrated.com
FUNCTION
Maxim Integrated │ 4
DS1775
Digital Thermometer and Thermostat in SOT23
Detailed Description
Figure 1 shows a block diagram of the DS1775. The
DS1775 consists of five major components:
1) Precision temperature sensor
2) Analog-to-digital converter
3) 2-wire interface electronics
4) Data registers
5) Thermostat comparator
The factory-calibrated temperature sensor requires no
external components. Upon power-up, the DS1775 begins
temperature conversions with the default resolution of 9
bits (0.5°C resolution). The host can periodically read the
value in the temperature register, which contains the last
completed conversion. As conversions are performed in
the background, reading the temperature register does
not affect the conversion in progress.
In power-sensitive applications, the user can put the
DS1775 into a shutdown mode, under which the sensor
complete and store the conversion in progress and revert
to a low-power standby state. In applications where small
incremental temperature changes are critical, the user
can change the conversion resolution from 9 bits to 10,
11, or 12. Each additional bit of resolution approximately
doubles the conversion time. This is accomplished by
programming the configuration register. The configuration
register defines the conversion state, thermometer resolution/conversion time, active state of the thermostat output,
number of consecutive faults to trigger an alarm condition,
and the method to terminate an alarm condition.
The user can also program overtemperature (TOS) and
undertemperature (THYST) setpoints for thermostatic
operation. The power-up state of TOS is +80°C and that
for THYST is +75°C. The result of each temperature conversion is compared with the TOS and THYST setpoints.
The DS1775 offers two modes for temperature control,
the comparator mode and the interrupt mode. This allows
the user the flexibility to customize the condition that
would generate and clear a fault condition. Regardless of
the mode chosen, the O.S. output becomes active only
after the measured temperature exceeds the respective
trip-point a consecutive number of times; the number of
consecutive conversions beyond the limit to generate an
O.S. is programmable. The power-up state of the DS1775
is in the comparator mode with a single fault generating
an active O.S.
Digital data is written to/read from the DS1775 via a
2-wire interface, and all communication is MSb first.
Block Diagram
2.7V - 5.5V
SUPPLY
VDD
PRECISION
REFERENCE
SDA
TO
CPU
OVERSAMPLING
MODULATOR
CONFIGURATION
REGISTER
SCL
I/O CONTROL
INPUT SENSE
DIGITAL
DECIMATOR
DS1775
THERMOMETER
REGISTER
O.S.
THERMOSTAT
REGISTERS
THERMOSTAT
COMPARATOR
GND
Figure 1. Block Diagram
www.maximintegrated.com
Maxim Integrated │ 5
DS1775
Digital Thermometer and Thermostat in SOT23
Operation
Measuring Temperature
The core of DS1775 functionality is its direct-to-digital
temperature sensor. The DS1775 measures temperature
through the use of an on-chip temperature measurement
technique with an operating range from -55°C to +125°C.
Temperature conversions are initiated upon power-up, and
the most recent result is stored in the thermometer register.
Conversions are performed continuously unless the user
intervenes by altering the configuration register to put the
DS1775 into a shutdown mode. Regardless of the mode
used, the digital temperature can be retrieved from the
temperature register by setting the pointer to that location
(00h, power-up default). The DS1775 power-up default
has the sensor automatically performing 9-bit conversions
continuously. Details on how to change the settings after
power-up are contained in the Programming section.
The resolution of the temperature conversion is configurable (9, 10, 11, or 12 bits), with 9-bit readings the default
state. This equates to a temperature resolution of 0.5°C,
0.25°C, 0.125°C, or 0.0625°C. Following each conversion, thermal data is stored in the thermometer register in
two’s complement format; the information can be retrieved
over the 2-wire interface with the device pointer set to the
temperature register. Table 1 describes the exact relationship of output data to measured temperature. The table
assumes the DS1775 is configured for 12-bit resolution; if
the device is configured in a lower resolution mode, those
bits contain zeros. The data is transmitted serially over the
2-wire serial interface, MSb first. The MSb of the temperature register contains the sign (S) bit, denoting whether the
temperature is positive or negative. For Fahrenheit usage,
a lookup table or conversion routine must be used.
Thermostat Control
In its comparator operating mode, the DS1775 functions
as a thermostat with programmable hysteresis, as shown
in Figure 2. When the DS1775’s temperature meets or
exceeds the value stored in the high temperature trip
register (TOS) a consecutive number of times, as defined
by the configuration register, the output becomes active
and stays active until the first time that the temperature
falls below the temperature stored in the low temperature
trigger register (THYST). In this way, any amount of hysteresis may be obtained. The DS1775 powers up in the
comparator mode with TOS = +80°C and THYST = +75°C
and can be used as a stand-alone thermostat (no 2-wire
interface required) with those setpoints.
In the interrupt mode, the O.S. output first becomes active
following the programmed number of consecutive conversions above TOS. The fault can only be cleared by either
setting the DS1775 in a shutdown mode or by reading any
register (temperature, configuration, TOS, or THYST) on
Table 1. Temperature/Data Relationships
S
26
25
24
2-2
2-3
2-4
MSb
2-1
23
22
21
(UNIT = °C)
20
MSB
LSb
0
0
0
0
LSB
TEMPERATURE
(°C)
DIGITAL OUTPUT
(BINARY)
DIGITAL OUTPUT
(HEX)
+125
0111 1101 0000 0000
7D00h
+25.0625
0000 1010 0010 0000
1910h
+10.125
0000 1010 0010 0000
0A20h
+0.5
0000 0000 1000 0000
0080h
0
0000 0000 0000 0000
0000h
-0.5
1111 1111 1000 0000
FF80h
-10.125
1111 0101 1110 0000
F5E0h
-25.0625
1110 0110 1111 0000
E6F0h
-55
1100 1001 0000 0000
C900h
www.maximintegrated.com
Maxim Integrated │ 6
DS1775
Digital Thermometer and Thermostat in SOT23
the device. Following a clear, a subsequent fault can only
occur if consecutive conversions fall below THYST. This
interrupt/clear process is thus cyclical (TOS, clear, THYST,
clear, TOS, clear, THYST, clear, etc.). Only the first of
multiple consecutive TOS violations activates O.S., even
if each fault is separated by a clearing function. The same
situation applies to multiple consecutive THYST events.
Regardless of the mode chosen, the O.S. output is
open-drain and the active state is set in the configuration register. The power-up default is active low. See the
Programming section for instructions in adjusting the thermostat setpoints, thermostat mode, and O.S. active state.
Programming
There are three areas of interest in programming the
DS1775: the configuration register, the TOS register, and
the THYST register. All programming is done via the 2-wire
interface by setting the pointer to the appropriate location.
Table 2 illustrates the pointer settings for the four registers
of the DS1775.
TOS
MEASURED
TEMPERATURE
THYST
CONVERSIONS
COMPARATOR MODE
INACTIVE
O.S.
OUTPUT
ACTIVE
CONVERSIONS
INTERRUPT MODE
INACTIVE
O.S.
OUTPUT
ACTIVE
ASSUMES A READ
HAS OCCURRED
THIS TRANSFER FUNCTION ASSUMES THE DS1775 IS CONFIGURED SUCH THAT 2
CONSECUTIVE CONVERSIONS OUT OF TOLERANCE CONSTITUTE AND O.S. FAULT
Figure 2. O.S. Output Transfer Function
Table 2. Pointer Register Structure
www.maximintegrated.com
POINTER
ACTIVE REGISTER
00h
Temperature (default)
01h
Configuration
02h
THYST
03h
TOS
Maxim Integrated │ 7
DS1775
Digital Thermometer and Thermostat in SOT23
The DS1775 powers up with the temperature register
selected. If the host wishes to change the data pointer, it
simply addresses the DS1775 in the write mode (R/W=
0), receives an acknowledge, and writes the 8 bits that
correspond to the new desired location. The last pointer
location is always maintained so that consecutive reads
from the same register do not require the host to always
provide a pointer address. The only exception is at powerup, in which case the pointer is always set to 00h, the
temperature register. The pointer address must always
precede data in writing to a register, regardless of which
address is currently selected. See the 2-Wire Serial Data
Bus section for details of the 2-wire bus protocol.
Configuration Register Programming
The configuration register is accessed if the DS1775
pointer is currently set to the 01h location. Writing to or
reading from the register is determined by the R/W bit of
the 2-wire control byte (see the 2-Wire Serial Data Bus
section). Data is read from or written to the configuration
register MSb first. The format of the register is illustrated
in Table 3. The effect each bit has on DS1775 functionality
is described below along with the power-up state of the
bit. The user has read/write access to all bits in the configuration register. The entire register is volatile, and thus
it powers up in the default state.
SD = Shutdown bit. If SD is 0, the DS1775 continuously
performs temperature conversions and stores the last
completed result in the thermometer register. If SD is
changed to 1, the conversion in progress is completed
and stored; then the device reverts to a low-power standby mode. The O.S. output is cleared if the device is in the
interrupt mode and remains unchanged in the comparator mode. The 2-wire port remains active. The power-up
default state is 0 (continuous conversion mode).
TM = Thermostat mode. If TM = 0, the DS1775 is in the
comparator mode. TM = 1 sets the device to the interrupt
mode. See the Thermostat Control section for a description of the difference between the two modes. The powerup default state of the TM bit is 0 (comparator mode).
POL = O.S. Polarity Bit. If POL = 1, the active state of
the O.S. output is high. A 0 stored in this location sets the
thermostat output to an active-low state. The user has
read/write access to the POL bit, and the power-up default
state is 0 (active low).
F0, F1 = O.S. Fault Tolerance bits. The fault tolerance
defines the number of consecutive conversions returning
a temperature beyond limits is required to set the O.S.
output in an active state. This may be necessary to add
margin in noisy environments. Table 4 defines the four
settings. The DS1775 powers up with F0 = F1 = 0, such
that a single occurrence triggers a fault.
R0, R1 = Thermometer resolution bits. Table 5 defines
the resolution of the digital thermometer, based on the
settings of these two bits. There is a direct trade-off
between resolution and conversion time, as shown in the
AC Electrical Characteristics. The default state is R0 = 0
and R1 = 0 (9-bit conversions).
Table 3. Configuration/Status Register
0
R1
R0
F1
F0
POL
TM
MSb
SD
LSb
Table 4. Fault Tolerance Configuration
F1
F0
CONSECUTIVE CONVERSIONS BEYOND LIMITS TO GENERATE FAULT
0
0
1
0
1
2
1
0
4
1
1
6
Table 5. Thermometer Resolution Configuration
R1
R0
THERMOMETER RESOLUTION (BITS)
MAX CONVERSION TIME (SECONDS)
0
0
0
9
0.1875
1
10
0.375
1
0
11
0.75
1
1
12
1.5
www.maximintegrated.com
Maxim Integrated │ 8
DS1775
Digital Thermometer and Thermostat in SOT23
Thermostat Setpoints Programming
The thermostat registers (TOS and THYST) can be
programmed or read via the 2-wire interface. TOS is
accessed by setting the DS1775 data pointer to the 03h
location, and to the 02h location for THYST.
The format of the TOS and THYST registers is identical to
that of the Thermometer register; that is, 12-bit 2’s complement representation of the temperature in °C. The user
can program the number of bits (9, 10, 11, or 12) for each
TOS and THYST that corresponds to the thermometer
resolution mode chosen. For example, if the 9-bit mode is
chosen the three least significant bits of TOS and THYST
are ignored by the thermostat comparator. Table 6 shows
the format for both TOS and THYST. The power-up default
for TOS is +80°C and for THYST is +75°C.
If the user does not wish to take advantage of the thermostat capabilities of the DS1775, the 24 bits can be
used for general storage of system data that need not be
maintained following a power loss.
2-WIRE Serial Data Bus
The DS1775 supports a bidirectional 2-wire bus and data
transmission protocol. A device that sends data onto 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 which generates the serial clock (SCL),
controls the bus access, and generates the START and
STOP conditions. The DS1775 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
(see Figure 3):
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 are interpreted as control signals.
Table 6. Thermostat Setpoint (TOS/THYST) Format
S
26
25
24
2-2
2-3
2-4
MSb
2-1
23
22
21
0
0
(UNIT = °C)
20
MSB
LSb
0
0
LSB
TEMPERATURE
(°C)
DIGITAL OUTPUT
(BINARY)
DIGITAL OUTPUT
(HEX)
+80
0101 0000 0000 0000
5000h
+75
0100 1011 0000 0000
4B00h
+10.125
0000 1010 0010 0000
0A20h
+0.5
0000 0000 1000 0000
0080h
0
0000 0000 0000 0000
0000h
-0.5
1111 1111 1000 0000
FF80h
-10.125
1111 0101 1110 0000
F5E0h
-25.0625
1110 0110 1111 0000
E6F0h
-55
1100 1001 0000 0000
C900h
www.maximintegrated.com
Maxim Integrated │ 9
DS1775
Digital Thermometer and Thermostat in SOT23
Accordingly, the following bus conditions have been
defined:
The information is transferred byte-wise and each receiver acknowledges with a ninth bit.
Bus not busy: Both data and clock lines remain HIGH.
Within the bus specifications a standard mode (100kHz
clock rate) and a fast mode (400kHz clock rate) are
defined. The DS1775 works in both modes.
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 must be changed during the LOW
period of the clock signal. There is one clock pulse per
bit of data.
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.
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 which 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 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 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.
SDA
MSB
SLAVE
ADDRESS
R/W
DIRECTION
BIT
ACKNOWLEDGEMENT
SIGNAL FROM
RECEIVER
ACKNOWLEDGEMENT
SIGNAL FROM
RECEIVER
SCL
1
2
6
7
8
9
1
2
3–8
8
ACK
START
CONDITION
9
ACK
REPEATED IF
MORE BYTES ARE
TRANSFERRED
STOP CONDITION
OR REPEATED
START CONDITION
Figure 3. Data Transfer on 2-Wire Serial Bus
www.maximintegrated.com
Maxim Integrated │ 10
DS1775
Digital Thermometer and Thermostat in SOT23
Figure 3 details 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:
1) Data transfer from a master transmitter to a slave
receiver. The first byte transmitted by the master is
the slave address. 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 first byte (the slave address) is transmitted by the master. 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’ is returned.
The master device generates all the 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 is not released.
The DS1775 can operate in the following two modes:
1) Slave receiver mode: Serial data and clock are received through SDA and SCL. 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
address and direction bit.
www.maximintegrated.com
2) Slave transmitter mode: The first byte is received
and handled as in the slave receiver mode. However,
in this mode, the direction bit indicates that the transfer direction is reversed. Serial data is transmitted on
SDA by the DS1775 while the serial clock is input on
SCL. START and STOP conditions are recognized as
the beginning and end of a serial transfer.
Slave Address
A control byte is the first byte received following the
START condition from the master device. The control
byte consists of a 4-bit control code; for the DS1775, this
is set as 1001 binary for read and write operations. The
next three bits of the control byte are the device select bits
(A2, A1, A0). These bits are set to 000 (A2 = 0, A1 = 0, A0
= 0) for the DS1775R and vary according to the device’s
part number as specified in the Ordering Information
table. They are used by the master device to select which
of eight devices are to be accessed. The set bits are in
effect the three least significant bits of the slave address.
The last bit of the control byte (R/W) defines the operation to be performed. When set to a 1 a read operation is
selected; when set to a 0 a write operation is selected.
Following the START condition, the DS1775 monitors the
SDA bus checking the device type identifier being transmitted. Upon receiving the 1001 code and appropriate
device select bits of 000, the DS1775 outputs an acknowledge signal on the SDA line. See Figure 4.
Maxim Integrated │ 11
DS1775
Digital Thermometer and Thermostat in SOT23
WRITE TO POINTER ADDRESS
SCL
SDA
S
1
0
0
1
0
0
0
W
0
A
0
0
0
0 P1 P0
POINTER BYTE
ADDRESS BYTE
DS1775
ACK
WRITE TO CONFIGURATION REGISTER (SINGLE BYTE)
START
0
A
P
DS1775
ACK
STOP
SCL
SDA
S
1
0
0
1
0
0
0
W
A
0
0
0
0
0
POINTER BYTE
DS1775
ACK
WRITE TO TOS / THYST REGISTER (TWO–BYTE)
ADDRESS BYTE
START
0
0
A
1
D7 D6 D5 D4 D3 D2 D1 D0
A
DATA BYTE
DS1775
ACK
P
DS1775 STOP
ACK
SCL
SDA
S
1
0
0
1
0
0
0
W
0
0
0
0
0
A D7 D6 D5 D4 D3 D2 D1 D0
0 P1 P0
POINTER BYTE
DS1775
ACK
ADDRESS BYTE
START
A
MSBYTE
DS1775
ACK
A
DS1775
ACK
SCL
A
D7 D6 D5 D4 D3 D2 D1 D0
SDA
P
DS1775 STOP
ACK
LSBYTE
READ SINGLE BYTE FROM CURRENT POINTER LOCATION (CONFIGURATION)
SCL
SDA
S
1
0
0
1
0
0
0
Rd
DS1775
ACK
ADDRESS BYTE
START
A D7 D6 D5 D4 D3 D2 D1 D0
DATA BYTE
N
P
MASTER
NACK
STOP
READ MULTIPLE BYTES FROM CURRENT POINTER LOCATION (TEMPERATURE, TOS, THYST)
SCL
SDA
S
1
0
0
1
0
0
0
Rd
A
D7 D6 D5 D4 D3 D2 D1 D0
START
ADDRESS BYTE
DS1775
ACK
READ SINGLE BYTE FROM NEW POINTER ADDRESS REGISTER
MSBYTE
A
D7 D6 D5 D4 D3 D2 D1 D0
MASTER
ACK
LSBYTE
N
P
MASTER
ACK
STOP
SCL
SDA
S
1
START
0
0
1
0
0
0
W
ADDRESS BYTE
A
0
0
0
DS1775
ACK
0
0
0 P1 P0
POINTER BYTE
A
R 1
DS1775 REPEATED
ACK
START
0
0
1 A2 A1 A0 Rd
ADDRESS BYTE
A
DS1775
ACK
SCL
SDA
D7 D6 D5 D4 D3 D2 D1 D0
DATA BYTE
N
P
MASTER
NACK
STOP
Figure 4. 2-Wire Serial Communication with DS1775
www.maximintegrated.com
Maxim Integrated │ 12
DS1775
Digital Thermometer and Thermostat in SOT23
SDA
tBUF
tLOW
tR
tF
tHD:STA
SCL
tHD:STA
tSU:STO
tSU:STA
tHD:DAT
STOP
tHIGH
tSU:DAT
START
REPEATED
START
Figure 5. Timing Diagram
Ordering Information
PART
ADDRESS
TOP MARK
TEMP RANGE
000
7750
-55°C to +125°C
5 SOT23
001
7751
-55°C to +125°C
5 SOT23
010
7752
-55°C to +125°C
5 SOT23
011
7753
-55°C to +125°C
5 SOT23
100
7754
-55°C to +125°C
5 SOT23
101
7755
-55°C to +125°C
5 SOT23
110
7756
-55°C to +125°C
5 SOT23
111
7757
-55°C to +125°C
5 SOT23
DS1775R+U
DS1775R+T&R
DS1775R1+U
DS1775R1+T&R
DS1775R2+U
DS1775R2+T&R
DS1775R3+U
DS1775R3+T&R
DS1775R4+U
DS1775R4+T&R
DS1775R5+U
DS1775R5+T&R
DS1775R6+U
DS1775R6+T&R
DS1775R7+U
DS1775R7+T&R
PIN-PACKAGE
+Denotes a lead(Pb)-free/RoHS-compliant package.
U = Cut tape.
T&R = Tape and reel.
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
OUTLINE NO.
LAND PATTERN NO.
5 SOT23
U5+1
21-0057
90-0174
www.maximintegrated.com
Maxim Integrated │ 13
DS1775
Digital Thermometer and Thermostat in SOT23
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
1
5/13
Updated the Absolute Maximum Ratings, Ordering Information, Package Information
sections
2
11/16
Added typical specification to the Thermometer Error parameter in the Electrical
Characteristics table and added Thermometer Error (TERR) typical spec in the
Electrical Characteristics table.
DESCRIPTION
12, 13
2
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2016 Maxim Integrated Products, Inc. │ 14
工商网监
湘ICP备2023018690号
