DS620 [DALLAS]
Low-Voltage, 0.5∑C Accuracy Digital Thermometer and Thermostat; 低电压， ±0.5 °C精度数字温度计和温度监控器
| 型号： | DS620 |
| 厂家： | 
DALLAS SEMICONDUCTOR |
| 描述： | Low-Voltage, 0.5∑C Accuracy Digital Thermometer and Thermostat |
| 文件： | 总15页 (文件大小：294K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DS620
Low-Voltage, M0.5°C Accuracy
Digital Thermometer and Thermostat
www.maxim-ic.com
GENERAL DESCRIPTION
FEATURES
The DS620 digital thermometer and thermostat
provides low-voltage (1.7V ? VDD ? 3.5V) temperature
measurements with M0.5°C accuracy from 0°C to
+70°C and an operating temperature range of -55°C
to +125°C. The DS620 communicates over a 2-wire
digital interface. For distributed-sensing applications,
it is multidroppable with three address pins that allow
up to eight DS620s to operate on a single bus.
Cꢀ Low-Voltage Operation: 1.7V to 3.5V
Cꢀ M0.5°C Accuracy from 0°C to +70°C
Cꢀ Operating Temperature Range: -55°C to +125°C
(-67°F to +257°F)
Cꢀ Temperature Measurements Require No
External Components
Cꢀ Resolution is User-Selectable to 10-, 11-, 12-, or
13-Bits (0.5°C, 0.25°C, 0.125°C, and 0.0625°C
LSb Weight, Respectively)
The DS620 has thermostat functionality with user-
defined thresholds stored in EEPROM registers, and
it can be configured for standalone thermostat
operation. The programmable output (PO) pin serves
as the thermostat output, and this pin can also be
configured to function as an active-low control for
peripheral devices.
Cꢀ Multidroppable
Cꢀ Fast (200ms max) Temperature-to-Digital
Conversion Time
Cꢀ Thermostatic Settings are User-Definable and
Nonvolatile
Cꢀ Standalone Thermostat Capability
Cꢀ Data is Read/Written Through a 2-Wire Serial
Interface
Cꢀ Package: 8-Pin ꢀSOP
APPLICATIONS
Portable Applications
ORDERING INFORMATION
Low-Voltage Temperature-Sensitive Applications
Computers/Servers
PART
TEMP RANGE
PIN-PACKAGE
8 µSOP,
Test Equipment
DS620U
-55°C to +125°C
Exposed Pad
8 µSOP
Medical Instruments
Industrial Applications
DS620U/T&R
-55°C to +125°C
Exposed Pad
Tape-and-Reel
PIN CONFIGURATION
TYPICAL OPERATING CIRCUIT
1.7V to 3.5V
1.7V to 3.5V
DS620
1
2
3
4
8
7
6
5
SDA
SCL
PO
VDD
A0
VDD
SDA
SCL
SDA
SCL
PO
DS620
A0
A1
A2
GND
A1
A2
Thermostat
HOST
GND
8-Pin ꢀSOP Package
Exposed Pad
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata.
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081004
DS620 Digital Thermometer and Thermostat
PIN DESCRIPTION
PIN
NAME
FUNCTION
Data Input/Output Pin for serial communication. Open drain. (No diode connection to VDD).
Clock Input Pin for 2-wire serial communication.
Programmable Output Pin. Open drain. (No diode connection to VDD).
Ground Pin.
1
2
3
4
5
6
7
8
SDA
SCL
PO
GND
A2
Address Input Pin.
Address Input Pin. Also serves as an input to trigger one-shot conversions during standalone use.
Address Input Pin.
Supply Voltage Pin. +1.7V to +3.5V power supply pin.
A1
A0
VDD
Figure 1. Block Diagram
DS620
Temp. Core
Digital Control
POR
Bandgap
ADC
Memory Array
Configuration Register
Conversion Control
TH, TL Registers
Digital Comparator
Temperature Register
Address/Command
Decode
PO Pin
Control
PO
Address Counter
2-Wire Interface
Temperature Counter
Charge Pump
User EEPROM Registers
SCL
SDA
Memory Interface Logic
A0
A2
A1
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DS620 Digital Thermometer and Thermostat
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin, Relative to Ground
Operating Temperature Range
Storage Temperature Range
-0.5V to +4.5V
-55°C to +125°C
-55°C to +125°C
Soldering Temperature
See IPC/JEDEC J-STD-020A Specification
4KV HBM
ESD rating on all pins
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 the absolute maximum rating conditions for extended periods may affect device.
RECOMMENDED DC OPERATING CONDITIONS
(3.5V ≥ VDD ≥ 1.7V, TA = -55°C to +125°C.)
PARAMETER
SYMBOL
VDD
CONDITIONS
(Note 1)
MIN
1.7
TYP
MAX
3.5
UNITS
Voltage Range on Any Pin,
Relative to Ground
Supply Voltage for EEPROM
Writes
V
V
VDD
(Note 1)
2.0
3.5
DC ELECTRICAL CHARACTERISTICS
(3.5V ≥ VDD ≥ 1.7V, TA = -55°C to +125°C.)
PARAMETER
Thermometer Error
SYMBOL
CONDITIONS
0°C to +70°C
MIN
TYP
MAX
UNITS
±0.5
±2
TERR
°C
-55°C to +125°C
(Note 1)
0.7 x
VDD
VDD
+
Input Logic High
Input Logic Low
VIH
VIL
V
V
0.5
0.3 x
VDD
0.4
0.6
(Note 1)
- 0.5
VOL1
VOL2
VOL
3mA sink current (Note 1)
6mA sink current (Note 1)
4mA sink current (Note 1)
0.4 < VI/O < 0.9 x VDD
0
0
0
SDA Output Logic Low Voltage
V
PO Saturation Voltage
Input Current for each I/O pin
I/O Capacitance
0.4
+10
10
V
-10
µA
pF
µA
CI/O
Standby Current
ISTBY
0°C to +70°C (Note 2)
2
Temperature conversion, -
55°C to +85°C (Note 3)
Temperature conversion,
+85°C to +125°C (Note 3)
800
µA
µA
ms
Active Supply Current
IDD
900
500
E2 write (Note 3)
10 bit
11 bit
12 bit
13 bit
25
50
Temperature Conversion Time
TTC
100
200
Note 1: All voltages are referenced to GND.
Note 2: Specified with SDA = VDD; A0, A1, A2 = 0V or VDD
.
Note 3: Specified with A0, A1, A2 = 0V or VDD
.
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DS620 Digital Thermometer and Thermostat
AC ELECTRICAL CHARACTERISTICS
EEPROM AC Electrical Characteristics
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
EEPROM Write Cycle Time
TWR
-40°C to +85°C
10
ms
-40°C ≤ TA ≤ +85°C
10k
20k
80k
(Note 1)
TA = +25°C (Note 1)
-40°C to +125°C (Note 2)
EEPROM Writes
NEEWR
tEEDR
writes
years
40k
10
EEPROM Data Retention
2-Wire AC Electrical Characteristics
PARAMETER SYMBOL
SCL Frequency fSCL
tBUF
CONDITIONS
MIN
0
TYP
MAX
400
UNITS
KHz
Bus Free Time Between a
STOP and START Condition
START and Repeat START
Hold Time from Falling SCL
1.3
µs
tHD:STA
(Note 3, 4)
0.6
µs
Low Period of SCL
High Period of SCL
tLOW
tHIGH
(Note 3)
(Note 3)
1.3
0.6
µs
µs
Repeated START Condition
Setup Time to Rising SCL
Data-Out Hold Time from
Falling SCL
tSU:STA
tHD:DAT
tSU:DAT
tR
(Note 3)
0.6
µs
µs
ns
ns
ns
µs
(Note 3)
0
0.9
Data-In Setup Time to Rising
SCL
(Note 3)
100
20 +
0.1xCB
20 +
Rise Time of SDA and SCL
(Note 3, 5)
(Note 3, 5)
1000
300
Fall Time of SDA and SCL
tF
0.1xCB
STOP Setup Time to Rising
TSU:STO
0.6
SCL
Capacitive Load for Each BUS
Line
CB
CI
400
50
pF
pF
ns
Input Capacitance
10
Spike Pulse Width that can be
Suppressed by Input Filter
0
Note 1: VDD must be 2.0V to 3.5V.
Note 2: Write done at 25°C.
Note 3: All values referenced to 0.9 VDD and 0.1 VDD
.
Note 4: After this period the first clock pulse is generated.
Note 5: For example, if CB = 300pF, then tR(MIN) = tF(MIN) = 50ns.
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DS620 Digital Thermometer and Thermostat
Figure 2. Timing Diagram
Table 1. Register Summary
Parameter
Information
TH and TL Registers
EEPROM
Size: 2-Bytes
Factory State:
TH = 15ºC (0000 0111 1000 0000) [0780h]
TL = 10ºC (0000 0101 0000 0000) [0500h]
Note that the 3 LSbs are always “don’t cares” for writes
(i.e., they are not saved) and always read out as 0s.
Configuration Register
Size: 2-Bytes
SRAM and EEPROM. See Figure 4 and Table 5 for
detailed information and power-up/factory state.
SRAM Power-Up State: -60ºC
Temperature Register
Size: 2-Bytes
(1110 0010 0000 0000) [E200h]
TEMPERATURE MEASUREMENT
The DS620 measures temperature using a bandgap-based temperature sensor. A delta-sigma, analog-to-digital
converter (ADC) converts measured temperature to a 10-, 11-, 12-, or 13-bit (user-selectable) digital value that is
calibrated in °C; for °F applications, a lookup table or conversion routine must be used. Throughout this data sheet,
the term “conversion” is used to refer to the entire temperature measurement and ADC sequence.
The DS620 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 AUTOC bit in the configuration register as explained in
the Configuration Register section of this data sheet.
The DS620 can be programmed to perform continuous consecutive conversions (continuous conversion mode) or
to perform single conversions on command (one-shot mode). The conversion mode is programmed through the
1SHOT bit in the configuration register as explained in the Configuration Register section of this data sheet. In
continuous conversion mode, conversions are performed after a Start Convert command is issued (or upon power-
up if the AUTOC bit in the configuration register is set to 1) until a Stop Convert command is issued, at which time
the device goes into a low-power standby state. Continuous conversions can be restarted at any time using the
Start Convert command. In one-shot mode, the DS620 performs a single temperature conversion either at power-
up (if AUTOC = 1) or when a Start Convert command is issued (if AUTOC = 0). When the conversion is complete,
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DS620 Digital Thermometer and Thermostat
the device enters a low-power standby state and remains in that state until a temperature conversion is again
initiated by a Start Convert command.
The R0 and R1 bits in the configuration register allow the user to set the conversion resolution to be 10, 11, 12, or
13 bits (0.5°C, 0.25°C, 0.125°C, and 0.0625°C LSb weight, respectively) as shown in Table 6. The default
resolution at power-up is 13-bits. Note that the conversion time doubles for each additional bit of resolution.
After each conversion, the digital temperature is stored as a 16-bit two’s complement number in the 2-byte
temperature register as shown in Figure 3. The temperature register is located in address spaces AAh (MSB) and
ABh (LSB) of the DS620 memory. The sign bit (S) indicates if the temperature is positive (S = 0) or negative (S =
1). Bits 2, 1, and 0 of the temperature register are hardwired to 0. When the device is configured for 13-bit
resolution, the 13 MSbs (bits 15 through 3) of the temperature register will contain temperature data. For 12-bit
resolution, the 12 MSbs (bits 15 through 4) of the temperature register will contain data, and bit 3 will be 0.
Likewise, for 11-bit resolution, the 11 MSbs (bits 15 through 5) will contain data, and for 10-bit the 10 MSbs (bits 15
through 6) will contain data, and all unused LSbs will contain 0s. Table 2 gives examples of 13-bit resolution output
data and the corresponding temperatures.
Figure 3. Temperature, TH, And TL Register Format
bit 15
S
bit 14
bit 13
Bit 12
bit 11
bit 10
bit 9
bit 8
MS Byte
LS Byte
27
26
25
24
23
22
21
bit 7
bit 6
bit 5
Bit 4
bit 3
bit 2
0
bit 1
0
bit 0
0
20
2-1
2-2
2-3
2-4
Table 2. 13-Bit Resolution Temperature/Data Relationship
Digital Output (binary)
0011 1110 1000 0000
0000 1100 1000 1000
0000 0101 0001 0000
0000 0000 0100 0000
0000 0000 0000 0000
1111 1111 1100 0000
1111 1010 1111 0000
1111 0011 0111 1000
1110 0100 1000 0000
Digital Output (hex)
3E80h
Temperature (LC)
+125
+25.0625
+10.125
+0.5
0
-0.5
-10.125
-25.0625
-55
0C88h
0510h
0040h
0000h
FFC0h
FAF0h
F378h
E480h
WRITING TO THE TEMPERATURE REGISTER
The user is given access to write to the DS620 temperature register. This feature can be used for system test and
debugging by allowing the user to force the temperature reading above or below fault thresholds without having to
heat or cool the device.
If data is written to the temperature register while conversions are in progress, the result of the next completed
conversion will overwrite any data that was written to the temperature register. Additionally, no update of the flag
bits in the configuration register, nor an update of the PO pin occur as a result of the temperature being written if a
conversion is taking place. To avoid this from happening, conversions should first be stopped before writing to the
temperature register. When writing to the temperature register, both the MSB and the LSB should be written. An
update of the flag bits and PO pin will only occur after the LSB has been written. See Writing to the DS620 for more
information.
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DS620 Digital Thermometer and Thermostat
THERMOSTAT OPERATION
The PO pin on the DS620 operates as the thermostat output when it is configured as PO-HIGH or PO-LOW through the
P01 and P02 bits of the configuration register. In both of these configurations, PO is updated after every
temperature conversion or write to the temperature register, and remains at the updated value until the next
conversion or write completes. PO-HIGH and PO-LOW are active-low and are activated and deactivated based on
user-defined upper and lower trip-points. PO-HIGH is activated when the measured temperature meets or exceeds
the value stored in the upper trip-point register (TH), and stays active until the temperature meets or falls below the
value stored in the lower trip-point register (TL) (see Figure 4a). This allows the user to program any amount of
hysteresis into the output response. Similarly, PO-LOW is activated when the measured temperature meets or goes
below the value stored in the low trip-point register (TL), and stays active until the temperature meets or exceeds
the value stored in the upper trip-point register (TH) (see Figure 4b). The TH register is located in address spaces
A0h (MSB) and A1h (LSB) and the TL register is located in address spaces A2h (MSB) and A3h (LSB) of the
DS620 memory.
The TH and TL registers (see Table 1) contain centigrade temperature values in two’s complement format and are
stored in EEPROM; therefore, they are nonvolatile (NV) and can be programmed prior to installation of the DS620
for use in standalone applications. All bits in the TH and TL registers are used in the comparison to the temperature
value in the temperature register for the thermostat operation, regardless of the number of bits used for the
temperature conversions as decided by the R0 and R1 bits in the configuration register. Therefore, to ensure
proper thermostat operation, any bits not used for the temperature measurement should be set to 0 in the TH and
TL registers. For example, for 11-bit temperature conversions, bits 3 and 4 in the TH and TL register should be set to
0 prior to comparison to the measured temperature. (Bits 0 to 2 are automatically set to 0).
Another thermostat feature is the temperature high and low flags (THF and TLF) in the configuration register.
These bits provide a record of whether the temperature has ever been equal to or greater than TH or equal to or
less than TL at anytime since power up or since the bits were last cleared. If the temperature ever meets or
exceeds the TH register value, the THF bit in the configuration register is set to 1, and if the temperature ever
meets or falls below the TL value, the TLF bit in the configuration register is set to 1. Once THF or TLF has been
set, it remains set until the power is cycled or it is overwritten with a 0 by the user.
Figure 4. Thermostat Operation
a) PO-high
b) PO-low
Logic 1
Logic 1
Logic 0
Logic 0
Tem
Tem
Temp
Temp
TL
TH
T
TH
STANDALONE THERMOSTAT OPERATION
The DS620 can function as a standalone thermostat, i.e., it can provide thermostat functionality without requiring
communication with a microcontroller. For standalone thermostat operation, the TH, TL, and configuration registers
must be programmed to the desired values prior to installation. For standalone operation, the AUTOC bit in the
configuration register must be set to 1 so that measurements begins automatically at power up. This also
configures the A1 pin as an input pin that can trigger a conversion. In addition, PO must be configured as PO-HIGH
or PO-LOW. The 1SHOT bit in the configuration register is used to enable the DS620 to perform continuous
conversions at power up (1SHOT = 0) or a single conversion (one-shot) at power up or upon request (1SHOT = 1).
In one-shot mode, one conversion is performed at power-up and then the device enters a low-power standby state
until A1 is toggled high. The A1 pin must be toggled low and back high again to start another conversion.
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DS620 Digital Thermometer and Thermostat
PO PIN
The PO pin is a user-programmable open-drain output, which is configured through the PO1 and PO2 bits in the
configuration register. PO can operate as a thermostat output (PO-HIGH or PO-LOW), or it can be forced low for control
of peripheral devices. When PO is configured as PO-HIGH or PO-LOW, this pin operates as described in the
Thermostat Operation section. This pin can be reconfigured at anytime to switch between functions. Table 3
defines the various configuration options for this pin.
Table 3. PO Configuration
Function
PO2
PO1
1
Thermostat Output (PO-high)
Thermostat Output (PO-low)
Force PO Low
1
1
0
0
X
EEPROM REGISTERS AND MEMORY MAP
The DS620 has a 14-byte linear address space with registers for temperature, thermostat thresholds, and control
as well as four bytes of user EEPROM for general use. All address space is shadowed by RAM. The DS620
Memory Map is shown in Table 4.
See the Writing to the DS620 and the Reading from the DS620 sections for details in writing to and reading from
the DS620 EEPROM registers and memory map.
Table 4. Memory Map
Address (hex) Description
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
AA
AB
AC
AD
TH MSB
TH LSB
TL MSB
TL LSB
User
User
User
User
Undefined
Undefined
Temperature MSB
Temperature LSB
Configuration MSB
Configuration LSB
CONFIGURATION REGISTER
The configuration register allows the user to program various DS620 options such as conversion resolution,
operating mode, and thermostat capability. It also provides information to the user about conversion status,
EEPROM activity, device address, and thermostat activity. The configuration register is arranged as shown in
Figure 5 and detailed descriptions of each bit are provided in Table 5. It is located in address spaces ACh (MSB)
and ADh (LSB) in the DS620 memory. Note that the R0, R1, AUTOC, 1SHOT, and PO1 bits are stored in
EEPROM so they can be programmed prior to installation if desired. All other configuration bits are SRAM and
power up in the state shown in Table 5.
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DS620 Digital Thermometer and Thermostat
Figure 5. Configuration Register
Address ACh
bit 15
bit 14
NVB
bit 13
THF
bit 12
bit 11
R1*
bit 10
R0*
bit 9
AUTOC*
bit 8
1SHOT*
MS Byte
LS Byte
DONE
TLF
Address ADh
bit 7
PO2
bit 6
PO1*
bit 5
A2
bit 4
A1
bit 3
A0
bit 2
M*
bit 1
M*
bit 0
M*
*Stored in EEPROM
Table 5. Configuration Register Bit Descriptions
Bit Name
User Access
Functional Description
At power-up, DONE = 1. (Unless AUTOC = 1)
DONE = 0—Temperature conversion is in progress.
DONE = 1—Temperature conversion is complete.
At power-up, NVB = 0
Read Only
DONE
Read Only
Read/Write
NVB = 1—Write to an E2 memory cell is in progress
NVB = 0—Nonvolatile memory is not busy.
At power-up, THF = 0
NVB
THF
THF = 1—The measured temperature has reached or exceeded the value
stored in the TH register at anytime since power-up or since the bit was last
cleared. THF remains a 1 until the power is cycled or it is overwritten with a
0 by the user.
At power-up, TLF = 0
TLF = 1—The measured temperature has met or fallen below the value
stored in the TL register at anytime since power-up or since the bit was last
cleared. TLF remains a 1 until the power is cycled or it is overwritten with a
0 by the user.
Read/Write
TLF
Used to set conversion resolution (see Table 6).
Read/Write
Read/Write
*
Factory state = 1
R1
Used to set conversion resolution (see Table 6).
Factory state = 1
*
R0
Determines whether the DS620 powers up idle or converting.
Factory state = 0
Read/Write
Read/Write
*
AUTOC = 1—DS620 powers-up converting temperature.
AUTOC = 0—DS620 powers-up idle.
AUTOC
Configures temperature conversion mode. Factory state = 0
1SHOT = 1: One-shot mode
Cꢀ For AUTOC = 0, the device powers up idle The Start Convert
command causes a single temperature conversion and then the
device returns to a low-power standby state.
Cꢀ If AUTOC = 1, the A1 pin is reconfigured as a conversion trigger for
standalone operation and the device powers up and performs 1
conversion. Single conversions can be initiated using the Start
Convert command or by toggling A1 high.
*
1SHOT
1SHOT = 0: Continuous conversion mode
Cꢀ For AUTOC = 0, the Start Convert command initiates continuous
conversions.
Cꢀ For AUTOC = 1, the device powers up performing continuous
conversions. Note: Changing the 1SHOT bit to 1 while continuous
conversions are in progress does not stop the conversions. A Stop
Convert command must first be issued after which one-shot
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DS620 Digital Thermometer and Thermostat
conversions can be performed.
See Writing the 1SHOT Bit Command Sequence section for writing more
information on writing the 1SHOT bit.
At power-up, PO2 = 1.
PO2 = 0 forces the PO pin low (see Table 3)
PO2 = 1 configures PO as the thermostat output (PO-HIGH or PO-LOW, as
determined by PO1).
Read/Write
Read/Write
PO2
When PO2 = 1, PO1 configures the PO pin as either PO-HIGH or PO-LOW (see
Table 3)
PO1*
When PO2 = 0, PO1 is a “don’t care”.
Factory state = 0
A2
Read Only
Read Only
Read Only
Read/Write
Shows address bit A2, as determined by pin A2.
Shows address bit A1, as determined by pin A1.
Shows address bit A0, as determined by pin A0.
User memory for general-purpose data storage.
A1
A0
M*
*Stored in EEPROM
Table 6. Resolution Configuration
Max Conversion
Time (ms)
R1
R0
Resolution
LSb Weight (°C)
0
0
1
1
0
1
0
1
10-bit
11-bit
12-bit
13-bit
0.5
0.25
0.125
0.0625
25
50
100
200
2-WIRE SERIAL DATA BUS
The DS620 communicates over a standard bidirectional 2-wire serial data bus that consists of a serial clock (SCL)
signal and serial data (SDA) signal. The DS620 interfaces to the bus through the SCL input pin and open-drain
SDA I/O pin. All communication is MSb first.
The following terminology is used to describe 2-wire communication:
Master Device: Microprocessor/microcontroller that controls the slave devices on the bus. The master device
generates the SCL signal and START and STOP conditions.
Slave: All devices on the bus other than the master. The DS620 always functions as a slave.
Bus Idle or Not Busy: Both SDA and SCL remain high. SDA is held high by a pullup resistor when the bus is idle,
and SCL must either be forced high by the master (if the SCL output is push-pull) or pulled high by a pullup resistor
(if the SCL output is open-drain).
Transmitter: A device (master or slave) that is sending data on the bus.
Receiver: A device (master or slave) that is receiving data from the bus.
START Condition: Signal generated by the master to indicate the beginning of a data transfer on the bus. The
master generates a START condition by pulling SDA from high to low while SCL is high (see Figure 6). A
“repeated” START is sometimes used at the end of a data transfer (instead of a STOP) to indicate that the master
will perform another operation.
STOP Condition: Signal generated by the master to indicate the end of a data transfer on the bus. The master
generates a STOP condition by transitioning SDA from low to high while SCL is high (see Figure 6). After the
STOP is issued, the master releases the bus to its idle state.
Acknowledge (ACK): When a device (either master or slave) is acting as a receiver, it must generate an
acknowledge (ACK) on the SDA line after receiving every byte of data. The receiving device performs an ACK by
pulling the SDA line low for an entire SCL period (see Figure 6). During the ACK clock cycle, the transmitting
device must release SDA. A variation on the ACK signal is the “not acknowledge” (NACK). When the master device
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DS620 Digital Thermometer and Thermostat
is acting as a receiver, it uses a NACK instead of an ACK after the last data byte to indicate that it is finished
receiving data. The master indicates a NACK by leaving the SDA line high during the ACK clock cycle.
Slave Address: Every slave device on the bus has a unique 7-bit address that allows the master to access that
device. The DS620’s 7-bit bus address is 1 0 0 1 A2 A1 A0, where A2, A1, and A0 are user-selectable via the
corresponding input pins. The three address pins allow up to eight DS620s to be multidropped on the same bus.
Control Byte: The control byte is transmitted by the master and consists of the 7-bit slave address plus a
read/write (R/¯W¯) bit (see Figure 7). If the master is going to read data from the slave device then R/¯W¯ = 1, and if
the master is going to write data to the slave device then R/¯W¯ = 0.
Address Byte: The address byte is used by the master to tell the DS620 which address location in the memory
map in Table 4 is going to be accessed during communication or which command should be performed. See
Command Set section.
Figure 6. START, STOP, AND ACK SIGNALS
SDA
SCL
STOP
START
ACK (or NACK)
From Receiver
Condition
Condition
Figure 7. Control Byte
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
1
0
0
1
A2
A1
A0
R/¯W¯
GENERAL 2-WIRE INFORMATION
CꢀAll data is transmitted MSb first over the 2-wire bus.
CꢀOne bit of data is transmitted on the 2-wire bus each SCL period.
CꢀA pullup resistor is required on the SDA line and, when the bus is idle, both SDA and SCL must remain in a logic-
high state.
CꢀAll bus communication must be initiated with a START condition and terminated with a STOP condition. During a
START or STOP is the only time SDA is allowed to change states while SCL is high. At all other times, changes
on the SDA line can only occur when SCL is low: SDA must remain stable when SCL is high.
CꢀAfter every 8-bit (1-byte) transfer, the receiving device must answer with an ACK (or NACK), which takes one
SCL period. Therefore, nine clocks are required for every one-byte data transfer.
INITIATING 2-WIRE COMMUNICATION
To initiate 2-wire communication, the master generates a START followed by a control byte containing the DS620
slave address. The R/W bit of the control byte must be a 0 (write) since the master next writes a command byte or
an address byte. The DS620 responds with an ACK after receiving the control byte. This must be followed by a
command byte from the master which indicates what type of command operation is to be performed, or an address
byte when the master intends to write to or read from the DS620. The DS620 again responds with an ACK after
receiving the command or address byte. The master can then issue a STOP to signal the end of the
communication sequence, or continue writing to the address memory. See the Command Set section for details on
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DS620 Digital Thermometer and Thermostat
the DS620 commands. See Writing to the DS620 or Reading from the DS620 for more information on reading from
and writing to the DS620.
WRITING TO THE DS620
The master can write data to the DS620 by issuing an address byte following the control byte. The R/W bit in the
control byte must be a 0 (write). After receiving an ACK from the DS620 in response to the control byte, the master
sends the address of the first register byte to be written, loading the address counter with the desired location. The
DS620 responds with another ACK, after which the master sends the data to be written. After receiving each byte
of data, the DS620 responds with an ACK. The master continues to write data to successive address locations until
it indicates there is no more data to be written by sending a STOP or repeated START condition. The DS620
ignores any data written once the address increments past ADh, the last defined register in the DS620 memory,
and indicates this by sending a NACK after each byte. It also ignores data written to undefined addresses A8h and
A9h. All writes to the DS620 are made to the shadow RAM. Once data is written to the shadow RAM, it is only
stored to EEPROM by issuance of a Copy Data command from the master. At that time all registers are copied to
EEPROM, except the Temperature registers, which are SRAM only, and the undefined registers. The DS620 must
be set to the continuous conversion mode and be actively converting temperature to enable the Copy Data
command to function properly. See Copying to EEPROM Command Sequence for more information.
READING FROM THE DS620
The master can read data from the DS620 by issuing an address byte following the control byte. The R/W bit in the
control byte must be a 0 (write). After receiving an ACK from the DS620 in response to the control byte, the master
writes the address of the first register byte to be read, loading the address counter with the desired location. The
DS620 will respond with another ACK. The master then must issue a repeated START (or a STOP and a START)
followed by a control byte with the same slave address as the first control byte. However, this time the R/W bit must
be a 1 which tells the DS620 that a “read” is being performed. After the DS620 sends an ACK in response to this
control byte, it begins transmitting the requested data on the next clock cycle. The master responds with an ACK
between each byte of data read from the DS620 until no further bytes of data are to be read, at which time the
master responds with a NACK followed by a STOP. The DS620 sends all 1’s (FFh) once the address increments
past ADh, the last defined register in the DS620 memory. There is no guaranteed state of data read from the
undefined registers, A8h and A9h. The Recall Data command should be issued before a read to assure that the
contents of the EEPROM will be in the Shadow RAM when read.
COMMAND SET
The DS620 command set is detailed below:
Start Convert [ 51h ]
0101 0001
Initiates temperature conversions. If the part is in one-shot mode (1SHOT = 1), only one conversion is performed.
In continuous mode (1SHOT = 0), continuous temperature conversions are performed until a Stop Convert
command is issued (even if 1SHOT is changed to a 1).
Stop Convert [ 22h ]
0010 0010
Stops temperature conversions when the device is in continuous conversion mode (1SHOT = 0). This command
has no function if the device is in one-shot mode (1SHOT = 1)
Recall Data [ B8h ]
1011 1000
Refreshes SRAM shadow register with EEPROM data.
Copy Data [ 48h ]
0100 1000
Copies data from all SRAM shadow registers to EEPROM.
NOTE: The DS620 must be set to the continuous conversion mode and be actively converting temperature to
enable the Copy Data command to function properly. See example command sequence in the Copying to
EEPROM Command Sequence section for more information.
Software POR [ 54h ]
0101 0100
Initiates a software power-on-reset (POR), which stops temperature conversions and resets all registers and logic
to their power-up states. The software POR allows the user to simulate cycling the power without actually powering
down the device. This command should not be issued while a Copy Data command is in progress.
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DS620 Digital Thermometer and Thermostat
COPYING TO EEPROM COMMAND SEQUENCE
Data is written to DS620 and then copied from SRAM to EEPROM
BUS
MASTER
MODE
TX
DATA
(MSB
DS620
MODE
RX
RX
TX
SEQUENCE
COMMENTS
NUMBER
FIRST)
START
Bus master initiates a START condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge bit.
1
2
3
TX
<address, 0>
RX
ACK
Bus master sends the address location of the first byte
of data to be written. (In this case the first byte of user
EEPROM).
TX
RX
A4h
4
RX
TX
RX
TX
RX
TX
RX
TX
TX
RX
TX
RX
TX
RX
TX
RX
ACK
<data>
ACK
DS620 generates acknowledge.
5
6
Bus master sends one byte of data to the SRAM
location for EEPROM address A4h.
DS620 generates acknowledge.
7
Bus master sends one byte of data to the SRAM
location for EEPROM for address A5h.
DS620 generates acknowledge.
<data>
ACK
8
9
Bus master sends one byte of data to the SRAM
location for EEPROM for address A6h.
DS620 generates acknowledge.
<data>
ACK
10
11
12
Bus master sends one byte of data to the SRAM
location for EEPROM for address A7h.
DS620 generates acknowledge.
<data>
RX
TX
TX
RX
TX
RX
RX
TX
ACK
START
13
14
15
16
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
<address, 0>
ACK
Bus master sends the address location of the MSb of
the configuration register (contains the 1SHOT bit).
This writes to the SRAM location corresponding the
EEPROM location. NOTE: Sequence numbers 17
through 23 need to be done only if DS620 is in 1SHOT
mode: 1SHOT = 1.
TX
RX
ACh
17
RX
TX
TX
RX
ACK
DS620 generates acknowledge.
18
19
Bus master writes to the configuration register putting
the DS620 in continuous conversion mode: 1SHOT =
0.
xxxxxxx0b
RX
TX
TX
RX
TX
RX
RX
TX
ACK
START
DS620 generates acknowledge.
20
21
22
23
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge
<address, 0>
ACK
Master sends START CONVERT command to DS620
to start temperature conversions.
TX
RX
51h
24
DS620 generates acknowledge bit and begins
conversions.
RX
TX
ACK
25
TX
TX
RX
RX
RX
TX
START
<address, 0>
ACK
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
26
27
28
Bus master sends the address location of the MSb of
the configuration register (contains the 1SHOT bit).
This writes to the SRAM location corresponding the
EEPROM location. NOTE: command sequence
numbers 29 through 34 need only be done if a return to
1SHOT mode operation is needed.
TX
RX
ACh
29
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DS620 Digital Thermometer and Thermostat
RX
TX
TX
RX
ACK
DS620 generates acknowledge.
30
31
Bus master writes to the configuration register putting
the DS620 back in 1SHOT mode: 1SHOT = 1.
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
xxxxxxx1b
TX
TX
RX
RX
RX
TX
START
<address, 0>
ACK
32
33
34
Master sends COPY DATA command to DS620 to
copy data in from SRAM memory to EEPROM memory.
DS620 generates acknowledge.
TX
RX
48h
35
RX
TX
TX
RX
TX
RX
RX
TX
ACK
START
36
37
38
39
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
<address, 0>
ACK
Bus master sends a STOP CONVERT command to
stop the DS620 from continuously converting
temperature. NOTE: Bus master should ensure that
EEPROM copy operation is complete before executing
the STOP CONVERT command by either waiting 10ms
from the time of the COPY DATA command or
checking the NVB bit in configuration register
DS620 generates acknowledge.
TX
RX
22h
40
RX
TX
TX
RX
ACK
41
42
Bus master sends STOP condition to end
communication with DS620. (The bus master could
send a repeated start condition if additional
communication with the DS620 is desired.)
STOP
WRITING THE 1SHOT BIT COMMAND SEQUENCE
Configuring from continuous mode to 1SHOT mode.
BUS
DS620
MODE
RX
RX
TX
DATA
SEQUENCE
NUMBER
MASTER
MODE
TX
COMMENTS
(MSB FIRST)
START
<address, 0>
ACK
Bus master initiates a START condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge bit.
1
2
3
TX
RX
Master sends START CONVERT command to DS620
to start temperature conversions.
TX
RX
51h
4
DS620 generates acknowledge bit and begins
conversions.
RX
TX
ACK
5
TX
TX
RX
RX
RX
TX
START
<address, 0>
ACK
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
6
7
8
Bus master sends the address location of the MSb of
the configuration register (contains the 1SHOT bit).
This writes to the SRAM location corresponding the
EEPROM location.
TX
RX
ACh
9
RX
TX
TX
RX
ACK
DS620 generates acknowledge.
10
11
Bus master writes to the configuration register putting
the DS620 in 1SHOT mode: 1SHOT = 1.
DS620 generates acknowledge.
xxxxxxx1b
RX
TX
TX
RX
TX
RX
RX
TX
ACK
START
12
13
14
15
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
<address, 0>
ACK
Master sends COPY DATA command to DS620 to
copy data in from SRAM memory to EEPROM
memory.
TX
RX
48h
16
14 of 15
DS620 Digital Thermometer and Thermostat
RX
TX
TX
RX
TX
RX
RX
TX
ACK
START
DS620 generates acknowledge.
17
18
19
20
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
<address, 0>
ACK
Bus master sends STOP CONVERT command to
stop the DS620 from continuously converting
temperature. NOTE: Bus master should ensure that
EEPROM copy operation is complete before
executing the STOP CONVERT command by either
waiting 10ms from the time of the COPY DATA
command or checking the NVB bit in configuration
register
TX
RX
22h
21
RX
TX
TX
RX
ACK
DS620 generates acknowledge.
22
23
Bus master sends STOP condition to end
communication with DS620. (The bus master could
send a repeated start condition if additional
communication with the DS620 is desired.)
STOP
Configuring from 1SHOT to mode to continuous conversion mode.
BUS
MASTER
MODE
TX
DATA
(MSB
DS620
MODE
RX
RX
TX
SEQUENCE
NUMBER
COMMENTS
FIRST)
START
<address, 0>
ACK
Bus master initiates a START condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge bit.
1
2
3
TX
RX
Bus master sends the address location of the MSb of
the configuration register (contains the 1SHOT bit).
This writes to the SRAM location corresponding the
EEPROM location.
TX
RX
ACh
4
RX
TX
TX
RX
ACK
DS620 generates acknowledge.
5
6
Bus master writes to the configuration register putting
the DS620 in continuous conversion mode: 1SHOT =
0.
xxxxxxx0b
RX
TX
TX
RX
TX
RX
RX
TX
ACK
START
DS620 generates acknowledge.
7
8
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
<address, 0>
ACK
9
10
Master sends START CONVERT command to DS620
to start temperature conversions.
TX
RX
51h
11
DS620 generates acknowledge bit and begins
conversions.
RX
TX
ACK
12
TX
TX
RX
RX
RX
TX
START
<address, 0>
ACK
Bus master generates a repeated start condition.
Bus master sends DS620 address, R/W = 0.
DS620 generates acknowledge.
13
14
15
Master sends COPY DATA command to DS620 to
copy data in from SRAM memory to EEPROM
memory.
TX
RX
RX
TX
48h
16
17
ACK
DS620 generates acknowledge.
Bus master sends STOP condition to end
communication with DS620. (The bus master could
send a repeated start condition if additional
communication with the DS620 is desired.)
TX
RX
STOP
18
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