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DS620U+
Low-Voltage, ±0.5°C Accuracy Digital Thermometer and Thermostat
GENERAL DESCRIPTION The DS620 digital thermometer and thermostat
provides low-voltage (1.7V ≤ VDD ≤ 3.5V) temperature
measurements with ±0.5°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.
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.
APPLICATIONS Portable Applications
Low-Voltage Temperature-Sensitive Applications
Computers/Servers
Test Equipment
Medical Instruments
Industrial Applications
TYPICAL OPERATING CIRCUIT
FEATURES Low-Voltage Operation: 1.7V to 3.5V ±0.5°C Accuracy from 0°C to +70°C Operating Temperature Range: -55°C to +125°C
(-67°F to +257°F) Temperature Measurements Require No
External Components 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) Multidroppable Fast (200ms max) Temperature-to-Digital
Conversion Time Thermostatic Settings are User-Definable and
Nonvolatile Standalone Thermostat Capability Data is Read/Written Through a 2-Wire Serial
Interface Package: 8-Pin μSOP
ORDERING INFORMATION
PART TEMP RANGE PIN-PACKAGE DS620U -55°C to +125°C 8 µSOP,
Exposed Pad
DS620U/T&R -55°C to +125°C
8 µSOP
Exposed Pad
Tape-and-Reel
PIN CONFIGURATION
DS620
Low-Voltage, ±0.5°C Accuracy
Digital Thermometer and Thermostat
VDD
PO SDA
SCL
A0
A1
A2
GND
1.7V to 3.5V
HOST
SDA
SCL
1.7V to 3.5V
Thermostat
DS620
PAD
PAD
8-Pin μSOP Package
Exposed Pad
SDA
SCL
GND
VDD
DS620 Digital Thermometer and Thermostat
PIN DESCRIPTION
PIN NAME FUNCTION 1 SDA
Data Input/Output Pin for serial communication. Open drain. (No diode connection to VDD). 2 SCL
Clock Input Pin for 2-wire serial communication. 3 PO
Programmable Output Pin. Open drain. (No diode connection to VDD). 4 GND
Ground Pin. 5 A2
Address Input Pin. 6 A1
Address Input Pin. Also serves as an input to trigger one-shot conversions during standalone use. 7 A0
Address Input Pin. 8 VDD
Supply Voltage Pin. +1.7V to +3.5V power supply pin. PAD
PAD. Connect to GND or float. DO NOT CONNECT TO SUPPLY. The exposed pad is the best way to conduct temperature into the package. Connecting PAD to a ground plane can assist in properly measuring the
temperature of the circuit board.
Figure 1. Block Diagram
Memory Array 2-Wire Interface
Charge Pump
Temp. Core Bandgap
ADC POR
Digital Control
PO Pin
Control
Address Counter
Address/Command
Decode
Conversion Control
Configuration Register
TH, TL Registers
Digital Comparator
Temperature Register
User EEPROM Registers
Temperature Counter
Memory Interface Logic
PO
SCL
SDA
A2
A1
A0
DS620
DS620 Digital Thermometer and Thermostat
ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin, Relative to Ground -0.5V to +4.5V
Operating Temperature Range -55°C to +125°C
Storage Temperature Range -55°C to +125°C
Soldering Temperature See IPC/JEDEC J-STD-020A Specification
ESD rating on all pins 4KV HBM
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 CONDITIONS MIN TYP MAX UNITS Voltage Range on Any Pin,
Relative to Ground VDD (Note 1) 1.7 3.5 V
Supply Voltage for EEPROM
Writes VDD (Note 1) 2.0 3.5 V
DC ELECTRICAL CHARACTERISTICS (3.5V ≥ VDD ≥ 1.7V, TA = -55°C to +125°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0°C to +70°C ±0.5 Thermometer Error TERR
-55°C to +125°C ±2
°C
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
VOL1 3mA sink current (Note 1) 0 0.4 SDA Output Logic Low Voltage VOL2 6mA sink current (Note 1) 0 0.6 V
PO Saturation Voltage VOL 4mA sink current (Note 1) 0 0.4 V
Input Current for each I/O pin 0.4 < VI/O < 0.9 x VDD -10 +10 µA
I/O Capacitance CI/O 10 pF
Standby Current ISTBY 0°C to +70°C (Note 2) 2 µA
Temperature conversion, -
55°C to +85°C (Note 3) 800
Temperature conversion,
+85°C to +125°C (Note 3) 900
µA Active Supply Current IDD 2 write (Note 3) 500 µA
10 bit 25
11 bit 50
12 bit 100 Temperature Conversion Time TTC
13 bit 200
ms
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. 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
(Note 1) 10k 20k EEPROM Writes NEEWR
TA = +25°C (Note 1) 40k 80k
writes
EEPROM Data Retention tEEDR -40°C to +125°C (Note 2) 10 years
2-Wire AC Electrical Characteristics
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SCL Frequency fSCL 0 400 KHz
Bus Free Time Between a
STOP and START Condition tBUF 1.3 µs
START and Repeat START
Hold Time from Falling SCL tHD:STA (Note 3, 4) 0.6 µs
Low Period of SCL tLOW (Note 3) 1.3 µs
High Period of SCL tHIGH (Note 3) 0.6 µs
Repeated START Condition
Setup Time to Rising SCL tSU:STA (Note 3) 0.6 µs
Data-Out Hold Time from
Falling SCL tHD:DAT (Note 3) 0 0.9 µs
Data-In Setup Time to Rising
SCL tSU:DAT (Note 3) 100 ns
Rise Time of SDA and SCL tR (Note 3, 5) 20 +
0.1xCB 1000 ns
Fall Time of SDA and SCL tF (Note 3, 5) 20 +
0.1xCB 300 ns
STOP Setup Time to Rising
SCL TSU:STO 0.6 µs
Capacitive Load for Each BUS
Line CB 400 pF
Input Capacitance CI 10 pF
Spike Pulse Width that can be
Suppressed by Input Filter 0 50 ns
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. DS620 Digital Thermometer and Thermostat
Figure 2. Timing Diagram
Table 1. Register Summary
Parameter Information
TH and TL Registers
Size: 2-Bytes Note that the 3 LSbs are always “don’t cares” for writes
(i.e., they are not saved) and always read out as 0s.
EEPROM
Factory State:
TH = 15ºC (0000 0111 1000 0000) [0780h]
TL = 10ºC (0000 0101 0000 0000) [0500h]
Configuration Register
Size: 2-Bytes SRAM and EEPROM. See Figure 4 and Table 5 for
detailed information and power-up/factory state.
Temperature Register
Size: 2-Bytes SRAM Power-Up State: -60ºC
(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-
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 bit 14 bit 13 Bit 12 bit 11 bit 10 bit 9 bit 8
MS Byte S 27 26 25 24 23 22 21 bit 7 bit 6 bit 5 Bit 4 bit 3 bit 2 bit 1 bit 0
LS Byte 20 2-1 2-2 2-3 2-4 0 0 0
Table 2. 13-Bit Resolution Temperature/Data Relationship
Temperature (°C) Digital Output (binary) Digital Output (hex) +125 0011 1110 1000 0000 3E80h
+25.0625 0000 1100 1000 1000 0C88h
+10.125 0000 0101 0001 0000 0510h
+0.5 0000 0000 0100 0000 0040h 0000 0000 0000 0000 0000h
-0.5 1111 1111 1100 0000 FFC0h
-10.125 1111 1010 1111 0000 FAF0h
-25.0625 1111 0011 0111 1000 F378h
-55 1110 0100 1000 0000 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.
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
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.
a) PO-high
TL TH Tem
Logic 0
Logic 1 TH
Logic 0
Logic 1
Tem
b) PO-low
TempTemp
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 Thermostat Output (PO-high) 1 1
Thermostat Output (PO-low) 1 0
Force PO Low 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 TH MSB
A1 TH LSB
A2 TL MSB
A3 TL LSB
A4 User
A5 User
A6 User
A7 User
A8 Undefined
A9 Undefined
AA Temperature MSB
AB Temperature LSB
AC Configuration MSB
AD 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.
