HDC2021
SNAS773A – DECEMBER 2019 – REVISEDHDC2021
JUNE 2020
SNAS773A – DECEMBER 2019 – REVISED JUNE 2020
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HDC2021 High-Accuracy, Low-Power Humidity and Temperature Sensor With
Assembly Protection Cover
1 Features
3 Description
•
The HDC2021 is an integrated relative humidity and
temperature sensor with a factory-installed polyimide
tape cover over the opening of the relative humidity
sensor element. The tape cover provides protection
against pollutants that can appear in certain stages of
the manufacturing process, such as SMT assembly,
PCB board wash, and conformal coating. The tape
design allows for a full conformal coating of the PCB,
and includes an adhesive free corner tab for quick
removal using tweezers.
•
•
•
•
•
•
•
•
•
•
Factory-installed polyimide tape to protect sensor
during assembly
RH measurement range: 0% to 100%
Temperature measurement range: –40°C to 125°C
Humidity accuracy: ±2% (typical), ±3% (maximum)
Temperature accuracy: ±0.2°C (typical), ±0.4°C
(maximum)
Supply voltage range: 1.62 V to 3.6 V
I2C interface compatibility
50 nA sleep mode current
550 nA average supply current (11-bit accuracy
option, 1 measurement/second)
Continuous conversion or one-shot measurement
mode
Backward-compatible with HDC2080
2 Applications
•
•
•
•
•
•
Thermostats
Smart speakers (with voice assistant)
Washers and dryers
HVAC sensor transmitters (temperature, pressure,
and humidity)
HVAC system controllers
Wireless environmental sensors
VDD
VDD
HDC2021
I2 C
Master
SDA
ADC
Registers
+
Logic
Temperature
Sensor
I2 C
DRDY/INT
Device Information
PART NUMBER
HDC2021
VDD
SCL
RH
Sensor
The HDC2021 device is backward-compatible with the
HDC2080, providing high accuracy measurements
with very low power consumption in a small DFN
package. The capacitive-based sensor includes new
integrated digital features and a heating element to
dissipate condensation and moisture. The HDC2021
digital features include programmable interrupt
thresholds to provide alerts and system wake-ups
without requiring a microcontroller to continuously
monitor the system. Combined with programmable
sampling intervals, low power consumption, and 1.8-V
supply voltage support, the HDC2021 is designed for
ultra-low power battery-operated systems.
(1)
PACKAGE
(1)
WSON (6)
BODY SIZE (NOM)
3.00 mm × 3.00 mm
For all available packages, see the orderable addendum at
the end of the data sheet.
10
GPIO
Typical
ADDR
MCU
9
8
Calibration
Typical Application
GND
Accuracy (r%RH)
GND
7
6
5
4
3
2
1
0
0
10
20
30
40
50
60
70
80
90
100
RH (%RH)
RH Accuracy (TA = 30°C)
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
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© 2020 Texas
Instruments
Incorporated
intellectual
property
matters
and other important disclaimers. PRODUCTION DATA.
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SNAS773A – DECEMBER 2019 – REVISED JUNE 2020
Table of Contents
1 Features............................................................................1
2 Applications..................................................................... 1
3 Description.......................................................................1
4 Revision History.............................................................. 2
5 Pin Configuration and Functions...................................3
Pin Functions.................................................................... 3
6 Specifications.................................................................. 4
6.1 Absolute Maximum Ratings........................................ 4
6.2 ESD Ratings............................................................... 4
6.3 Recommended Operating Conditions.........................4
6.4 Thermal Information....................................................4
6.5 Electrical Characteristics.............................................5
6.6 Switching Characteristics............................................6
6.7 Timing Diagram...........................................................7
6.8 Typical Characteristics................................................ 8
7 Detailed Description......................................................10
7.1 Overview................................................................... 10
7.2 Functional Block Diagram......................................... 10
7.3 Feature Description...................................................11
7.4 Device Functional Modes..........................................18
7.5 Programming............................................................ 18
7.6 Register Maps...........................................................20
8 Application and Implementation.................................. 33
8.1 Application Information............................................. 33
8.2 Typical Application.................................................... 33
9 Power Supply Recommendations................................35
10 Layout...........................................................................35
10.1 Layout Guidelines................................................... 35
10.2 Layout Example...................................................... 36
11 Device and Documentation Support..........................37
11.1 Documentation Support.......................................... 37
11.2 Receiving Notification of Documentation Updates.. 37
11.3 Support Resources................................................. 37
11.4 Trademarks............................................................. 37
11.5 Electrostatic Discharge Caution.............................. 37
11.6 Glossary.................................................................. 37
12 Mechanical, Packaging, and Orderable
Information.................................................................... 38
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from December 19, 2019 to June 26, 2020 (from Revision * (December 2019) to
Revision A (June 2020))
Page
• Changed data sheet status from Advanced Information to Production Data......................................................1
• Updated the numbering format for tables, figures, and cross-references throughout the document..................1
2
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5 Pin Configuration and Functions
SDA
1
6
SCL
GND
2
5
VDD
ADDR
3
4
DRDY/INT
Figure 5-1. DEB Package 6-Pin WSON Transparent Top View
Pin Functions
PIN
NAME
NO.
TYPE(1)
DESCRIPTION
ADDR
3
I
Address select pin – connect to VDD, GND or float.
Connect to GND or float: address= 1000000X
Connect to VDD: address= 1000001X
where 'X' represents the read-write (R/W) bit.
DRDY/INT
4
O
Data ready/Interrupt. Push-Pull Output.
GND
2
G
Ground
SCL
6
I
Serial clock line for I2C.
SDA
1
I/O
VDD
5
P
(1)
Serial data line for I2C. Open-drain output that requires a pullup resistor.
Positive Supply Voltage
The definitions below define the functionality of the TYPE cells for each pin:
• I = input
• O = output
• I/O = input/output
• G = ground
• P = power
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)
MIN
MAX
VDD
Applied Voltage on VDD pin
–0.3
3.9
V
ADDR
Applied Voltage on ADDR pin
–0.3
3.9
V
SCL
Applied Voltage on SCL pin
–0.3
3.9
V
SDA
Applied Voltage on SDA pin
–0.3
3.9
V
DRDY/INT
Applied Voltage on DRDY/INT pin
–0.3
VDD+ 0.3
V
TJ
Junction temperature
–40
150
°C
Tstg
Storage temperature
–65
150
°C
(1)
UNIT
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under
Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device
reliability.
6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)
±2000
Charged device model (CDM), per JEDEC specification JESD22-C101(2)
±500
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
PARAMETER
MIN
MAX
1.62
3.6
Temperature Sensor - Operating free-air temperature
–40
125
°C
Relative Humidity Sensor - Operating free-air temperature
–20
70
°C
–40
85
°C
20
80
%RH
VDD
Supply voltage
TTEMP
TRH
THEATER Integrated Heater - Operating free-air temperature
RHOR
(1)
Relative Humidity Sensor (Non-condensing)(1)
UNIT
V
Recommended humidity operating range is 20% to 80% RH (non-condensing) over 0°C to 60°C. Prolonged operation beyond these
ranges may result in a shift of sensor reading, with slow recovery time.
6.4 Thermal Information
HDC2021
THERMAL
METRIC(1)
WSON (DEB)
UNIT
6 PINS
RθJA
Junction-to-ambient thermal resistance
57.9
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
58.7
°C/W
RθJB
Junction-to-board thermal resistance
27.0
°C/W
ΨJT
Junction-to-top characterization parameter
5.6
°C/W
ΨJB
Junction-to-board characterization parameter
26.9
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
16.5
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report SPRA953.
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6.5 Electrical Characteristics
TA = 30°C, VDD = 1.8 V, 20% ≤ RH ≤ 80% (unless otherwise noted)
PARAMETER
TEST CONDITION
MIN
TYP
MAX
UNIT
±2
±3
%RH
RELATIVE HUMIDITY SENSOR
RHACC
Accuracy(3) (4) (5)
RHREP
Repeatability(6)
RHHYS
Hysteresis(8)
RHRT
Response
time(9)
RHCT
Conversion time(6)
RHLTD
Long-term drift(11)
RHPSRR
Supply Sensitivity accuracy
14 bit accuracy option
Rising, 30% to 75% RH, t63%
step(10)
±0.1
%RH
±1
%RH
6
s
9 bit accuracy option
254
µs
11 bit accuracy option
383
µs
14 bit accuracy option
640
µs
±0.25
%RH/yr
VDD = 1.8V to 3.6V
±0.3
%RH/V
5°C ≤ TA ≤ 60°C
±0.2
±0.7
°C
±0.4
°C
TEMPERATURE SENSOR
TEMPACC
Accuracy(7)
10°C ≤ TA ≤ 35°C
±0.2
TEMPREP
Repeatability(6)
14 bit accuracy option
±0.1
°C
9 bit accuracy option
208
µs
TEMPCT
Conversion time(6)
11 bit accuracy option
336
µs
14 bit accuracy option
594
µs
TEMPPSRR
Supply Sensitivity accuracy
VDD = 1.8V to 3.6V
0.05
℃/V
TEMPLTD
Long term
drift(6)
High Temperature Operating Life (HTOL) tested at
125°C for 1000 hours
Normalized using Arrhenius-Peck Acceleration Model
TA = 30°C, 0.7eV activation energy
±0.04
°C/yr
POWER CONSUMPTION
Averaged at 1 sample per
RH & TEMP sensor: 14 bit second
accuracy option(1) (2)
Averaged at 1 sample
every two seconds
No Measurement (Sleep
Mode)
IDD
Supply current
µA
0.3
µA
One-shot
0.05
Continuous conversion
0.1
µA
0.05
0.1
µA
During RH + TEMP measurement(1)
650
890
µA
During TEMP measurement only(1)
550
730
µA
Startup
Serial Bus Active. fSCL =
400 kHz
IHEATER
0.55
Peak
200
µA
Average
80
µA
One-shot
12
µA
Continuous conversion
12
µA
Integrated
heater (enabled)
VDD = 3.3V; THEATER - TA = 80°C
Steady state measurement
90
mA
Power-on reset voltage
TA = -40°C to 125°C
1.4
V
SUPPLY RAIL
VDD_POR
SCL, SDA PINS
VIH
High level input voltage
VIL
Low level input voltage
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0.7 x
VDD
V
0.3 x
VDD
V
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PARAMETER
TEST CONDITION
VOL
Low level output voltage
IOL = 3 mA
CI
Input pin capacitance(12)
VI = VDD or GND
II
Input leakage current
VI = VDD, or 3.6V, or GND
MIN
TYP
MAX
0.4
SCL
1.7
SDA
1.6
UNIT
V
pF
pF
SCL
-0.1
0.1
µA
SDA
-0.1
0.1
µA
DRDY/INT PIN
VDD = 1.62V to 3.60V
High Level Output Voltage
(Figure 6-11)
VDD = 3.3V
VOH
VDD = 1.8V
VOL
Low Level Output Voltage
(Figure 6-10)
IOZ_DRDY
Output leakage current in
Hi-Z
VDD = 1.62V to 3.60V
VDD = 3.3V
VDD = 1.8V
IOH = -100 µA.
IOH = -2 mA.
VDD –
0.2
V
2.4
V
1.1
V
IOL = 100 µA.
IOL = 2 mA.
DRDY/INT Pin = Hi-Z.
-0.1
0.2
V
0.4
V
0.45
V
0.1
µA
(1)
(2)
(3)
(4)
Does not include I2C read/write communication or pullup resistor current through SCL and SDA
Average current consumption while conversion is in progress
Excludes hysteresis and long-term drift
Excludes the impact of dust, gas phase solvents and other contaminents such as vapors from packaging materials, adhesives, or
tapes, etc.
(5) Limits apply over the humidity operating 20% to 80% RH (non-condensing) from 0°C to 60°C
(6) This parameter is specified by design and/or characterization and is not tested in production
(7) Over-temperature performance is specified by design and/or characterization
(8) The hysteresis value is the difference between the RH measurement in a rising and falling RH environment, at a specific RH point
(9) Actual response times will vary dependent on system thermal mass and air-flow
(10) Time for the RH output to change by 63% of the total RH change after a step change in environmental humidity
(11) Drift due to aging effects at typical conditions (30°C and 20% to 50% RH). This value may be impacted by dust, vaporized solvents,
outgassing tapes, adhesives, packaging materials, etc.
(12) Guaranteed by design/characterization; not production tested
6.6 Switching Characteristics
TA = -40°C to 125°C and VDD = 1.62V to 3.60V (unless otherwise noted)
PARAMETER
MIN
TYP
MAX
UNIT
400
kHz
SCL, SDA PINS
fSCL
SCL clock frequency(1)
10
tLOW
LOW period of the SCL clock(1)
1.3
µs
tHIGH
High period of the SCL
clock(1)
tSU;DAT
Setup Time: Data(1)
tHD;DAT
Hold Time:
tSU;STA
Set-up time: Repeated START condition(1)
condition(1) (2)
tHD;STA
Hold time: Repeated START
tSU;STO
Set-up time: STOP condition(1)
µs
ns
0
µs
0.6
µs
0.6
µs
0.6
µs
tR;SCL
Rise Time:
SCL(1)
300
ns
tR;SDA
Rise Time: SDA(1)
300
ns
tF;SCL
Fall Time:
SCL(1)
20*(VDD/5.5V)
300
ns
tF;SDA
Fall Time: SDA(1)
20*(VDD/5.5V)
300
ns
tBUF
Bus free time between a STOP and START
tVD;DAT
Data valid time(1) (3)
tVD;ACK
6
Data(1)
0.6
100
Data valid acknowledge
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time(1) (4)
condition(1)
1.3
µs
0.9
µs
0.9
µs
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PARAMETER
MIN
TYP
MAX
UNIT
SUPPLY RAIL
Power-On Reset or Software Reset Duration(1)
tPOR
(1)
(2)
(3)
(4)
3.5
ms
This parameter is specified by design and/or characterization and is not tested in production
After this period, the first clock pulse is generated
Time for data signal from SCL low to SDA output (high to low, depending on which is worse)
Time for acknowledement signal from SCL low to SDA output (high or low, depending on which is worse)
6.7 Timing Diagram
S
P
tLOW
tR
tHD:DAT
tHIGH
SCL
VIH(MIN)
VIL(MAX)
tF
tHD:STA
tSU:DAT
Sr
P
tSU:STA
tSU:STO
VIH(MIN)
VIL(MAX)
SDA
tBUF
Figure 6-1. I2C Timing Diagram
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6.8 Typical Characteristics
Unless otherwise noted, TA = 30°C, VDD = 1.8 V.
1
10
Typical
9
0.9
8
0.8
7
0.7
Accuracy (r°C)
Accuracy (r%RH)
Typical
6
5
4
0.6
0.5
0.4
0.3
3
0.2
2
0.1
1
0
-40
0
0
10
20
30
40
50
60
70
80
90
100
-25
-10
5
20
Figure 6-2. RH Accuracy vs. RH Set Point
65
80
95
110
125
800
T = -40°C
T = -20°C
T = 0°C
T = 25°C
T = 85°C
T = 125°C
750
700
750
700
VDD = 1.71V
VDD = 1.8V
VDD = 2.5V
VDD = 3V
VDD = 3.3V
VDD = 3.6V
650
IDD (nA)
650
IDD (nA)
50
Figure 6-3. Temperature Accuracy vs. Temperature
Set Point
800
600
600
550
550
500
500
450
450
400
1.6
35
Temp (°C)
RH (%RH)
1.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
400
-40
3.6
-15
10
35
60
85
110
125
Temp (°C)
VDD (V)
Figure 6-4. Supply Current vs. Supply Voltage,
Figure 6-5. Supply Current vs. Temperature,
Average at 1 Measurement/Second, RH (11-Bit) and Average at 1 Measurement/Second, RH (11-Bit) and
Temperature (11-Bit)
Temperature (11-Bit)
400
400
T = -40°C
T = -20°C
T = 0°C
T = 25°C
T = 50°C
T = 85°C
T = 125°C
350
300
350
300
250
IDD (nA)
IDD (nA)
250
200
150
100
100
50
50
1.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
VDD (V)
Figure 6-6. Supply Current vs. Supply Voltage,
Sleep Mode
8
200
150
0
1.6
VDD = 1.71V
VDD = 1.8V
VDD = 2.5V
VDD = 3V
VDD = 3.3V
VDD = 3.6V
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0
-40
-15
10
35
60
85
110
125
Temp (°C)
Figure 6-7. Supply Current vs. Temperature, Sleep
Mode
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Figure 6-8. Supply Sensitivity- Humidity
Measurement Accuracy
Figure 6-10. Average Measurement Sensitivity vs.
Accuracy Option
Figure 6-12. Output Voltage (DRDY/INT Pin) vs.
Output Current (Logic High)
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Figure 6-9. Supply Sensitivity- Temperature
Measurement Accuracy
Figure 6-11. Output Voltage (DRDY/INT Pin) vs.
Output Current (Logic Low)
Figure 6-13. Sampling Period Variation
(Continuous Conversion Mode) vs. Temperature
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7 Detailed Description
7.1 Overview
The HDC2021 is a highly integrated digital humidity and temperature sensor that incorporates both humiditysensing and temperature-sensing elements, an analog-to-digital converter, calibration memory, and an I2C
interface that are all contained in a 3.00-mm × 3.00-mm, 6-pin WSON package. The HDC2021 provides
excellent measurement accuracy with very low power consumption and features configurable accuracy options
for both the humidity and temperature sensors:
• Temperature accuracy options: 9, 11, or 14 bits
• Humidity accuracy options: 9, 11, or 14 bits
The conversion time during measurements is dependent upon the configured accuracy option for humidity and
temperature. The flexable programmability allows the device to be configured for optimal measurement accuracy
and power consumption.
The HDC2021 device incorporates a state-of-the-art polymer dielectric to provide capacitive-sensing
measurements. As with most relative humidity sensors that include this type of technology, the user must meet
these application requirements to ensure optimal device performance for the sensing element:
•
•
•
•
Follow the correct storage and handling procedures during board assembly. See Humidity Sensor: Storage
and Handling Guidelines. (SNIA025) for these guidelines.
Protect the sensor from contaminants during operation.
Reduce prolonged exposure to both high temperature and humidity extremes that may impact sensor
accuracy.
Follow the correct layout guidelines for best performance. See Optimizing Placement and Routing for
Humidity Sensors (SNAA297) for these guidelines.
7.2 Functional Block Diagram
VDD
HDC2021
SCL
RH
Sensor
SDA
ADC
Registers
+
Logic
Temperature
Sensor
I2C
DRDY/INT
ADDR
Calibration
GND
10
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7.3 Feature Description
7.3.1 Factory Installed Polyimide Tape
A polyimide tape covers the opening of the humidity sensor element. The tape protects the humidity sensor
element from pollutants that can be produced as part of the manufacturing process, such as SMT assembly,
PCB board wash, and conformal coating. The tape must be removed after the final stages of assembly for
accurate measurement of relative humidity in the ambient environment. The tape can withstand at least three
standard reflow cycles.
To remove the polyimide tape from the humidity sensor element, TI recommends to use a ESD-safe tweezer to
grip the adhesive free tab in the lower right corner, then slowly peel from the bottom right corner towards the top
left corner (pin 1 designator) in an upward direction (as opposed to across the surface). This will help to reduce
the risk of scratching the humidity sensor element.
7.3.2 Sleep Mode Power Consumption
One key feature of the HDC2021 is the low power consumption designed for battery-powered or energyharvesting applications. In these applications, the HDC2021 can be put into sleep mode with a typical current
consumption of 50 nA, minimizing the average power consumption and self-heating. The sleep mode is the
default operating mode upon power-on reset.
7.3.3 Measurement Modes: One-Shot vs. Continuous Conversion
There are two types of measurement modes are available on the HDC2021: one-shot mode and continuous
conversion mode.
During one-shot mode, each measurement is initiated through an I2C command on an as-needed basis. After
the measurement is completed, the device goes back to the sleep mode automatically until another I2C
command to initiate a measurement is received.
The HDC2021 can also be configured to perform measurements on a periodic basis in continuous conversion
mode to eliminate the need to initiate multiple measurement requests through I2C commands. The user can
adjust the Device Configuration register to select one of 7 different sampling rates spanning from 1 sample every
2 minutes to 5 samples every second. In continuous conversion mode, the HDC2021 periodically wakes up from
the sleep mode based on the selected sampling rate.
7.3.4 Heater
The HDC2021 includes an integrated heating element that can be switched on briefly to prevent or remove any
condensation that may build up in high humidity environments. Additionally, the heater can be used to verify
functionally of the integrated temperature sensor.
If the dew point of an application is continuously calculated and tracked, and the application firmware is written
such that it can detect a potential condensing situation (or a period of it), a software subroutine can be run, as a
precautionary measure, to activate the onboard heater as an attempt to remove the condensate. The device
shall continue to measure and track the %RH level after the heater is activated. Once the %RH reading goes to
zero % (or near it), the heater can be subsequently turned off, allowing the device to cool down. Cooling of the
device can takes minutes and temperature measurement shall continue to be performed to ensure the device
goes back to normal operating condition before restarting the device for normal service.
Note once the heater activates, the operating temperature of the device shall be limited to below 100°C. The
heater has a typical current draw of 90 mA at 3.3-V operation and 55 mA at 1.8-V operation.
It is important to recognize that the integrated heater evaporates condensate that forms on top of the humidity
sensor, but does not remove any dissolved contaminants. Any contaminant residue, if present, may impact the
accuracy of the humidity sensor.
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7.3.5 Interrupt
Note
When multiple bits are enabled, the DRDY/INT pin can only reflect the status of one interrupt bit at a
time. The DRDY/INT pin DOES NOT function as the logical ‘OR’ of interrupt bits that have been
enabled.
The highest priority is given to TH_ENABLE bit, followed by TL_ENABLE, HH_ENABLE, and
HL_ENABLE bits in descending order. Therefore, programming recommendations are provided as
below. Note the DataReady (DRDY) interrupt has the same priority as the winner of the other 4
interrupts (TH_ENABLE, TL_ENABLE, HH_ENABLE, and HL_ENABLE).
• The DRDY/INT will track the HL_ENABLE, if enabled, and all other ENABLE bits are disabled.
• The DRDY/INT will track the HH_ENABLE, if enabled, and the TH_ENABLE and TL_ENABLE are
disabled.
• The DRDY/INT will track the TL_ENABLE, if enabled, and the TH_ENABLE is disabled.
• The DRDY/INT will track the TH_ENABLE, if enabled, and is independent of other ENABLE bit
settings.
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7.3.5.1 DataReady (DRDY) Interrupt
When DRDY_ENABLE is enabled in the Interrupt Configuration register (address 0x07), and a humidity and/or
temperature conversion is complete, the DRDY_STATUS bit of the Status register (address 0x04) is asserts to 1.
To enable hardware interrupt generation on the DRDY/INT pin of HDC2021, the DRDY/INT_EN bit must be set
to 1 and the INT_MODE bit must be set to 0 in the Device Configuration register (address 0x0E). If these bits are
not configured, the DRDY/INT pin is kept in high impedance regardless of the interrupt status. The INT_POL bit
of this register defines the interrupt polarity of the DRDY/INT pin. Figure 7-1 and Figure 7-2 display the output
behavior of the DRDY/INT pin for both interrupt polarity cases: INT_POL= 0 and INT_POL= 1. The interrupt is
cleared upon reading the Status register (address 0x04).
Previous Data
New Data Available
1
DRDY_STATUS
0
VDD
DRDY/INT
[INT_POL = 1]
0
Figure 7-1. Data Ready Interrupt - Active High (INT_POL = 1)
Previous Data
New Data Available
1
DRDY_STATUS
0
VDD
DRDY/INT
[INT_POL = 0]
0
Figure 7-2. Data Ready Interrupt - Active Low (INT_POL = 0)
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7.3.5.2 Threshold Interrupt
7.3.5.2.1 Temperature High (TH)
When TH_ENABLE is enabled in the Interrupt Configuration register (address 0x07) and the temperature is over
the programmed threshold level stored in the Temperature Threshold HIGH register (address 0x0B), the
TH_STATUS bit of the Status register (address 0x04) asserts to 1. The interrupt is cleared upon reading the
Status register.
The polarity and interrupt mode of the TH_STATUS bit and the DRDY/INT pin can be configured through the
INT_POL and INT_MODE bits of the Device Configuration Register (address 0x0E). The INT_MODE bit sets the
threshold to either comparator mode or clear-on-read mode. When the INT_MODE bit is set to 0, the
TH_STATUS bit remains set to 1 until it is read. When the INT_MODE bit is set to 1, the TH_STATUS bit status
reflects the current temperature conversion result. The polarity of the DRDY/INT pin is set by INT_POL bit.
T [°C]
Temperature Threshold High
Time
TH_STATUS
[INT_MODE = 0]
1
0
DRDY/INT pin
[INT_MODE = 0]
[INT_POL = 1]
VDD
DRDY/INT pin
[INT_MODE = 0]
[INT_POL = 0]
VDD
TH_STATUS
[INT_MODE = 1]
Status Register
Read
0
0
1
0
DRDY/INT pin
[INT_MODE = 1]
[INT_POL = 1]
VDD
DRDY/INT pin
[INT_MODE = 1]
[INT_POL = 0]
VDD
0
0
Figure 7-3. INTERRUPT on Threshold - Temperature High
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7.3.5.2.2 Temperature Low (TL)
When TL_ENABLE is enabled in the Interrupt Configuration register (address 0x07) and the temperature is
under the programmed threshold level stored in the Temperature Threshold LOW register (address 0x0C), the
TL_STATUS bit of the Status register (address 0x04) asserts to 1. The interrupt is cleared upon reading the
Status register.
The polarity and interrupt mode of the TL_STATUS bit and the DRDY/INT pin can be configured through the
INT_POL and INT_MODE bits of the Device Configuration Register (address 0x0E). The INT_MODE bit sets the
threshold to either comparator mode or clear-on-read mode. When the INT_MODE bit is set to 0, the
TL_STATUS bit remains set to 1 until it is read. When the INT_MODE bit is set to 1, the TL_STATUS bit status
reflects the current temperature conversion result. The polarity of the DRDY/INT pin is set by INT_POL bit.
T [°C]
Temperature Threshold Low
Time
TL_STATUS
[INT_MODE = 0]
1
Status Register
Read
0
V
DRDY/INT pin
[INT_MODE = 0]
[INT_POL = 1]
0
DD
V
DRDY/INT pin
[INT_MODE = 0]
[INT_POL = 0]
0
DD
TL_STATUS
[INT_MODE = 1]
1
0
VDD
DRDY/INT pin
[INT_MODE = 1]
[INT_POL = 1]
0
V
DRDY/INT pin
[INT_MODE = 1]
[INT_POL = 0]
0
DD
Figure 7-4. INTERRUPT on Threshold - Temperature Low
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7.3.5.2.3 Humidity High (HH)
When HH_ENABLE is enabled in the Interrupt Configuration register (address 0x07) and the temperature is
under the programmed threshold level stored in the Humidity Threshold HIGH register (address 0x0D), the
HH_STATUS bit of the Status register (address 0x04) asserts to 1. The interrupt is cleared upon reading the
Status register.
The polarity and interrupt mode of the HH_STATUS bit and the DRDY/INT pin can be configured through the
INT_POL and INT_MODE bits of the Device Configuration Register (address 0x0E). The INT_MODE bit sets the
threshold to either comparator mode or clear-on-read mode. When the INT_MODE bit is set to 0, the
HH_STATUS bit remains set to 1 until it is read. When the INT_MODE bit is set to 1, the HH_STATUS bit status
reflects the current temperature conversion result. The polarity of the DRDY/INT pin is set by INT_POL bit.
H [%RH]
Humidity Threshold High
Time
1
HH_STATUS
[INT_MODE = 0]
Status Register
Read
0
VDD
DRDY/INT pin
[INT_MODE = 0]
[INT_POL = 1]
0
VDD
DRDY/INT pin
[INT_MODE = 0]
[INT_POL = 0]
0
HH_STATUS
[INT_MODE = 1]
1
DRDY/INT pin
[INT_MODE = 1]
[INT_POL = 1]
VDD
DRDY/INT pin
[INT_MODE = 1]
[INT_POL = 0]
VDD
0
0
0
Figure 7-5. INTERRUPT on Threshold - Humidity High
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7.3.5.2.4 Humidity Low (HL)
When HL_ENABLE is enabled in the Interrupt Configuration register (address 0x07) and the temperature is
under the programmed threshold level stored in the Humidity Threshold HIGH register (address 0x0E), the
HL_STATUS bit of the Status register (address 0x04) asserts to 1. The interrupt is cleared upon reading the
Status register.
The polarity and interrupt mode of the HL_STATUS bit and the DRDY/INT pin can be configured through the
INT_POL and INT_MODE bits of the Device Configuration Register (address 0x0E). The INT_MODE bit sets the
threshold to either comparator mode or clear-on-read mode. When the INT_MODE bit is set to 0, the
HL_STATUS bit remains set to 1 until it is read. When the INT_MODE bit is set to 1, the HL_STATUS bit status
reflects the current temperature conversion result. The polarity of the DRDY/INT pin is set by INT_POL bit.
H [%RH]
Humidity Threshold Low
Time
1
HL_STATUS
[INT_MODE = 0]
DRDY/INT pin
[INT_MODE = 0]
[INT_POL = 1]
DRDY/INT pin
[INT_MODE = 0]
[INT_POL = 0]
HL_STATUS
[INT_MODE = 1]
Status Register
Read
0
VDD
0
VDD
0
1
0
DRDY/INT pin
[INT_MODE = 1]
[INT_POL = 1]
VDD
DRDY/INT pin
[INT_MODE = 1]
[INT_POL = 0]
VDD
0
0
Figure 7-6. INTERRUPT on Threshold - Humidity Low
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7.4 Device Functional Modes
The HDC2021 has two modes of operation: sleep mode and measurement mode.
7.4.1 Sleep Mode vs. Measurement Mode
After power up, the HDC2021 defaults to sleep mode and waits for an I2C instruction to set programmable
conversion times, trigger a measurement or conversion, or read or write valid data. When a measurement is
triggered, the HDC2021 switches to measurement mode that converts temperature or humidity values from
integrated sensors through an internal ADC and stores the information in their respective data registers. The
DRDY/INT pin can be monitored to verify if data is ready after measurement conversion. The DRDY/INT pin
polarity and interrupt mode are set according to the configuration of the Interrupt Configuration (address 0x07)
and Device Configuration (address: 0x0E) registers. After completing the conversion, the HDC2021 returns to
sleep mode.
7.5 Programming
7.5.1 I2C Serial Bus Address Configuration
To communicate with the HDC2021, the master must first address slave devices through a slave address byte.
The slave address byte consists of seven address bits and a direction bit that indicates the intent to execute a
read or write operation. The HDC2021 features an address pin (ADDR) to allow up to 2 devices to be addressed
on a single bus. Table 7-1 describes the pin logic levels used to connect up to two devices, with 'X' representing
the read-write (R/W) bit. The ADDR pin shall be configured before any activity on the interface occurs and
remain constant while the device is powered up.
Table 7-1. HDC2021 I2C Slave Address
ADDR
ADDRESS
GND or floating
1000000X
VDD
1000001X
Note that the ADDR is recommended not to be left floating if the device is to be used in noisy environment.
7.5.2 I2C Interface
The HDC2021 operates only as a slave device on the I2C bus interface. It is not allowed to have multiple devices
on the same I2C bus with the same address. Connection to the bus is made through the SDA and SCL pins. The
SDA and SCL pins feature integrated spike-suppression filters and Schmitt triggers to minimize the effects of
input spikes and bus noise. After power-up, the sensor needs at least 3.5 ms to be ready to start RH and
temperature measurement. After power-up the device defaults in sleep mode until a communication or
measurement is performed. All data bytes are transmitted MSB first.
7.5.3 Read and Write Operations
Register content of the HDC2021 can be accessed and modified through a pointer mechanism using a pointer
register. The user can write a register address to the pointer register to access a particular register on the
device. The value for the pointer register is the first byte transferred after the slave address byte with the R/W bit
low (refer to Table 7-2). Every write operation to the device requires a value for the pointer register.
When reading from the device, the last value stored in the pointer register by a write operation is used to
determine which register is read during a read operation. To change the register pointer for a read operation, a
new value must be written to the pointer register. The user can issue an address byte with the R/W bit low,
followed by the pointer register byte to write a new value for the pointer register (refer to Table 7-4). No additional
data is required. The master can then generate a START condition and send the slave address byte with the
R/W bit high to initiate the read command.
The device also support Multibyte write and Multibyte read operations of which the register pointer is
incremented automatically until the master issues a STOP (for Multibyte write) or NACK (for Multibyte read).
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Note all data transferred are sent MSB first. A write operation to a read-only register such as DEVICE ID or
MANUFACTURER ID returns a NACK after each data byte. A read or write operation to an unused register
returns a NACK after the pointer register byte, and a read or write operation with incorrect device slave address
returns a NACK after the device slave address byte.
Table 7-2. Write Single Byte
Master
Device Slave address (W)
100000X0
START
Register Pointer
Slave
ACK
DATA
STOP
ACK
ACK
Table 7-3. Write Multibyte
Master
START
Device Slave
address (W)
100000X0
Slave
Register
Pointer
ACK
DATA
DATA
ACK
………
ACK
STOP
ACK
Table 7-4. Read Single Byte
Master
START
Device Slave address
(W) 100000X0
Slave
Register
Pointer
ACK
Start
Device Slave
address (R)
100000X1
NACK
ACK
ACK
STOP
DATA
Table 7-5. Read Multibyte
Master START
Slave
Device Slave
address (W)
100000X0
Register
Pointer
ACK
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Start
ACK
Device Slave
address (R)
100000X1
ACK
ACK
DATA
ACK
……
NACK
STOP
DATA
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7.6 Register Maps
The HDC2021 contains registers that hold configuration information, temperature and humidity measurement
results, and status information.
Table 7-6. Register Map
20
ADDRESS (HEX)
NAME
RESET VALUE
(HEX)
DESCRIPTION
0x00
TEMPERATURE LOW
0
Temperature data [7:0]
0x01
TEMPERATURE HIGH
0
Temperature data [15:8]
0x02
HUMIDITY LOW
0
Humidity data [7:0]
0x03
HUMIDITY HIGH
0
Humidity data [15:8]
0x04
STATUS
0
DataReady and threshold status
0x05
TEMPERATURE MAX
0
Maximum measured temperature
(one-shot mode only)
0x06
HUMIDITY MAX
0
Maximum measured humidity
(one-shot mode only)
0x07
INTERRUPT ENABLE
0
Interrupt enable
0x08
TEMP_OFFSET_ADJUST
0
Temperature offset adjustment
0x09
HUM_OFFSET_ADJUST
0
Humidity offset adjustment
0x0A
TEMP_THR_L
1
Temperature threshold low
0x0B
TEMP_THR_H
FF
Temperature threshold high
0x0C
RH_THR_L
0
Humidity threshold low
0x0D
RH_THR_H
FF
Humidity threshold high
0x0E
DEVICE CONFIGURATION
0
Soft reset and interrupt reporting configuration
0x0F
MEASUREMENT CONFIGURATION
0
Device measurement configuration
0xFC
MANUFACTURER ID LOW
49
Manufacturer ID lower-byte
0xFD
MANUFACTURER ID HIGH
54
Manufacturer ID higher-byte
0xFE
DEVICE ID LOW
D0
Device ID lower-byte
0xFF
DEVICE ID HIGH
7
Device ID higher0byte
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7.6.1 Temperature Low (Address: 0x00)
Table 7-7. Temperature Low Register (Address 0x00)
7
6
5
4
3
2
1
0
TEMP[7:0]
Table 7-8. Temperature Low Register Field Descriptions
BIT
FIELD
[7:0]
RESET
(HEX)
TYPE
TEMPERATURE [7:0]
R
DESCRIPTION
Temperature data- lower byte
0
The temperature data is a 16-bits value that spans accross the Temperature Low (address 0x00) and
Temperature High (address 0x01) registers. The Temperature Low register containts the lower-byte of the 16-bits
temperature data.
The temperature can be calculated from the output data using Equation 1:
Temperature (qC)
§ TEMPERATURE [15 : 0] ·
¨
¸ u 165 40
©
¹
216
(1)
7.6.2 Temperature High (Address: 0x01)
Table 7-9. Temperature High Register (Address 0x01)
7
6
5
4
3
2
1
0
TEMP[15:8]
Table 7-10. Temperature High Register Field Descriptions
BIT
FIELD
[15:8]
TEMPERATURE [15:8]
RESET
(HEX)
TYPE
R
0
DESCRIPTION
Temperature data- higher byte
The temperature data is a 16-bits value that spans accross the Temperature Low (address 0x00) and
Temperature High (address 0x01) registers. The Temperature High register containts the higher-byte of the 16bits temperature data.
The temperature can be calculated from the output data using Equation 2:
Temperature (qC)
§ TEMPERATURE [15 : 0] ·
¨
¸ u 165 40
©
¹
216
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7.6.3 Humidity Low (Address 0x02)
Table 7-11. Humidity Low Register (Address 0x02)
7
6
5
4
3
2
1
0
HUMIDITY[7:0]
Table 7-12. Humidity Low Register Field Descriptions
BIT
FIELD
[7:0]
RESET
(HEX)
TYPE
HUMIDITY [7:0]
R
DESCRIPTION
Humidity data- lower byte
0
The humidity data is a 16-bits value that spans accross the Humidity Low (address 0x02) and Humidity High
(address 0x03) registers. The Humidity Low register containts the lower-byte of the 16-bits humidity data.
The humidity can be calculated from the output data using Equation 3:
§ HUMIDITY [15 : 0] ·
¨
¸ u 100
216
©
¹
Humidity (%RH)
(3)
7.6.4 Humidity High (Address 0x03)
Table 7-13. Humidity High Register (Address 0x03)
7
6
5
4
3
2
1
0
HUMIDITY[15:8]
Table 7-14. Humidity High Register Field Descriptions
BIT
FIELD
[15:8]
HUMIDITY[15:8]
RESET
(HEX)
TYPE
R
0
DESCRIPTION
Humidity data- higher byte
The humidity data is a 16-bits value that spans accross the Humidity Low (address 0x02) and Humidity High
(address 0x03) registers. The Humidity High register containts the higher-byte of the 16-bits temperature data.
The humidity can be calculated from the output data using Equation 4:
Humidity (%RH)
22
§ HUMIDITY [15 : 0] ·
¨
¸ u 100
216
©
¹
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7.6.5 Status (Address 0x04)
Table 7-15. Status Register (Address 0x04)
7
6
5
4
3
2
1
0
DRDY_STATUS
TH_STATUS
TL_STATUS
HH_STATUS
HL_STATUS
RES
RES
RES
Table 7-16. Status Register Field Descriptions
BIT
FIELD
RESET
(HEX)
TYPE
DESCRIPTION
7
DRDY_STATUS
R
0
DataReady bit status
0 = Data Not Ready
1 = Data Ready
6
TH_STATUS
R
0
Temperature threshold HIGH Interrupt status
0 = No interrupt
1 = Interrupt
5
TL_STATUS
R
0
Temperature threshold LOW Interrupt status
0 = No interrupt
1 = Interrupt
4
HH_STATUS
R
0
Humidity threshold HIGH Interrupt status
0 = No interrupt
1 = Interrupt
3
HL_STATUS
R
0
Humidity threshold LOW Interrupt status
0 = No interrupt
1 = Interrupt
2
RES
0
Reserved
1
RES
0
Reserved
0
RES
0
Reserved
The DRDY_STATUS bit indicates that temperature and/or humidity conversion is completed, and its behavior is
defined by the Device Configuration Register (0x0E). This bit is cleared when the any of the following registers is
read: Temperature Low (0x00), Temperature High (0x01), Humidity Low (0x02), Humidity High (0x03), and
Status (0x04). The bit is also cleared upon RESET.
The TL_STATUS bit indicates that the Temperature Threshold LOW value is exceeded, and its behavior is
defined by the Device Configuration Register (0x0E). The bit is cleared when the Status Register (0x04) is read.
The bit is also cleared upon RESET.
The TH_STATUS bit indicates that the Temperature Threshold HIGH value is exceeded, and its behavior is
defined by the 0x0E Configuration register value. The bit is cleared when the Status Register (0x04) is read. The
bit is also cleared upon RESET.
The HH_STATUS bit indicates that the Humidity Threshold HIGH value is exceeded, and its behavior is defined
by the Device Configuration Register (0x0E). The bit is cleared when the Status Register (0x04) is read. The bit
is also cleared upon RESET.
The HL_STATUS bit indicates that the Humidity Threshold LOW value is exceeded, and its behavior is defined
by the Device Configuration Register (0x0E). The bit is cleared when the Status Register (0x04) is read. The bit
is also cleared upon RESET.
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7.6.6 Temperature MAX (Address: 0x05)
Table 7-17. Temperature MAX Register (Address: 0x05)
7
6
5
4
3
2
1
0
TEMPERATUREMAX[7:0]
Table 7-18. Temperature Max Field Descriptions
BIT
FIELD
[7:0]
RESET
[HEX]
TYPE
TEMPERATUREMAX[7:0]
R
DESCRIPTION
Maximum temperature measurement data (one-shot mode only)
0
This register implements temperature peak detector function. The register stores the highest temperature value
converted after the last reset (power-on reset or software reset).
The temperature can be calculated from the output data using Equation 5:
Temperature (qC)
§ TEMPERATURE [7 : 0] ·
¨
¸ u 165 40
28
©
¹
(5)
7.6.7 Humidity MAX (Address: 0x06)
Table 7-19. Humidity MAX Register (Address: 0x06)
7
6
5
4
3
2
1
0
HUMIDITYMAX[7:0]
Table 7-20. Humidity MAX Field Descriptions
BIT
RESET
FIELD
[7:0]
HUMIDITYMAX[7:0]
(HEX)
TYPE
R
0
DESCRIPTION
Maximum humidity measurement data (one-shot mode only)
This register implements humidity peak detector function. The register stores the highest humidity value
converted after the last reset (power-on reset or software reset).
The humidity can be calculated from the output data using Equation 6:
Humidity (%RH)
24
§ 100 ·
HUMIDITYMAX >7 : 0 @ u ¨ 8 ¸
© 2 ¹
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7.6.8 Interrupt Enable (Address: 0x07)
Table 7-21. Interrupt Enable Register (Address: 0x07)
7
6
5
4
3
2
1
0
DRDY_ENABLE
TH_ENABLE
TL_ENABLE
HH_ENABLE
HL_ENABLE
RES
RES
RES
Table 7-22. Interrupt Enable Register Field Descriptions
BIT
FIELD
RESET
(HEX)
TYPE
DESCRIPTION
7
DRDY_ENABLE
R/W
0
DataReady Interrupt enable
0 = DataReady Interrupt disabled
1 = DataReady Interrupt enabled
6
TH_ENABLE
R/W
0
Temperature threshold HIGH Interrupt enable
0 = Temperature high Interrupt disabled
1 = Temperature high Interrupt enabled
5
TL_ENABLE
R/W
0
Temperature threshold LOW Interrupt enable
0 = Temperature low Interrupt disabled
1 = Temperature low Interrupt enabled
4
HH_ENABLE
R/W
0
Humidity threshold HIGH Interrupt enable
0 = Humidity high Interrupt disabled
1 = Humidity high Interrupt enabled
3
HL_ENABLE
R/W
0
Humidity threshold LOW Interrupt enable
0 = Humidity low Interrupt disabled
1 = Humidity low Interrupt enabled
2
RES
0
Reserved
1
RES
0
Reserved
0
RES
0
Reserved
The Interrupt Enable register enables or disables interrupt asserstion on the DRDY/INT pin from DataReady,
Temperature threshold High, Temperature threshold Low, Humidity threshold High, or Humidity threshold Low.
The Status register (address 0x04) content is unaffected by this register.
Note the settings of this regsiter only takes effect if the DRDY/INT_EN bit of the Device Configuration register
(address 0x0E) is set to 1.
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7.6.9 Temperature Offset Adjustment (Address: 0x08)
Table 7-23. Temperature Offset Adjustment Register (Address: 0x08)
7
6
5
4
3
2
1
0
TEMP_OFFSET_ADJUST[7:0]
Table 7-24. Temperature Offset Adjustment Register Field Descriptions
BIT
FIELD
[7:0]
RESET
(HEX)
TYPE
TEMP_OFFSET_ADJUST [7:0]
R/W
0
DESCRIPTION
Temperature offset adjustment value. The value is added to the
converted temperature data.
The reported temperature conversion data can be adjusted by programming the Temperature Offset Adjustment
Register. The following table summarizes the equivalent offset value added or subtracted for each bit of the
register:
7
6
5
4
3
2
1
0
–20.63°C
+10.31°C
+5.16°C
+2.58°C
+1.29°C
+0.64°C
+0.32°C
+0.16°C
The value is added to the converted temperature value for offset adjustment as shown in Figure 7-7.
Converted Value
+
Temperature Output
User Temperature Offset
Figure 7-7. Temperature Output Calculation
The resulting temperature offset is a summation of the register bits that have been enabled (that is, programmed
to 1). Some examples:
1. Programming TEMP_OFFSET_ADJUST to 00000001 adjusts the reported temperature by +0.16°C.
2. Programming TEMP_OFFSET_ADJUST to 00000111 adjusts the reported temperature by +1.12°C.
3. Programming TEMP_OFFSET_ADJUST to 00001101 adjusts the reported temperature by +2.08°C.
4. Programming TEMP_OFFSET_ADJUST to 11111111 adjusts the reported temperature by –0.16°C.
5. Programming TEMP_OFFSET_ADJUST to 11111001 adjusts the reported temperature by –1.12°C.
6. Programming TEMP_OFFSET_ADJUST to 11110011 adjusts the reported temperature by –2.08°C.
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7.6.10 Humidity Offset Adjustment (Address 0x09)
Table 7-25. Humidity Offset Adjustment Register (Address: 0x09)
7
6
5
4
3
2
1
0
HUM_OFFSET_ADJUST [7:0]
Table 7-26. Humidity Offset Adjustment Register Field Descriptions
BIT
FIELD
[7:0]
RESET
(HEX)
TYPE
HUM_OFFSET_ADJUST [7:0]
R/W
0
DESCRIPTION
Humidity offset adjustment value. The value is added to the
converted humidity data.
The reported humidity conversion data can be adjusted by programming the Humidity Offset Adjustment
Register. The following table summarizes the equivalent offset value added or subtracted for each bit of the
register:
7
6
5
4
3
2
1
0
–25%RH
+12.5%RH
+6.3%RH
+3.1%RH
+1.6%RH
+0.8%RH
+0.4%RH
+0.2%RH
The value is added to the converted humidity value for offset adjustment as shown in Figure 7-8
Converted Value
+
Humidity Output
User Humidity Offset
Figure 7-8. Humidity Output Calculation
The resulting humidity offset is a summation of the register bits that have been enabled (that is, programmed to
1). Some examples:
1. Programming HUM_OFFSET_ADJUST to 00000001 adjusts the reported humidity by +0.20%RH.
2. Programming HUM_OFFSET_ADJUST to 00000101 adjusts the reported humidity by +1.00%RH.
3. Programming HUM_OFFSET_ADJUST to 00001010 adjusts the reported humidity by +2.00%RH.
4. Programming HUM_OFFSET_ADJUST to 11111111 adjusts the reported humidity by –0.10%RH.
5. Programming HUM_OFFSET_ADJUST to 11111011 adjusts the reported humidity by –0.90%RH.
6. Programming HUM_OFFSET_ADJUST to 11110101 adjusts the reported humidity by –2.10%RH.
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7.6.11 Temperature Threshold LOW (Address 0x0A)
Table 7-27. Temperature Threshold LOW Register (Address: 0x0A)
7
6
5
4
3
2
1
0
TEMP_THRES_LOW[7:0]
Table 7-28. Temperature Threshold LOW Field Descriptions
BIT
FIELD
[7:0]
RESET
(HEX)
TYPE
TEMP_THRES_LOW[7:0]
R/W
DESCRIPTION
Temperature threshold LOW value
1
The Temperature Threshold LOW register configures the temperature threshold setting for interrupt generation if
the TL_ENABLE interrupt is enabled. The threshold value can be calculated using Equation 7:
Temperature threshold low (qC)
§ TEMP_THRES_LOW [7 : 0] ·
¨
¸ u 165 40
©
¹
28
(7)
7.6.12 Temperature Threshold HIGH (Address 0x0B)
Table 7-29. Temperature Threshold HIGH Register (Address 0x0B)
7
6
5
4
3
2
1
0
TEMP_THRES_HIGH[7:0]
Table 7-30. Temperature Threshold HIGH Register Field Descriptions
BIT
FIELD
[7:0]
TEMP_THRES_HIGH[7:0]
TYPE
R/W
RESET
(HEX)
FF
DESCRIPTION
Temperature threshold HIGH value
The Temperature Threshold HIGH register configures the temperature threshold setting for interrupt generation if
the TH_ENABLE interrupt is enabled. The threshold value can be calculated using Equation 8:
Temperature threshold high (qC)
28
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§ TEMP_THRES_HIGH [7 : 0] ·
¨
¸ u 165 40
©
¹
28
(8)
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7.6.13 Humidity Threshold LOW (Address 0x0C)
Table 7-31. Humidity Threshold LOW Register (Address 0x0C)
7
6
5
4
3
2
1
0
HUMI_THRES_LOW[7:0]
Table 7-32. Humidity Threshold LOW Register Field Descriptions
BIT
FIELD
[7:0]
RESET
(HEX)
TYPE
HUMI_THRES_LOW[7:0]
R/W
0
DESCRIPTION
Humidity threshold LOW value
The Humidity Threshold LOW register configures the humidity threshold setting for interrupt generation if the
HL_ENABLE interrupt is enabled. The threshold value can be calculated with using Equation 9:
Humidity threashold low (%RH)
§ HUMI_THRES_LOW [7 : 0] ·
¨
¸ u 100
28
©
¹
(9)
7.6.14 Humidity Threshold HIGH (Address 0x0D)
Table 7-33. Humidity Threshold HIGH Register (Address: 0x0D)
7
6
5
4
3
2
1
0
HUMI_THRES_HIGH[7:0]
Table 7-34. Humidity Threshold HIGH Register Field Descriptions
BIT
FIELD
[7:0]
HUMI_THRES_HIGH[7:0]
TYPE
R/W
RESET
(HEX)
FF
DESCRIPTION
Humidity threshold HIGH value
The Humidity Threshold HIGH register configures the temperature threshold setting for interrupt generation if the
HH_ENABLE interrupt is enabled. The threshold value can be calculated using Equation 10:
Humidity threshold high (%RH)
Copyright © 2020 Texas Instruments Incorporated
§ HUMI_THRES_HIGH [7 : 0] ·
¨
¸ u 100
©
¹
28
(10)
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7.6.15 Device Configuration (Address: 0x0E)
Table 7-35. Device Configuration Register (Address: 0x0E)
7
6
5
SOFT_RES
4
CC[2:0]
3
2
1
0
HEAT_EN
DRDY/INT_EN
INT_POL
INT_MODE
Table 7-36. Device Configuration Register Field Descriptions
BIT
FIELD
7
DESCRIPTION
SOFT_RES
R/W
0
0 = Normal Operation
1 = Trigger a Soft Reset. This bit self-clears after RESET.
CC[2:0]
R/W
0
Configure the measurement mode to one-shot or continuous
conversion. The bits also allow sampling frequency to be
programmed in continuous conversion mode.
000 = Continuous conversion disabled (one-shot mode)
001 = 1/120Hz (1 samples every 2 minutes)
010 = 1/60Hz (1 samples every minute)
011 = 0.1Hz (1 samples every 10 seconds)
100 = 0.2 Hz (1 samples every 5 second)
101 = 1Hz (1 samples every second)
110 = 2Hz (2 samples every second)
111 = 5Hz (5 samples every second)
3
HEAT_EN
R/W
0
0 = Heater off
1 = Heater on
2
DRDY/INT_EN
R/W
0
DRDY/INT_EN pin configuration
0 = High Z
1 = Enable
1
INT_POL
R/W
0
Interrupt polarity
0 = Active Low
1 = Active High
0
INT_MODE
R/W
0
Interrupt mode
0 = Clear-on-read mode
1 = Comparator mode
[6:4]
30
RESET
(HEX)
TYPE
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7.6.16 Measurement Configuration (Address: 0x0F)
Table 7-37. Measurement Configuration Register (Address: 0x0F)
7
6
5
TACC[1:0]
4
3
HACC[1:0]
2
RES
1
MEAS_CONF[1:0]
0
MEAS_TRIG
Table 7-38. Measurement Configuration Register Field Descriptions
BIT
FIELD
RESET
(HEX)
TYPE
DESCRIPTION
7:6
TACC[1:0]
R/W
0
Temperature accuracy option:
00: 14 bit
01: 11 bit
10: 9 bit
11: NA
5:4
HACC[1:0]
R/W
0
Humidity accuracy option:
00: 14 bit
01: 11 bit
10: 9 bit
11: NA
RES
R/W
0
Reserved
MEAS_CONF[1:0]
R/W
0
Measurement configuration:
00: Humidity + Temperature
01: Temperature only
10: NA
11: NA
MEAS_TRIG
R/W
0
Measurement trigger:
0: No action
1: Start measurement
Setting this bit to 1 to start a single measurement in one-shot
mode or continuous measurements in continuous conversion
mode. This bit self-clears to 0 once the measurement starts.
3
2:1
0
7.6.17 Manufacturer ID Low (Address: FC)
Table 7-39. Manufacturer ID Low Register (Address: FC)
7
6
5
4
3
2
1
0
MANUFACTURER ID[7:0]
Table 7-40. Manufacturer ID Low Field Descriptions
BIT
FIELD
[7:0]
MANUFACTURER ID [7:0]
TYPE
R
RESET
(HEX)
49
DESCRIPTION
Manufacturer ID- lower byte value
The Manufacturer ID Low and Manufacturer ID High registers contain a factory-programmable identification
value that identifies this device as being manufactured by Texas Instruments. The manufacturer ID helps
distinguish the device from other devices that are on the same I2C bus. The manufacturer ID reads 0x5449 and
spans across the two registers.
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7.6.18 Manufacturer ID High (Address: FD)
Table 7-41. Manufacturer ID High Register (Address: FD)
7
6
5
4
3
2
1
0
MANUFACTURER ID[15:8]
Table 7-42. Manufacturer ID High Register Field Descriptions
BIT
FIELD
[7:0]
RESET
(HEX)
TYPE
MANUFACTURER ID [15:8]
R
54
DESCRIPTION
Manufacturer ID- higher byte value
The Manufacturer ID Low and Manufacturer ID High registers contain a factory-programmable identification
value that identifies this device as being manufactured by Texas Instruments. The manufacturer ID helps
distinguish the device from other devices that are on the same I2C bus. The manufacturer ID reads 0x5449 and
spans across the two registers.
7.6.19 Device ID Low (Address: FE)
Table 7-43. Device ID Low Register (Address: FE)
7
6
5
4
3
2
1
0
DEVICE ID[7:0]
Table 7-44. Device ID Low Register Field Descriptions
BIT
FIELD
[7:0]
RESET
(HEX)
TYPE
DEVICE ID [7:0]
R
D0
DESCRIPTION
Device ID - lower byte value
The Device ID Low and Device ID High registers contain a factory-programmable identification value that
identifies this device as a HDC2021. The device ID helps distinguish the device from other devices that are on
the same I2C bus. The Device ID for the HDC2021 is 0x07D0.
7.6.20 Device ID High (Address: FF)
Table 7-45. Device ID High Register (Address: FF)
7
6
5
4
3
2
1
0
DEVICE ID[15:8]
Table 7-46. Device ID High Register Field Descriptions
BIT
FIELD
[7:0]
DEVICE ID [15:8]
RESET
(HEX)
TYPE
R
7
DESCRIPTION
Device ID - higher byte value
The Device ID Low and Device ID High registers contain a factory-programmable identification value that
identifies this device as a HDC2021. The device ID helps distinguish the device from other devices that are on
the same I2C bus. The Device ID for the HDC2021 is 0x07D0.
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8 Application and Implementation
Note
Information in the following applications sections is not part of the TI component specification, and TI
does not warrant its accuracy or completeness. TI’s customers are responsible for determining
suitability of components for their purposes. Customers should validate and test their design
implementation to confirm system functionality.
8.1 Application Information
An HVAC system thermostat control is made up of environmental sensors and a microcontroller. The
microcontroller acquires data from humidity and temperature sensors and controls the heating and cooling
system. The collected data are then shown on a display that can be easily controlled by the microcontroller.
Based on data from the humidity and temperature sensor, the heating and cooling system then maintains the
environment at the customer-defined preferred conditions.
8.2 Typical Application
In a battery-powered HVAC system thermostat, one of the key parameters in the selection of components is the
power consumption. The HDC2021, with a current consumption of 550 nA (the average consumption over 1s for
RH and Temperature measurements), and in conjunction with the MSP430, represents one way an engineer can
obtain low power consumption to extend battery life. A system block diagram of a battery-powered thermostat is
shown in Figure 8-1.
DISPLAY
TEMPERATURE: 25°C/ 77°F
Relative Humidity (RH): 25%
Red
+
Lithium
Ion Battery
TIME: XX:XX
DATE: XX:XX:XX
1.8 V
VDD
HDC2021
RH
Violet
Sensor
MUX
MUX
ADC
Red
1.8 V
Registers/
Red
Logic
I2 C
Red
Interface
SCL
SDA
INT
VDD
MCU
I2C Red
Peripheral
Red
GPIOs
GPIO
Orange
ADDR
Temp
Violet
Sensor
GPIOs
±
GND
Calibration
Red
Coefficients
GND
KEYPAD
Button1
C
Button2
C
C
Button3
C
Button4
C
Figure 8-1. Typical Application Schematic HVAC
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8.2.1 Design Requirements
To improve measurement accuracy, TI recommends to isolate the HDC2021 from all heat sources in the form of
active circuitry, batteries, displays, and resistive elements. If design space is a constraint, cutouts surrounding
the device or the inclusion of small trenches can help minimize heat transfer from PCB heat sources to the
HDC2021. To avoid self-heating the HDC2021, TI recommends to configure the device for a maximum sample
rate of 1 Hz (1 sps).
8.2.2 Detailed Design Procedure
When a circuit board layout is created from the schematic shown in Figure 8-1 , a small circuit board is possible.
The accuracy of a RH and temperature measurement depends on the sensor accuracy and the setup of the
sensing system. The HDC2021 samples relative humidity and temperature in its immediate environment, it is
therefore important that the local conditions at the sensor match the monitored environment. Use one or more
openings in the physical cover of the thermostat to obtain a good airflow even in static conditions. Refer to the
layout (Figure 10-1) for a PCB layout that minimizes the thermal mass of the PCB in the region of the HDC2021,
which can improve measurement response time and accuracy.
8.2.3 Application Curve
These results were acquired at TA = 30°C using a humidity chamber that sweeps RH%. The sweep profile used
was 20% > 30% > 40% > 50% > 60% > 70% > 60% > 50% > 40% > 30% > 20%. Each RH% set point was held
for 20 minutes.
Figure 8-2. RH% Readings of Humidity Chamber and HDC2021 vs. Time
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9 Power Supply Recommendations
The HDC2021 requires a voltage supply within 1.62 V and 3.6 V. TI recommends a multilayer ceramic bypass
X7R capacitor of 0.1 µF between the VDD and GND pins located close to the device.
10 Layout
10.1 Layout Guidelines
The HDC2021’s relative humidity-sensing element is located on the top side of the package.
TI recommends that the user eliminate the copper layers below the device (GND, VDD) and create slots in the
PCB around the device to enhance the thermal isolation of the HDC2021. To ensure the temperature sensor
performance, TI highly recommends that the user follow the Land Pattern, Solder Mask, and Solder Paste
examples depicted in the Mechanical, Packaging, and Orderable Informationsection.
10.1.1 Guidelines for HDC2021 Storage and PCB Assembly
10.1.1.1 Storage and Handling
As with all humidity sensors, the HDC2021 must follow special guidelines regarding handling and storage that
are not common with standard semiconductor devices. Long exposure to UV and visible light, or exposure to
chemical vapors for prolonged periods, should be avoided as it may affect RH% accuracy. Additionally, the
device should be protected from out-gassed solvent vapors produced during manufacturing, transport, operation,
and package materials (that is, adhesive tapes, stickers, bubble foils). For further detailed information, see
Humidity Sensor: Storage and Handling Guidelines (SNIA025).
10.1.1.2 Soldering Reflow
For PCB assembly, standard reflow soldering ovens may be used. The HDC2021 uses the standard soldering
profile IPC/JEDEC J-STD-020 with peak temperatures at 260°C. When soldering the HDC2021, it is mandatory
to use no-clean solder paste, and the paste must not be exposed to water or solvent rinses during assembly
because these contaminants may affect sensor accuracy. After reflow, it is expected that the sensor will
generally output a shift in relative humidity, which, once the polyimide tape is peeled off, will reduce over time as
the sensor is exposed to typical indoor ambient conditions. These conditions include 30-40% RH at room
temperature during a duration of several days. Following this rehydration procedure allows the polymer to
correctly settle after reflow and return to the calibrated RH accuracy.
10.1.1.3 Rework
The polyimide tape of the HDC2021 can withstand at least three standard reflow cycles. In the case of tape
removal, TI recommends to limit the HDC2021 to a single IR reflow with no rework, but a second reflow may be
possible if the following guidelines are met:
• The exposed polymer (humidity sensor) is kept clean and undamaged.
• The no-clean solder paste is used and the process is not exposed to any liquids, such as water or solvents.
• The peak soldering temperature does not exceed 260°C.
10.1.1.4 High Temperature and Humidity Exposure
Long exposure outside the recommended operating conditions may temporarily offset the RH output. The
recommended humidity operating range is 20% to 80% RH (non-condensing) over 0°C to 60°C. Prolonged
operation beyond these ranges may shift the sensor reading with a slow recovery time.
10.1.1.5 Bake/Rehydration Procedure
Prolonged exposure to extreme conditions or harsh contaminants may impact sensor performance. In the case
that permanent offset is observed from contaminants, the following procedure is suggested, which may recover
or reduce the error observed in sensor performance:
1. Baking: 100°C, at less than 5%RH, for 5 to 10 hours
2. Rehydration: Between 20°C to 30°C, 60%RH to 75%RH, for 6 to 12 hours
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10.2 Layout Example
The only component next to the device is the supply decoupling capacitor. The relative humidity is dependent on
the temperature, so the HDC2021 should be positioned away from hot spots present on the board, such as a
battery, display, or microcontroller. Slots around the device can be used to reduce the thermal mass for a quicker
response to environmental changes.
The device package has a thermal pad which can be soldered to the PCB. The thermal pad can be left floated or
connected to the ground. Applying a different voltage other than ground to thermal pad can lead to permanent
device damage. If the user intends to use the integrated heater in the device, it is recommended NOT to solder
the thermal pad to PCB to achieve faster heating response.
The below diagram shows an example layout of the device on a single-layer PCB board with no VIAs and ADDR
pin grounded.
SDA
SCL
SDA
SCL
GND
VDD
ADDR
DRDY/INT
Decoupling
Capacitor
GND
VDD
TI does NOT recommend to solder the thermal pad to PCB to achieve faster heating response if the integrated heater is used.
Figure 10-1. HDC2021 PCB Layout Example
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11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation see the following:
• Texas Instruments, Humidity Sensor: Storage and Handling Guidelines application report (SNIA025)
• Texas Instruments, Optimizing Placement and Routing for Humidity Sensors application report (SNAA297)
11.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. Click on
Subscribe to updates to register and receive a weekly digest of any product information that has changed. For
change details, review the revision history included in any revised document.
11.3 Support Resources
TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight
from the experts. Search existing answers or ask your own question to get the quick design help you need.
Linked content is provided "AS IS" by the respective contributors. They do not constitute TI specifications and do
not necessarily reflect TI's views; see TI's Terms of Use.
11.4 Trademarks
TI E2E™ is a trademark of Texas Instruments Incorporated.
All other trademarks are the property of their respective owners.
11.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled
with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may
be more susceptible to damage because very small parametric changes could cause the device not to meet its published
specifications.
11.6 Glossary
TI Glossary
This glossary lists and explains terms, acronyms, and definitions.
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12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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Copyright © 2020 Texas Instruments Incorporated
PACKAGE OUTLINE
DEB0006A
WSON - 0.92 mm max height
SCALE 4.000
PLASTIC SMALL OUTLINE - NO LEAD
3.1
2.9
B
A
(45 X 0.6)
PIN 1 INDEX AREA
3.1
2.9
(1)
PEELABLE COVER TAPE
IP66 RATED & 260 C CAPABLE
NOTE 4
(1)
3X (R0.375)
ADHESIVE FREE
SURFACE
( 2.75)
(0.32)
0.92 MAX
0.8
0.7
C
SEATING PLANE
0.08 C
(0.2) TYP
0.05
0.00
1.5 0.1
EXPOSED
THERMAL PAD
3
2X
2
4
7
2.4 0.1
4X 1
6
1
6X
PIN 1 ID
0.5
6X
0.3
0.45
0.35
0.1
0.05
C A B
C
4224371/D 01/2020
NOTES:
1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.
4. IPXY Rating represents environmental ingress protection from both dust and high pressure water sprays. X=6 represents
resistance to dust and Y=6 represents high pressure water spray resistance per IEC60529 testing conditions.
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EXAMPLE BOARD LAYOUT
DEB0006A
WSON - 0.92 mm max height
PLASTIC SMALL OUTLINE - NO LEAD
(1.5)
SYMM
6X (0.6)
6
1
6X (0.4)
SYMM
7
(2.4)
(0.95) TYP
4X (1)
3
4
(R0.05) TYP
( 0.2)
TYP
(1) TYP
(2.8)
LAND PATTERN EXAMPLE
EXPOSED METAL SHOWN
SCALE:20X
0.07 MIN
ALL AROUND
0.07 MAX
ALL AROUND
EXPOSED
METAL
EXPOSED
METAL
SOLDER MASK
OPENING
METAL
METAL UNDER
SOLDER MASK
NON SOLDER MASK
DEFINED
(PREFERRED)
SOLDER MASK
OPENING
SOLDER MASK
DEFINED
SOLDER MASK DETAILS
4224371/D 01/2020
NOTES: (continued)
5. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature
number SLUA271 (www.ti.com/lit/slua271).
6. Vias are optional depending on application, refer to device data sheet. If any vias are implemented, refer to their locations shown
on this view. It is recommended that vias under paste be filled, plugged or tented.
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EXAMPLE STENCIL DESIGN
DEB0006A
WSON - 0.92 mm max height
PLASTIC SMALL OUTLINE - NO LEAD
SYMM
6X (0.6)
METAL
TYP
6
1
6X (0.4)
(0.63)
7
SYMM
4X (1)
2X (1.06)
3
4
(R0.05) TYP
2X (1.38)
(2.8)
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
EXPOSED PAD 7:
81% PRINTED SOLDER COVERAGE BY AREA UNDER PACKAGE
SCALE:20X
4224371/D 01/2020
NOTES: (continued)
7. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
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PACKAGE OPTION ADDENDUM
www.ti.com
13-Nov-2023
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
(3)
Device Marking
Samples
(4/5)
(6)
HDC2021DEBR
ACTIVE
WSON
DEB
6
3000
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 125
HDC2021DEBT
LIFEBUY
WSON
DEB
6
250
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 125
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of