ENS210
Relative Humidity and Temperature
Sensor with I²C Interface
ENS210 Datasheet
Revision:
2
Release Date:
2021-03-01
Document Status: Production
Content Guide
General Description ........................ 3
Key Benefits and Features ............................... 3
Applications ....................................................... 4
Block Diagram .................................................... 4
Pin Assignments ............................. 5
Absolute Maximum Ratings ............... 6
Electrical Characteristics.................. 7
I²C Timing Characteristics ............................... 8
Temperature Sensor Characteristics ............. 8
Relative Humidity Sensor Characteristics ..... 9
System Timing Characteristics ...................... 10
Functional Description.................... 11
Temperature Sensor ....................................... 12
Relative Humidity Sensor............................... 13
RH Accuracy at Various Temperatures ......... 14
The I²C Interface............................................. 15
I²C Operations on Registers........................... 15
The I²C Slave Address ..................................... 17
Sensor Control ................................................. 17
Sensor Timing .................................................. 18
The Sensor Readout Registers....................... 20
Computing CRC-7 ............................................ 21
Processing T_VAL and H_VAL ........................ 22
Reading PART_ID and UID .............................. 24
Register SYS_CTRL (Address 0x10) ............... 27
Register SYS_STAT (Address 0x11) ............... 27
Register SENS_RUN (Address 0x21) .............. 28
Register SENS_START (Address 0x22) .......... 28
Register SENS_STOP (Address 0x23) ............ 29
Register SENS_STAT (Address 0x24)............. 29
Register T_VAL (Address 0x30) ..................... 30
Register H_VAL (Address 0x33) ..................... 30
Application Information .................. 31
Typical Application ......................................... 31
Recommended Operating Conditions .......... 32
Soldering & Storage Information ....... 33
Soldering .......................................................... 33
Storage and Handling ..................................... 35
Reconditioning ................................................ 36
After Soldering ................................................ 36
After Extreme Conditions .............................. 36
Package Drawings & Markings ........... 37
Marking Information ....................................... 38
Ordering & Contact Information ........ 39
RoHS Compliant & ScioSense
Green Statement .......................... 40
Copyrights & Disclaimer.................. 41
Register Description ....................... 25
Register Overview ........................................... 25
Detailed Register Description ....................... 26
Register PART_ID (Address 0x00).................. 26
Register DIE_REV (Address 0x02) .................. 26
Register UID (Address 0x04) .......................... 26
2
Document Status .......................... 42
Revision Information...................... 43
ENS210 Datasheet SC-000897-DS-3 / 2021-03-01
CONTENTS PAGE
General Description
The ENS210 integrates one relative humidity sensor and one high-accuracy temperature
sensor. The device is encapsulated in a QFN4 package and includes an I²C slave interface for
communication with a master processor.
Ordering Information appears at the end of the datasheet.
Key Benefits and Features
The benefits and features of ENS210, Relative Humidity and Temperature Sensor with I²C
Interface are listed below:
Figure 1:
Added Value of Using ENS210
Benefits
Features
• Ultra-accurate
• Temperature sensor (±0.15°C)
• Relative humidity sensor (Typ:±2.0%RH)
• Wide sensing range
• Temperature operating range (–40°C to 100°C)
• Relative humidity operating range (0% to 100%)
• Wide operating voltage
• 1.71V to 3.60V
• Small foot-print
• 2.0mm x 2.0mm x 0.75mm
• Industry standard two-wire interface
• Standard (100kbit/s) and fast (400kbit/s) I²C
• Low power
• Automatic low-power standby when not measuring
• Active current: 6.6μA @ 1Hz (1.8V)
• Standby current: 40nA
• Cost effective
• Digital pre-calibrated relative humidity and
temperature sensor
• Output directly in %RH and Kelvin
• Wide supply voltage range
• High reliability
• Long-term stability
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CONTENTS PAGE
Applications
The ENS210 applications include:
• Building Automation / Smart home / HVAC1
◦ Indoor air quality detection
◦ Demand-controlled ventilation
◦ Smart thermostats
• Home appliances
◦ Air cleaners / purifiers
◦ Refrigerators, washing machines, dishwashers, dryers
• Mobiles / Wearables
• IoT devices
• Portable devices for personal health and wellness
• Weather stations
Block Diagram
The internal block diagram of ENS210 is shown in Figure 2. The I²C (communication) interface
is connected to a controller which acts as the command interpreter and as bus master of the
internal Advanced Peripheral Bus (APB). The memory and sensors are slaves of the APB. The MTP
memory is used to store the sensor calibration parameters and unique ID.
To reduce power consumption the controller only powers the measurement engine when needed.
Figure 2:
Functional Blocks of ENS210
Note(s):
1. HVAC = Heat, Ventilation and Air Conditioning
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CONTENTS PAGE
Pin Assignments
The ENS210 pin assignment is described in Figure 3 and Figure 4.
Figure 3:
Pin Diagram of ENS210
Figure 4:
Pin Description of ENS210
Pin Number
Pin Name
Description
1
VDD
Supply voltage
2
SCL
I²C bus serial clock input (SCL)
3
SDA
I²C bus serial bidirectional data line (SDA)
4
VSS
Ground supply voltage; must be connected
5
VSS
Ground supply voltage; must be connected
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CONTENTS PAGE
Absolute Maximum Ratings
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage
to the device. These are stress ratings only. Functional operation of the device at these or any
other conditions beyond those indicated under Electrical Characteristics is not implied. Exposure
to absolute maximum rating conditions for extended periods may affect device reliability.
Figure 5:
Absolute Maximum Ratings of ENS210
Symbol
Parameter
Min
Max
Units
Comments
Electrical Parameters
VDD
Supply voltage
Ilu
Latch-up current
-0.30
4.60
V
100
mA
I/O; –0.5Vdd < VI < 1.5Vdd;
Tj < 125°C
Electrostatic Discharge
ESDHBM
Human body model;
all pins
±2000
V
JEDEC JS-001-2014
ESDCDM
Charged model
device; all pins
±500
V
JEDEC JS-002-2014
Operating and Storage Conditions
MSL
6
Moisture sensitivity
level
Maximum floor life time is
unlimited
1
TSTRG
Storage
temperature
10
50
RHNC
Relative humidity
(non-condensing)
20
60
%RH
TA
Operating ambient
temperature
–40
100
°C
HA
Operating ambient
relative humidity
0
100
%RH
°C
Preferably in sealed ESD bag
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CONTENTS PAGE
Electrical Characteristics
All limits are guaranteed. The parameters with min and max values are guaranteed with
production tests or SQC (Statistical Quality Control) methods.
Figure 6:
Electrical Characteristics
Symbol
VDD
Parameter
Supply voltage
Conditions
Max ripple 100mVPP between
0-1MHz
Min
1.71
Standby state
IDD
Supply current
Continuous run mode
T and RH measurement at 1Hz
Typ (1)
Max
Unit
1.80 (3.30) 3.60
V
0.04 (0.5)
μA
58 (61)
μA
6.6 (7.1)
μA
VIH
High-level input
voltage
0.7×VDD
VDD+0.5 V
VIL
Low-level input
voltage
–0.5
0.3×VDD V
IOL
Low-level
output current
VOL = 0.4V
3
mA
VOL = 0.6V
6
mA
Note(s):
1.Values in parenthesis are for VDD=3.30 V.
2.TA = 25 °C and at 1.80 V supply voltage, unless otherwise specified
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I²C Timing Characteristics
ENS210 is compliant to the I²C standard; it supports standard and fast mode as per I²C-bus
specifications [UM10204, I²C-bus specification and user manual, Rev. 6, 4 April 2014].
Temperature Sensor Characteristics
Figure 7:
Temperature Sensor Characteristics
Symbol
Parameter
Conditions
Trange
Temperature
range
Tacc
Temperature
accuracy 3
Tres
Temperature
resolution
tresp
Response time 2
T step of 10°C by submersion
(in 0°C to 70°C range); τ63 % 1
Trep
Temperature
repeatability
3σ of consecutive measurement
values at constant conditions
ΔT
Temperature long
term drift
Min
Typ
-40
TA = 0°C to 70°C;
0.15
TA = −40°C to 100°C;
Max
100
°C
0.2
°C
0.3
°C
0.016
°C
1
-0.1
s
0.1
0.005
Unit
°C
°C/year
Note(s):
1.63% indicates that if a T step of 10°C, e.g. from 20°C to 30°C is made, it will take tresp seconds to reach 63% of that step.
2.In an application the temperature response time depends on heat conductivity of the sensor PCB.
3. Typical and maximum accuracy specification refers to, respectively, 2 and 3 standard deviations, assuming normal
distribution of accuracy errors. After industrial calibration, on each production lot through statistical analysis, a population
of sensors is tested on typical room conditions (e.g. 25°C, 45%RH) and only lots passing the verification qualify for customer
deliveries.
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Relative Humidity Sensor Characteristics
Figure 8:
Relative Humidity Sensor Characteristics
Symbol
Parameter
Hrange
Relative humidity
range
Hacc
Relative humidity
accuracy 3
Hres
Conditions
Typ
0
Max
Unit
100
%RH
TA=25°C; RH=0%RH to 85% RH;
excluding hysteresis
2
3
%RH
TA=25°C; RH=>85%RH to 95% RH;
excluding hysteresis
3
4
%RH
Relative humidity
resolution
4
Min
0.03
RH step of 20%RH (in 40%RH to
80%RH range); τ63%1; 1m/s flow;
TA = 25°C
%RH
tresp
Response time
3
s
Hhys
Relative humidity
hysteresis
TA = 25°C; RH = 20%RH to 90%RH;
2 hours exposure time
±0.55
%RH
Hrep
Relative humidity
repeatability
3σ of consecutive measurement
values at TA = 25°C and
RH = 40%RH
±0.1
%RH
ΔH
Relative humidity
long term drift 2
TA = 25°C
0.25
%RH/year
Note(s):
1.63% indicates that if an RH step of 20%RH is made, e.g. from 40%RH to 60%RH, it will take t resp seconds to reach 63%
of that step.
2. Values are linearized averages over the lifetime of the product. Due to non-linear behavior a larger drift is expected
in the first years.
3. Typical and maximum accuracy specification refers to, respectively, 2 and 3 standard deviations, assuming normal
distribution of accuracy error.
4. Device only performance. Application response time will depend on the design-in of the sensor
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System Timing Characteristics
Figure 9:
System Timing Characteristics
Symbol
Parameter
tbooting
Booting time 1
tconv
Conditions
Min
Typ
Max
Unit
1
1.2
ms
T only, single shot
(includes tbooting)
105
110
ms
T only, continuous
104
109
ms
T and RH, single shot
(includes tbooting)
122
130
ms
T and RH, continuous
225
238
ms
Conversion time
Note(s):
1. Time in transient state booting (see Figure 10).
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Functional Description
The ENS210 integrates two sensor blocks: temperature and relative humidity.
The device is normally in the standby state (Figure 10): the measurement engine (see Figure
2) is unpowered, but the I²C interface is operational and register write/read operation can be
performed. When a measurement command is given, the device is first booting to active then it
starts a measurement. When the measurement is completed, the device returns to the standby
state. Since the I²C interface is operational in standby, the measurement result can be read out.
Figure 10:
The ENS210 Power States
In continuous run mode (see Register SENS_RUN) or when low power is disabled (see Register
SYS_CTRL), the device remains in active state.
The system power status is observable (see Register SENS_STAT).
When powering up from off, the device is first booting to active, but then falls immediately back
to standby (since no measurement is pending, and by default low power is enabled).
Note that the booting state is a transient state (the system automatically transitions to the next
state – active); the booting time is given in Figure 9.
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Temperature Sensor
The temperature sensor block (Figure 11) determines the ambient temperature, and outputs a
calibrated value in Kelvin.
Figure 11:
Band Gap Temperature Measurement
The temperature is measured using a high-precision (12 bits) zoom-ADC. The analog part is able
to measure a strongly temperature dependent X = VBE/ΔVBE. The X is found by first applying
a coarse search (successive approximation), and then a sigma-delta in a limited range. The
accuracy of the sensor is shown in Figure 12. The conversion time is shown in Figure 9.
Figure 12:
Absolute Accuracy of the Temperature Sensor
Note(s):
1. Dash line indicates natural physical behavior
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Relative Humidity Sensor
The relative humidity sensor as shown in Figure 13 determines the ambient relative humidity
and outputs a calibrated value in %RH. The transducer (the CX on the top left) consists of a
large-area capacitor covered with a humidity-sensitive material. The capacitance change is
proportional to the change in relative humidity, and has a linear dependence on temperature.
The capacitance is measured by a high-precision 2nd order sigma-delta converter.
Figure 13:
Relative Humidity Sensor
Reading the relative humidity sensor will output a temperature compensated value. The
accuracy of the sensor is shown in Figure 14. The conversion time is shown in Figure 9.
Figure 14:
Absolute Accuracy of the Relative Humidity Sensor at 25°C
Max
Typ
Note(s):
1. Dash line indicates natural physical behavior
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CONTENTS PAGE
RH Accuracy at Various Temperatures
Typical RH accuracy at 25°C is defined in Figures 8 and 14. The relative humidity accuracy has
also been evaluated at temperatures other than 25°C. The values shown in Figure 15 are an
indication only, which may be important for your application, but are not guaranteed.
Figure 15:
Accuracy of Relative Humidity Measurements (%RH) as Function of Temperature and Relative
Humidity
Absolute accuracy of relative humidity measurements (%RH)
(typical values)
100
±4.5 ±5.5
±3
90
±3.5 ±4.5
±3.5
80
Relative humidity (%RH)
70
60
±2.5
50
±2.5
±3.5
±2
40
30
±3.5
20
±3.5 ±4.5
±3
±3
10
0
0
+5
+15
+25
+35
+45
+55
+65
Temperature (°C)
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CONTENTS PAGE
The I²C Interface
The ENS210 is an I²C slave device. The I²C interface supports standard (100kbit/s) and fast
(400kbit/s) mode.
Details on I²C protocol is according to I²C-bus specifications [UM10204, I²C-bus specification and
user manual, Rev. 6, 4 April 2014].
The device applies all mandatory I²C protocol features for slaves: START, STOP, Acknowledge,
7-bit slave address. ENS210 does not use clock stretching.
None of the other optional features (10-bit slave address, General Call, Software reset, or
Device ID) are supported, nor are the master features (Synchronization, Arbitration, START byte).
I²C Operations on Registers
The ENS210 uses a register model to interact with it. This means that an I²C master can write a
value to one of the registers of a slave, or that it can read from one of the registers of the slave.
In the ENS210, registers are addressed using 1 byte. The values stored in a register are also 1
byte. However, the ENS210 implements “auto increment” which means that it is possible to read,
for example, two bytes by supplying the address of the first byte and then reading two bytes.
Figure 16:
I²C Transaction Formats
A typical write transaction (see Figure 16) therefore has the following format. The master
initiates a transaction with a so-called start condition “s”. This blocks the bus. Next, the master
sends the 7 bits ENS210 slave address followed by a 1 bit direction (a 0 indicating write “w”).
This byte is acknowledged “a” by the slave. The master continues by sending the 8 bit register
address, which is acknowledged by the slave.
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This register address is stored in an internal CRA register (“Current Register Address”). Finally,
the master sends the 8 bit register value, which is acknowledged by the slave (or nack’ed when
the address is not writeable). This value is written to the register pointed to by the CRA, and the
CRA is incremented by
1.Optionally, the master sends more 8 bit values, for the next registers (auto incrementing CRA),
each of which is (n)ack’ed by the slave. Finally, the master generates a stop condition “p”,
unblocking the bus for other transactions.
A read transaction (see Figure 16) starts with a write (of the register address), followed by a
read. Consequently, it has the following format. The master initiates the transaction with a start
condition. Next, the master sends the 7 bits ENS210 slave address followed by a 1 bit direction
(a 0 indicating write). This byte is acknowledged by the slave. The master continues by sending
the 8 bit register address, which is acknowledged by the slave and stored in the CRA register.
Then the master sends another start condition (a so-called repeated start condition, keeping
the bus blocked) followed by the 7 bits ENS210 slave address followed by a 1 bit direction (a
1 indicating read “r”), which is acknowledged by the slave. Next, the slave sends an 8 bits
register value from the register pointed to by the CRA register, and the CRA is incremented by 1.
This byte is acknowledged by the master. The master may read another 8 bits (auto increment
feature) from the slave and acknowledge that, until the master sends a nack “n” followed by a
stop to unblock the bus.
The ENS210 has an 8 bit address space, potentially addressing 256 registers. In reality, only few
addresses are actually backed by a register (see Register Overview). All other addresses are
reserved. A write transaction to a reserved (or read-only) register causes a not-acknowledge. A
read transaction for a reserved register will return a 0.
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The I²C Slave Address
The ENS210 is an I²C slave device with a fixed slave address of 0x43. This means that the first
byte after a start condition is 1000 011x, where x indicates the data direction, so 0x86
(1000 0110) for write and 0x87 (1000 0111) for read.
Sensor Control
The ENS210 contains a temperature and a relative humidity sensor. Both sensors have two run
modes: single shot run mode and continuous run mode (enabled via SENS_RUN), see Figure 17.
Figure 17:
The Sensor Modes
When in the single shot run mode, starting a measurement is under control of the master. By
default a sensor is idle; it can be started by writing a 1 to the corresponding bit in SENS_START.
After a start, the sensor stops when the measurement is completed. Whether a sensor is idle or
active measuring can be detected by reading SENS_STAT. The measured values can be obtained
via their respective readout registers (T_VAL and H_ VAL). Writing to SENS_STOP in single shot
has no effect.
When in the continuous run mode, the sensor performs measurement after measurement after a
1 is written to the corresponding bit in SENS_START. The result of each measurement is stored in
the aforementioned readout registers. Writing 1 to the corresponding bit in SENS_STOP stops the
repeat cycle after the ongoing measurement is completed.
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The device operates in a step-wise way. In each step, either one or both sensors are active. The
step ends when the measurement(s) are completed. For the next step, the device inspects its
register settings, and either one or both sensors are activated again, or there is no measurement
request and the device goes into standby (unless low power is disabled by SYS_ CTRL).
This means that multiple writes to START during a step have no effect; the measurement
is started once, and only a write to START after the measurement has completed starts the
measurement again. Similarly, multiple writes to STOP have no effect; when the measurement
completes (in continuous mode) the stop request is effectuated once. When START and STOP are
both requested, the measurement is started, and when completed, stopped.
Sensor Timing
There are differences between single shot measurements and continuous measurements. Figure
18 shows the timing of a single shot T measurement.
Figure 18:
Single Shot Temperature Measurement
Signal T_RUN is written low to select a single shot measurement. Note that T_STOP is typically
low (cleared by a previous measurement), but its state is ignored in a single shot measurement.
T_START is written high to start measuring: T_VALID in T_VAL is cleared and the device starts
booting to active. Once active SYS_ACTIVE goes high, and measurement starts (T_STAT goes high).
When the measurement is completed (T_STAT goes low) the data register (T_DATA) becomes
valid (T_VALID goes high) and the device goes back to standby (SYS_ACTIVE goes low). The
T_START and T_STOP are cleared.
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Figure 19 shows the timing of a continuous T measurement.
Figure 19:
Continuous Temperature Measurement
Signal T_RUN is written high to select a continuous measurement. Note that T_STOP is typically
low (cleared by a previous measurement), and it should stay low otherwise continuous mode
will stop after one measurement. T_START is written high to start measuring: T_VALID in T_VAL
is cleared and the device starts booting to active. Once active SYS_ACTIVE goes high, and
measurement starts (T_STAT goes high).
When the first measurement is completed the data register (T_DATA) becomes valid (T_VALID goes
high), and the device starts a new measurement. When the next measurement is completed the
data register (T_DATA) is updated; T_VALID stays high. The device starts a new measurement.
At some point in time, a stop command is given (T_STOP is written high). As soon as the current
measurement is completed, the data register (T_DATA) is once more updated and the device goes
back to standby (SYS_ACTIVE goes low). The T_START and T_STOP are cleared.
Note that writes to the SENS_XXX registers only take effect when no measurement is ongoing. In
other words, measurements are always sequential (so we can have three types: T only, RH only or
T and RH and changes occur when the measurements are finished.
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The Sensor Readout Registers
The sensor readout registers (T_VAL and H_VAL) consist of three parts: the actual measured
data, a valid flag and a checksum (see Figure 20). It is not mandatory to read the valid flag or
the checksum when reading the data.
Figure 20:
The Layout of the Sensor Readout Registers
The checksum is a cyclic redundancy check over the data and the valid flag; the stored
checksum is the result of CRC-7 (polynomial x7+x3+1, see https://en.wikipedia.org/wiki/Cyclic_
redundancy_check) with 0x7F as initial vector (i.e. with all bits flipped), see Computing CRC-7 for
sample C code.
The valid flag is cleared when a measurement is started (irrespective of the run mode). Once the
measurement is completed the valid flag is set. In continuous mode, a new measurement is then
started without clearing the valid flag; so data is always valid after the first measurement (but it
might be several milliseconds old).
The data field is a 16 bits fixed point number, whose format and unit depends on the sensor (see
Register T_VAL and Register H_VAL).
To ensure consistent view, these multi-byte readout registers are double buffered. When the first
byte (i.e. the byte with the lowest register address) is read, the device copies all bytes from
the measurement registers to the I²C registers, and then the value from the first I²C register is
returned. Reads to the other bytes of the multi-byte register (i.e. with higher register addresses)
are always directly from the I²C registers.
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Computing CRC-7
CRC algorithm uses a 7 bit polynomial (see lines 4, 5, and 6), and a 17 bit payload. The crc7()
function below uses the following constants defining the CRC width, (the coefficients of the)
polynomial and the initial vector (start value of the CRC), and some constants describing the
payload data size.
//
// Polynomial
//
0b
0x
7654
1000
8
3211
1001 ~ x^7+x^3+x^0
9
#define CRC7WIDTH
#define CRC7POLY
#define CRC7IVEC
// Payload data
7
// 7 bits CRC has polynomial of 7th order (has 8 terms)
0x89 // The 8 coefficients of the polynomial
0x7F // Initial vector has all 7 bits high
#define DATA7WIDTH
#define DATA7MASK
#define DATA7MSB
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