SI7020-A20-GMR_技术文档

Si7020-A20

I²C HUMIDITY AND TEMPERATURE SENSOR

Features



Precision Relative Humidity Sensor



Factory-calibrated

 ± 4% RH (max), 0–80% RH

High Accuracy Temperature Sensor

±0.4 °C (max), –10 to 85 °C

0 to 100% RH operating range

Up to –40 to +125 °C operating

range

Wide operating voltage

(1.9 to 3.6 V)

Low Power Consumption

150 µA active current

60 nA standby current



I²C Interface



Integrated on-chip heater

3x3 mm DFN Package

Excellent long term stability

Optional factory-installed cover

Low-profile



Protection during reflow

Excludes liquids and particulates

Ordering Information:

See page 29.

Applications

Pin Assignments

Top View



HVAC/R



Micro-environments/data centers

Automotive climate control and

Thermostats/humidistats

Respiratory therapy

White goods

defogging



Asset and goods tracking

Mobile phones and tablets

Indoor weather stations

SDA

GND

1

2

3

6

5

4

SCL

VDD

DNC

Description

The Si7020 I²C Humidity and Temperature Sensor is a monolithic CMOS IC

integrating humidity and temperature sensor elements, an analog-to-digital

converter, signal processing, calibration data, and an I²C Interface. The patented

use of industry-standard, low-K polymeric dielectrics for sensing humidity enables

the construction of low-power, monolithic CMOS Sensor ICs with low drift and

hysteresis, and excellent long term stability.

DNC

Patent Protected. Patents pending

The humidity and temperature sensors are factory-calibrated and the calibration

data is stored in the on-chip non-volatile memory. This ensures that the sensors

are fully interchangeable, with no recalibration or software changes required.

The Si7020 is available in a 3x3 mm DFN package and is reflow solderable. It can

be used as a hardware- and software-compatible drop-in upgrade for existing RH/

temperature sensors in 3x3 mm DFN-6 packages, featuring precision sensing

over a wider range and lower power consumption. The optional factory-installed

cover offers a low profile, convenient means of protecting the sensor during

assembly (e.g., reflow soldering) and throughout the life of the product, excluding

liquids (hydrophobic/oleophobic) and particulates.

The Si7020 offers an accurate, low-power, factory-calibrated digital solution ideal

for measuring humidity, dew-point, and temperature, in applications ranging from

HVAC/R and asset tracking to industrial and consumer platforms.

Rev. 1.2 8/16

Si7020-A20

Functional Block Diagram

Vdd

Si7020

1.25V

Ref

Calibration

Memory

Humidity

Sensor

Control Logic

ADC

Temp

Sensor

SDA

SCL

I²C Interface

GND

2

Rev. 1.2

Si7020-A20

TABLE OF CONTENTS

Section

Page

1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. Typical Application Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

3. Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

4. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4.1. Relative Humidity Sensor Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

4.2. Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4.3. Prolonged Exposure to High Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4.4. PCB Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4.5. Protecting the Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

4.6. Bake/Hydrate Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

4.7. Long Term Drift/Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

5. I2C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

5.1. Issuing a Measurement Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

5.2. Reading and Writing User Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

5.3. Electronic Serial Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

5.4. Firmware Revision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

5.5. Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

6. Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

6.1. Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

7. Pin Descriptions: Si7020 (Top View) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

8. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

9. Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

9.1. Package Outline: 3x3 6-pin DFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

9.2. Package Outline: 3x3 6-pin DFN with Protective Cover . . . . . . . . . . . . . . . . . . . . . .31

10. PCB Land Pattern and Solder Mask Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

11. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

11.1. Si7020 Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

11.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

12. Additional Reference Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Rev. 1.2

3

Si7020-A20

1. Electrical Specifications

Unless otherwise specified, all min/max specifications apply over the recommended operating conditions.

Table 1. Recommended Operating Conditions

Symbol

VDD

TA

Test Condition

Min

1.9

Typ

—

Max

3.6

Unit

V

Parameter

Power Supply

Operating Temperature

I and Y grade

G grade

–40

—

+125

+85

°C

TA

—

Table 2. General Specifications

1.9 < VDD < 3.6 V; TA = –40 to 85 °C (G grade) or –40 to 125 °C (I/Y grade); default conversion time unless otherwise noted.

Parameter

Symbol

Test Condition

SCL, SDA pins

Min

0.7xVDD

—

Typ

—

Max

—

Unit

V

Input Voltage High

Input Voltage Low

Input Voltage Range

Input Leakage

V

IH

VIL

VIN

IIL

SCL, SDA pins

—

0.3xVDD

VDD

1

V

SCL, SDA pins with respect to GND

SCL, SDA pins

0.0

—

V

—

μA

V

Output Voltage Low

VOL

SDA pin; IOL = 2.5 mA; VDD = 3.3 V

—

0.6

SDA pin; IOL = 1.2 mA;

VDD = 1.9 V

—

0.4

V

Current

Consumption

IDD

RH conversion in progress

—

150

90

180

120

0.62

3.8

4.0

—

μA

Temperature conversion in progress

2

Standby, –40 to +85 °C

0.06

μA

2

Standby, –40 to +125 °C

0.06

μA

3

Peak IDD during powerup

3.5

mA

2

4

Peak IDD during I C operations

3.5

5

Heater Current

I

3.1 to 94.2

HEAT

Notes:

1. Initiating a RH measurement will also automatically initiate a temperature measurement. The total conversion time will

be t_CONV(RH) + t_CONV(T).

2. No conversion or I²C transaction in progress. Typical values measured at 25 °C.

3. Occurs once during powerup. Duration is <5 msec.

4. Occurs during I²C commands for Reset, Read/Write User Registers, Read EID, and Read Firmware Version. Duration is

<100 µs when I²C clock speed is >100 kHz (>200 kHz for 2-byte commands).

5. Additional current consumption when HTRE bit enabled. See Section “5.5. Heater” for more information.

4

Rev. 1.2

Si7020-A20

Table 2. General Specifications (Continued)

1.9 < VDD < 3.6 V; TA = –40 to 85 °C (G grade) or –40 to 125 °C (I/Y grade); default conversion time unless otherwise noted.

Parameter

Symbol

Test Condition

12-bit RH

Min

—

Typ

10

5.8

3.7

2.6

7

Max

12

Unit

1

Conversion Time

t_CONV

11-bit RH

7

10-bit RH

4.5

3.1

10.8

6.2

3.8

2.4

25

8-bit RH

ms

14-bit temperature

13-bit temperature

12-bit temperature

11-bit temperature

4

2.4

1.5

18

Powerup Time

t_PU

From VDD ≥ 1.9 V to ready for a

conversion, 25 °C

From VDD ≥ 1.9 V to ready for a

conversion, full temperature range

—

5

80

15

ms

After issuing a software reset

command

Notes:

1. Initiating a RH measurement will also automatically initiate a temperature measurement. The total conversion time will

be t_CONV(RH) + t_CONV(T).

2. No conversion or I²C transaction in progress. Typical values measured at 25 °C.

3. Occurs once during powerup. Duration is <5 msec.

4. Occurs during I²C commands for Reset, Read/Write User Registers, Read EID, and Read Firmware Version. Duration is

<100 µs when I²C clock speed is >100 kHz (>200 kHz for 2-byte commands).

5. Additional current consumption when HTRE bit enabled. See Section “5.5. Heater” for more information.

Rev. 1.2

5

Si7020-A20

Table 3. I²C Interface Specifications¹

1.9  V_DD 3.6 V; T_A= –40 to +85 °C (G grade) or –40 to +125 °C (I/Y grade) unless otherwise noted.

Parameter

Hysteresis

Symbol

Test Condition

Min

Typ

Max

Unit

V

High-to-low versus low-to- 0.05 x V

high transition

—

V

HYS

DD

2

SCLK Frequency

SCL High Time

SCL Low Time

Start Hold Time

Start Setup Time

Stop Setup Time

Bus Free Time

SDA Setup Time

SDA Hold Time

SDA Valid Time

f

—

400

—

kHz

µs

ns

µs

ns

SCL

t

0.6

1.3

0.6

SKH

t

—

SKL

t

—

STH

t

—

STS

SPS

BUF

t

—

Between Stop and Start

1.3

100

—

t

—

DS

DH

t

—

t

From SCL low to data valid

0.9

—

VD;DAT

VD;ACK

SDA Acknowledge Valid Time

t

—

3

Suppressed Pulse Width

t

50

SPS

Notes:

1. All values are referenced to V_ILand/or V_IH.

2. Depending on the conversion command, the Si7020 may hold the master during the conversion (clock stretch). At

above 100 kHz SCL, the Si7020 may also hold the master briefly for user register and device ID transactions. At the

highest I²C speed of 400 kHz the stretching will be <50 µs.

3. Pulses up to and including 50 ns will be suppressed.

tSKH

tSKL

1/fSCL

tSP

SCL

SDA

tBUF

tSTH

tDS

tDH

tSPS

D6

D5

D4

D0

R/W

ACK

Start Bit

tSTS

Stop Bit

t_VD

:

ACK

Figure 1. I²C Interface Timing Diagram

6

Rev. 1.2

Si7020-A20

Table 4. Humidity Sensor

1.9 ≤ V_DD≤ 3.6 V; T_A= 30 °C; default conversion time unless otherwise noted.

Parameter

Symbol

Test Condition

Non-condensing

0 – 80% RH

Min

0

Typ

Max

100

±4

Unit

%RH

1

Operating Range

—

±3

2, 3

Accuracy

—

80 – 100% RH

See Figure 2.

0.025

0.05

Repeatability/Noise

12-bit resolution

—

11-bit resolution

%RH RMS

10-bit resolution

0.1

8-bit resolution

0.2

1 m/s airflow, with cover

1 m/s airflow, without cover

18

4

Response Time

τ

S

63%

17

Drift vs. Temperature

Hysteresis

0.05

%RH/°C

%RH

±1

3

Long Term Stability

< 0.25

%RH/yr

Notes:

1. Recommended humidity operating range is 20% to 80% RH (non-condensing) over –10 °C to 60 °C. Prolonged

operation beyond these ranges may result in a shift of sensor reading, with slow recovery time.

2. Excludes hysteresis, long term drift, and certain other factors and is applicable to non-condensing environments only.

See Section “4.1. Relative Humidity Sensor Accuracy” for more details.

3. Drift due to aging effects at typical room conditions of 30 °C and 30% to 50% RH. May be impacted by dust, vaporized

solvents or other contaminants, e.g., out-gassing tapes, adhesives, packaging materials, etc. See Section “4.7. Long

Term Drift/Aging” .

4. Response time to a step change in RH. Time for the RH output to change by 63% of the total RH change.

Rev. 1.2

7

Si7020-A20

Figure 2. RH Accuracy at 30 °C

8

Rev. 1.2

Si7020-A20

Table 5. Temperature Sensor

1.9 ≤ V_DD≤ 3.6 V; TA = –40 to +85 °C (G grade) or –40 to +125 °C (I/Y grade) default conversion time, unless otherwise noted.

Parameter

Symbol

Test Condition

I and Y Grade

G Grade

Min

–40

—

Typ

—

Max

+125

+85

Unit

°C

Operating Range

—

°C

1

Accuracy

–10 °C< t < 85 °C

±0.3

Figure 3.

0.01

0.02

0.04

0.08

0.7

±0.4

°C

A

–40 < t < 125 °C

A

Repeatability/Noise

14-bit resolution

13-bit resolution

12-bit resolution

11-bit resolution

Unmounted device

Si7020-EB board

—

°C RMS

2

Response Time

τ

s

63%

5.1

s

Long Term Stability

 0.01

°C/Yr

Notes:

1. 14b measurement resolution (default).

2. Time to reach 63% of final value in response to a step change in temperature. Actual response time will vary

dependent on system thermal mass and air-flow.

Rev. 1.2

9

Si7020-A20

Figure 3. Temperature Accuracy*

*Note: Applies only to I and Y grade devices beyond +85 °C.

10

Rev. 1.2

Si7020-A20

Table 6. Thermal Characteristics

Parameter

Symbol

Test Condition

DFN-6

Unit

Junction to Air Thermal Resistance



JEDEC 2-Layer board,

No Airflow

256

°C/W

JA

Junction to Air Thermal Resistance



JEDEC 2-Layer board,

1 m/s Airflow

224

205

°C/W

JA



JEDEC 2-Layer board,

2.5 m/s Airflow

JA

Junction to Case Thermal Resistance

Junction to Board Thermal Resistance



JEDEC 2-Layer board

22

°C/W

JC



134

JB

Table 7. Absolute Maximum Ratings¹

Parameter

Symbol

Test Condition

Min

Typ

Max

Unit

Ambient temperature

under bias

–55

—

125

°C

2

Storage Temperature

Voltage on I/O pins

–65

–0.3

—

150

°C

V

+0.3 V

DD

Voltage on VDD with

respect to GND

4.2

V

ESD Tolerance

HBM

CDM

MM

—

2

kV

V

1.25

250

Notes:

1. Absolute maximum ratings are stress ratings only, operation at or beyond these conditions is not implied and may

shorten the life of the device or alter its performance.

2. Special handling considerations apply; see application note, “AN607: Si70xx Humidity Sensor Designer’s Guide”.

Rev. 1.2

11

Si7020-A20

2. Typical Application Circuits

The primary function of the Si7020 is to measure relative humidity and temperature. Figure 4 demonstrates the

typical application circuit to achieve these functions.

1.9 to 3.6V

0.1µF

10k

5

V_DD

6

1

SCL

SDA

SCL

SDA

Si7020

GND

2

Figure 4. Typical Application Circuit for Relative Humidity and Temperature Measurement

12

Rev. 1.2

Si7020-A20

3. Bill of Materials

Table 8. Typical Application Circuit BOM for Relative Humidity and Temperature Measurement

Reference

Description

Mfr Part Number

CR0603-16W-103JT

C0603X7R160-104M

Si7020-A20-GM

Manufacturer

Venkel

R1

R2

C1

U1

Resistor, 10 k, ±5%, 1/16 W, 0603

Capacitor, 0.1 µF, 16 V, X7R, 0603

IC, Digital Temperature/humidity Sensor

Venkel

Silicon Labs

Rev. 1.2

13

Si7020-A20

4. Functional Description

Vdd

Si7020

1.25V

Ref

Calibration

Memory

Humidity

Sensor

Control Logic

ADC

Temp

Sensor

SDA

SCL

I²C Interface

GND

Figure 5. Si7020 Block Diagram

The Si7020 is a digital relative humidity and temperature sensor that integrates temperature and humidity sensor

elements, an analog-to-digital converter, signal processing, calibration, polynomial non-linearity correction, and an

2

I C interface all in a single chip. The Si7020 is individually factory-calibrated for both temperature and humidity,

with the calibration data stored in on-chip non-volatile memory. This ensures that the sensor is fully

interchangeable, with no recalibration or changes to software required. Patented use of industry-standard CMOS

and low-K dielectrics as a sensor enables the Si7020 to achieve excellent long term stability and immunity to

contaminants with low drift and hysteresis. The Si7020 offers a low-power, high-accuracy, calibrated and stable

solution ideal for a wide range of temperature, humidity, and dew-point applications including medical and

instrumentation, high-reliability automotive and industrial systems, and cost-sensitive consumer electronics.

While the Si7020 is largely a conventional mixed-signal CMOS integrated circuit, relative humidity sensors in

general and those based on capacitive sensing using polymeric dielectrics have unique application and use

requirements that are not common to conventional (non-sensor) ICs. Chief among those are:

The need to protect the sensor during board assembly, i.e., solder reflow, and the need to subsequently

rehydrate the sensor.

The need to protect the senor from damage or contamination during the product life-cycle.

The impact of prolonged exposure to extremes of temperature and/or humidity and their potential effect on

sensor accuracy.

The effects of humidity sensor “memory”.

Each of these items is discussed in more detail in the following sections.

14

Rev. 1.2

Si7020-A20

4.1. Relative Humidity Sensor Accuracy

To determine the accuracy of a relative humidity sensor, it is placed in a temperature and humidity controlled

chamber. The temperature is set to a convenient fixed value (typically 25–30 °C) and the relative humidity is swept

from 20 to 80% and back to 20% in the following steps: 20% – 40% – 60% – 80% – 80% – 60% – 40% – 20%. At

each set-point, the chamber is allowed to settle for a period of 60 minutes before a reading is taken from the

sensor. Prior to the sweep, the device is allowed to stabilize to 50%RH. The solid trace in Figure 6, “Measuring

Sensor Accuracy Including Hysteresis,” shows the result of a typical sweep.

Figure 6. Measuring Sensor Accuracy Including Hysteresis

The RH accuracy is defined as the dotted line shown in Figure 6, which is the average of the two data points at

each relative humidity set-point. In this case, the sensor shows an accuracy of 0.25%RH. The Si7020 accuracy

specification (Table 4) includes:

Unit-to-unit and lot-to-lot variation

Accuracy of factory calibration

Margin for shifts that can occur during solder reflow

The accuracy specification does not include:

Hysteresis (typically ±1%)

Effects from long term exposure to very humid conditions

Contamination of the sensor by particulates, chemicals, etc.

Other aging related shifts ("Long-term stability")

Variations due to temperature (see Drift vs. Temperature in Table 4). RH readings will typically vary with

temperature by less than  0.05%  C.

Rev. 1.2

15

Si7020-A20

4.2. Hysteresis

The moisture absorbent film (polymeric dielectric) of the humidity sensor will carry a memory of its exposure

history, particularly its recent or extreme exposure history. A sensor exposed to relatively low humidity will carry a

negative offset relative to the factory calibration, and a sensor exposed to relatively high humidity will carry a

positive offset relative to the factory calibration. This factor causes a hysteresis effect illustrated by the solid trace

in Figure 6. The hysteresis value is the difference in %RH between the maximum absolute error on the decreasing

humidity ramp and the maximum absolute error on the increasing humidity ramp at a single relative humidity

setpoint and is expressed as a bipolar quantity relative to the average error (dashed trace). In the example of

Figure 6, the measurement uncertainty due to the hysteresis effect is ±1.0%RH.

4.3. Prolonged Exposure to High Humidity

Prolonged exposure to high humidity will result in a gradual upward drift of the RH reading. The shift in sensor

reading resulting from this drift will generally disappear slowly under normal ambient conditions. The amount of

shift is proportional to the magnitude of relative humidity and the length of exposure. In the case of lengthy

exposure to high humidity, some of the resulting shift may persist indefinitely under typical conditions. It is generally

possible to substantially reverse this affect by baking the device (see Section “4.6. Bake/Hydrate Procedure” ).

4.4. PCB Assembly

4.4.1. Soldering

Like most ICs, Si7020 devices are shipped from the factory vacuum-packed with an enclosed desiccant to avoid

any RH accuracy drift during storage and to prevent any moisture-related issues during solder reflow. The following

guidelines should be observed during PCB assembly:

Si7020 devices are compatible with standard board assembly processes. Devices should be soldered

using reflow per the recommended card reflow profile. See Section “10. PCB Land Pattern and Solder

Mask Design” for the recommended card reflow profile.

A "no clean" solder process is recommended to minimize the need for water or solvent rinses after

soldering. Cleaning after soldering is possible, but must be done carefully to avoid impacting the

performance of the sensor. See “AN607: Si70xx Humidity Sensor Designer’s Guide” for more information

on cleaning.

It is essential that the exposed polymer sensing film be kept clean and undamaged. This can be

accomplished by careful handling and a clean, well-controlled assembly process. When in doubt or for

extra protection, a heat-resistant, protective cover such as Kapton™ KPPD-1/8 polyimide tape can be

installed during PCB assembly.

Si7020s may be ordered with a factory-fitted, solder-resistant protective cover. This cover provides protection

during PCB assembly or rework but without the time and effort required to install and remove the Kapton tape. It

can be left in place for the lifetime of the product, preventing liquids, dust or other contaminants from coming into

contact with the polymer sensor film. See Section “8. Ordering Guide” for a list of ordering part numbers that

include the cover.

4.4.2. Rehydration

The measured humidity value will generally shift slightly after solder reflow. A portion of this shift is permanent and

is accounted for in the accuracy specifications in Table 4. After soldering, an Si7020 should be allowed to

equilibrate under controlled RH conditions (room temperature, 45–55%RH) for at least 48 hours to eliminate the

remainder of the shift and return the device to its specified accuracy performance.

16

Rev. 1.2

Si7020-A20

4.4.3. Rework

To maintain the specified sensor performance, care must be taken during rework to minimize the exposure of the

device to excessive heat and to avoid damage/contamination or a shift in the sensor reading due to liquids, solder

flux, etc. Manual touch-up using a soldering iron is permissible under the following guidelines:

The exposed polymer sensing film must be kept clean and undamaged. A protective cover is

recommended during any rework operation (Kapton® tape or the factory installed cover).

Flux must not be allowed to contaminate the sensor; liquid flux is not recommended even with a cover in

place. Conventional lead-free solder with rosin core is acceptable for touch-up as long as a cover is in

place during the rework.

If possible, avoid water or solvent rinses after touch-up. Cleaning after soldering is possible, but must be

done carefully to avoid impacting the performance of the sensor. See “AN607: Si70xx Humidity Sensor

Designer’s Guide” for more information on cleaning.

Minimize the heating of the device. Soldering iron temperatures should not exceed 350 °C and the contact

time per pin should not exceed five seconds.

Hot air rework is not recommended. If a device must be replaced, remove the device by hot air and solder

a new part in its place by reflow following the guidelines above.

*Note: All trademarks are the property of their respective owners.

Figure 7. Si7020 with Factory-Installed Protective Cover

Rev. 1.2

17

Si7020-A20

4.5. Protecting the Sensor

Because the sensor operates on the principal of measuring a change in capacitance, any changes to the dielectric

constant of the polymer film will be detected as a change in relative humidity. Therefore, it is important to minimize

the probability of contaminants coming into contact with the sensor. Dust and other particles as well as liquids can

affect the RH reading. It is recommended that a cover is employed in the end system that blocks contaminants but

allows water vapor to pass through. Depending on the needs of the application, this can be as simple as plastic or

metallic gauze for basic protection against particulates or something more sophisticated such as a hydrophobic

membrane providing up to IP67 compliant protection.

The Si7020 may be ordered with a factory-fitted, solder-resistant cover that can be left in place for the lifetime of

the product. It is very low-profile, hydrophobic and oleophobic. See Section “8. Ordering Guide” for a list of

ordering part numbers that include the cover. A dimensioned drawing of the IC with the cover is included in Section

“9. Package Outline” . Other characteristics of the cover are listed in Table 9.

Table 9. Specifications of Protective Cover

Parameter

Value

PTFE

Material

Operating Temperature

–40 to 125 °C

260 °C

Maximum Reflow Temperature

IP Rating (per IEC 529)

IP67

4.6. Bake/Hydrate Procedure

After exposure to extremes of temperature and/or humidity for prolonged periods, the polymer sensor film can

become either very dry or very wet, in each case the result is either high or low relative humidity readings. Under

normal operating conditions, the induced error will diminish over time. From a very dry condition, such as after

shipment and soldering, the error will diminish over a few days at typical controlled ambient conditions, e.g.,

48 hours of 45 ≤ %RH ≤ 55. However, from a very wet condition, recovery may take significantly longer. To

accelerate recovery from a wet condition, a bake and hydrate cycle can be implemented. This operation consists of

the following steps:

Baking the sensor at 125 °C for ≥ 12 hours

Hydration at 30 °C in 75% RH for ≥ 10 hours

Following this cycle, the sensor will return to normal operation in typical ambient conditions after a few days.

4.7. Long Term Drift/Aging

Over long periods of time, the sensor readings may drift due to aging of the device. Standard accelerated life

testing of the Si7020 has resulted in the specifications for long-term drift shown in Table 4 and Table 5. This

contribution to the overall sensor accuracy accounts only for the long-term aging of the device in an otherwise

benign operating environment and does not include the effects of damage, contamination, or exposure to extreme

environmental conditions.

18

Rev. 1.2

Si7020-A20

5. I²C Interface

2

The Si7020 communicates with the host controller over a digital I C interface. The 7-bit base slave address is

0x40.

2

Table 10. I C Slave Address Byte

A6

A5

A4

A3

A2

A1

A0

R/W

1

0

2

Master I C devices communicate with the Si7020 using a command structure. The commands are listed in the I C

command table. Commands other than those documented below are undefined and should not be sent to the

device.

Table 11. I²C Command Table

Command Description

Measure Relative Humidity, Hold Master Mode

Command Code

0xE5

Measure Relative Humidity, No Hold Master Mode

Measure Temperature, Hold Master Mode

Measure Temperature, No Hold Master Mode

Read Temperature Value from Previous RH Measurement

Reset

0xF5

0xE3

0xF3

0xE0

0xFE

Write RH/T User Register 1

0xE6

Read RH/T User Register 1

0xE7

Write Heater Control Register

0x51

Read Heater Control Register

0x11

Read Electronic ID 1st Byte

0xFA 0x0F

0xFC 0xC9

0x84 0xB8

Read Electronic ID 2nd Byte

Read Firmware Revision

Rev. 1.2

19

Si7020-A20

5.1. Issuing a Measurement Command

The measurement commands instruct the Si7020 to perform one of two possible measurements; Relative Humidity

or Temperature. The procedure to issue any one of these commands is identical. While the measurement is in

progress, the option of either clock stretching (Hold Master Mode) or Not Acknowledging read requests (No Hold

Master Mode) is available to indicate to the master that the measurement is in progress; the chosen command

code determines which mode is used.

Optionally, a checksum byte can be returned from the slave for use in checking for transmission errors. The

checksum byte will follow the least significant measurement byte if it is acknowledged by the master. The

checksum byte is not returned if the master “not acknowledges” the least significant measurement byte. The

8

5

4

checksum byte is calculated using a CRC generator polynomial of x + x + x + 1, with an initialization of 0x00.

The checksum byte is optional after initiating an RH or temperature measurement with commands 0xE5, 0xF5,

0xE3, and 0xF3. The checksum byte is required for reading the electronic ID with commands 0xFA 0x0F and 0xFC

0xC9. For all other commands, the checksum byte is not supported.

Table 12. I²C Bit Descriptions

Name

Symbol

Description

START

S

P

SDA goes low while SCL high.

SDA goes high while SCL high.

STOP

Repeated START

Sr

SDA goes low while SCL high. It is allowable to generate a STOP before the

repeated start. SDA can transition to high before or after SCL goes high in

preparation for generating the START.

READ

R

W

—

Read bit = 1

Write bit = 0

WRITE

All other bits

SDA value must remain high or low during the entire time SCL is high (this is

the set up and hold time in Figure 1).

2

In the I C sequence diagrams in the following sections, bits produced by the master and slave are color coded as

shown:

Master

Slave

20

Rev. 1.2

Si7020-A20

Sequenceꢀtoꢀperformꢀaꢀmeasurementꢀandꢀreadꢀbackꢀresultꢀ(HoldꢀMasterꢀMode)ꢀ

Clockꢀstretchꢀ

duringꢀ

measurementꢀ

Slaveꢀ

Addressꢀ

Measureꢀ

Cmdꢀ

Slaveꢀ

Addressꢀ

Sꢀ

Wꢀ Aꢀ

Aꢀ Srꢀ

Rꢀ Aꢀ

ꢀꢀ

MSꢀByteꢀ

Aꢀ

LSꢀByteꢀ

NAꢀ Pꢀ

Aꢀ Checksumꢀ NA Pꢀ

Note: Device will NACK the slave address byte until conversion is complete.

Rev. 1.2

21

Si7020-A20

5.1.1. Measuring Relative Humidity

Once a relative humidity measurement has been made, the results of the measurement may be converted to

percent relative humidity by using the following expression:



125 RH_Code

%RH = --------------------------------------- – 6

65536

Where:

%RH is the measured relative humidity value in %RH

RH_Code is the 16-bit word returned by the Si7020

A humidity measurement will always return XXXXXX10 in the LSB field.

Due to normal variations in RH accuracy of the device as described in Table 4, it is possible for the measured value

of %RH to be slightly less than 0 when the actual RH level is close to or equal to 0. Similarly, the measured value

of %RH may be slightly greater than 100 when the actual RH level is close to or equal to 100. This is expected

behavior, and it is acceptable to limit the range of RH results to 0 to 100%RH in the host software by truncating

values that are slightly outside of this range.

5.1.2. Measuring Temperature

Each time a relative humidity measurement is made a temperature measurement is also made for the purposes of

temperature compensation of the relative humidity measurement. If the temperature value is required, it can be

read using command 0xE0; this avoids having to perform a second temperature measurement. The measure

temperature commands 0xE3 and 0xF3 will perform a temperature measurement and return the measurement

value, command 0xE0 does not perform a measurement but returns the temperature value measured during the

relative humidity measurement.

The checksum output is not available with the 0xE0 command.

SequenceꢀtoꢀreadꢀtemperatureꢀvalueꢀfromꢀpreviousꢀRHꢀmeasurementꢀ

Slaveꢀ

Addressꢀ

Slaveꢀ

Addressꢀ

Sꢀ

Wꢀ Aꢀ

0xE0ꢀ

Aꢀ Srꢀ

Rꢀ Aꢀ

MSꢀByteꢀ

ꢀ

Aꢀ

LSꢀByteꢀ

NAꢀ Pꢀ

22

Rev. 1.2

Si7020-A20

The results of the temperature measurement may be converted to temperature in degrees Celsius (°C) using the

following expression:



175.72 Temp_Code

Temperature (C = ------------------------------------------------------- – 46.85

65536

Where:

Temperature (°C) is the measured temperature value in °C

Temp_Code is the 16-bit word returned by the Si7020

A temperature measurement will always return XXXXXX00 in the LSB field.

Rev. 1.2

23

Si7020-A20

5.2. Reading and Writing User Registers

There is one user register on the Si7020 that allows the user to set the configuration of the Si7020. The procedure

for accessing that register is described below.

The checksum byte is not supported after reading a user register.

Sequence to read a register

Slave

Read Reg

Cmd

Slave

S

W

A

Sr

R

A

Read Data

NA

P

Address

Sequence to write a register

Write Reg Cmd

S

Slave Address

W

A

Write Data

A

P

5.3. Electronic Serial Number

2

The Si7020 provides a serial number individualized for each device that can be read via the I C serial interface.

2

Two I C commands are required to access the device memory and retrieve the complete serial number. The

command sequence, and format of the serial number response is described in the figure below:

Master

Slave

First access:

S

Slave Address

SNA_3

W

R

ACK

CRC

0xFA

ACK

0X0F

ACK

SNA_2

SNA_0

ACK

CRC

ACK

SNA_1

NACK

P

2nd access:

S

Slave Address

SNB_3

W

R

ACK

0xFC

ACK

0XC9

ACK

P

ACK

SNB_2

SNB_0

ACK

CRC

ACK

SNB_1

NACK

The format of the complete serial number is 64-bits in length, divided into 8 data bytes. The complete serial number

sequence is shown below:

SNA_3

SNA_2

SNA_1

SNA_0

SNB_3

SNB_2

SNB_1

SNB_0

The SNB3 field contains the device identification to distinguish between the different Silicon Labs relative humidity

and temperature devices. The value of this field maps to the following devices according to this table:

24

Rev. 1.2

Si7020-A20

0x00 or 0xFF engineering samples

0x0D=13=Si7013

0x14=20=Si7020

0x15=21=Si7021

5.4. Firmware Revision

2

The internal firmware revision can be read with the following I C transaction:

Slave

S

W

A

0x84

A

0xB8

A

S

Address

R

A

FWREV

NA

P

The values in this field are encoded as follows:

0xFF = Firmware version 1.0

0x20 = Firmware version 2.0

5.5. Heater

The Si7020 contains an integrated resistive heating element that may be used to raise the temperature of the

sensor. This element can be used to test the sensor, to drive off condensation, or to implement dew-point

measurement when the Si7020 is used in conjunction with a separate temperature sensor such as another Si7020

(the heater will raise the temperature of the internal temperature sensor).

The heater can be activated using HTRE, bit 2 in User Register 1. Turning on the heater will reduce the tendency

of the humidity sensor to accumulate an offset due to "memory" of sustained high humidity conditions. Several

different power levels are available. The various settings are adjusted using the Heater Control Register and are

described in the following table.

Table 13. Heater Control Settings

*

HEATER[3:0]

Typical Current Draw (mA)

0000

0001

0010

...

3.09

9.18

15.24

...

0100

...

27.39

...

1000

...

51.69

...

1111

94.20

*Note: Assumes VDD = 3.3 V.

Rev. 1.2

25

Si7020-A20

6. Control Registers

Table 14. Register Summary

Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

User Register 1

RES1

VDDS

RSVD

HTRE

RSVD

RES0

Heater Control

Register

RSVD

HEATER[3:0]

Notes:

1. Any register not listed here is reserved and must not be written. The result of a read operation on these bits is

undefined.

2. Except where noted, reserved register bits will always read back as “1,” and are not affected by write operations. For

future compatibility, it is recommended that prior to a write operation, registers should be read. Then the values read

from the RSVD bits should be written back unchanged during the write operation.

6.1. Register Descriptions

Register 1. User Register 1

Bit

D7

D6

VDDS

R

D5

D4

D3

D2

D1

D0

Name

Type

RES1

R/W

RSVD

R/W

RSVD

HTRE

R/W

RSVD

R/W

RES0

R/W

Reset Settings = 0011_1010

Bit

Name

Function

D7; D0

RES[1:0]

Measurement Resolution:

RH

Temp

14 bit

12 bit

13 bit

11 bit

00:

01:

10:

11:

12 bit

8 bit

10 bit

11 bit

D6

VDDS

V

Status:

DD

0:

1:

V

OK

Low

DD

The minimum recommended operating voltage is 1.9 V. A transi-

tion of the V status bit from 0 to 1 indicates that V is

DD

between 1.8 V and 1.9 V. If the V drops below 1.8 V, the

DD

device will no longer operate correctly.

D5, D4, D3

D2

RSVD

HTRE

Reserved

1 = On-chip Heater Enable

0 = On-chip Heater Disable

D1

RSVD

Reserved

26

Rev. 1.2

Si7020-A20

Register 2. Heater Control Register

Bit

D7

D6

D5

D4

D3

D2

Heater [3:0]

R/W

D1

D0

Name

Type

RSVD

R/W

Reset Settings = 0000_0000

Bit

Name

Function

D3:D0 HEATER[3:0]

D3

0

D2

D1

0

D0

0

Heater Current

0

3.09 mA

9.18 mA

15.24 mA

0

1

0

1

0

...

0

1

0

1

0

1

27.39 mA

...

0

51.69 mA

94.20 mA

...

1

D7,D6,

D5,D4

RSVD

Reserved

Rev. 1.2

27

Si7020-A20

7. Pin Descriptions: Si7020 (Top View)

SDA

GND

1

2

3

6

5

4

SCL

VDD

DNC

Pin Name

SDA

Pin #

Pin Description

2

1

2

I C data

GND

Ground. This pin is connected to ground on the circuit board through a trace. Do not

connect directly to GND plane.

VDD

SCL

DNC

5

6

Power. This pin is connected to power on the circuit board.

2

I C clock

3,4

These pins should be soldered to pads on the PCB for mechanical stability; they can be

electrically floating or tied to V (do not tie to GND).

DD

T

Paddle This pad is connected to GND internally. This pad is the main thermal input to the

GND

on-chip temperature sensor. The paddle should be soldered to a floating pad.

28

Rev. 1.2

Si7020-A20

8. Ordering Guide

Table 15. Device Ordering Guide

P/N

Description

Max.

Pkg

Operating

Protective Packing

Accuracy

Range (°C)

Cover

Format

Temp

RH

Si7020-A20-GM Digital temperature/ humidity sensor

Si7020-A20-GMR Digital temperature/ humidity sensor

Si7020-A20-GM1 Digital temperature/ humidity sensor

Si7020-A20-GM1R Digital temperature/ humidity sensor

±0.4 °C ± 4% DFN 6

–40 to +85 °C

N

Y

N

Y

N

Y

Cut

Tape

Tape &

Reel

Cut

Tape

Tape &

Reel

Si7020-A20-IM

Digital temperature/ humidity sensor – ±0.4 °C ± 4% DFN 6 –40 to +125 °C

industrial temp range

Cut

Tape

Si7020-A20-IMR Digital temperature/ humidity sensor – ±0.4 °C ± 4% DFN 6 –40 to +125 °C

industrial temp range

Tape &

Reel

Si7020-A20-IM1 Digital temperature/ humidity sensor – ±0.4 °C ± 4% DFN 6 –40 to +125 °C

industrial temp range

Cut

Tape

Si7020-A20-IM1R Digital temperature/ humidity sensor – ±0.4 °C ± 4% DFN 6 –40 to +125 °C

industrial temp range

Tape &

Reel

Si7020-A20-YM0 Digital temperature/ humidity sensor – ±0.4 °C ± 4% DFN 6 –40 to +125 °C

automotive

Cut

Tape

Si7020-A20-YM0R Digital temperature/ humidity sensor – ±0.4 °C ± 4% DFN 6 –40 to +125 °C

automotive

Tape &

Reel

Si7020-A20-YM1 Digital temperature/ humidity sensor – ±0.4 °C ± 4% DFN 6 –40 to +125 °C

automotive

Cut

Tape

Si7020-A20-YM1R Digital temperature/ humidity sensor – ±0.4 °C ± 4% DFN 6 –40 to +125 °C

automotive

Tape &

Reel

Note: The “A” denotes product revision A and “20” denotes firmware version 2.0.

Rev. 1.2

29

Si7020-A20

9. Package Outline

9.1. Package Outline: 3x3 6-pin DFN

Figure 10. 3x3 6-pin DFN

Table 16. 3x3 6-pin DFN Package Diagram Dimensions

Dimension

Min

Nom

Max

A

A1

b

0.70

0.00

0.35

0.75

0.02

0.80

0.05

0.45

0.40

D

3.00 BSC.

1.50

D2

e

1.40

1.60

1.00 BSC.

3.00 BSC.

2.40

E

E2

H1

H2

L

2.30

0.85

1.39

0.35

2.50

0.95

1.49

0.45

0.90

1.44

0.40

aaa

bbb

ccc

ddd

eee

fff

0.10

0.05

0.10

0.05

Notes:

1. All dimensions shown are in millimeters (mm).

2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.

30

Rev. 1.2

Si7020-A20

9.2. Package Outline: 3x3 6-pin DFN with Protective Cover

Figure 8 illustrates the package details for the Si7020 with the optional protective cover. The table below lists the

values for the dimensions shown in the illustration.

Figure 8. 3x3 6-pin DFN with Protective Cover

Table 17. 3x3 6-pin DFN with Protective Cover Package Diagram Dimensions

Dimension

Min

—

Nom

—

Max

1.21

0.05

0.80

0.45

A

A1

A2

b

0.00

0.70

0.35

0.02

0.75

0.40

D

3.00 BSC.

1.50

D2

e

1.40

1.60

1.00 BSC.

3.00 BSC.

2.40

E

E2

F1

F2

h

2.30

2.70

0.76

0.35

0.45

2.50

2.90

0.90

0.45

0.55

2.80

0.83

L

0.40

R1

aaa

bbb

ccc

ddd

eee

0.50

0.10

0.05

0.10

0.05

Notes:

1. All dimensions are shown in millimeters (mm).

2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.

Rev. 1.2

31

Si7020-A20

10. PCB Land Pattern and Solder Mask Design

Figure 9. Si7020 PCB Land Pattern

Table 18. PCB Land Pattern Dimensions

Symbol

C1

mm

2.90

1.00

1.60

2.50

0.45

0.85

E

P1

P2

X1

Y1

Notes:

General

1. All dimensions shown are at Maximum Material Condition (MMC). Least Material

Condition (LMC) is calculated based on a Fabrication Allowance of 0.05 mm.

2. This Land Pattern Design is based on the IPC-7351 guidelines.

Solder Mask Design

3. All metal pads are to be non-solder mask defined (NSMD). Clearance between the

solder mask and the metal pad is to be 60 µm minimum, all the way around the

pad.

Stencil Design

4. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls

should be used to assure good solder paste release.

5. The stencil thickness should be 0.125 mm (5 mils).

6. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pins.

7. A 2x1 array of 1.00 mm square openings on 1.30 mm pitch should be used for the

center ground pad to achieve a target solder coverage of 50%.

Card Assembly

8. The recommended card reflow profile is per the JEDEC/IPC J-STD-020

specification for Small Body Components.

32

Rev. 1.2

Si7020-A20

11. Top Marking

11.1. Si7020 Top Marking

11.2. Top Marking Explanation

Mark Method:

Font Size

Laser

0.30 mm

Pin 1 Indicator:

Line 1 Marking:

Circle = 0.30 mm Diameter

Upper-Left Corner

TTTT = Mfg Code

Rev. 1.2

33

Si7020-A20

12. Additional Reference Resources

AN607: Si70xx Humidity Sensor Designer’s Guide

34

Rev. 1.2

Si7020-A20

DOCUMENT CHANGE LIST

Revision 0.9 to Revision 0.91

 Updated Table 2 on page 4.

Revision 0.91 to Revision 1.0

 Updated document revision to 1.0.

Revision 1.0 to Revision 1.1

 Updated note 2 in Table 3.

 Updated Section 4.5.

 Updated Table 9.

2

 Corrected a typo in the I C sequence for no-hold

mode in Section 5.1.

 Corrected a typo in Table 12.

 Updated Table 17, dimensions F1 and F2.

Revision 1.1 to Revision 1.2

 Updated diagram in "5.4. Firmware Revision" on

page 25.

 Updated notes in Table 18, “PCB Land Pattern

Dimensions,” on page 32.

 Changed packing format from tube to cut tape for all

non-tape & reel part numbers without protective filter

covers.

Rev. 1.2

35

Smart.

Connected.

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www.silabs.com/products

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Disclaimer

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using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific

device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories

reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy

or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply

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型号：	SI7020-A20-GMR
厂家：	SILICON
描述：	Serial Switch/Digital Sensor, 14 Bit(s), 0.40Cel, Square, Surface Mount, DFN-6 输出元件传感器换能器
文件：	总36页 (文件大小：1441K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

SI7020-A20-GMR [SILICON]

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