SI7034-A10-IMR - SILICON LABS

Si7034-A10

DIGITAL I2C HUMIDITY AND TEMPERATURE SENSOR

Features

Applications

Description

The Si7034 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 sen sing humidity enables

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

hysteresis, and excellent long-term stability.

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 calibration or software changes required.

The Si7034 is available in a 2x2 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 2x2 mm QFN-6 packages. The Si7034 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.

Precision Relative Humidity Sensor

 ± 4% RH (max), 0–80% RH

High Accuracy Temperature Sensor

±0.4 °C (max), –10 to 85 °C

0 to 100% RH operating range

–40 to +125 °C operating range

Low Voltage Operation

Low Power Consumption

50 nA, standby current

Factory-calibrated

I2C Interface

Integrated on-chip heater

2x2 mm QFN package

Excellent long term stability

Mobile smartphones an d tablets

Consum er el e ctronics

HVAC/R

Respiratory therapy

White goods

Asset and goods tracking

Thermostats/humidistats

Micro-environments/data centers

Indoor weather stations

Patent Protected. Patents pending

Ordering Information:

See page 23.

Pin Assignments

Top View

DNC

SCL

VDD 1

GND

SDA

DNC

Si7034-A10

2 Rev. 1.0

Functional Block Diagram

ADC

GND

Humidity

Sensor Control Logic

SCL

Si7034

Temp

Sensor

1.25V

Ref

I2C Interface SDA

Vdd

Calibration

Memory

Si7034-A10

Rev. 1.0 3

TABLE OF CONTENTS

Section Page

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

2. Typical Application Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

3. Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

4. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

4.1. Relative Humidity Sensor Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

4.2. Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4.3. Prolonged Exposure to High Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4.4. PCB Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4.5. Protecting the Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

4.6. Bake/Hydrate Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

4.7. Long Term Drift/Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

5. I2C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

5.1. Issuing a Measurement Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

5.2. Reading and Writing User Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

5.3. Measuring Relative Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

5.4. Measuring Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

5.5. Firmware Revision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

5.6. Electronic Serial Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

5.7. Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

6. Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

7. Pin Descriptions: Si7034 (Top View) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

8. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

9. Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

9.1. Package Outline: 2x2 6-pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

10. PCB Land Pattern and Solder Mask Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

11. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

11.1. Si7034 Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

11.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

12. Additional Reference Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Si7034-A10

4 Rev. 1.0

1. Electrical Specifications

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

Table 1. Recommended Operating Conditions

Parameter Symbol Test Condition Min Typ Max Unit

Power Supply VDD 1.67 — 1.98 V

Operating Temperature TA–40 — +125 °C

Table 2. General Specifications

1.67  VDD  1.98 V; TA = –40 to +125 °C unle s s otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Input Voltage High VIH SCL, SDA pins 0.7xVDD — — V

Input Voltage Low VIL SCL, SDA pins — — 0.3xVDD V

Input Voltage Range VIN SCL, SDA pins with respect to GND 0.0 — VDD+2 V

Input Leakage IIL SCL, SDA pins — — 1 μA

Output Voltage Low VOL SDA pin; IOL = 1.5 mA — — 0.4 V

Current Consumption IDD Normal Mode, Temperature conversion in

progress1— 245 288 μA

Normal Mode, RH conversion in progress1— 106 145 μA

Fast Mode, parallel temperature and RH

conversion in progress2— 337 398 μA

Fast Mode, RH conversion in progress3— 106 145 μA

Standby, –40 to +85 °C5 — 0.05 0.56 μA

Standby, –40 to +125 °C5 — 0.05 5.2 μA

Peak IDD during powerup6 —45.1 mA

Peak IDD during I2C operations7 —3.5 4 mA

After writing to user registers8 — 11.6 17 µA

Heater Current9IHEAT — 6.4 to 53.5 — mA

Notes:

1. In Normal Mode, a temperature conversion is performed first, followed by an RH conversion.

2. In Fast Mode, both a temperature conversion and an RH conversion are initiated at the same time and occur in parallel.

3. Current consumption of RH conversion after the temperature conversion has finished. In Fast Mode , the temperature

conversion finishes before the RH conversion.

4. Additional time for RH conversion after the temperature conversion has finished.

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

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

7. 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).

8. IDD after a user register write. Initiating any other subsequent I2C transaction on the same bus (such as a user register

read, starting an RH measurement, or traffic directed at other I2C devices) will transition the device to standby mode.

9. Additional current consumption when HTRE bit enabled.

Si7034-A10

Rev. 1.0 5

Conversion Time tCONV Normal Mode, RH conversion15.8 8.5 ms

Normal Mode, Temperature conversion13.7 6 ms

Fast Mode, parallel Temp and RH conver-

sion20.9 1.5 ms

Fast Mode, additional RH conv ersion

time41.6 2.5 ms

Powerup Time tPU From VDD ≥1.67 V to ready for a

conversion, 25 °C — 10 15 ms

From VDD ≥1.67 V to ready for a

conversion, full temperature range — —50

After issuing a software reset

command —1.22.0

Table 3. I2C Interface Specifications1

1.67  VDD  1.98 V; TA = –40 to +125 °C unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Hysteresis VHYS High-to-low versus

low-to-high transition 0.05 x VDD ——V

SCLK Frequency2fSCL — — 400 kHz

SCL High Time tSKH 0.6 — — µs

SCL Low Time tSKL 1.3 — — µs

Start Hold Time tSTH 0.6 — — µs

Notes:

1. All values are referenced to V IL and/or VIH.

2. Depending on the conversion command, the Si7034 may hold the master during the conversi on (clock stretch). At

above 300 kHz SCL, the Si7034 may 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.

Table 2. General Specifications (Continued)

1.67  VDD  1.98 V; TA = –40 to +125 °C unle s s otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Notes:

1. In Normal Mode, a temperature conversion is performed first, followed by an RH conversion.

2. In Fast Mode, both a temperature conversion and an RH conversion are initiated at the same time and occur in parallel.

3. Current consumption of RH conversion after the temperature conversion has finished. In Fast Mode , the temperature

conversion finishes before the RH conversion.

4. Additional time for RH conversion after the temperature conversion has finished.

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

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

7. 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).

8. IDD after a user register write. Initiating any other subsequent I2C transaction on the same bus (such as a user register

read, starting an RH measurement, or traffic directed at other I2C devices) will transition the device to standby mode.

9. Additional current consumption when HTRE bit enabled.

Si7034-A10

6 Rev. 1.0

Figure 1. I2C Interface Timing Dia gram

Start Setup Time tSTS 0.6 — — µs

Stop Setup Time tSPS 0.6 — — µs

Bus Free Time tBUF Between Stop and Start 1.3 — — µs

SDA Setup Time tDS 100 — — ns

SDA Hold Time tDH 100 — — ns

SDA Valid Time tVD;DAT From SCL low to data valid — — 0.9 µs

SDA Acknowledge Valid Time tVD;ACK From SCL low to data valid — — 0.9 µs

Suppressed Pulse Width 3tSP 50 — — ns

Table 3. I2C Interface Specifications1 (Continued)

1.67  VDD  1.98 V; TA = –40 to +125 °C unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Notes:

1. All values are referenced to V IL and/or VIH.

2. Depending on the conversion command, the Si7034 may hold the master during the conversi on (clock stretch). At

above 300 kHz SCL, the Si7034 may 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.

SCL

1/fSCL tSKH

SDA

tSKL

tSTH

D6 D5 D0 R/W ACK

tDS tDH

Start Bit Stop Bit

tBUF

tSTS tVD : ACK

tSPS

tSP

Si7034-A10

Rev. 1.0 7

Figure 2. RH Accuracy at 30 °C

Table 4. Humidity Sensor

1.67 ≤ VDD ≤ 1.98 V ; TA = 30 °C unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Operating Range1Non-condensing 0 — 100 %RH

Accuracy2, 3 0 – 80% RH — ±3 +4 %RH

80 – 100% RH See Figure 2

Repeatability/Noise4Normal — 0.15 — %RH RMS

Fast — 0.45 —

Response Time5τ63% 1m/s airflow — 18 — S

Drift vs. Temperature — 0.05 — %RH/°C

Hysteresis — ±1 — %RH

Long Term Stability3—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 rang es 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 Relative Humidity Se nsor Accuracy for more details.

3. Drift due to aging effect s 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. 3-sigma measurement deviation.

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

Si7034-A10

8 Rev. 1.0

Figure 3. Temperature Accuracy

Table 5. Temperature Sensor

1.67 ≤ VDD ≤1.98 V; TA= –40 to +125 °C unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Operating Range –40 — +125 °C

Accuracy1tA =30 °C — ±0.3 ±0.4 °C

–40 < tA< 125°C Figure3

Repeatability/Noise2Normal — 0.03 — °C RMS

Fast — 0.09 —

Response Time3τ63% Unmounted device — 0.7 — s

Si7034-EB — 5.1 —

Long Term Stability — < 0.01 — °C/Yr

Notes:

1. Normal conversion time.

2. 3-sigma measurement deviation.

3. 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.

Si7034-A10

Rev. 1.0 9

Table 6. Thermal Characteristics

Parameter Symbol Test Condition QFN-6 Unit

Junction to Air Thermal Resistance JA JEDEC 2-Layer Boar d, No Airflo w 173 °C/W

Junction to Air Thermal Resistance JA JEDEC 2-Layer Board, 1 m/s Airflow 153 °C/W

Junction to Air Thermal Resistance JA JEDEC 2-Layer Board, 2 m/s Airflow 146 °C/W

Junction to Case Thermal Resistance JC JEDEC 2-Layer Board 84 °C/W

Junction to Board Thermal Resistance JB JE DEC 2-Layer Board 114 °C/W

Table 7. Absolute Maximum Ratings1,2

Parameter Symbol Test Condition Min Typ Max Unit

Ambient temperature

under bias –55 — 125 °C

Storage Temperature –65 — 150 °C

Voltage on I/O pins –0.3 — VDD+2.0 V V

Voltage on VDD with

Respect to GND –0.3 — 2.3 V

ESD Tolerance HBM 2 kV

CDM 1.25 kV

MM 250 V

Notes:

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

shorten the life of the device or alter its performance.

2. Special handling considerations apply; see applicati on note, “AN607: Si70xx Humidity and Temperature Sensor

Designer’s Guide”.

Si7034-A10

10 Rev. 1.0

2. Typical Application Circuit

The primary function of the Si7034 is to measure relative humidity and temperature. Figure 4 demonstrates the

typical application circuit to achieve these functions; pins 3 and 6 are not required and must be left unconnected.

Do not connect pins 3 and 6 to ground or pull up to VDD. They should be soldered to floating pads for mechanical

stability of the package.

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

1. to 1. V

SCL

SDA

Si7034

VDD

SCL

DNC

3DNC 6

SDA 4

GND 5

0.1uF

10K

Si7034-A10

Rev. 1.0 11

3. Bill of Materials

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

Reference Description Mfr Part Number Manufacturer

R1 R esis tor, 10 k, ±5%, 1/16W, 0402 CR0402-16W-103JT Venkel

R2 R esis tor, 10 k, ±5%, 1/16W, 0402 CR0402-16W-103JT Venkel

C1 Capacitor, 0.1 µF, 6.3 V, X7R, 0402 C0402X7R6R3-104MNP Venkel

U1 IC, Digital Temperature/humidity Sensor Si7034-A10-IM Silicon Labs

Si7034-A10

12 Rev. 1.0

4. Functional Description

Figure 5. Si7034 Block Diagram

The Si7034 is a d igital r elative humidity and temp erature sensor that integrates temperature and humidity sensor

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

I2C interface all in a single chip. The Si7034 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

low-K dielectrics as a sensor enables the Si7034 to achieve excellent long term stability and immunity to

contaminants with low drift and hysteresis. The Si7034 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 Si7034 is largely a conventional mixed-signal CMOS integrated circuit, relative humidity sensors in

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

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

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

rehydrate th e se nso r.

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

The impact of prolong ed expo sure to extremes o f tempe r ature an d/or hu midity and the ir poten tial effect on

sensor accuracy.

The effects of humidity sensor “memory”.

Each of these items is disc us se d in more detail in the following sections.

ADC

GND

Humidity

Sensor Control Logic

SCL

Si7034

Temp

Sensor

1.25V

Ref

I2C Interface SDA

Vdd

Calibration

Memory

Si7034-A10

Rev. 1.0 13

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 30 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 Si7034 accuracy

specification (Table 4) includes:

Unit-t o- un it an d lot -to -lo t va ri ation in non-linearity compensation

Accuracy of factory calibration

Margin for shifts that can occur during IR solder reflow (compensation for shift due to reflow is included in

the linearization procedure below)

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. RH readings will typically vary with temperature by < +0.05% / °C.

Si7034-A10

14 Rev. 1.0

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 5. 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 5, 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 condition s. 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, Si7034 devices are shipped from the factory vacuum-packed with an enclosed desiccant to avoid

any RH accuracy drif t durin g storage and to prevent any mo isture-related issues during solder reflo w. The following

guidelines should be observed during PCB assembly:

Si7034 devices are compatible with standard board assembly process. 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 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(R) KPPD-1/8 polyimide tape can be

installed during PCB assembly.

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 Si7034 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.

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 un der the following guidelines:

The exposed polymer sensing film must be kept clean and un damaged. A Kapton ® tape protective cover is

recommended during any rework operation.

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 th e 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 for more information on

cleaning.

Si7034-A10

Rev. 1.0 15

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

contact time p er pin should not exceed 5 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 guide line s ab o ve.

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

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 th e RH reading . Depending on the needs of th e application , there may be a need for basic protection ag ainst

particulates or something more sophisticated such as a hydrophobic membrane providing up to IP67 compliant

protection, during PCB assembly and/or the end system.

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 Si7034 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.

Si7034-A10

16 Rev. 1.0

5. I2C Interface

The Si7034 communicates with the Host controller over a digital I2C interface. The 7-bit base slave address is

0x70.

Master I2C devices communicate with the Si7034 using a command structure. The commands are listed in the I2C

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

device.

Table 9. I2C Slave Address Byte

A6 A5 A4 A3 A2 A1 A0 R/W

11100001/0

Table 10. I2C Command Table

Command Hold/No Hold Mode Hex Code

Read Electronic ID:

Two Separate IDs with checksum — 0xFA 0x0F

Read Electronic ID:

Two Separate IDs with checksum — 0xFC 0xC9

Soft Reset — 0xFE

Temperature and Relative Humidity

Measurement:

Normal Mode

Hold Mode 0x7C 0xA2

Temperature and Relative Humidity

Measurement:

Normal Mode

No Hold Mode 0x78 0x66

Temperature and Relative Humidity

Measurement:

Fast Mode

Hold Mode 0x64 0x58

Temperature and Relative Humidity

Measurement:

Fast Mode

No Hold Mode 0x60 0x9C

Query Device Device will ACK command,

No Functional Effect or

response

0x80 0x5D

Query Device Response 0x00 0x47 0x2B 0xEF 0xC8

Write Heater Control Regis ter Hold Mode 0xE6

Read Heater Control Register Hold Mode 0xE7

Read Firmware Revision — 0x84 0xF1

Si7034-A10

Rev. 1.0 17

5.1. Issuing a Measurement Command

The measurement commands instruct the Si7034 to perform Relative Humidity and Temperature measurements.

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. A checksum byte is returned from the slave for use in checking for transmission errors. The

checksum byte will follow the least significant measurement byte. The checksum byte is calculated using a CRC

generator polyn omial of x8 + x5 + x4 + 1, with an initialization of 0xFC.

In the I2C sequence diagrams in the following sections, bits produced by the master and slave are color coded as

shown:

Table 11. I2C Bit Descriptions

Name Symbol Description

START S SDA goes low while SCL high.

STOP P SDA goes high while SCL high.

Repeated START Sr SDA goes low while SCL high. It is allowable to generate a

STOP befor e the repeated start. SDA can transition to high

before or af ter SCL goes high in preparation for generating the

START.

READ R R ea d bit = 1

WRITE W Write bit = 0

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).

Master Slave

Sequencetoperformameasurementandreadbackresult(HoldMode)

SSlave

Address WACommand

Byte1ACommand

Byte2ASrSlave

Address

R A ClockStretchDuring

Measurement TempMSB ATempLSB AChecksum A

Humidity

MSB AHumidity

LSB AChecksum NA P

Si7034-A10

18 Rev. 1.0

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

5.2. Reading and Writing User Registers

The Heater Control Register allows the user to set the configuration of the Si7034. The procedure for accessing

this register is described below. A checksum byte is not provided after reading a user register.

Sequencetoperformameasurementandreadbackresult(NoHoldMode)

SSlave

Address WACommand

Byte1ACommand

Byte2ASrSlave

Address

RNA* Sr SlaveAddress R ATempMSB ATempLSB AChecksum A

Humidity

MSB AHumidity

LSB AChecksum NA P

Sequencetoreadaregister

SSlave

Address WA

Read

Reg

Cmd

ASr

Slave

Address R A Read

Data NA P

Sequencetowritearegister

SSlave

Address WAWriteReg

Cmd AWrite

Data AP

Si7034-A10

Rev. 1.0 19

5.3. 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:

Where:

%RH is the measured relative humidity value in %RH

RH_Code is the 16-bit word returned by the Si7034

5.4. 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.The results of the temperature measurement

may be converted to tem p er at ur e in de gr ees Ce lsiu s (°C ) usin g th e fo llo wing expr e ssio n:

Where:

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

Temp_Code is the 16-bit word returned by the Si7034

5.5. Firmware Revision

The internal firmware revision can be read with the following I2C transaction:

The values in this field are encoded as follows:

0x10 = Firmware version 1.0

SSlave

Address WA0x84A0xF1ASrSlave

Address

R A FWREV ANA P

%RH 100 RH_Code

216

----------------------------

=

T45–175 Temp_Code

216

----------------------------------

+=

Si7034-A10

20 Rev. 1.0

5.6. Electronic Serial Number

The Si7034 provides a serial number individualized for each device that can be rea d via the I2C serial interface.

Two I2C 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:

First access:

The format of the complete serial number is 6 4-bit s in length , divid ed into 8 dat a bytes. The comp lete serial number

sequence is shown below:

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:

0x00 or 0xFF engineering samples

0x22 = Si7034

5.7. Heater

The Si7034 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 Si7034 is used in conjunction with a separate temperature sensor such as another Si7034

(the heater will raise the temperature of the internal temperature sensor). The heater can be activated using HTRE,

bit 4 in the Heater Control Register. Turning on the heater will reduce the tendency of the humidity sensor to

accumulate an offset due to “memory” of sustained high humidity conditions. The heater current can be configured

using bits 3:0 of the Heater Control Register.

Master Slave

SSlaveAddress W ACK 0xFA ACK 0X0F ACK

SSlaveAddress R ACK

SNA_3 ACK CRC ACK SNA_2 ACK CRC ACK

SNA_1 ACK CRC ACK SNA_0 ACK CRC NACK P

2nd access:

SSlaveAddress W ACK 0xFC ACK 0XC9 ACK

SSlaveAddress R ACK

SNB_3 ACK SNB_2 ACK CRC ACK

SNB_1 ACK SNB_0 ACK CRC NACK P

SNA_3 SNA_2 SNA_1 SNA_0 SNB_3 SNB_2 SNB_1 SNB_0

Si7034-A10

Rev. 1.0 21

6. Control Registers

Reset Settings = 0000_0000

Table 12. Register Summary

Heater Control

Notes:

1. Any register not listed here is reserved and must not be written.The result of a read operation on these registers 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, regi sters should be read. Then the values read

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

BitD7D6D5D4D3D2D1D0

Name RSVD HTRE Heater [3:0]

Type R/W R/W

Bit Name Function

D4 HTRE 1 = On-chip Heater Enable

0 = On-chip Heater Disable

D3:D0 HEATER[3:0] D3 D2 D1 D0 Heater Current

0000

6.4 mA

0001

9.7 mA

0010

13.1 mA

...

0100

19.6 mA

...

1000

32.4 mA

...

1 1 1 1 53.5 mA

D7,D6,

D5 RSVD Reserved

Si7034-A10

22 Rev. 1.0

7. Pin Descriptions: Si7034 (Top View)

Pin Name Pin # Pin Description

VDD 1 Power. This pin is connected to the power supply on the circuit board.

SCL 2 I2C clock

DNC 3,6 Do not connect electrically. It is recommended to solder to floating pads for mech an ica l

stability. Do not connect to GND or GND plane.

SDA 4 I2C data

GND 5 Ground. This pin is connected to ground on the circuit board.

DNC

SCL

VDD 1

GND

SDA

DNC

Si7034-A10

Rev. 1.0 23

8. Ordering Guide

Table 13. Device Ordering Guide

P/N Description Max. Accuracy Package Operating

Range (°C) Packing

Format

Temp RH

Si7034-A10-IM Digital temperature/

humidity sensor ±0.4 °C ± 4% 6-pin QFN –40 to +125 °C Cut tape

Si7034-A10-IMR Digital temperature/

humidity sensor ±0.4 °C ± 4% 6-pin QFN –40 to +125 °C Tape-and-reel

Si7034-A10

24 Rev. 1.0

9. Package Outline

9.1. Package Outline: 2x2 6-pin QFN

Figure 7 illustrates the package details for the Si7034.

Figure 7. Si7034 Package Drawing

Table 14. Package Dimensions

Dimension Min Nom Max

A 0.70 0.75 0.80

b 0.30 0.35 0.40

D 2.00 BSC

E 2.00 BSC

e 1.00 BSC

D2 0.60 0.70 0.80

E2 1.50 1.60 1.70

g 0.20 0.25 0.30

H1 0.70 0.75 0.80

H2 1.20 1.25 1.30

L 0.30 0.35 0.40

aaa 0.10

bbb 0.10

ccc 0.08

ddd 0.10

eee 0.05

fff 0.05

Notes:

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

2. Dimensioning and Toleranci ng per ANSI Y14.5 M-1 994.



Si7034-A10

Rev. 1.0 25

10. PCB Land Pattern and Solder Mask Design

Figure 8. PCB Land Pattern Dimensions

Table 15. PCB Land Pattern Dimensions

Symbol mm

C1 2.00

E1.00

X1 0.40

Y1 0.75

X2 1.70

Y2 0.80

Notes:

General

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

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

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

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

Solder Mask Design

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

solder mask and the metal pad is to be 60 µ m mini mum, all the way around the pad.

Stencil Design

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

be used to assure good solder paste release.

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

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

8. A 2x1 array of 0.55 mm square openin gs on 0.90 mm pitch should be used fo r the

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

Card Assembly

9. A No-Clean, Type-3 solder paste is recommended.

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

for Small Body Components.



Si7034-A10

26 Rev. 1.0

11. Top Marking

11.1. Si7034 Top Marking

11.2. Top Marking Explanation

Mark Method: Laser

Font Size: 0.30 mm

Line 1 Marking: Circle = 0.25 mm Diameter, Pin #1 Indicator

T = Manufacturing Trace Code Digit 1

Line 2 Marking: TT = Manufacturing Trace Code Digits 2-3

Si7034-A10

Rev. 1.0 27

12. Additional Reference Resources

AN607: Si70xx Humidity and Temperature Sensor Designer’s Guide

Si7034-A10

28 Rev. 1.0

DOCUMENT CHANGE LIST

Revision 0.11 to Revision 0.3

Updates to Section 1. “Electrical Specifications”.

Updated Table 2. “General Sp ecif ica tio ns” .

Updated Figu re 1. “I2C Interface Timing Diagram”.

Updated Table 12. “I2C Command Table”.

Updated Section 4.4. “PCB Assembly”.

Updated Section 5.2. “Reading and Writing User

Registers”.

Updated Section 5.3. “Measuring Relative Humidity”.

Updated Section 5.4. “Measuring Temperature”.

Updated Section 5.6. “Electronic Serial Number”.

Updated Section 6. “Con tr ol Reg ist er s” .

Updated Section 7. “Pin Descriptions”.

Updated Section 8. “Package Outline”.

Revision 0.3 to Revision 0.4

Updated Features on page 1.

Updated Block Diag ra m .

Updated Table 1.

Updated Table 2.

Updated Table 3.

Updated Table 4.

Updated Table 5.

Updated Table 6.

Updated Table 7.

Updated Table 8.

Updated Section 4.4.

Updated Table 12.

Updated Section 5.

Added Section 6.

Updated Table 13.

Updated Section 9.

Updated Section 10.

Revision 0.4 to Revision 0.5

Added ESD specifications to Table 7.

Revised Heater Control Register settings.

Updated Firmware Revision command address.

Corrected pin numbering in Figure 7 and Figure 8.

Updated Table 4, “Humidity Sensor,” on page 7.

Updated Table 5, “Temperature Sensor,” on page 8.

Changed power supply voltage range to ±10%.

Revision 0.5 to Revision 0.8

Updated Table 6, “Thermal Characteristics,” on

page 9.

Updated Table 2.

Updated Table 10.

Updated Section 5.3.

Updated Section 5.4.

Updated Section 11.

Revision 0.8 to Revision 0.9

Updated Table 2.

Updated footnotes in Table 3.

Updated Table 4.

Updated descriptions in Table 10.

Updated Table 13.

Updated Section 5.1.

Updated Section 5.3.

Added Section 5.5.

Updated Section 6.

Revision 0.9 to Revision 1.0

Updated features on page 1.

Updated Table 2.

Updated Figure 4

Updated Section 5.1.

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