L-FW843-07-DB - LSI CORPORATION

Si7005

DIGITAL I2C HUMIDITY AND TEMPERATURE SENSOR

Features

Applications

Description

The Si7005 is a digital relative humidity and temperature sensor. This

monolithic CMOS IC integrates temperature and humidity sensor

elements, an analog-to-digital converter, signal processing, calibration

data, and an I2C host interface. The patented use of industry-standard,

low-K polymeric dielectrics for sensing humidity enables the construction

of a low-power, monolithic CMOS sensor IC with low drift and hysteresis

and excellent long term stability.

Both the temperature and humidity 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 Si7005 is packaged in a 4x4 mm QFN package and is reflow

solderable. The optional factory-installed protective 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 Si7005 offers an accurate, low-power, factory-calibrated digital

solution ideal for measuring temperature, humidity, and dew-point in

applications ranging from HVAC/R and asset tracking to industrial and

consumer platforms.

Relative Humidity Sensor

± 4.5% RH (maximum @ 0–80% RH)

Temperature Sensor

±0.5 ºC accuracy (typical)

±1 ºC accuracy (maximum @ 0 to 70 °C)

0 to 100% RH operating range

–40 to +85 °C (GM) or 0 to +70 °C

operating range (FM)

Wide operating voltage range

(2.1 to 3.6 V)

Low Power Consumption

240 µA during RH conversion

I2C host interface

Integrated on-chip heater

4x4 mm QFN package

Excellent long term stability

Factory calibrated

Optional factory-installed

cover

Low-profile

Protection during reflow

Excludes liquids and

particulates

(hydrophobic/oleophobic)

Industrial HVAC/R

Thermostats/humidistats

Respiratory therapy

White goods

Micro-environments/data centers

Automotive climate control and

de-fogging

Asset and goods tracking

Patent protected; patents pending

Ordering Information

See Ordering Guide.

Pin Assignments

GND

DNC

SDA

SCL

DNC

GND

CEXT

VDD

GND

DNC

GND

DNC

Si7005

2 Rev. 1.5

Functional Block Diagram

Si7005

VDD

C = 0.1 µF

C = 4.7 µF

VDD

CEXT

GND

SCL

SDA

Humidity

Sensor

Temperature

Sensor

MUX ADC

NV CAL

32 kHz Osc

Logic I2C

Serial

VDD

R = 10 k (typ)

I2C pullups may be

integrated in microcontroller

Microcontroller

PXx

PXz

PXy

Si7005

Rev. 1.5 3

TABLE OF CONTENTS

Section Page

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

2. Typical Application Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

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

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

4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

4.2. Relative Humidity Sensor Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

4.3. Linearization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

4.4. Temperature Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4.5. Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4.6. Prolonged Exposure to High Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4.7. PCB Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.8. Protecting the Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

4.9. Bake/Hydrate Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

4.10. Long Term Drift/Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5. Host Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

5.1. I2C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

5.2. I2C Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

6. Si7005 Connection Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

7. Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

7.1. Register Detail (Defaults in Bold) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

8. Pin Descriptions: Si7005 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

9. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

10. Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

10.1. 24-Pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

10.2. 24-Pin QFN with Protective Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

11. PCB Land Pattern and Solder Mask Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

12. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

12.1. Si7005 Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

12.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

13. Additional Reference Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Si7005

4 Rev. 1.5

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 2.1 3.3 3.6 V

Operating Temperature TAG grade –40 — 85 °C

Operating Temperature TAF grade 0 — 70 °C

Table 2. General Specifications

2.1  VDD  3.6 V; TA= 0 to 70 °C (F grade) or –40 to 85 °C (G grade) unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

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

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

Input Voltage Range VIN SCL, SDA pins with respect

to GND

0.0 — 3.6 V

CS, CEXT pin with respect to

GND

0.0 — VDD V

Input Leakage IIL CS, SCL, SDA pins — — ±1 µA

Output Voltage Low VOL SDA pin; IOL = 8.5 mA;

VDD = 3.3 V

——0.6V

SDA pin; IOL = 3.5 mA;

VDD = 2.1 V

——0.4V

Notes:

1. Si7005 can draw excess current if VDD and CS are ramped high together. To enter the lowest power mode, either hold

CS low while VDD ramps or pulse CS low after VDD reaches its final value.

2. SDA and SCL pins have an internal 75 k pull-up resistor to VDD.

Si7005

Rev. 1.5 5

Power Consumption IDD RH conversion in progress — 240 560 µA

Temperature conversion in

progress

— 320 565 µA

Average for 1 temperature

and 1 RH conversion /

minute

—1—µA

CS < VIL; no conversion in

progress; VDD = 3.3 V;

SDA = SCL ≥ VIH

— 150 — µA

CS > VIH ——100µA

CS < VIL; no conversion in

progress; VDD = 3.3 V;

SDA = SCL ≥ VIH; HEAT = 1

—2431

Conversion Time tCONV 14-bit temperature; 12-bit RH

(Fast = 0)

35 40

13-bit temperature; 11-bit RH

(Fast = 1)

18 21

Wake Up Time tCS From CS < VIL to ready for a

temp/RH conversion

10 15 ms

Power Up Time tPU From VDD ≥ 2.1V to ready for

a temp/RH conversion

10 15 ms

Table 2. General Specifications (Continued)

2.1  VDD  3.6 V; TA= 0 to 70 °C (F grade) or –40 to 85 °C (G grade) unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Notes:

1. Si7005 can draw excess current if VDD and CS are ramped high together. To enter the lowest power mode, either hold

CS low while VDD ramps or pulse CS low after VDD reaches its final value.

2. SDA and SCL pins have an internal 75 k pull-up resistor to VDD.

Si7005

6 Rev. 1.5

Figure 1. I2C Interface Timing Diagram

Table 3. I2C Interface Specifications*

2.1 VDD  3.6 V; TA = 0 to 70 °C (F grade) or –40 to +85 °C (G grade) 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 Frequency fSCL — — 400 kHz

SCL high time tSKH 0.6 — — µs

SCL low time tSKL 1.3 — — µs

Start hold time tSTH 0.6 — — µs

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

*Note: All values are referenced to VIL and/or VIH.

SCL

1/fSCL tSKH

SDA

tSKL

tSTH

D6 D5 D0 R/W ACK

tDS tDH

Start Bit Stop Bit

tBUF

tSTS tVD : ACK

tSPS

Si7005

Rev. 1.5 7

Figure 2. RH Accuracy at 30 °C

Table 4. Humidity Sensor

2.1  VDD  3.6 V; TA = 25 °C; tCONV = 35 ms unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Operating Range1Non-condensing 0 — 100 %RH

Resolution2— — 12 bit

Accuracy3,4 20–80% RH — ±3.0 ±4.5 %RH

0–100% RH See Figure 2

Repeatability—Noise — 0.05 — %RH

RMS

Response Time5 63% 1 m/s airflow — 18 — s

Hysteresis — ±1 — %RH

Long Term Stability4—0.25 — %RH/yr

Notes:

1. Recommended humidity operating range is 20 to 80% RH (non-condensing) over 0 to 60 °C. Prolonged operation

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

2. The Si7005 has a nominal output of 16 codes per %RH, with 0h0000 = –24%RH.

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

See section “4.2. Relative Humidity Sensor Accuracy” for more details.

4. May be impacted by dust, vaporized solvents or other contaminants, e.g., out-gassing tapes, adhesives, packaging

materials, etc. See section “4.10. Long Term Drift/Aging”.

5. Time for sensor output to reach 63% of its final value after a step change.

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

RHMeasurementError(±%)

RelativeHumidity(%)

RHAccuracy

Max.RHError(±%) Typ.RHError(±%)

Si7005

8 Rev. 1.5

Figure 3. Temperature Accuracy

Table 5. Temperature Sensor

2.1  VDD  3.6 V; TA = 0 to 70 °C (F grade) or –40 to +85 °C (G grade); tCONV = 35 ms unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Unit

Operating Range –40 — 85 °C

Resolution1——14Bit

— — 1/32 °C

Accuracy2Typical at 25 °C — ±0.5 ±1.0 °C

Maximum See Figure 3. °C

Repeatability—Noise — 0.1 — °C

RMS

Response Time3Time to reach 63% of final value — 1.5 — s

Long Term Stability — <0.05 — °C/yr

Notes:

1. The Si7005 has a nominal output of 32 codes /°C, with 0000 = –50 °C

2. Temperature sensor accuracy is for VDD = 2.3 to 3.6 V.

3. Actual response times will vary dependent on system thermal mass and air-flow.

0.5

1.5

2.5

3.5

Ͳ40

Ͳ35

Ͳ30

Ͳ25

Ͳ20

Ͳ15

Ͳ10

Ͳ5

100

105

110

115

120

125

Temperature MeasurementError(°C)

Temperature(°C)

TemperatureAccuracy

Max.TError(°C) Typ.TError(°C)

Si7005

Rev. 1.5 9

Table 6. Thermal Characteristics

Parameter Symbol Test Condition QFN-24 Unit

Junction-to-Air Thermal Resistance JA JEDEC 4-layer board 55 °C/W

Junction-to-Air Thermal Resistance JA 2-layer evaluation PCB with

minimal thermal pad

110 °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 SDA or SCL pin with

respect to GND

–0.3 — 3.9 V

Voltage on CS pin with respect to

GND

–0.3 — VDD + 0.3 V

Voltage on VDD with respect to GND –0.3 — 4.2 V

ESD Tolerance HBM — — 3 kV

CDM — — 750 V

MM — — 300 V

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. For best accuracy, after removal from the sealed shipping bags, the Si7005 should be stored in climate controlled

conditions (10 to 35 °C, 20 to 60 %RH). Exposure to high temperature and/or high humidity environments can cause a

small upwards shift in RH readings.

Si7005

10 Rev. 1.5

2. Typical Application Circuits

Note: If the Si7005 shares an I2C bus with other slave devices, it should be powered down when the master controller is com-

municating with the other slave devices.

The Si7005 can be powered down either by setting the CS signal to logic high or setting the VDD pin to 0 V. Refer to

Figure 5 for an illustration of this method of powering the Si7005 from an MCU GPIO (the Si7005 VDD is powered from

an MCU port pin).

Figure 4. Typical Application Circuit

Figure 5. Typical Application Circuit for Battery-Powered Applications

SDA

SCL

VDD

CSb

GND

10K

Si7005

DNC 13

DNC 14

SDA

DNC

SCL

DNC

GND

CS 15

DNC 16

DNC 17

DNC 18

DNC

GND

Cext

GND

VDD

GND 19

DNC 24

DNC 20

DNC 23

DNC 22

DNC 21

DNC

7EPAD 25

0.1uF

4.7uF

SDA

SCL

Port Pin

GND

VDD

15.0

10K

Si7005

DNC 13

DNC 14

SDA

DNC

SCL

DNC

GND

CS 15

DNC 16

DNC 17

DNC 18

DNC

GND

Cext

GND

VDD

GND 19

DNC 24

DNC 20

DNC 23

DNC 22

DNC 21

DNC

7EPAD 25

0.1uF

10K

4.7uF

Si7005

Rev. 1.5 11

3. Bill of Materials

Table 8. Typical Application Circuit BOM

Reference Description Mfr Part Number Manufacturer

C1 Capacitor, 4.7 µF, 6.3 V, X5R, 0603 C0603X5R6R3-475M Venkel

C2 Capacitor, 0.1 µF, 6.3 V, X7R, 0603 C0603X7R6R3-104M Venkel

R1*Resistor, 10 k, ±5%, 1/16W, 0603 CR0603-16W-1002J Venkel

R2*Resistor, 10 k, ±5%, 1/16W, 0603 CR0603-16W-1002J Venkel

U1 IC, digital temperature/humidity sensor Si7005 Silicon Labs

*Note: Typical value shown. Optimal value depends on bus capacitance and speed of bus operation; not needed if present

elsewhere in the system.

Table 9. Typical Application Circuit for Battery-Powered Applications BOM

Reference Description Mfr Part Number Manufacturer

C1 Capacitor, 4.7 µF, 6.3 V, X5R, 0805 C0805X5R160-475M Venkel

C2 Capacitor, 0.1 µF, 6.3 V, X7R, 0603 C0603X7R6R3-104M Venkel

R1*Resistor, 10 k, ±5%, 1/16W, 0603 CR0603-16W-1002J Venkel

R2*Resistor, 10 k, ±5%, 1/16W, 0603 CR0603-16W-1002J Venkel

R3 Resistor, 15 , ±5%, 1/16W, 0603 CR0603-16W-15R0J Venkel

U1 IC, digital temperature/humidity sensor Si7005 Silicon Labs

*Note: Typical value shown. Optimal value depends on bus capacitance and speed of bus operation; not needed if present

elsewhere in the system.

Si7005

12 Rev. 1.5

4. Functional Description

Figure 6. Si7005 Functional Block Diagram

4.1. Overview

The Si7005 is a digital relative humidity and temperature sensor. This monolithic CMOS IC integrates temperature

and humidity sensor elements, an analog-to-digital converter, signal processing, calibration data, and an I2C host

interface. Both the temperature and humidity sensors on each unit 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.

While the Si7005 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:

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 sensor from damage or contamination during the product life-cycle

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

sensor accuracy

The effects of humidity sensor “memory”

The need to apply temperature correction and linearization to the humidity readings

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

Si7005

VDD

C = 0.1 µF

C = 4.7 µF

VDD

CEXT

GND

SCL

SDA

Humidity

Sensor

Temperature

Sensor

MUX ADC

NV CAL

32 kHz Osc

Logic I2C

Serial

VDD

R = 10 k (typ)

I2C pullups may be

integrated in microcontroller

Microcontroller

PXx

PXz

PXy

Si7005

Rev. 1.5 13

4.2. 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 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 top and bottom trace in Figure 7,

“Measuring Sensor Accuracy Including Hysteresis,” shows the result of a typical sweep after non-linearity

compensation.

Figure 7. Measuring Sensor Accuracy Including Hysteresis



Ͳ5

Ͳ4

Ͳ3

Ͳ2

Ͳ1

10 20 30 40 50 60 70 80 90

%RHAccuracy

%RHSetͲpoint

RHAccuracyvs.RHSetͲPoint

Hysteresis

Si7005

14 Rev. 1.5

The RH accuracy is defined as the center (dashed) line shown in Figure 7, 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 Si7005

accuracy specification (Table 4) includes:

Unit-to-unit and lot-to-lot variation in non-linearity compensation

Accuracy of factory calibration

Margin for shifts that can occur during 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 (a temperature compensation method is described in section “4.4.

Temperature Compensation”). After application of temperature compensation, RH readings will typically

vary by less than ±0.05%/°C.

Si7005

Rev. 1.5 15

4.3. Linearization

Capacitive relative humidity sensors require linearization. The Si7005 accuracy specification (Table 4) applies after

correction of non-linearity errors. The recommended linearization technique is to correct the measured relative

humidity value with a 2nd order polynomial; the linear relative humidity (RH) value is calculated as follows:

Where:

RHLinear is the corrected relative humidity value in %RH

RHValue is the uncorrected (measured) relative humidity value in %RH

A2, A1, and A0 are unit-less correction coefficients derived through characterization of Si7005s by Silicon

Laboratories; their values depend on whether compensation for a typical solder reflow is required

The values for the correction coefficients are shown in Table 10.

Table 10. Linearization Coefficients

Coefficient Value

A0–4.7844

A10.4008

A2–0.00393

RHLinear RHValue RHValue



2A2RHValue A1A0

++–=

Si7005

16 Rev. 1.5

4.4. Temperature Compensation

The Si7005 relative humidity sensor is calibrated at a temperature of 30 °C; it is at this temperature that the sensor

will give the most accurate relative humidity readings. For relative humidity measurements at other temperatures,

the RH reading from the Si7005 must be compensated for the change in temperature relative to 30 °C.

Temperature compensated relative humidity readings can be calculated as follows:

Where:

RHTempCompensated is the temperature compensated relative humidity value in %RH.

RHLinear is the linear corrected relative humidity value in %RH.

Temperature is the ambient temperature in °C as measured by the Si7005 on chip temperature sensor.

Q1 and Q0 are unit-less correction coefficients derived through characterization of Si7005s by Silicon

Laboratories.

This temperature compensation is most accurate in the range of 15–50 °C. The values for the correction

coefficients are shown in Table 11.

4.5. 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 top

and bottom traces in Figure 7. 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, the center dashed trace in

Figure 7. In the case of Figure 7, the measurement uncertainty due to the hysteresis effect is ±1.05%RH.

4.6. 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 “4.9. Bake/Hydrate Procedure”).

Table 11. Linearization Coefficients

Coefficient Value

Q00.1973

Q10.00237

RHTempCompensated RHLinear Temperature 30–RHLinear Q1Q0

++=

Si7005

Rev. 1.5 17

4.7. PCB Assembly

4.7.1. Soldering

Like most ICs, Si7005 devices are shipped from the factory vacuum-packed with an enclosed desiccant to avoid

any drift during storage and to prevent any moisture-related issues during solder reflow. Devices should be

soldered using reflow and a “no clean” solder process, as a water or solvent rinse after soldering may affect

accuracy. See "11. PCB Land Pattern and Solder Mask Design" on page 34 for the recommended card reflow

profile.

It is essential that the exposed polymer sensing film be kept clean and undamaged. It is recommended that a

protective cover of some kind be in place during PCB assembly. Kapton®* polyimide tape is recommended as a

protective cover. See Table 12 below for examples of tape products that may be used for protection during the

soldering operation.

Alternatively, Si7005s may be ordered with a factory-fitted, solder-resistant protective cover that 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 "9. Ordering Guide" on page 31 for a list of ordering part numbers that include the cover.

4.7.2. Rehydration

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

is accounted for when using the linearization procedure given above. After soldering, an Si7005 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.

4.7.3. 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.

Avoid water or solvent rinses after touch-up.

Minimize the heating of the device. It is recommended that soldering iron temperatures not exceed 350 °C

and that the contact time per pin does 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 8. Si7005 with Fact ory-Installed Protective Cover

Table 12. Tape Products for Protection During Soldering

Manufacturer Part Number* Manufacturer

KPPD-1/8 Kaptontape.com

*Note: Provided for information only.

Si7005

18 Rev. 1.5

4.8. 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 Si7005 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 “9. 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 “10.

Package Outline”. Other characteristics of the cover are listed in the table below.

4.9. 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.

4.10. 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 Si7005 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 affects of damage, contamination, or exposure to extreme

environmental conditions.

Table 13. Specifications of Protective Cover

Parameter Value

Material PTFE

Operating Temperature –40 to +125 °C

Maximum Reflow Temperature 260 °C

IP Rating (per IEC 529) IP67

Si7005

Rev. 1.5 19

5. Host Interface

5.1. I2C Interface

The Si7005 has an I2C serial interface with a 7-bit address of 0x40. The Si7005 is a slave device supporting data

transfer rates up to 400 kHz. Table 24 shows the register summary of the Si7005.

5.1.1. Perfo rm in g a Re lat iv e Humidit y M ea sur e m ent

The following steps should be performed in sequence to take a relative humidity measurement:

1. Set START (D0) in CONFIG to begin a new conversion

2. Poll RDY (D0) in STATUS (register 0) until it is low (= 0)

3. Read the upper and lower bytes of the RH value from DATAh and DATAl (registers 0x01 and 0x02),

respectively. Table 14 shows the format of the 12-bit relative humidity result.

4. Convert the RH value to %RH using the following equation:

where RH is the measured value returned in DATAh:DATAI

5. Apply temperature compensation and/or linearization as discussed elsewhere in this data sheet

Table 15 shows the 12-bit values that correspond to various measured RH levels.

The above sequence assumes normal mode, i.e., tCONV = 35 ms (typical). Conversions may be performed in fast

mode. See section “5.1.3. Fast Conversion Mode”.

Table 14. 12-Bit Relative Humidity Result Available in Registers 1 and 2

DATAh DATAI

D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0

12-Bit Relative Humidity Code 0 0 0 0

Table 15. Typical %RH Measurement Codes for 0 to 100% RH Range

%RH 12 Bit Code

Dec Hex

0 384 180

10 544 220

20 704 2C0

30 864 360

40 1024 400

50 1184 4A0

60 1344 540

70 1504 5E0

80 1664 680

90 1824 720

100 1984 7C0

%RH RH

---------





24–=

Si7005

20 Rev. 1.5

5.1.2. Perfo rm i ng a Temperature Me a su r em en t

The following steps should be performed in sequence to take a temperature measurement:

6. Set START (D0) and TEMP (D4) in CONFIG (register 0x03) to begin a new conversion, i.e., write CONFIG with

0x11

7. Poll RDY (D0) in STATUS (register 0) until it is low (=0)

8. Read the upper and lower bytes of the temperature value from DATAh and DATAl (registers 0x01 and 0x02),

respectively

Table 16 shows the format of the 14-bit temperature result. This value may be converted to °C using the following

equation:

where TEMP is the measured value returned in DATAh:DATAI.

Table 17 shows the 14-bit values that correspond to various measured temperature levels.

The above sequence assumes normal mode, i.e., tCONV = 35 ms (typical). Conversions may be performed in fast

mode. See section “5.1.3. Fast Conversion Mode”.

Table 16. 14-Bit Temperature Result Available in Registers 1 and 2

DATAh DATAI

D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0

14-Bit Temperature Code 0 0

Temperature C TEMP

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





50–=

Si7005

Rev. 1.5 21

Table 17. Typical Temperature Measurement Codes for the –40 °C to 100 °C Range

Temp(°C) 14 Bit Code

Dec Hex

–40 320 0140

–30 640 0280

–20 960 03C0

–10 1280 0500

0 1600 0640

10 1920 0780

20 2240 08C0

30 2560 0A00

40 2880 0B40

50 3200 0C80

60 3520 0DC0

70 3840 0F00

80 4160 1040

90 4480 1180

100 4800 12C0

Si7005

22 Rev. 1.5

5.1.3. Fast Convers ion Mode

The time needed to perform a temperature or RH measurement can be reduced from 35 ms (typical) to 18 ms

(typical) by setting FAST (D5) in CONFIG (register 0x03). Fast mode reduces the total power consumed during a

conversion or the average power consumed by the Si7005 when making periodic conversions. It also reduces the

resolution of the measurements. Table 18 is a comparison of the normal and fast modes.

5.1.4. Heater

The Si7005 relative humidity sensor contains an integrated, resistive heating element that may be used to raise the

temperature of the humidity sensor. This element can be used to drive off condensation or to implement dew-point

measurement when the Si7005 is used in conjunction with a separate temperature sensor such as another Si7005.

The heater can be activated by setting HEAT (D1) in CONFIG (register 0x03). Turning on the heater will reduce the

tendency of the humidity sensor to accumulate an offset due to “memory” of sustained high humidity conditions.

When the heater is enabled, the reading of the on-chip temperature sensor will be affected (increased).

5.1.5. Device Identification

The Si7005 device and its revision level can be determined by reading ID (register 0x11). Table 19 lists the values

for the various device revisions and may include revisions not yet in existence.

Table 18. Normal vs. Fast Mode

Parameter Value

Normal Mode Fast Mode

tCONV (typical) 35ms 18ms

Temperature resolution 14-bit 13-bit

RH resolution 12-bit 11-bit

Table 19. Device ID Revision Values

Device ID Value Device

Type Revision

Level

D[7:4] D[3:0]

0101 0000 Si7005 B

Si7005

Rev. 1.5 23

5.2. I2C Operation

The Si7005 uses a digital I2C interface. If the Si7005 shares an I2C bus with other slave devices, it should be

powered down when the master controller is communicating with the other slave devices. The Si7005 can be

powered down either by setting the CS signal to logic high or setting the VDD pin to 0 V. A method of achieving this

by powering the Si7005 from an MCU GPIO is shown in Figure 5.

The format of the address byte is shown in Table 20.

5.2.1. I2C Write Operation

To write to a register on the Si7005, the master should issue a start command (S) followed by the slave address,

0x40. The slave address is followed by a 0 to indicate that the operation is a write. Upon recognizing its slave

address, the Si7005 issues an acknowledge (A) by pulling the SDA line low for the high duration of the ninth SCL

cycle. The next byte the master places on the bus is the register address pointer, selecting the register on the

Si7005 to which the data should be transferred. After the Si7005 acknowledges this byte, the master places a data

byte on the bus. This byte will be written to the register selected by the address pointer. The Si7005 will

acknowledge the data byte, after which the master issues a Stop command (P). See Table 21.

Table 20. I2C Slave Address Byte

A6 A5 A4 A3 A2 A1 A0 R/W

10000001/0

Master Slave

Table 21. I2C Write Sequence

Sequence to Write to a Register

S Slave Address W A Address Pointer ARegister DataAP

Sequence to Start a Relative Humidity Conversion

S0x40 0

A 0x03 A 0x01 AP

Sequence to Start a Temperature Conversion

S0x40 0

A 0x03 A 0x11 AP

Si7005

24 Rev. 1.5

5.2.2. I2C Read Operation

To read a register on the Si7005, the master must first set the address pointer to indicate the register from which

the data is to be transferred. Therefore, the first communication with the Si7005 is a write operation. The master

should issue a start command (S) followed by the slave address, 0x40. The slave address is followed by a 0 to

indicate that the operation is a write. Upon recognizing its slave address, the Si7005 will issue an acknowledge (A)

by pulling the SDA line low for the high duration of the ninth SCL cycle. The next byte the master places on the bus

is the register address pointer selecting the register on the Si7005 from which the data should be transferred. After

the Si7005 acknowledges this byte, the master issues a repeated start command (Sr) indicating that a new transfer

is to take place. The Si7005 is addressed once again with the R/W bit set to 1, indicating a read operation. The

Si7005 will acknowledge its slave address and output data from the previously-selected register onto the data bus

under the control of the SCL signal, the master should not acknowledge (A) the data byte and issue a stop (P)

command (see Table 22). However, if a RH or Temperature conversion result (two bytes) is to be read, the master

should acknowledge (A) the first data byte and continue to activate the SCL signal. The Si7005 will automatically

output the second data byte. Upon receiving the second byte, the master should issue a not Acknowledge (A)

followed by a stop command. (See Table 23).

Table 22. I2C Read Sequence for a Single Register

Sequence to Read from a Single Register

S Slave Address W A Address Pointer ASr Slave Address R ARegister Data A P

Sequence to Read Device ID

S0x40 0

A 0x11 ASr 0x40 1 AID A P

Sequence to Read RDY bit

S0x40 0

A0x00 ASr 0x40 1 A — RDY A P

Table 23. I2C Read Sequence for RH or Temperature Conversion Result

Sequence to Read Conversion Result

SSlave

Address

WAAddress

Pointer

ASr Slave

Address

R A Register 1

Data

ARegister 2

Data

A P

S0x40 0

A0x01ASr 0x40 1 AData H A Data L A P

Si7005

Rev. 1.5 25

6. Si7005 Connection Diagrams

The Si7005 is a simple-to-use device requiring a minimum of external components. Figure 9 shows the typical

connection diagram for the Si7005 connected to an MCU. (Refer to section “8. Pin Descriptions: Si7005” for full pin

descriptions). The values for the two I2C pull-up resistors depend on the capacitance of the I2C bus lines and the

desired speed of operation. Refer to the I2C specification for further details. In this diagram CS is shown controlled

by the MCU, allowing the Si7005 to be placed in standby mode when not in use. A detailed schematic and bill-of-

materials for this circuit can be found in section “2. Typical Application Circuits” and section “3. Bill of Materials”.

Figure 9. Typical Connection Diagram

For ultra-low-power operation, such as in battery-powered applications, connection as shown in Figure 10 is

recommended. In this case, the Si7005 is powered from one of the MCU’s GPIOs. The GPIO can be driven high to

powerup the Si7005, once the measurement results are obtained, the GPIO can be driven low to power-down the

Si7005, reducing its current consumption to zero. The GPIO must be capable of sourcing 320 µA for the duration of

the conversion time (<200 ms for relative humidity and temperature conversions) and up to 40 mA for a period of

5 ms at power-up. The GPIO must also be capable of sinking up to 40 mA for a period of 5 ms at powerdown. If the

GPIO is not capable of sourcing/sinking 40 mA, then the Si7005 will take longer to powerup and powerdown. The

purpose of the 15  resistor is to isolate the Si7005 from potential high-frequency switching noise present on the

MCU GPIO. A detailed schematic and bill-of-materials for this circuit can be found in section “2. Typical Application

Circuits” and section “3. Bill of Materials”.

0.1 µF

4.7µF

CEXT GND

VDD

SCL

SDA

Si7005

SCL

SDA

Px.x

MCU

GND

VDD

C8051Fxxx

2.1 to 3.6 V

Si7005

26 Rev. 1.5

Figure 10. Recommended Connection Diagram for Low-Power Battery Operation

15 Ohm

0.1 µF

4.7µF

CEXT GND

VDD

SCL

SDA

Si7005

SCL

SDA

MCU

GND

VDD

C8051Fxxx

2.1 to 3.6 V

Px.x

Si7005

Rev. 1.5 27

7. Control Registers

Table 24 contains a summary of the Si7005 register set. Each register is described in more detail below.

7.1. Register Detail (Defaults in Bold)

Reset Settings = 0000_0001

Table 24. Si7005 Register Summary

I2C Register Summary

0 STATUS RSVD RSVD RSVD RSVD RSVD RSVD RSVD /RDY

1 DATAh Relative Humidity or Temperature, High Byte

2 DATAl Relative Humidity or Temperature, Low Byte

3 CONFIG RSVD RSVD FAST TEMP RSVD RSVD HEAT START

17 ID ID3 ID2 ID1 ID0 0 0 0 0

Notes:

1. Any register address not listed here is reserved and must not be written.

2. Reserved register bits (RSVD) must always be written as zero; the result of a read operation on these bits is

undefined.

BitD7D6D5D4D3D2D1D0

Name /RDY

Type R

Bit Name Function

7:1 Reserved Reserved. Reads undefined.

0 /RDY Ready.

0 = conversion complete; results available in DATAh:DATAl.

1 = conversion in progress.

Si7005

28 Rev. 1.5

Reset Settings = 0000_0000

BitD7D6D5D4D3D2D1D0

Name Relative Humidity or Temperature, High Byte

Type R

Bit Name Function

7:0 DATAh Data, High Byte.

Eight most significant bits of a temperature or humidity measurement. See Table 14 or

Table 16 for the measurement format.

BitD7D6D5D4D3D2D1D0

Name Relative Humidity or Temperature, Low Byte

Type Read

Bit Name Function

7:0 DATAl Data, Low Byte.

Eight least significant bits of a temperature or humidity measurement. See Table 14 or

Table 16 for the measurement format.

Si7005

Rev. 1.5 29

Reset Settings = 0000_0000

Reset Settings = 0101_0000

BitD7D6D5D4D3D2D1D0

Name FAST TEMP HEAT START

Type R/W R/W R/W

Bit Name Function

7:6 Reserved Reserved. Reads undefined. Always write as zero.

5 FAST Fast Mode Enable.

0 = 35 ms (typical)

1 = 18 ms (typical)

4TEMPTemperature Enable.

0 = Relative humidity

1 = Temperature

3:2 Reserved Reserved. Reads undefined. Always write as zero.

1HEATHeater Enable.

0 = heater off

1 = heater on

0STARTConversion Start.

0 = do not start a conversion

1 = start a conversion

BitD7D6D5D4D3D2D1D0

Name ID7ID6ID5ID4ID3ID2ID1ID0

Type RRRRRRRR

Bit Name Function

7:0 ID Identification.

See section “5.1.5. Device Identification”.

Si7005

30 Rev. 1.5

8. Pin Descriptions: Si7005

Table 25. Pin Descriptions

Pin # Pin Name Pin Type* Description

1, 8, 11, 19 GND G Ground.

2, 5–7, 12–14,

16–18, 20–24

DNC Do Not Connect.

Do not connect any of these pins to supply, ground or any other

signal. Internal pull-ups or pull-downs will prevent any of these pins

from floating.

3SCLI

I2C Clock Signal.

This pin is voltage-tolerant. See Table 2.

4SDAI/O

I2C Data Signal.

This pin is voltage-tolerant. See Table 2.

DD SVDD Power Supply (2.1 V < VDD < 3.6 V).

10 CEXT IDecoupling Input for Internal Circuitry.

Connect a 4.7 µF capacitor between this pin and GND.

15 CS IChip Select—Active Low Signal.

Epad TGND GThermal Paddle.

This pad is connected to GND internally. The pad can be con-

nected to GND externally or it can be left open-circuit and used as

a thermal input to the on-chip temperature sensor.

*Note: G = Ground, S = Power Supply, I = Digital Input, O = Digital Output, I/O = Input/Output.

GND

DNC

SDA

SCL

DNC

GND

CEXT

VDD

GND

DNC

GND

DNC

Si7005

Rev. 1.5 31

9. Ordering Guide

Table 26. Si7005 Device Ordering Guide

P/N Description

Typ. Accuracy

Pkg Operating

Range (°C) Filter

Cover Packing

Format

Temp RH

Si7005-B-FM1 Digital temperature/humidity sensor ±0.5 °C ±3% QFN-24 0 to 70 °C Y Cut Tape

Si7005-B-GM1 Digital temperature/humidity sensor ±0.5 °C ±3% QFN-24 –40 to +85 °C Y Cut Tape

Si7005-B-FMR Digital temperature/humidity sensor ±0.5 °C ±3% QFN-24 0 to 70 °C N Tape-and-reel

Si7005-B-FM1R Digital temperature/humidity sensor ±0.5 °C ±3% QFN-24 0 to 70 °C Y Tape-and-reel

Si7005-B-GMR Digital temperature/humidity sensor ±0.5 °C ±3% QFN-24 –40 to +85 °C N Tape-and-reel

Si7005-B-GM1R Digital temperature/humidity sensor ±0.5 °C ±3% QFN-24 –40 to +85 °C Y Tape-and-reel

Si7005-B-FM Digital temperature/humidity sensor ±0.5 °C ±3% QFN-24 0 to 70 °C N Cut Tape

Si7005-B-GM Digital temperature/humidity sensor ±0.5 °C ±3% QFN-24 –40 to +85 °C N Cut Tape

Si7005USB-

DONGLE USB demonstration/evaluation board

Si7005-EVB Si7005 daughter card with flex cable

Si7005EVB-UDP Si7005 UDP plug-in daughter card

Si7005EVB-

UDP-F960

Low-power data logger demo/devel-

opment kit with C8051F960 MCU

Si7005

32 Rev. 1.5

10. Package Outline

10.1. 24-Pin QFN

Figure 11 illustrates the package details for the Si7005. Tables 27 and 28 list the values for the dimensions shown

in the illustration. There are two package variants with slightly different height dimensions. The two package

variants are otherwise interchangeable.

Figure 11. 24-Pin Quad Flat No Lead (QFN)

Note: All Dimensions are in mm unless otherwise noted.

Table 27. 24-Pin Package Diagram Dimensions

Dimension Min Nom Max Dimension Min Nom Max

A1 0.00 0.02 0.05 H1 1.03 1.08 1.13

b 0.18 0.25 0.30 H2 1.68 REF

D 4.00 BSC. L 0.30 0.35 0.40

D2 2.55 2.65 2.75 aaa — — 0.15

e 0.50 BSC. bbb — — 0.15

E 4.00 BSC. ccc — — 0.08

E2 2.55 2.65 2.75 ddd ——

0.10

Notes:

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

2. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components.

Table 28. Package Variants

Variant A Variant B

Dimension Min Nom Max Min Nom Max

A 0.800.901.000.700.750.80



Si7005

Rev. 1.5 33

10.2. 24-Pin QFN with Protective Cover

Figure 12 illustrates the package details for the Si7005 with the optional protective cover. Tables 29 and 30 list the

values for the dimensions shown in the illustration. There are two package variants with slightly different height

dimensions. The two package variants are otherwise interchangeable.

Figure 12. 24-Pin Quad Flat No Lead (QFN) W ith Protective Cover

Note: All Dimensions are in mm unless otherwise noted.

Table 29. 24-Pin Package Diagram Dimensions

Dimension Min Nom Max Dimension Min Nom Max

A1 0.00 0.02 0.05 h 0.76 0.83 0.90

b 0.18 025 0.30 L 0.30 0.35 0.40

D 4.00 BSC. R1 0.45 0.50 0.55

D2 2.55 2.65 2.75 aaa — — 0.15

e 0.50 BSC. bbb — — 0.15

E 4.00 BSC. ccc — — 0.08

E2 2.55 2.65 2.75 ddd — — 0.10

F1 3.60 3.75 3.90

F2 3.60 3.75 3.90

Notes:

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

2. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components.

Table 30. Package Variants

Variant A Variant B

Dimension Min Nom Max Min Nom Max

A — 1.27 1.41 — 1.07 1.21

A2 0.80 0.90 1.00 0.70 0.75 0.80



Si7005

34 Rev. 1.5

11. PCB Land Pattern and Solder Mask Design

Figure 13 illustrates the recommended PCB land pattern for use with the Si7005's 4x4 mm QFN package.

Figure 13. Typical QFN-24 PCB Land Pattern

Si7005

Rev. 1.5 35

Table 31. PCB Land Pattern Dimensions

Symbol mm

C1 4.00

C2 4.00

E0.50

P1 2.75

P2 2.75

X1 0.30

Y1 0.75

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 De s ign

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m 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 2x2 array of 0.95 mm square openings on 1.35 mm pitch should be used

for the center ground pad.

Card Assembly

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

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

specification for Small Body Components.

Si7005

36 Rev. 1.5

12. Top Marking

12.1. Si7005 Top Marking

12.2. Top Marking Explanation

Location Marking Explanation

Upper Left 7005 Part Number

Upper Right TTTT Manufacturing trace code

Lower Left (Dot) Pin 1 Identifier

Lower Right YYWW Manufacturing date code

YY = year

WW = week

Note: The top mark may not be visible if the optional protective cover is installed. If needed, the device can be identified by

reading the identification register as explained in section “5.1.5. Device Identification”.

7005

WWYY

T T T T

Si7005

Rev. 1.5 37

13. Additional Reference Resources

Si7005USB Dongle User’s Guide

Si7005EVB-UDP User's Guide

AN607: Si70xx Humidity Sensor Designer’s Guide

Si7005

38 Rev. 1.5

DOCUMENT CHANGE LIST

Revision 0.1 to Revision 0.2

Updated Table 2, “General Specifications*,” on

page 4.

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

New Note 1.

Added Table 6, “Thermal Characteristics,” on

page 9.

Updated Table 7, “Absolute Maximum Ratings1,2,”

on page 9.

Updated max value for “Voltage on SDA or SCL pin with

respect to GND” parameter.

Updated Figure 2 on page 7.

Updated Figure 3 on page 8.

Updated "2.1.1. Steps to Perform Relative Humidity

Measurement" on page 9.

Updated Table 12, “14-Bit Temperature Result

Available in Registers 1 and 2,” on page 10.

Revised title.

Added "2.1.6. RSVD" on page 11.

Updated "2.2. I2C Operation" on page 12.

Updated Table 22, “I2C Read Sequence for a Single

Updated Table 23, “I2C Read Sequence for RH or

Temperature Conversion Result,” on page 24.

Revision 0.2 to Revision 0.9

Updated Features/Applications/Description

Added pinout drawing to front page

Updated Electrical Specifications

Clarified voltage tolerance of CS, SDA, and SCL

pins

Updated Typical Application Circuits and BOMs

Updated and expanded Functional Description

Updated Host Interface

Updated register descriptions

Added drawing and photo of device with cover

Updated and expanded Ordering Guide

Expanded Additional Reference Resources

Revision 0.9 to Revision 1.0

Updated and expanded General Specification

Tab l e 2

Updated and expanded General Specification

Tab l e 3

Updated Figure 1.

Updated Figure 2.

Updated Bill of Materials

Added Linearization Coefficients Table 10,11

Updated Host Interface

Updated I2C Operation

Amended Connection Diagram

Amended Ordering Guide

Expanded Additional Reference Resources

Revision 1.0 to Revision 1.1

Updated Figures 2 and 3.

Clarified RH and temperature accuracy graphs.

Updated Figure 7.

Replaced with black and white version.

Updated “4.7 Soldering” to “4.7. PCB Assembly”.

Updated Table 19, “Device ID Revision Values,” on

page 22.

Corrected title.

Revision 1.1 to Revision 1.2

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

Updated typical response time.

Updated Table 7, “Absolute Maximum Ratings1,2,”

on page 9.

Added ESD tolerance specs.

Revision 1.2 to Revision 1.3

Added nominal values to Dimension A in Table 30

Revision 1.3 to Revision 1.4

Minor modification to description and dimensions of

protective cover due to the addition of a second

cover supplier.

Revision 1.4 to Revision 1.5

Changed packing format from tube to cut tape for all

non-tape & reel part numbers without protective filter

covers.

Disclaimer

Silicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers

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

or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products must not be used within any Life Support System without the specific

written consent of Silicon Laboratories. A "Life Support System" is any product or system intended to support or sustain life and/or health, which, if it fails, can be reasonably expected

to result in significant personal injury or death. Silicon Laboratories products are generally not intended for military applications. Silicon Laboratories products shall under no

circumstances be used in weapons of mass destruction including (but not limited to) nuclear, biological or chemical weapons, or missiles capable of delivering such weapons.

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