Si7005 Data Sheet

Si7005
D IGITA L I 2 C H UMIDITY AND TEMPERATURE S ENSOR
Features

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
liquids and
particulates
(hydrophobic/oleophobic)
Ordering Information
Excludes
See Ordering Guide.
Patent protected; patents pending
Applications
DNC
DNC
DNC
DNC
DNC
GND
23
22
21
20
19
1
18 DNC
DNC
2
17 DNC
SCL
3
16 DNC
11
12
GND
DNC
13 DNC
10
DNC
CEXT
14 DNC
6
9
15 CS
5
VDD
4
8
SDA
DNC
7
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.
GND
DNC
Description
24
Pin Assignments
Micro-environments/data centers
 Automotive climate control and
de-fogging
 Asset and goods tracking

GND
Industrial HVAC/R
 Thermostats/humidistats
 Respiratory therapy
 White goods

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 lowprofile, 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.
Rev. 1.3 6/14
Copyright © 2014 by Silicon Laboratories
Si7005
Si7005
Functional Block Diagram
CEXT
MUX
ADC
Temperature
Sensor
GND
2
Si7005
Rev. 1.3
Logic
I2C
Serial
IF
I2C pullups may be
integrated in microcontroller
32 kHz Osc
Humidity
Sensor
R = 10 k (typ)
NV CAL
VDD
C = 4.7 µF
C = 0.1 µF
VDD
R = 10 k (typ)
VDD
SCL
PXx
SDA
PXy
PXz
CS
Microcontroller
Si7005
TABLE O F C ONTENTS
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
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Rev. 1.3
3
Si7005
1. Electrical Specifications
Unless otherwise specified, all min/max specifications apply over the recommended operating conditions.
Table 1. Recommended Operating Conditions
Symbol
Parameter
Power Supply
Test Condition
VDD
Min
Typ
Max
Unit
2.1
3.3
3.6
V
Operating Temperature
TA
G grade
–40
—
85
°C
Operating Temperature
TA
F 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
IIL
CS, SCL, SDA pins
—
—
±1
µA
VOL
SDA pin; IOL = 8.5 mA;
VDD = 3.3 V
—
—
0.6
V
SDA pin; IOL = 3.5 mA;
VDD = 2.1 V
—
—
0.4
V
Input Leakage
Output Voltage Low
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.
4
Rev. 1.3
Si7005
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
Power Consumption
Conversion Time
Symbol
Test Condition
Min
Typ
Max
Unit
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
—
—
100
µA
CS < VIL; no conversion in
progress; VDD = 3.3 V;
SDA = SCL ≥ VIH; HEAT = 1
—
24
31
tCONV
mA
14-bit temperature; 12-bit RH
(Fast = 0)
35
40
13-bit temperature; 11-bit RH
(Fast = 1)
18
21
ms
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
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.
Rev. 1.3
5
Si7005
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-tohigh 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
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
Between Stop and Start
*Note: All values are referenced to VIL and/or VIH.
tSKH
1/fSCL
tSKL
SCL
tBUF
tSTH
tDS
D7
SDA
D6
tDH
D5
D0
tSPS
R/W
ACK
Start Bit
Stop Bit
tVD : ACK
tSTS
Figure 1. I2C Interface Timing Diagram
6
Rev. 1.3
Si7005
Table 4. Humidity Sensor
2.1  VDD  3.6 V; TA = 25 °C; tCONV = 35 ms unless otherwise noted.
Parameter
Symbol
Operating Range1
Test Condition
Min
Typ
Max
Unit
Non-condensing
0
—
100
%RH
—
—
12
bit
—
±3.0
±4.5
%RH
Resolution2
Accuracy3,4
20–80% RH
0–100% RH
See Figure 2
Repeatability—Noise
—
0.05
—
%RH
RMS
—
18
—
s
Hysteresis
—
±1
—
%RH
Long Term Stability4
—
0.25
—
%RH/yr
Response Time5
 63%
1 m/s airflow
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.
RHAccuracy
Max.RHError(±%)
Typ.RHError(±%)
10
RHMeasurementError(±%)
9
8
7
6
5
4
3
2
1
0
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
RelativeHumidity(%)
Figure 2. RH Accuracy at 30 °C
Rev. 1.3
7
Si7005
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
–40
—
85
°C
—
—
14
Bit
—
—
1/32
°C
—
±0.5
±1.0
°C
Operating Range
Resolution1
Accuracy2
Typical at 25 °C
Maximum
See Figure 3.
Repeatability—Noise
Response Time3
Time to reach 63% of final value
Long Term Stability
°C
—
0.1
—
°C
RMS
—
1.5
—
s
—
<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.
TemperatureAccuracy
Max.TError(°C)
Typ.TError(°C)
3.5
3
2.5
2
1.5
1
Temperature(°C)
Figure 3. Temperature Accuracy
8
Rev. 1.3
125
120
115
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
5
10
0
Ͳ5
Ͳ10
Ͳ15
Ͳ20
Ͳ25
Ͳ30
0
Ͳ35
0.5
Ͳ40
TemperatureMeasurementError(°C)
4
Si7005
Table 6. Thermal Characteristics
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
Parameter
Table 7. Absolute Maximum Ratings1,2
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
HBM
—
—
3
kV
CDM
—
—
750
V
MM
—
—
300
V
Parameter
ESD Tolerance
Symbol
Test Condition
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.
Rev. 1.3
9
Si7005
2. Typical Application Circuits
19
GND
20
21
DNC
DNC
DNC
15
14
13
DNC
VDD
16
12
8
GND
DNC
7
17
CS
DNC
DNC
6
18
DNC
Si7005
SDA
5
DNC
22
23
DNC
DNC
U1
SCL
4
SDA
DNC
GND
SCL
DNC
DNC
11
3
GND
Cext
2
9
R2
10K
10
1
R1
10K
DNC
EPAD
VDD
24
25
Note: 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. 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).
CSb
C1
4.7uF
C2
0.1uF
GND
SDA
19
GND
20
DNC
DNC
21
DNC
22
DNC
18
17
16
15
14
13
12
DNC
DNC
DNC
7
C1
4.7uF
CS
DNC
DNC
6
DNC
Si7005
GND
5
U2
SCL
11
SDA
DNC
Cext
4
DNC
10
SCL
DNC
VDD
3
GND
9
2
GND
R2
10K
8
1
R1
10K
DNC
15.0
DNC
EPAD
R3
Port Pin
24
25
VDD
23
Figure 4. Typical Application Circuit
C2
0.1uF
GND
Figure 5. Typical Application Circuit for Battery-Powered Applications
10
Rev. 1.3
Si7005
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.
Rev. 1.3
11
Si7005
4. Functional Description
CEXT
MUX
ADC
Temperature
Sensor
GND
Logic
I 2C
Serial
IF
Si7005
I2C pullups may be
integrated in microcontroller
32 kHz Osc
Humidity
Sensor
R = 10 k (typ)
NV CAL
VDD
C = 4.7 µF
C = 0.1 µF
VDD
R = 10 k (typ)
V DD
SCL
PXx
SDA
PXy
PXz
CS
Microcontroller
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.
12
Rev. 1.3
Si7005
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.
RHAccuracyvs.RHSetͲPoint
5
4
Hysteresis
3
%RHAccuracy
2
1
0
Ͳ1
10
20
30
40
50
60
70
80
90
Ͳ2
Ͳ3
Ͳ4
Ͳ5
%RHSetͲpoint
Figure 7. Measuring Sensor Accuracy Including Hysteresis
Rev. 1.3
13
Si7005
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
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:
Accuracy
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.
14
Rev. 1.3
Si7005
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:
2
RH Linear = RH Value –   RH Value   A 2 + RH Value  A 1 + A 0 
Where:
RHLinear
RHValue
is the corrected relative humidity value in %RH
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
A1
0.4008
A2
–0.00393
Rev. 1.3
15
Si7005
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:
RH TempCompensated = RH Linear +  Temperature – 30    RH Linear  Q 1 + Q 0 
Where:
RHTempCompensated
RHLinear
is the temperature compensated relative humidity value in %RH.
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.
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.
Q1
Table 11. Linearization Coefficients
Coefficient
Value
Q0
0.1973
Q1
0.00237
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”).
16
Rev. 1.3
Si7005
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.
Table 12. Tape Products for Protection During Soldering
Manufacturer Part Number*
Manufacturer
KPPD-1/8
Kaptontape.com
*Note: Provided for information only.
Figure 8. Si7005 with Factory-Installed Protective Cover
Rev. 1.3
17
Si7005
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 filter 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.
Si7005s may be ordered with a factory fitted, solder-resistant cover, which can be left in place for the lifetime of the
product. It is very low-profile, hydrophobic and oleophobic, and excludes particulates down to 0.35 microns in size.
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
Table 13. The sensor should be protected from direct sunlight to prevent heating effects as well as possible
material degradation.
Table 13. Specifications of Protective Cover
Parameter
Value
Material
ePTFE
Water Entry Pressure
2.7 bar
Pore Size
0.35µ
Operating Temperature
–40 to +125 °C
Maximum Reflow Temperature
Oleophobicity (AATCC 118 – 1992)
IP Rating (per IEC 529)
260 °C
7
IP67
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.
18
Rev. 1.3
Si7005
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. Performing a Relative Humidity Measurement
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:
RH
%RH =  --------- – 24
16
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.
Table 14. 12-Bit Relative Humidity Result Available in Registers 1 and 2
DATAh
D7
D6
D5
D4
D3
DATAI
D2
D1
D0
D7
D6
D5
12-Bit Relative Humidity Code
D4
D3
D2
D1
D0
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
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”.
Rev. 1.3
19
Si7005
5.1.2. Performing a Temperature Measurement
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:
TEMP
Temperature  C  =  ----------------- – 50
 32 
where TEMP is the measured value returned in DATAh:DATAI.
Table 17 shows the 14-bit values that correspond to various measured temperature levels.
Table 16. 14-Bit Temperature Result Available in Registers 1 and 2
DATAh
D7
D6
D5
D4
D3
DATAI
D2
D1
D0
D7
14-Bit Temperature Code
D6
D5
D4
D3
D2
D1
D0
0
0
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”.
20
Rev. 1.3
Si7005
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
Rev. 1.3
21
Si7005
5.1.3. Fast Conversion 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.
Table 18. Normal vs. Fast Mode
Parameter
Value
Normal Mode
Fast Mode
tCONV (typical)
35 ms
18 ms
Temperature resolution
14-bit
13-bit
RH resolution
12-bit
11-bit
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 19. Device ID Revision Values
Device ID Value
22
D[7:4]
D[3:0]
0101
0000
Rev. 1.3
Device
Type
Revision
Level
Si7005
B
Si7005
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.
Table 20. I2C Slave Address Byte
A6
A5
A4
A3
A2
A1
A0
R/W
1
0
0
0
0
0
0
1/0
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.
Master Slave
Table 21. I2C Write Sequence
Sequence to Write to a Register
S
Slave Address
W
A
Address Pointer
A
Register Data
A
P
A
P
A
P
Sequence to Start a Relative Humidity Conversion
S
0x40
0
A
0x03
A
0x01
Sequence to Start a Temperature Conversion
S
0x40
0
A
0x03
Rev. 1.3
A
0x11
23
Si7005
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
A
Sr
Slave Address
R
A
Register Data
A
P
1
A
ID
A
P
1
A
A
P
Sequence to Read Device ID
S
0x40
0
A
0x11
A
Sr
0x40
Sequence to Read RDY bit
S
0x40
0
A
A
0x00
Sr
0x40
—
RDY
Table 23. I2C Read Sequence for RH or Temperature Conversion Result
Sequence to Read Conversion Result
S
Slave
Address
W
A
Address
Pointer
A
Sr
Slave
Address
R
A
Register 1
Data
A
Register 2
Data
A
P
S
0x40
0
A
0x01
A
Sr
0x40
1
A
Data H
A
Data L
A
P
24
Rev. 1.3
Si7005
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-ofmaterials for this circuit can be found in section “2. Typical Application Circuits” and section “3. Bill of Materials”.
2.1 to 3.6 V
0.1 µF
VDD
VDD
Si7005
CEXT
SCL
SCL
SDA
SDA
CS
Px.x
GND
MCU
C8051Fxxx
4.7µF
GND
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”.
Rev. 1.3
25
Si7005
2.1 to 3.6 V
VDD
15 Ohm
Px.x
0.1 µF
VDD
Si7005
SCL
SCL
SDA
SDA
CS
CEXT
GND
MCU
C8051Fxxx
4.7µF
GND
Figure 10. Recommended Connection Diagram for Low-Power Battery Operation
26
Rev. 1.3
Si7005
7. Control Registers
Table 24 contains a summary of the Si7005 register set. Each register is described in more detail below.
Table 24. Si7005 Register Summary
Register
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
RSVD
RSVD
RSVD
/RDY
I2C Register Summary
0
STATUS
RSVD
RSVD
RSVD
RSVD
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.
7.1. Register Detail (Defaults in Bold)
Register 0. STATUS
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Name
/RDY
Type
R
Reset Settings = 0000_0001
Bit
7:1
0
Name
Function
Reserved Reserved. Reads undefined.
/RDY
Ready.
0 = conversion complete; results available in DATAh:DATAl.
1 = conversion in progress.
Rev. 1.3
27
Si7005
Register 1. DATAh
Bit
D7
D6
D5
D4
D3
D2
Name
Relative Humidity or Temperature, High Byte
Type
R
D1
D0
Reset Settings = 0000_0000
Bit
Name
7:0
DATAh
Function
Data, High Byte.
Eight most significant bits of a temperature or humidity measurement. See Table 14 or
Table 16 for the measurement format.
Register 2. DATAI
Bit
D7
D6
D5
D4
D3
D2
Name
Relative Humidity or Temperature, Low Byte
Type
Read
D1
D0
Reset Settings = 0000_0000
28
Bit
Name
7:0
DATAl
Function
Data, Low Byte.
Eight least significant bits of a temperature or humidity measurement. See Table 14 or
Table 16 for the measurement format.
Rev. 1.3
Si7005
Register 3. CONFIG
Bit
D7
D6
D5
D4
Name
FAST
TEMP
Type
R/W
R/W
D3
D2
D1
D0
HEAT
START
R/W
Reset Settings = 0000_0000
Bit
7:6
Name
Function
Reserved Reserved. Reads undefined. Always write as zero.
5
FAST
Fast Mode Enable.
0 = 35 ms (typical)
1 = 18 ms (typical)
4
TEMP
Temperature Enable.
0 = Relative humidity
1 = Temperature
3:2
Reserved Reserved. Reads undefined. Always write as zero.
1
HEAT
Heater Enable.
0 = heater off
1 = heater on
0
START
Conversion Start.
0 = do not start a conversion
1 = start a conversion
Register 17. ID
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Name
ID7
ID6
ID5
ID4
ID3
ID2
ID1
ID0
Type
R
R
R
R
R
R
R
R
Reset Settings = 0101_0000
Bit
Name
7:0
ID
Function
Identification.
See section “5.1.5. Device Identification”.
Rev. 1.3
29
Si7005
DNC
DNC
DNC
DNC
DNC
GND
24
23
22
21
20
19
8. Pin Descriptions: Si7005
DNC
5
14 DNC
DNC
6
13 DNC
12
15 CS
DNC
4
11
SDA
GND
16 DNC
10
3
CEXT
SCL
9
17 DNC
VDD
2
8
DNC
GND
18 DNC
7
1
DNC
GND
Table 25. Pin Descriptions
Pin #
Pin Name
Pin Type*
1, 8, 11, 19
GND
G
2, 5–7, 12–14,
16–18, 20–24
DNC
3
SCL
Description
Ground.
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.
I
I2C Clock Signal.
This pin is voltage-tolerant. See Table 2.
4
SDA
I/O
I2C Data Signal.
This pin is voltage-tolerant. See Table 2.
9
VDD
S
VDD Power Supply (2.1 V < VDD < 3.6 V).
10
CEXT
I
Decoupling Input for Internal Circuitry.
Connect a 4.7 µF capacitor between this pin and GND.
15
CS
I
Chip Select—Active Low Signal.
Epad
TGND
G
Thermal Paddle.
This pad is connected to GND internally. The pad can be connected 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.
30
Rev. 1.3
Si7005
9. Ordering Guide
Table 26. Si7005 Device Ordering Guide
Typ. Accuracy
P/N
Description
Temp
RH
Pkg
Operating
Range (°C)
Filter
Cover
Packing
Format
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
Tube
Si7005-B-GM
Digital temperature/humidity sensor
±0.5 °C
±3%
QFN-24
–40 to +85 °C
N
Tube
Si7005USBDONGLE
USB demonstration/evaluation board
Si7005-EVB
Si7005 daughter card with flex cable
Si7005EVB-UDP
Si7005 UDP plug-in daughter card
Si7005EVBUDP-F960
Low-power data logger demo/development kit with C8051F960 MCU
Rev. 1.3
31
Si7005
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)
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
D
D2
4.00 BSC.
2.55
2.65
2.75
1.68 REF
L
0.30
0.35
0.40
aaa
—
—
0.15
e
0.50 BSC.
bbb
—
—
0.15
E
4.00 BSC.
ccc
—
—
0.08
ddd
—
—
0.10
E2
2.55
2.65
2.75
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
0.80
0.90
1.00
0.70
0.75
0.80
Note: All Dimensions are in mm unless otherwise noted.
32
Rev. 1.3
Si7005
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) With Protective Cover
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
R1
0.45
0.50
0.55
D
D2
4.00 BSC.
aaa
—
—
0.15
e
2.55
0.50 BSC.
2.65
2.75
bbb
—
—
0.15
E
4.00 BSC.
ccc
—
—
0.08
ddd
—
—
0.10
E2
2.55
2.65
2.75
F1
3.70
3.80
3.90
F2
3.70
3.80
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
Note: All Dimensions are in mm unless otherwise noted.
Rev. 1.3
33
Si7005
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
34
Rev. 1.3
Si7005
Table 31. PCB Land Pattern Dimensions
Symbol
mm
C1
4.00
C2
4.00
E
0.50
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 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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.
Rev. 1.3
35
Si7005
12. Top Marking
12.1. Si7005 Top Marking
TTTT
7005
YYWW
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”.
36
Rev. 1.3
Si7005
13. Additional Reference Resources
Si7005USB
Dongle User’s Guide
Si7005EVB-UDP User's Guide
AN607: Si70xx Humidity Sensor Designer’s Guide
Rev. 1.3
37
Si7005
Added Linearization Coefficients Table 10,11
 Updated Host Interface
DOCUMENT CHANGE LIST

Revision 0.1 to Revision 0.2
Updated I2C Operation
 Amended Connection Diagram
 Amended Ordering Guide
 Expanded Additional Reference Resources

Updated Table 2, “General Specifications*,” on
page 4.
 Updated Table 4, “Humidity Sensor,” on page 7.

New


Note 1.
Revision 1.0 to Revision 1.1
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
Clarified

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
Register,” on page 24.
 Updated Table 23, “I2C Read Sequence for RH or
Temperature Conversion Result,” on page 24.
Replaced










Corrected




38
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

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

with black and white version.
Updated “4.7 Soldering” to “4.7. PCB Assembly”.
 Updated Table 19, “Device ID Revision Values,” on
page 22.
Revision 0.2 to Revision 0.9

RH and temperature accuracy graphs.
Updated Figure 7.

title.

Updated Figures 2 and 3.
Updated and expanded General Specification
Table 2
Updated and expanded General Specification
Table 3
Updated Figure 1.
Updated Figure 2.
Updated Bill of Materials
Rev. 1.3
Added nominal values to Dimension A in Table 30
Si7005
CONTACT INFORMATION
Silicon Laboratories Inc.
400 West Cesar Chavez
Austin, TX 78701
Tel: 1+(512) 416-8500
Fax: 1+(512) 416-9669
Toll Free: 1+(877) 444-3032
Please visit the Silicon Labs Technical Support web page:
https://www.silabs.com/support/pages/contacttechnicalsupport.aspx
and register to submit a technical support request.
Patent Notice
Silicon Labs invests in research and development to help our customers differentiate in the market with innovative low-power, small size, analogintensive mixed-signal solutions. Silicon Labs' extensive patent portfolio is a testament to our unique approach and world-class engineering team.
The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without notice.
Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences resulting from
the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the functioning of undescribed features or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon Laboratories makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Silicon Laboratories assume any
liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation
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Rev. 1.3
39