Low Pressure
Digital Sensor
SM7221, SM7321, SM7421 Series
Gauge & Differential Pressure Sensors
FEATURES
•
•
•
•
•
•
•
•
Pressure ranges from 0.15 to 0.29 psi; gauge, differential and
asymmetric outputs
Accuracy: ±1% full scale
14-bit digital, pressure calibrated and temperature compensated
output
I
2
C Digital Interface
Compensated temperature range: -20 to 85
o
C
Insensitive to mounting orientation
Robust JEDEC SOIC-16 package for automated assembly
Manufactured according to ISO9001 and ISO/TS 16949 standards
DESCRIPTION
The SM7221, SM7321 & SM7421 series is a digital, low pressure
MEMS sensor family offering state-of-the-art pressure transducer
technology and CMOS mixed signal processing technology to
produce a digital, fully conditioned, multi-order pressure and
temperature compensated sensor in JEDEC standard SOIC-16
package with a dual vertical porting option. It is available in both
compound gage or differential pressure configurations. With the
dual porting, a vacuum-gage measurement is possible to minimize
altitude errors due to changes in ambient pressure.
Combining the pressure sensor with a signal-conditioning ASIC in a
single package simplifies the use of advanced silicon micro-machined
pressure sensors. The pressure sensor can be mounted directly on a
standard printed circuit board and a high level, calibrated pressure
signal can be acquired from the digital interface. This eliminates the
need for additional circuitry, such as a compensation network or
microcontroller containing a custom correction algorithm.
Customer-specified pressure ranges and supply voltages are
available.
The SM7221, SM7321 & SM7421 series is shipped in sticks or tape &
reel.
Medical
Sleep Apnea
CPAP
Ventilators
Gas Flow Instrumentation
Air Flow Monitors
Negative Pressure Wound Therapy
Industrial
Airflow Measurement
Pneumatic Gauges
Pressure Switches
Safety Cabinets
Life Sciences
Gas Flow Instrumentation
Consumer
Sports Equipment
Appliances
Silicon Microstructures, Inc. 2001-2017 All rights reserved
DOC # 40DS7960.04
+1-(408) 577-0100
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sales@si-micro.com
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SM7221, SM7321, SM7421 Series
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Absolute Maximum Ratings
All parameters are specified at Vdd = 3.3 V supply voltage at 25
o
C, unless otherwise noted.
No.
1
2
3
4
5
6
7
8
Characteristic
Supply Voltage
Supply Current
Update Period
Compensated Temperature
Operating Temperature
(a)
Storage Temperature
(a)
Proof Pressure
(a, b)
Burst Pressure
(a, c)
Symbol
V
DD
I
VDD
Minimum
2.7
Typical
2.00
Maximum
6.00
4.00
2
Units
V
mA
ms
°C
°C
°C
psi
psi
-20
T
OP
T
STG
P
Proof
P
Burst
-40
-40
-
+85
+105
+125
1.4
2.8
Notes:
a. Tested on a sample basis.
b. Proof pressure is defined as the maximum pressure to which the device can be taken and still perform within specifications after
returning to the operating pressure range
c. Burst pressure is the pressure at which the device suffers catastrophic failure resulting in pressure loss through the device.
Silicon Microstructures, Inc. 2001-2017 All rights reserved
DOC # 40DS7960.04
+1-(408) 577-0100
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sales@si-micro.com
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SM7221, SM7321, SM7421 Series
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OPERATING CHARACTERISTICS TABLE
All parameters are specified at Vdd = 3.3 V DC supply voltage at 25
o
C, unless otherwise noted.
No.
9
10
11
12
13
14
Characteristic
Supply Voltage*
Pressure Output
@
P
MIN
Pressure Output
@
P
MAX
Full Scale Span
Resolution
Accuracy
(e, f, g)
Symbol
V
DD
OUT
MIN
OUT
MAX
FSP
Minimum
3.0
4.75
Typical
3.3
5.0
1,638
14,745
13,107
14
Maximum
3.6
5.25
Units
V
Counts
Counts
Counts
Bits
ACC
-1
+1
%FS
No.
15
16
17
Device Type
SM7221 – Gauge
SM7321 – Differential
SM7421 – Asymmetric
Calibrated Pressure Ranges
P
MIN
(psi)
P
MAX
(psi)
0
-0.29 to -0.15
-0.29 to 0
+0.15 to +0.29
+0.15 to +0.29
0 to +0.29
Comment
Absolute value of P
MIN
must match absolute value of P
MAX
Delta between P
MIN
and P
MAX
must be at least 0.15 psi
Notes:
e. The accuracy specification applies over all operating conditions. This specification includes the combination of linearity, repeatability, and
hysteresis errors over pressure, temperature, and voltage.
f. Maximum 10-year zero pressure offset shift < ±2%FS based on 1000 hours of HTOL , TC and THB testing.
g. For less demanding applications, devices with relaxed accuracy specifications are available
*Custom calibration pressures and voltages are available to meet specific customer demands.
Media Compatibility - Clean, dry gas compatible with wetted materials. Wetted materials include silicon, epoxy, RTV, gold and aluminum.
Silicon Microstructures, Inc. 2001-2017 All rights reserved
DOC # 40DS7960.04
+1-(408) 577-0100
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sales@si-micro.com
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www.si-micro.com
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SM7221, SM7321, SM7421 Series
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SM7X21 Series – I
2
C Communications
1. SCL Clock frequency:
•
100kHz to 400kHz
2. Slave Address
•
The factory setting for the I
2
C slave address is 28HEX. The
part will only respond to the set address.
•
For the Read_DF3 data fetch command (Data Fetch 3
Bytes), the sensor returns three bytes in response to the
master sending the slave address and the READ bit (1): two
bytes of bridge data with the two status bits as the MSBs
and then 1 byte of temperature data (8-bit accuracy). After
receiving the required number of data bytes, the master
sends the NACK and stop condition to terminate the read
operation.
For the Read_DF4 command, the master delays sending the
NACK and continues reading an additional final byte to
acquire the full corrected 11-bit temperature measurement.
In this case, the last 5 bits of the final byte of the packet are
undetermined and should be masked off in the application.
The Read_DF2 command is used if corrected temperature is
not required. The master terminates the READ operation
after the two bytes of bridge data.
3. Read Operations
•
For read operations, the I
2
C master command starts with
the 7-bit slave address with the 8th bit = 1 (READ). The
sensor as the slave sends an acknowledge (ACK) indicating
success.
The sensor has four I
2
C read commands: Read_DF2,
Read_DF3, and Read_DF4. The following figures show the
structure of the measurement packet for three of the four
I
2
C read commands, which are further explained below.
•
•
•
3.1 I
2
C Read_DF (Data Fetch):
•
For the Data Fetch commands, the number of data bytes
returned by the sensor is determined by when the master
sends the NACK and stop condition.
Silicon Microstructures, Inc. 2001-2017 All rights reserved
DOC # 40DS7960.04
+1-(408) 577-0100
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sales@si-micro.com
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SM7221, SM7321, SM7421 Series
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Parameter
SCL Clock Frequency
Start Condition Hold Time Relative to SCL Edge
Minimum SCL Clock Low Width1
Minimum SCL Clock High Width1
Start Condition Hold Time Relative to SCL Edge
Data Hold Time on SDA Relative to SCL Edge
Data Setup Time on SDA Relative to SCL Edge
Stop Condition Setup Time on SCL
Bus Free Time Between Stop Condition and Start Condition
Symbol
FSCL
tHDSTA
tLOW
tHIGH
tSUSTA
tHIDDAT
tSUDAT
tSUSTO
tBUS
Minimum
100
0.1
0.6
0.6
0.1
0.0
0.1
0.1
2.0
Typical Maximum
400
Units
kHz
µs
µs
µs
µs
µs
µs
µs
µs
Silicon Microstructures, Inc. 2001-2017 All rights reserved
DOC # 40DS7960.04
+1-(408) 577-0100
|
sales@si-micro.com
I
www.si-micro.com
Page 5
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