SDP600 Series (SDP6xx/5xx)
Low-cost Digital Differential Pressure Sensor
Accuracy better than 0.2% FS near zero
Digital output (I2C)
Excellent repeatability, even below 10 Pa
Calibrated and temperature compensated
Excellent long-term stability
Flow measurement in bypass configuration
Product Summary
The SDP600 sensor family is Sensirion’s series of digital
differential pressure sensors designed for high-volume
applications. They measure the pressure of air and nonaggressive gases with superb accuracy and no offset drift.
The sensors cover a pressure range of up to ±500 Pa
(±2 inch H2O / ±5 mbar) and deliver outstanding accuracy
even at the bottom end of the measuring range.
The SDP600 series operates from a 3.3V supply voltage
and features a digital 2-wire interface, which makes it easy
to connect directly to a microprocessor. The signal is
internally linearized and temperature compensated.
The outstanding performance of these sensors is based
on Sensirion’s patented CMOSens® sensor technology,
which combines the sensor element, signal processing
and digital calibration on a tiny microchip. The differential
pressure is measured by a thermal sensor element using
flow-through technology. Compared with membranebased sensors, the SDP600 features an extended
dynamic range, better long-term stability, and improved
repeatability, especially near zero.
The well-proven CMOS technology is perfectly suited for
high-quality mass production and is the ideal choice for
demanding and cost-sensitive OEM applications.
Applications
Sensor chip
The SDP600 series features a fourth-generation silicon
sensor chip called SF04. In addition to a thermal mass
flow sensor element, the chip contains an amplifier, A/D
converter, EEPROM memory, digital signal processing
circuitry, and interface. The highly sensitive chip requires
only a minuscule amount of gas flow through the sensor.
Medical
HVAC
Automotive
Process automation
Burner control
OEM options
A variety of custom options can be implemented for highvolume OEM applications. Ask us for more information.
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1. Sensor Performance
1.1
Physical specifications1
Parameter
SDP600-500Pa
SDP610-500Pa
SDP600-125Pa
SDP610-125Pa
SDP600-25Pa
SDP610-25Pa
SDP601
SDP611
SDP500
SDP510
SDP501
SDP511
Short Description
Standard
Low DP
Lowest DP
“Mass Flow”
Low cost
Low cost
“Mass Flow”
Calibrated range2
– 500 Pa
to + 500 Pa
– 125 Pa
to + 125 Pa
– 25 Pa
to + 25 Pa
– 500 to + 500
Pa
0 Pa
to +500 Pa
(± 2.0 in. H2O)
(± 0.5 in. H2O)
(± 0.1 in. H2O)
(± 2.0 in. H2O)
(0 to 2.0 in. H2O)
yes
yes
yes
mass flow3
Temperaturecompensation
0.2 Pa
Span accuracy5,6
Zero point
repeatability5,6
mass flow3
12 bits preset4 (adjustable from 9 to 16 bit)
Resolution
Zero point accuracy5,6
yes
0.1 Pa
0.2 Pa
3% of reading
0.1 Pa
0.05 Pa
4.5% of reading
0.03 Pa
0.1 Pa
Span repeatability5,6
0.5% of reading
Offset shift due to
temperature variation
(less than resolution)
None
Span shift due to
temperature variation
< 0.5% of reading per 10°C
Offset stability
< 0.1 Pa/year
Response time4
4.6 ms typical at 12-bit resolution
Warm-up time for first
reliable measurement
(first measurement typically after 16 ms)
Typ. 50 ms
1
Unless otherwise noted, all sensor specifications are valid at 25°C with Vdd = 3.3 V and absolute pressure = 966 mbar.
The SDP50x/SDP51x sensors can detect negative differential pressures in the range of -500 to 0Pa. A negative differential pressure is represented
by a negative value. The accuracy of the negative differential pressure is not specified and might have significant inter-sensor variation.
3 Please see chapter 5.3 for details.
4 See Application Note for response times with other resolutions, e.g. 1.3 ms with 10 bits.
5 With 12-bit resolution; includes repeatability and hysteresis.
6 Total accuracy/repeatability is a sum of zero-point and span accuracy/repeatability.
2
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1.2
Ambient conditions
Parameter
Calibrated for7
Media compatibility
Calibrated temperature range
Operating temperature
Storage temperature7
Position sensitivity
1.3
SDP5xx / SDP6xx Series
Air, N2
Air, N2, O2
-20 °C to +80 °C
-20 °C to +80 °C
-40 °C to +80 °C
Less than repeatability error
Materials
Parameter
Wetted materials
REACH, RoHS
SDP5xx / SDP6xx Series
PBT (polybutylene terephthalate), glass (silicon nitride, silicon oxide), silicon, gold,
FR4, silicone as static sealing, epoxy, copper alloy, lead-free solder
REACH and RoHS compliant
2. Electrical Specifications
Parameter
Operating voltage
SDP5xx / SDP6xx
3.0– 3.6 V
(A supply voltage of 3.3 V is recommended)
Current drain
Interface
Bus clock frequency
< 6 mA typical in operation
Digital 2-wire interface (I2C)
100 kHz typical, 400 kHz max.
Default I2C address
64 (binary: 1000 000)
factor8
Scale
SDP6xx-500Pa & SDP5xx
SDP6x0-125Pa
SDP6x0-25Pa
Scale factor to alternative
units9
SDP 6x0-125Pa
SDP6x0-25Pa
60 Pa-1
240 Pa-1
1200 Pa-1
For all 500 Pa versions:
6’000 mbar-1
413’686 psi-1
14’945 (inch H2O)-1
24’000 mbar-1
1'654’744 psi-1
59’780 (inch H2O)-1
120’000 mbar-1
8’273’719 psi-1
298’900 (inch H2O)-1
Contact Sensirion for information about other gases, wider calibrated temperature ranges and higher storage temperatures.
section 5.1. The scale factor may vary with other configurations.
9 Instead of the standard scale factor (to get the physical value in Pa), the sensor output may be divided by alternative scale factors to receive the physical
value in another unit.
7
8 See
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3. Interface Specifications
The serial interface of the SDP600 series is compatible
with I2C interfaces. For detailed specifications of the I2C
protocol, see The I2C Bus Specification (source: NXP).
Transmission STOP Condition (P): The STOP condition
is a unique situation on the bus created by the master,
indicating to the slaves the end of a transmission
sequence (the bus is considered free after a STOP).
I2C Transmission Stop Condition
SDA
3.1
Interface connection – external
components
SCL
Bi-directional bus lines are implemented by the devices
(master and slave) using open-drain output stages and a
pull-up resistor connected to the positive supply voltage.
The recommended pull-up resistor value depends on the
system setup (capacitance of the circuit or cable and bus
clock frequency). In most cases, 10 kΩ is a reasonable
choice.
The capacitive loads on SDA and SCL line have to be the
same. It is important to avoid asymmetric capacitive loads.
I2C Transmission Start Condition
VDD
master
Rp
Rp
P
STOP condition
A LOW to HIGH transition on the SDA line while SCL is HIGH.
Acknowledge (ACK) / Not Acknowledge (NACK): Each
byte (8 bits) transmitted over the I2C bus is followed by an
acknowledge condition from the receiver. This means that
after the master pulls SCL low to complete the
transmission of the 8th bit, SDA will be pulled low by the
receiver during the 9th bit time. If after transmission of the
8th bit the receiver does not pull the SDA line low, this is
considered to be a NACK condition.
If an ACK is missing during a slave to master transmission,
the slave aborts the transmission and goes into idle mode.
slave (SDP600)
SDA
I2C Acknowledge / Not Acknowledge
SCL
not acknowledge
Both bus lines, SDA and SCL, are bi-directional and therefore
require an external pull-up resistor.
SDA
acknowledge
SCL
3.2
I2 C
Address
The I2C address consists of a 7-digit binary value. By
default, the I2C address is set to 64 (binary: 1000 000).
The address is always followed by a write bit (0) or read
bit (1). The default hexadecimal I2C header for read
access to the sensor is therefore h81.
3.3
Transfer sequences
Transmission START Condition (S): The START condition is a unique situation on the bus created by the master,
indicating to the slaves the beginning of a transmission
sequence (the bus is considered busy after a START).
I2 C
R/_W
ACK
D7
D0
ACK
Each byte is followed by an acknowledge or a not
acknowledge, generated by the receiver
Handshake procedure (Hold Master): In a master-slave
system, the master dictates when the slaves will receive or
transmit data. However, in some situations a slave device
may need time to store received data or prepare data to
be transmitted. Therefore, a handshake procedure is
required to allow the slave to indicate termination of
internal processing.
I2C Hold Master
SDA
Transmission Start Condition
SCL
R/_W
SDA
SCL
D7
Hold master:
SCK line pulled LOW
S
START condition
A HIGH to LOW transition on the SDA line while SCL is HIGH
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ACK
D0
ACK
data ready: SCK line released
After the SCL pulse for the acknowledge signal, the SDP600
series sensor (slave) can pull down the SCL line to force the
master into a wait state. By releasing the SCL line, the sensor
indicates that its internal processing is completed and
transmission can resume. (The bold lines indicate that the
sensor controls the SDA/SCL lines.)
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A command is represented by an 8-bit command code.
The data direction may not change after the command
byte, since the R/_W bit of the preceding I2C header has
already determined the direction to be master-to-slave. In
order to execute commands in Read mode using I2C, the
following principle is used. On successful (acknowledged)
receipt of a command byte, the sensor stores the
command nibble internally. The Read mode of this
command is then invoked by initiating an I2C data transfer
sequence with R/_W = 1.
If a correctly addressed sensor recognizes a valid
command and access to this command is granted, it
responds by pulling down the SDA line during the
subsequent SCL pulse for the acknowledge signal (ACK).
Otherwise it leaves the SDA line unasserted (NACK).
The two most important commands are described in this
data sheet, and the data transfer sequences are specified.
Contact Sensirion for advanced sensor options.
Measurement triggering
Each individual measurement is triggered by a separate
read operation.
Note that two transfer sequences are needed to perform a
measurement. First write command byte hF1 (trigger
measurement) to the sensor, and then execute a read
operation to trigger the measurement and retrieve the flow
or differential pressure information.
On receipt of a header with R/_W=1, the sensor generates
the Hold Master condition on the bus until the first
measurement is completed. After the Hold Master
condition is released, the master can read the result as
two consecutive bytes. A CRC byte follows if the master
continues clocking the SCL line after the second result
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3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18
1 1 1 1 0 0 0 1
W
I2CAdr
1
2
3
4
5
6
7
8
S 1 0 0 0 0 0 0 1
Command
9
ACK
2
Hold Master
R
I2CAdr
LSByte MeasData
Check Byte
ACK
MSByte MeasData
ACK
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
P
Hatched areas indicate that the sensor controls the SDA line.
Note that the first measurement result after reset is not
valid.
4.2
4. Command Set and Data Transfer
Sequences
4.1
1
S 1 0 0 0 0 0 0 0
Soft reset
This command forces a sensor reset without switching the
power off and on again. On receipt of this command, the
sensor reinitializes the control/status register contents
from the EEPROM and starts operating according to these
settings.
I2C Soft Reset
8-bit command code: hFE
Command: Soft reset
1
2
3
4
5
6
7
8
S 1 0 0 0 0 0 0 0
I2CAdr
4.3
W
9
10 11 12 13 14 15 16 17 18
1 1 1 1 1 1 1 0
ACK
The value of the R/_W bit in the header determines the
data direction for the rest of the data transfer sequence. If
R/_W = 0 (WRITE) the direction remains master-to-slave,
while if R/_W = 1 (READ) the direction changes to slaveto-master after the header byte.
8-bit command code: hF1
Command: Trigger differential pressure measurement
ACK
A data transfer sequence is initiated by the master
generating the Start condition (S) and sending a header
byte. The I2C header consists of the 7-bit I2C device
address and the data direction bit (R/_W).
I2C Measurement
ACK
Data is transferred in byte packets in the I2C protocol,
which means in 8-bit frames. Each byte is followed by an
acknowledge bit. Data is transferred with the most
significant bit (MSB) first.
byte. The sensor checks whether the master sends an
acknowledge after each byte and aborts the transmission
if it does not.
ACK
Data transfer format
ACK
3.4
system reboot
Command
CRC-8 Redundant Data Transmission
Cyclic redundancy checking (CRC) is a popular technique
used for error detection in data transmission. The
transmitter appends an n-bit checksum to the actual data
sequence. The checksum holds redundant information
about the data sequence and allows the receiver to detect
transmission errors. The computed checksum can be
regarded as the remainder of a polynomial division, where
the dividend is the binary polynomial defined by the data
sequence and the divisor is a “generator polynomial”.
The sensor implements the CRC-8 standard based on the
generator polynomial
x8 + x5 + x4 +1.
Note that CRC protection is only used for date transmitted
from the slave to the master.
For details regarding cyclic redundancy checking, please
refer to the relevant literature.
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5. Conversion to Physical Values
5.1
1500
2250
3000
Signal scaling and physical unit
The calibrated signal read from the sensor is a signed
INTEGER number (two's complement number). The
INTEGER value can be converted to the physical value by
dividing it by the scale factor (pressure = sensor output
scale factor). The scale factor is specified in Section 2.
5.2
Temperature compensation
The SDP600 sensor series features digital temperature
compensation. The temperature is measured on the
CMOSens® chip by an on-chip temperature sensor. This
data is fed to a compensation circuit that is also integrated
on the CMOSens® sensor chip. No external temperature
compensation is necessary.
5.3
Mass flow temperature compensation
A sensor output proportional to mass flow is necessary for
measuring mass flow in a bypass configuration. Even
though the output of the SDP sensors with mass flow
temperature compensation is still differential pressure, the
temperature compensation is adapted especially for mass
flow measurements in a bypass configuration. At
calibration temperature both calibrations are equivalent.
Please find the application note “Bypass Configuration
Differential Pressure Sensor SDPxxx” on our website.
5.4
842
766
697
1.15
1.26
1.38
Example: At 750 m above sea level and a sensor reading
of 40 Pa, the effective differential pressure is 41.8 Pa.
Note: In many HVAC applications such as air flow
measurement in a bypass configuration, the described
dependence on absolute pressure is actually welcome
because the quantity that must effectively be controlled is
the mass flow and not the volume flow. Mass flow is
dependent on differential pressure and absolute pressure.
For details please refer to our application note “Measuring
Flow in a Bypass Configuration”.
6. OEM Options
A variety of custom options can potentially be
implemented for high-volume OEM applications. Contact
Sensirion for more information.
Altitude correction
The SDP600 sensor series achieves its unsurpassed
performance by using a dynamic measurement principle.
The applied differential pressure forces a small flow of gas
through the sensor, which is measured by the flow sensor
element. As a result, any variation in gas density affects
the sensor reading. While temperature effects are
compensated internally, variations in atmospheric
pressure (elevation above sea level) can be compensated
by a correction factor according to the following formula:
DPeff = DPsensor (Pcal / Pamb)
DPeff: Effective differential pressure
DPsensor: Differential pressure indicated by the sensor
Pcal:
Absolute pressure at calibration (966 mbar)
Pamb: Actual ambient absolute pressure.
Altitude correction factors:
Altitude
Ambient pressure (Pamb) Correction factor
[meters]
[mbar]
(Pcal / Pamb)
0
250
425
500
750
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1013
984
966
958
925
0.95
0.98
1.00
1.01
1.04
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7.4
7. Mechanical Specifications
7.1
SDP61x/SDP51x – Tube connection
Mechanical concept
The SDP600 Series is designed for through-hole
technology and can be wave-soldered or hand-soldered to
a PCB.
7.2
The SDP60x/SDP50x can be directly connected
to a manifold using two O-rings.
The SDP61x/SDP51x sensors have ports for
connecting standard-size plastic tubes.
Mechanical characteristics
Parameter
PCB attachment
Allowable
overpressure
Rated burst pressure
Gas flow through
sensor
Weight
Protection rating
7.3
Clip-in and hand or wave soldering.
Additional mechanical attachment
depending on force requirements
1 bar (100 kPa, 400 inches H2O)
> 5 bar
Figure 3: SDP61x/SDP51x version with ports for tube
connection. All dimensions are in mm.
< 150 ml/min