Pressure sensors
C32 series
Absolute pressure sensor die for wet media
Preliminary data
Symbols and terms
1)
Maximum power supply VDD
This is the maximal allowed voltage, which may be applied to the piezoresistive bridge circuit without damage.
2)
Operating temperature range Ta
This is the operating Temperature range Ta,min to Ta,max. Because most of the sensor parameters depend on assembling
conditions like gluing, wire bonding etc, the die has to be tested over the operating temperature range by the customer
fully assembled. For design verification and process control samples, mounted in AK transducer package (AK2 series)
are tested over a reduced measuring temperature range of Tmeas,min to Tmeas,max
.
3)
Storage temperature range Tst
If the pressure sensor dies are stored in the temperature range Tst,min to Tst,max without applied voltage power supply, this
will not affect the performance of the pressure sensor dies.
4)
5)
6)
Operating pressure range pr
In the operating pressure range 0 to pr,max the pressure sensor die output characteristic is as defined in this specification.
Over pressure pOV
Pressure cycles in the pressure range 0 to pov do not affect the performance of the pressure sensor dies.
Burst pressure pberst
Up to the burst pressure pberst the diaphragm of the sensor die will not be destroyed mechanically. This parameter is
tested at room temperature on samples mounted on an aluminium socket by applying the specified burst pressure for
10 minutes. The evaluation of this test is done by optical inspection of the diaphragm.
7)
Operating power supply VDD
The pressure sensor parameters are defined for a power supply voltage of VDD = 5 V. In the operating power supply
voltage range VDD,min to VDD,max the ratiometric parameters r(VDD) like sensitivity, offset voltage and the temperature
coefficient of the offset voltage are defined by:
VDD
r
VDD = r(5[V])
( )
5[V]
8)
9)
Total bridge resistance RS
The total bridge resistance is defined between pad X5 and X2, (see the dimensional drawing in this data sheet) of the
closed piezoresistive bridge circuit. The total bridge resistance is in a good approximation the output impedance of the
piezoresistive bridge circuit. This parameter is tested completely on a wafer (wafer level test measurement).
Temperature coefficients of resistance αRs and βRs
The temperature coefficients of resistance are tested for design verification on samples, mounted on AK transducer
package (AK2 series) over a reduced temperature range Tmeas min = –20 °C to Tmeas max = 80 °C with TR = 25 °C.
:
,
,
The temperature coefficients of first and second order are defined with the polynomial:
2
R (T)=R (T=25°C ) 1+α
S
Rs T−25°C
+β
Rs T−25°C
S
The coefficients αRs and βRs are calculated using the three measurement points of Rs(T) at Tmeas,min, TR and Tmeas,max
.
10)
Offset voltage V0
The offset voltage V0 is the output voltage Vout(p = 0 bar absolute) at zero absolute pressure and for a bridge voltage
power supply VDD = 5 V. The high range of the allowed offset voltage is due to the reference pressure in the glass cap
from 0 to 0.3 bar and to the tolerance of the sensitivity. The typical value of the reference pressure is 0.2 bar.
Before anodic glass bonding the offset voltage is tested completely on a wafer (wafer level test measurement)
with limits –25 mV < V0 < 25 mV. For design verification V0 is measured on samples, mounted in AK transducer package
(AK2 series) by extrapolating the output characteristic to zero bar.
It should be noted that this parameter may be influenced by assembly.
Temperature coefficients of offset voltage TCV0+ and TCV0
11)
–
The temperature coefficients of offset voltage are defined for a bridge voltage power supply VDD = 5 V.
These parameters strongly depend on assembly conditions like gluing, wire bonding etc.
The temperature coefficients of offset voltage are tested for design verification on samples, mounted on AK transducer
package (AK2 series) over a reduced temperature range Tmeas min
,
= –20 °C to Tmeas,max = 80 °C with TR = 25 °C.
Assuming the offset voltage is mainly due to induce stress TCV0 may be calculated by extrapolating using:
V0(T) =
1+ αs(T − 25°C) + βs(T − 25°C)2 ) (
Vo(25°C) + v1(T − 25°C) + v2(T − 25°C)2
AS SEN PD
2009-08-03
Please read Cautions and warnings and
Important notes at the end of this document.
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