AS1716
C a pa c i t i v e S e n s o r I n t e r f a c e
D a ta s h e e t
1 General Description
AS1716 is an analog front end specifically designed for
unbiased Capacitive Sensors, as for instance Knock
Sensors in Automotive, to be interfaced with Analog Dig-
ital Converters with Sample and Hold input stages.
The device provides differential inputs, a 1st order low
pass filter to cutoff the high frequency noise compo-
nents, differential to single ended conversion, program-
mable gain stage and a 2 pole low pass Multiple
Feedback Filter.
The Knock Sensor is a Piezo Electric device that gener-
ates a voltage if it is stressed. It senses knock and trans-
mits information to the electronic engine management
control unit. This influences process control in the
engine, for example timing and fuel injection until knock
is eliminated.
The capacitive sensor is biased via resistors to a voltage
level of V
DDA
/2.
2 Key Features
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Differential input stage with wide input range
Resistive sensor biasing (V
DDA
/2)
Programmable Gain (x0.5, x1, x2, x4)
Internal 2 order low pass Multiple Feedback Filter
with a min. cut off frequency of 16kHz
Single supply operation: 4.5V to 5.5V
Operating Temperature range: -40°C to +125°C
High CMRR: 55dB (min)
EMC characterized by IEC 61967-4
(1Ω / 150Ω Method)
EMC characterized by IEC 62132-4
(Direct Power Injection)
Automotive qualified to AECQ100 for IC and PPAP
level 3
8-pin SOIC Package
nd
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3 Applications
Analog front end for Capacitive Sensors to Analog to
Digital Converters and DSP.
Figure 1. AS1716 Block Diagram
VDDA
VSSA
NC
INN
VDDA
-
+
VDDA/2
+
-
VDDA/2
Gain Control
x0.5, x1, x2, x4
-
+
VDDA/2
-
+
OUT
Multiple Feedback LP Filter
fc ~23kHz typ.
INP
-
+
VDDA/2
AS1716
VDDA/2
GA
GB
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