Datasheet
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
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 Digital Converters with Sample and Hold
input stages.
The device provides differential inputs, a 1st order low pass filter to
cutoff the high frequency noise components, differential to single
ended conversion, programmable gain stage and a 2 pole low pass
Multiple Feedback Filter.
The Knock Sensor is a Piezo Electric device that generates a voltage
if it is stressed. It senses knock and transmits information to the elec-
tronic engine management control unit. This influences process con-
trol 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
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
3 Applications
Analog front end for Capacitive Sensors to Analog to Digital Convert-
ers 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
www.austriamicrosystems.com/Capacitive-Sensors/AS1716
Revision 1.02
1 - 12
AS1716
Datasheet - P i n o u t
4 Pinout
Pin Assignment
Figure 2. Pin Assignments (Top View)
VDDA 1
GA
2
8 OUT
7 VSSA
AS1716
GB 3
INP 4
6 NC
5 INN
Pin Description
Table 1. Pin Description
Pin Name
VDDA
GA
GB
INP
INN
NC
VSSA
OUT
Pin Number
1
2
3
4
5
6
7
8
Positive Supply
Gain selection.
Internal pull-down of 100kΩ
Gain selection.
Internal pull-down of 100kΩ
Non-Inverting Input
Inverting Input
Not Connected.
Must be left unconnected in the application
Negative Supply
Signal Output
Description
www.austriamicrosystems.com/Capacitive-Sensors/AS1716
Revision 1.02
2 - 12
AS1716
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in
Table 2
may cause permanent damage to the device. These are stress ratings only, and functional operation of
the device at these or any other conditions beyond those indicated in
Electrical Characteristics on page 4
is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Table 2. Absolute Maximum Ratings
Parameter
Electrical Parameters
VDDA, VSSA
GA, GB, OUT, INP, INN, NC
Input Current (latch-up immunity)
Electrostatic Discharge
Electrostatic Discharge HBM
Temperature Ranges and Storage Conditions
Storage Temperature Range
Junction Temperature
-65
+150
+150
ºC
ºC
The reflow peak soldering temperature (body
temperature) specified is in accordance with
IPC/
JEDEC J-STD-020 “Moisture/Reflow Sensitivity
Classification for Non-Hermetic Solid State Surface
Mount Devices”.
The lead finish for Pb-free leaded packages is matte tin
(100% Sn).
Represents a max. floor life time of 168h
±4
kV
Norm:
AEC-Q100-002, @
T
A
= +25ºC
+7
VSSA - VDDA +
0.3
0.3
-100
+100
V
V
mA
To get an overvoltage protection of up to +16V at the
system level, apply external resistors (typ. 1kΩ) on the
pins INP and INN.
Norm:
AEC-Q100-004, @
T
A
= +25ºC
Min
Max
Units
Comments
Package Body Temperature
+260
ºC
Humidity non-condensing
Moisture Sensitive Level
5
3
85
%
www.austriamicrosystems.com/Capacitive-Sensors/AS1716
Revision 1.02
3 - 12
AS1716
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
Parameters are measured at V
DDA
= 4.5V to 5.5V, R
LOAD
= 100Ω serial to C
LOAD
= 10nF, T
A
= +25ºC and are refering to VSSA, unless other-
wise specified. Typical values are listed for reference only and will not be tested.
All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality Control)
methods.
Table 3. Electrical Characteristics
Symbol
T
AMB
V
DDA
I
DDA
PSRR
V
CM
CMRR
R
IN
V
REF
V
OFF
V
IL
V
IH
I
LEAK
V
HYST
R
PD
Gain0.5
Gain1
Gain2
Gain4
R
L
C
L
I
SHORT+
I
SHORT-
V
OUT-L
V
OUT-H
1
1
Parameter
Operating Temperature Range
Supply Voltage Range
Supply Current
Power Supply Rejection Ratio
Common Mode input Range
Common Mode Rejection Ratio
Differential Input Resistance
Internal Common Mode Input
Voltage
Offset Voltage
Logic Low (GA, GB)
Logic High (GA, GB)
Leakage Current (GA, GB)
Hysteresis
Pull-Down Resistor
Overall gain 0.5
Overall gain 1
Overall gain 2
Overall gain 4
External Serial Resistor
External Capacitive Load
Positive Short Circuit Current
Negative Short Circuit Current
Output Range Low
Output Range High
Condition
Min
-45
Typ
Max
+125
Unit
°C
V
mA
dB
V
dB
kΩ
V
mV
V
V
µA
mV
DC Electrical Characteristics
@ pin VDDA
@ pin VDDA
4.5
3
5
4.5
5.5
9
6
@ pins INN, INP
between pins INN and INP
INP shorted to INN
Gain1, V
INP
= V
INN
@ V
CM
= V
DDA
/2,
@ pin OUT
@ pin GA and GB
@ pin GA and GB
V
DDA
= 5V, Gain4
@ pin GA and GB
@ pin GA and GB
GA = GB = 1
GA = 1, GB = 0
GA = 0, GB = 1
GA = GB = 0, default setting
R
L
serial to C
L
(see Figure 13 on page 8)
V
OUT
is driven to V
DDA
and V
OUT
is connected
to V
SSA
V
OUT
is driven to V
SSA
and V
OUT
is connected
to V
DDA
@ pin VOUT
@ pin VOUT
100
50
0.5-10%
1-10%
2-5%
4-5%
100
0.01
25
25
V
SSA
+0
.05
V
DDA
-
0.05
2.0
1
200
100
0.5
1
2
4
150
0.5+10%
1+10%
2+5%
4+5%
1k
10
Ω
nF
mA
mA
V
V
V
SSA
55
70
100
130
V
DDA
/2
+2%
V
REF
+10
1.2
V
DDA
/2 - V
DDA
/2
2%
V
REF
10
-
V
DDA
kΩ
AC Electrical Characteristics
f
C
THD
V
NOISE
Filter Cut-off Frequency
Total Harmonic Distortion
RMS noise at OUT
V
DDA
= 4.5V, GA = GB = 0, INP-INN = 1V
PP,
f
IN
= 16kHz and 29kHz
V
DDA
= 5V, f
IN
= 1kHz, INP-INN = 8V
PP
, Gain0.5
Gain4, f
C
= 50Hz - 23kHz
16
23
80
1
29
kHz
dB
mV
RMS
1. Guaranteed by design
www.austriamicrosystems.com/Capacitive-Sensors/AS1716
Revision 1.02
4 - 12
AS1716
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
7 Typical Operating Characteristics
V
DDA
= 5.0V, T
A
= +25ºC (unless otherwise specified).
Figure 3. CMRR vs. Temperature; GA = GB = 0
100
95
Figure 4. Supply Current vs. Temperature;
10
9
85
Supply Current (mA)
0
20
40
60
80 100 120
90
8
7
6
5
4
3
2
1
0
-40 -20
0
20
40
60
80
100 120
CMRR (dB)
80
75
70
65
60
55
50
-40 -20
Temperature (°C)
Figure 5. THD vs. Temperature
-75
-76
-77
-78
Temperature (°C)
Figure 6. THD vs. Frequency
20
0
-20
THD (dbV)
0
20
40
60
80 100 120
THD (dB)
-79
-80
-81
-82
-83
-84
-85
-40 -20
-40
-60
-80
-100
-120
-140
10
100
1000
10000
100000
Temperature (°C)
Figure 7. Transfer Characteristics
10
0
-10
-30
-40
-50
-60
-70
-80
-90
-100
1
10
100
1000
10000
min
t yp
max
Frequency (Hz)
Figure 8. Phase Gain
100
Transfer Characteristic (dB)
0
Phase Gain (deg)
-20
-100
-200
-300
min
t yp
max
-400
1
10
100
1000
10000
Frequency (kHz)
www.austriamicrosystems.com/Capacitive-Sensors/AS1716
Revision 1.02
Frequency (kHz)
5 - 12
