HT7610A 데이터 시트보기 (PDF) - Holtek Semiconductor
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HT7610A Datasheet PDF : 12 Pages
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· Options for setting the comparator window to be 1 ,
16
1
11.3
or
1
9
(VDD-VEE).
The
default
is
1
16
(VDD-VEE).
PIR Amplifier
Consult the diagram below for details on the PIR front
end amplifier.
In the Fig.2 below there are 2 op-amps with different ap-
plications. OP1 can be used independently as a first
stage inverting or non-inverting amplifier for the PIR.
O P 1O
O P 1N
O P 1P
O P 2O
O P 2N
O P 2P
V DD
O P1
C o m p a ra to r
V CP
O P2
V CN
VEE
R e g u la to r
Fig.2 PIR Amplifier
As the output of OP2 is directly connected to the input of
the comparator, it is used as a second stage amplifying
device. The non-inverting input of OP2 is connected to
the comparator¢s window center point and can be used
to check this voltage and to provide a bias voltage that is
equal to the center point voltage of the comparator. In
Fig.2 the comparator can have 3 window levels set by
mask
option.
1.
1
16
(VDD-VEE),
2.
1
11.3 (VDD-VEE),
3.
1
9
(VDD-VEE).
HT761X
If the window level fails to be specified the default win-
dow
is
set
to
1
16
(VDD-VEE).
The
preset
voltage
of
VDD-VEE is 4V. The default values of VCP and VCN are
therefore 0.25V, ( 4 V ).
16
Second Stage Amplifier
Usually the second stage PIR amplifier is a simple ca-
pacitively coupled inverting amplifier with a low pass
configuration. The noninverting input terminal is biased
to the center point of the comparator window and the
output of the second stage amplifier is directly coupled
to the comparator center point.
In Fig.3 OP2P is directly connected to the comparator
window center, and with the C3 filter it can act as the
R2
bias for OP2. For this configuration AV =
, low cutoff
R1
1
frequency
fL=
2
p
,
R1C1
high
cutoff
frequency
1
fH= 2pR2C2 . By changing the value of R2 the sensitiv-
ity can be varied. C1 and C3 should be of low leakage
types to prevent the DC operating point from changing
due to current leakage.
Each op-amp current consumption is approximately
5mA with the op-amps and comparator¢s working volt-
age all provided by the regulator.
Consult the following diagrams for typical PIR front end
circuit.
First Stage of PIR Amplifier
Fig.4 shows a typical first stage amplifier. C2 and R2
form a simple low pass filter with cut off frequency at
7Hz. The low frequency response is governed by R1
and C1 with cut-off frequency at 0.33Hz.
( R1+ R2 )
AV =
R1
V DD
O P 2O
RW
C2
0 .0 2 2 m F
R1
R2
22kW
1M W
O P 2N
O P2
RW
C1
O P 2P
22mF
fir s t s ta g e
V DD
o u tp u t
RW
C3
RW
10mF
VEE
Fig.3 Typical Second Stage Amplifier
Rev. 1.30
6
October 12, 2009
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