ZXF36L01
ISSUE 3 - JANUARY 2002
1
VARIABLE Q FILTER
DESCRIPTION
The ZXF36L01 is a versatile analog high Q bandpass
filter. The device contains two sections:
1
Variable Q bandpass filter.
2
Mixer block.
The basic filter section requires 2 resistors and 2
capacitors to set the centre frequency.
The filter
operates up to a frequency of 150kHz.
Two external
resistors control filter Q Factor. The Q can be varied up
to 50.
The mixer is included to extend the frequency range up
to 700kHz and to permit the centre frequency to be
tuned.
The local oscillator can be any waveform,
making microprocessor control convenient.
APPLICATIONS
Many filter applications including: -
Audio bandpass and notch
Micro controlled frequency
Adaptive filtering
Sonar and Ultrasonic Systems
Instrumentation
FEATURES AND BENEFITS
Centre Frequency up to 700kHz
Tuneable centre frequency
Variable Q
Low power
Standby mode for improved battery life
SYSTEM DIAGRAM
PART NUMBER
PACKAGE
PART
MARK
ZXF36L01W24
SO24W
ZXF36L01
ORDERING INFORMATION
PART NUMBER
CONTAINER
INCREMENT
ZXF36L01W24TC
Reel 13"
330mm
1000
ZXF36L01W24
Tube
31
ABSOLUTE MAXIMUM RATINGS
Voltage on any pin
7.0V (relative to Vss)
Operating temperature range
0 to 70C (de-rated for -40 to 85C)
Storage temperature
-55 to 125C
ELECTRICAL CHARACTERISTICS
Test Co
ditions: Temperature =25C, V
DD
= 5.00V, V
SS
= 0.00V
GENERAL CHARACTERISTICS
Parameter
Conditions
Min.
Typical
Max.
Units
Operating current
PD= V
DD
2.2
3.4
4.5
mA
Shutdown current
PD = V
SS
160
300
A
IIH (PD)
VIH =5V (WRT V
SS
)
1.0
A
IIL (PD)
VIL =0V (WRT V
SS
)
-1.0
A
FILTER CHARACTERISTICS
Max. operating frequency
150
kHz
Q usable range
0.5
50
Centre frequency temperature
coefficient
Q=30,
fo = 1kHz
Note 1
10
ppm/C
Average Q temperature
coefficient
Q=30,
fo = 1kHz
Note 2
0.1
% /C
Voltage noise
1 100 kHz
20
nV/
Hz
Input impedance
30
50
k
Max. output swing
Output load
10 k
1.6
V pk-pk
Output sink current
150
A
Output source current
150
A
MIXER CHARACTERISTICS
Max. operating frequency
700
kHz
Maximum signal input
300
mV pk-pk
Maximum Local Oscillator input
100
mV pk-pk
Minimum Local Oscillator input
5
mV pk-pk
Local Oscillator input Impedance
60
NOTE 1
Centre frequency temperature coefficient is dominated by the external R & C components. On chip drift is
negligable.
Note 2
Average Q temperature coefficient is dominated by the external R components.
ZXF36L01
ISSUE 3 - JANUARY 2002
2
TYPICAL ELECTRICAL CHARACTERISTICS
Test Co
ditions:V
DD
= 5.00V, V
SS
= 0.00V
ZXF36L01
ISSUE 3 - JANUARY 2002
3
Typical Gain at Fo V Q Factor
(Fo = 140 KHz)
20
25
30
35
40
45
50
10
20
30
40
50
60
70
80
90
100
Q Factor
Ga
i
n
(
d
B
)
Q Factor V Frequency
16
18
20
22
24
26
28
30
32
0
20
40
60
80
100
120
140
160
180
200
Frequency (kHz)
QF
a
c
t
o
r
Gain at fo describes the peak gain of
the notch pass filter. This gain is
defined by the value of Q Factor.
Components used: 1/8 watt metal
film resistors (+/- 50 ppm). Ceramic
capacitors (+/- 50 ppm).
The curve shows Q Factor over
frequency for a fixed loop gain
(Rf/Ri).
ZXF36L01
ISSUE 3 - JANUARY 2002
4
DESCRIPTION OF PIN FUNCTIONS
V
DD
Positive supply connection (5 volts). Both pins to be connected.
To be decoupled with a 100nF capacitor to V
SS
.
V
SS
Negative supply connection; system ground (0 volts). Both pins to be connected.
BG
Bias Generator output. To be decoupled with a 100nF capacitor to V
SS
.
BI
Bias inputs for internal circuitry, both to be connected to BG.
(or external supply referenced to V
SS
)
PD
Active low. This feature can be used to reduce power consumption for applications that
have a standby mode.
FI1,Fl2
Filter input, FI1 or FI2 depending on filter configuration.
FO
Filter output for all configurations.
LO
Local Oscillator signal input.
MXI
Mixer signal input.
MXO
Mixer signal output.
C1, RC1
Phase advance network nodes. Values R and C set centre frequency, fo.
R2, RC2
Phase retard network nodes. Values R and C set centre frequency, fo.
GP1,2,3
Loop gain programming nodes.
CONNECTION DIAGRAM
V
SS
FI1
C1
R2
RC1
RC2
V
DD
FI2
FO
BI
GP1
GP3
GP2
MXO
V
SS
MXI
LO
BI
BG
N/C
N/C
N/C
PD
V
DD
1
ZXF36L01
ISSUE 3 - JANUARY 2002
5
R=10k
C=100nF
Rf=19.5k
Ri=10k
FILTER CONFIGURATIONS AND RESPONSES
Notch Filter
Filter AC Performance
Notch Filter Gain Response
-35
-30
-25
-20
-15
-10
-5
0
5
10
100
1000
10000
Frequency (Hz)
Gai
n
(dB
)
Notch Filter Phase Response
90
120
150
180
210
240
270
10
100
1000
10000
Frequency (Hz)
P
h
as
e
(
D
e
g
r
ees
)
f
RC
Q
R
R
o
f
i
=
1
2
(
/
)
Where R, Ri and Rf
10k
and C
50 pF
See "Designing for a Value of Q" for more
details.
T y p i c a l r e s p o n s e s f o r t h e c i r c u i t w i t h
component values shown in circuit diagram.
Output Signal
Input Signal
V
DD
FI2
FO
V
SS
FI1
C1
RC1
RC2
GP1
GP2
GP3
R2
BI
MXO
V
SS
MXI
LO
BI
BG
N/C
N/C
N/C
PD
V
DD
C
C
Rf
Ri
1
24
5V
5V
100nF
100nF
100nF
R
R
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