NJU7505
BAND PASS FILTER FOR AUDIO SPECTRUM ANALYZER DISPLAY
!
GENERAL DESCRIPTION
The NJU7505 is a band pass filter for audio spectrum
analyzer display.
It consists of high and low band pass filters, CR oscillation
circuit, control circuit and DC transfer circuit.
Each band pass filter using the switched capacitor filter
technology operates at the shared time by 5 bands which
filter constant is switched by the internal clock.
Therefore, the audio signal shared of 5 bands is output from
a serial output terminal.
The 10 bands version using the double by the cascade
connection is prepared.
!
PACKAGE OUTLINE
NJU7505XD
NJU7505XM
!
FEATURES
"
BPF for the audio spectrum analyzer display of the 5 bands
"
10 bands extension is available by the cascade connection
(Version of A: For 5-band application by the single)
(Version of B: For 10-band application by the double)
"
BPF using the switched capacitor filter technology
"
CR oscillation circuit on chip
(External clock input is available)
"
Power-on initialization circuit on chip
(External reset input is available)
"
C-MOS Technology
DIP8, DMP8
"
Package Outline
!
PIN CONFIGURATION
OSC1
OSC2
RST/CLKO
RD
1
2
3
4
5
6
7
8
V
DD
A
IN
A
OUT
V
SS
!
BLOCK DIAGRAM
RST/CLKO
RD
Audi o Signal
Control Signa
Crock Signal
OSC1
OSC2
OSC
f
OSC
f
OSC/16
Cont rol Circuit
f
OSC/4
i
H
i
L
R
L
R
H
Power-on
Initialize
Φ
H
Φ
L
BPF
High Band
High Band
Peak Detector
Lev el Shif ter
&
Out Put BUF
A
OUT
A
IN
Input BUF
LPF
BPF
Low Band
Low Band
Peak Detector
V
DD
V
DD
A
GND
V
SS
V
SS
Ver.2004-06-04
-1-
NJU7505
!
TERMINAL DESCRIPTION
NO.
SYMBOL
FUNCTION
1
OSC1
External Resistor connecting terminal.
2
OSC2
External Resistor connecting terminal or External clock input terminal.
Both as Reset input terminal
3
RST/CLKO
and the clock of (2/3)*fosc output terminal.
4
RD
Trigger signal for reading-out the A
OUT
of each band output terminal.
5
V
SS
GND
0V
V
DD
8
Positive power supply +5.0 V
6
A
OUT
Peak voltage of each band output terminal.
7
A
IN
Audio signal input terminal.
!
VERSION LINEUP AND PEAK FREQUENCY
The NJU7505 prepares two version of A and B which are different of the peak frequency of each bands.
The version of A is recommended for the 5 bands application using the single and the version of B is
recommended for the 10 bands using the double by the cascade connection, however, the version of A can be
used for the 10 bands using the double and the version of B can be used for the 5 bands using the single.
Peak Frequency ( Hz )
Using the single
Using the double
Version of A
Version of B
Version of A
Version of B
12k
18k
12k
18k
-
-
8k
12k
3.5k
5.3k
3.5k
5.3k
-
-
2.3k
3.5k
1k
1.5k
1k
1.5k
-
-
670
1k
250
375
250
375
-
-
165
250
63
95
63
95
*
-
-
42
63
Band
f1a
f1b
f2a
f2b
f3a
f3b
f4a
f4b
f5a
f5b
Note 1) The bands of f1a, f2a, ... f5a correspond to the master side and the bands of f1b, f2b, ... f5b correspond
to the slave side at the cascade connection of the double.
Note 2) It may not be output along the expectation at the peak frequency of * marking, since the sampling time is
not enough.
The example of using the single
OSC1
A
OUT
f 1a to f5a
OSC1
The example of using the double
A
OUT
f 1a to f5a
OSC1
A
OUT
f 1b to f5b
NJU7505
f
OSC
OSC2
f
OSC
NJU7505
Master
RST/CLKO
2/3 * f
OSC
NJU7505
Slave
OSC2
-2-
Ver.2004-06-04
NJU7505
!
FUNCTIONAL DESCRIPTION
#
Interface to external controller
The example of the interface between the NJU7505 and the external controller is shown below;
(1) Example of the interface to the external controller ( Using the single )
After the RST signal from the external controller is input and then the internal circuit is initialized, each band data
is output as shown below timing chart;
Since the RD signal is output before each band is switched, the external controller is to count the number of the
RD signal and is to recognize the status of the band and is to read the output data from the A
OUT
terminal through
the external A/D converter.
The output type of the external controller connected to the RST/CLKO terminal as the RST input should be the
N-channel and open-drain type or the diode should be connected between the RST/CLKO terminal and the
output terminal of the external controller, so that the voltage of the RST/CLKO terminal is not gotten over the V
SS
level.
A
IN
OSC1
NJU7505
A/D
CONVERTER
A
OUT
OSC2
f
OSC
V
SS
RST/CLKO
RD
µ COM
3*2
14
/ fO
SC
A OUT
RD
RST
f1
f1
f2
f2
f3
f3
f5
f5
f1
f1
f2
f2
f4
f4
f3
f3
f1
f1
f1
f2
f2
f3
248 / fosc
Since the RD signal is output before 248/f
OSC
of each
band switched, the output data should be read out
within the limited time as shown right;
A
OUT
RD
Available Period
of Read-out
8 / fosc
A
OUT
fn
f1
If the RST signal which pulse width is more than
4/f
OSC
is input, the internal circuit is initialized and the
data of f1 band is output from the A
OUT
terminal after
52/f
OSC
of the rise edge of the RST signal.
4/ fosc[MIN] 52/ f osc
RST
Ver.2004-06-04
-3-
NJU7505
(2) Example of the interface to the external controller (Using the double)
The 10 bands application is available using the cascade connection of the double NJU7505 as shown blow.
After the RST signals from the external controller are input to each of the master and the slave of the NJU7505
and then each internal circuit is initialized, each band data is output as shown below timing chart;
Since the RD signals are output from the master and the slave before each band is switched, the external
controller is to count the number of the RD signals and is to recognize the status of the band and is to read the
output data from each A
OUT
terminals through the external A/D converter.
The master clock for the slave is provided with the output signal from the RST/CLKO terminal of the master. The
master clock for the slave is stopped when the RST signal is input from the external controller to the master, so
that the RST/CLKO terminal of the master is used both as the RST input of the master and the master clock for
the slave.
The output type of the external controller connected to each RST/CLKO terminal as the RST input should be the
N-channel and open-drain type or the diode's should be connected between each RST/CLKO terminal and the
output terminals of the external controller, so that the voltage of each RST/CLKO terminal is not gotten over the
V
SS
level.
A
IN
A
IN
OSC1
OSC2
A/D
CONVERTER
A
OUT
NJU7505
Slave
A
OUT
NJU7505
OSC2
Master
V
SS
RST/CLKO
RD
RST/CLKO
RD
µ COM
Master
A OUT
RD
RST
f1
f1
f2
f2
3*2
14
/ fO
SC
f3
f3
f5
f5
f1
f1
f2
f2
f4
f4
f3
f3
f1
f1
f2
f2
f3
f3
f1
f1
f2
Slave
A OUT
f1
f1
RD
RST
3*2
14
/ fO * 3/2
SC
f2
f2
f3
f3
f5
f5
f1
f1
f2
f2
f4
f4
f3
f3
f1
f1
f2
-4-
Ver.2004-06-04
NJU7505
Since each RD signal of the master and the slave is
output before 248/f
OSC
(248/f
OSC
*3/2) of each band
switched, the output data should be read out within the
limited time as shown right;
* The "( )" is corresponded to the slave.
248 / fosc
(248/ fosc*3/2)
A
OUT
RD
Available Period
of Read-out
8 / fosc
(8/ fosc*3/2)
If the RST signal which pulse width is more than
4/f
OSC
is input to the master, the internal circuit is
initialized and the data of f1 band is output from the
A
OUT
terminal of the master after 52/f
OSC
of the rise
edge of the RST signal.
The RST signal for the slave should be set to "L" level
while the RST signal for the master is "L" level and
should keep "L" level more than 6/f
OSC
. So the slave
operates as same as the master after 78/f
OSC
of the
rise edge of the RST signal for the slave.
A
OUT
(Master)
4/fosc[MIN]
RST
(Master)
fn
f1
52/ fsoc
RST
(Slave)
6/fosc[MIN]
A
OUT
(Slave)
f n’
78/ fsoc
f 1’
Ver.2004-06-04
-5-
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