BA3835S [ROHM]
Band-pass filter for spectrum analyzer; 带通滤波器，用于频谱分析仪
| 型号： | BA3835S |
| 厂家： | 
ROHM |
| 描述： | Band-pass filter for spectrum analyzer |
| 文件： | 总10页 (文件大小：132K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Audio ICs
Band-pass filter for spectrum analyzer
BA3835S / BA3835F
The BA3835S and BA3835F are 5-band, band-pass filter ICs that use microprocessor time division to produce serial
output for spectrum analyzer displays. To minimize the number of external components required and enable compact
and reliable designs, all of the capacitors for the filters are on the chip.
FApplications
CD radio cassette players, mini-component stereo sys-
tems, car stereos
FFeatures
1) Five band-pass filter elements for spectrum analyzer
displays.
3) Discharge time constant circuit for each band is on
the chip.
2) High-speed readout
4) Differential input amplifier rejects common-mode
(output response time : 5µsec. Typ.).
noise.
5) Single 5V power supply.
FAbsolute maximum ratings (Ta = 25_C)
FRecommended operating conditions (Ta = 25_C)
601
Audio ICs
BA3835S / BA3835F
FBlock diagram 1 (BA3835S)
602
Audio ICs
BA3835S / BA3835F
FBlock diagram 2 (BA3835F)
603
Audio ICs
BA3835S / BA3835F
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 5V, RL = 10MΩ, VAIN = *30dBV and
SEL = 1)
604
Audio ICs
BA3835S / BA3835F
FMeasurement circuit (BA3835S)
605
Audio ICs
BA3835S / BA3835F
FOutput select logic table
FTiming chart
606
Audio ICs
BA3835S / BA3835F
FApplication example (BA3835S)
607
Audio ICs
BA3835S / BA3835F
FOperation notes
(1) Frequency characteristics
And from this, the following condition is obtained :
The frequency characteristics of this IC are determined
by the resistor connected between the RREF terminal and
GND. For the specification conditions, the value of this
resistor is 100kΩ. If it is necessary to set the frequency
characteristics accurately, use a variable resistor (note :
all bands will shift together).
R < 30kΩ
In this case, the “L” level voltage V2 for the IC will
be :
V2 < 0.75V
(2) Load characteristics
(4) Recommended operating ranges
ToconvertthebiassenseoutputsignaltotheGNDsense
signal, the IC performs a V / I conversion, and then an
I / V conversion using a 10kΩ resistor (typ.) for the out-
put.
Providedthat the IC is operated within the recommended
operating conditions and the recommended temperature
range, the basic circuit functions are guaranteed. Within
these ranges, ratings for electrical characteristics for
conditions other than those stipulated cannot be guaran-
teed, but the inherent function of the bandpass filter will
be maintained.
Therefore, if the load circuit connected to the A OUT pin
has a MOS structure there is no problem (eg. micropro-
cessor input port), but if the connected circuit has a low
input impedance, it may cause the output level to drop.
(5) Application circuit
Provided the recommended circuit constants are used,
theapplicationcircuitshouldfunctioncorrectly. However,
werecommendthatyouconfirmthecharacteristicsofthe
circuitsinactualuseandpaydueattentiontothecaution-
ary notes given below.
(3) External resistor for the control pin
When using a common port for the output select control
andFLdrive, youmustaddadiodeandresistorasshown
in Fig. 4 to prevent the FL drive “L” voltage from destroy-
ing the IC.
If you change the circuit constants, check both the static
andtransientcharacteristicsofthecircuit, andallowsuffi-
cient margin to accommodate variations between both
ICs and external components. Note, also, that Rohm has
not been able to conduct a sufficient study into patent
rights.
In this case, the “L” voltage applied to the internal
comparator input terminal V1 is given by :
R1)R
V1 =
Vref
R1)R2)R
To maintain a noise margin of at least 2.5V with re-
spect to the comparator threshold level Vref, the rep-
resentativevaluesforVref, R1 andR2 are1.5V, 20kΩ,
and 10kΩ respectively. This gives :
20kΩ)R
1.5V)0.25V<1.5V
20kΩ)10kΩ)R
608
Audio ICs
BA3835S / BA3835F
(6) Output offset voltage
The relationship between the output offset voltage and
the output selection cycle (cycle time) for this IC is shown
in Fig.5. The maximum output offset voltage of 150mV
that is given in the electrical characteristics table is under
the condition that Ts = 200ms. When Ts is greater than
50ms, the graph of the output offset voltage is a straight
line at 150mV. When Ts is below 50ms, due to transient
characteristics of the peak hold circuit, the graph is a line
sloping downwards to the right. In other words, the short-
er the cycle, the larger the output offset voltage.
Furthermore, the output offset voltage may shift due to
soldering or other temperature stresses from the sur-
roundings. Therefore, when setting the spectral analyzer
light level, take into consideration the points given above
and make sure that it does not light by mistake during
quiescent periods. Use the chart below as a guide for
this, and, if necessary, leave even a larger margin.
FElectrical characteristics curves
609
Audio ICs
BA3835S / BA3835F
FExternal dimensions (Units: mm)
610
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