BA3835F データシートの表示（PDF） - ROHM Semiconductor

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BA3835F

Band-pass filter for spectrum analyzer

ROHM Semiconductor 

Audio ICs

FOperation notes

(1) Frequency characteristics

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).

(2) Load characteristics

To convert the bias sense output signal to the GND sense

signal, the IC performs a V / I conversion, and then an

I / V conversion using a 10kΩ resistor (typ.) for the out-

put.

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.

(3) External resistor for the control pin

When using a common port for the output select control

and FL drive, you must add a diode and resistor as shown

in Fig. 4 to prevent the FL drive “L” voltage from destroy-

ing the IC.

BA3835S / BA3835F

And from this, the following condition is obtained :

R < 30kΩ

In this case, the “L” level voltage V2 for the IC will

be :

V2 < 0.75V

(4) Recommended operating ranges

Provided that 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.

(5) Application circuit

Provided the recommended circuit constants are used,

the application circuit should function correctly. However,

we recommend that you confirm the characteristics of the

circuits in actual use and pay due attention to the caution-

ary notes given below.

If you change the circuit constants, check both the static

and transient characteristics of the circuit, and allow suffi-

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 :

V1 =

R1)R

R1)R2)R

Vref

To maintain a noise margin of at least 2.5V with re-

spect to the comparator threshold level Vref, the rep-

resentative values for Vref, R1 and R2 are 1.5V, 20kΩ,

and 10kΩ respectively. This gives :

20kΩ)R

1.5V)0.25V<1.5V

20kΩ)10kΩ)R

608

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