BA338 Просмотр технического описания (PDF) - ROHM Semiconductor

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BA338

Mute detector IC

ROHM Semiconductor 

Audio ICs

(5) Capacitor CW and resistor RW (Pin 1) for setting out-

put pulse width

The relation between CW, RW and the output pulse width

TW is as follows :

TW 0.69 CW (µF) RW (kΩ) ms

TW is almost independent of the supply voltage.

If RW is small (less than 10kΩ), errors increase.

See Fig. 8.

(6) Capacitor CD and resistor RD (Pin 2) for setting song

gap detection time

The relation between CD, RD and the detection time TD

(the duration from the point when the input signal goes

below the input decision level to the generation of the out-

put pulse) is as follows :

BA336 :

TD = 0.69 CD (µF) RD (kΩ)

BA338 / BA338L :

TD = 0.69 CD (µF) RD (kΩ)

TD = =)0.15 CN (µF) RN (kΩ)

(The internal resistor RN is 25 to 100kΩ.)

TD is almost independent of the supply voltage.

If RD is small (less than 10kΩ), errors increase.

See Fig. 8.

BA336 / BA338 / BA338L

If a CN is added in the case of the BA338 / BA338L, its

discharge time will cause TD to be slightly longer than it

is when CN = 0.

Caution is required if TD is made short or a large CN is

used. (See Fig. 9).

FOperation notes

(1) The input decision level of the BA336 / BA338 /

BA338L is a highly sensitive -52dBm. This can cause the

output current to return to the input through the common

impedance of the ground line. Be sure to decouple the

power supply line and prevent common impedance with

the ground line. Adding a 0.1µF capacitor between Pin 8

and GND is effective, and we strongly recommend doing

so when high current is used.

(2) The maximum output current of the BA336 /

BA338 / BA338L can be up to 150mA (typical). However,

if left in the current limited state for a long time when using

a high voltage power supply, damage to the IC can result.

Be sure not to exceed the rated power dissipation and the

over-current protection time.

(3) When the BA336 / BA338 / BA338L is input into a

counter IC, make sure the input is above the 2VF thresh-

old (approximately 1.3V). Otherwise, there is a possibility

that a miscount will occur due to the output pulse gener-

ated (approximately 0.5V, see Fig. 4) when the power is

turned on or off.

FDifferences between the noise filters of the BA336

and BA338 / BA338L

The basic configurations of the BA336 and BA338 /

BA338L are the same, however, the noise filters are dif-

ferent.

BA336

The noise filter only operates from the time the

power is turned on or muting is turned off to the

arrival of the input signal. The power must be

turned off or muting turned on each time an out-

put signal is generated.

BA338 / BA338L The noise filter operates continuously

while the power is on. However, as

noted previously the song gap detec-

tion time can change slightly due to

the capacitor CN connected to the

noise filter pin.

731

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