795

Audio ICs

BA6810F

FCircuit operation

(1)

Input block

The AC input pins are pins 23 and 25, and the DC input

pins are pins 27 and 28. Pin 2 is used to switch between

the AC and DC inputs. When the input to pin 2 is “H”, AC

input is selected (pins 23 and 25). Therefore, by using pin

2 to switch between the AC and DC modes, the IC can

do two jobs, using one fluorescent tube. For example,

pins 23 and 25 can be used for audio signal input, and

pins 27 and 28 can be used as the input for the signal me-

ter output from a tuner (DC).

(2)

Peak hold circuit

The BA6810F features a peak hold circuit that temporari-

ly holds peak signal levels in AC input mode.

The peak hold function can be used with the upper 8

points (5 to 12). The peak hold time depends on the oscil-

lator frequency. It is 2 sec. (typ.) for an oscillator frequen-

cy of 2kHz.

(3)

MUTE function

The display can be turned off by driving the MUTE termi-

nal “H”.

(4)

Meter sensitivity adjustment terminal

Connect a potentiometer of about 10k

Ω, and adjust it so

that the 8th point lights when the for an AC input of

nels is

"1.0dB.

(5)

Grid output

The pin 6 and 7 grid outputs are open-collector NPN tran-

sistors. The logic is active low (the fluorescent tube lights

when the output is “L”), so connect two PNP transistors

drive the fluorescent tubes (see Fig. 4).

(6)

Segment output block

Pins 8 to 19 are the segment outputs. The output circuits

are open-collector PNP transistors. When grid 1 is “L”,

the ch1 level is output (pin 23 or 27 input level), and when

grid 2 is “L”, the ch2 level is output (pin 25 or 28 input lev-

el). Refer to Fig. 5.

(7)

Grid and segment output timing chart.

The grid and segment output timing is shown in Fig. 6.

(8)

Attack and recovery times

The output response characteristic for AC input signals

is set by pins 24 and 26. The comparator level may

change somewhat due to the sag of the CR circuit dis-

charge.

(9)

Oscillator frequency

The resistor and capacitor connected to pin 21 determine

and grid output period (T) are related as follows: