BA6800 ROHM [Rohm], BA6800 Datasheet - Page 5

• Manufacturer Part Number: BA6800
• Description: Fluorescent display tube level meter driver, 16-point x 2 channel, VU scale, bar display
• Manufacturer: ROHM [Rohm]

FCircuit operation
(1)
The AC input pins are pins 1 and 3, and the DC input pins
are pins 5 and 6. Pin 7 is used to switch between the AC
and DC inputs. When the input to pin 7 is “H”, AC input
is selected (pins 1 and 3). Therefore, by using pin 7 to
switch between the AC and DC modes, the IC can do two
jobs. For example, pins 1 and 3 can be used for audio sig-
nal input, and pins 5 and 6 can be used as the input for
the signal meter output from a tuner (DC).
The AC input impedance of pins 1 and 3 is a low 250
(Typ.), so connect potentiometers (VR
ries with the inputs to adjust the sensitivity and ch1 and
ch2 balance.
(2)
The BA6800AF have peak hold circuits that temporarily
holds peak signal levels in AC input mode.
The peak hold function can be used with the upper 12
points (5 to 16). The peak hold time depends on the oscil-
lator frequency. It is 2 sec. (Typ.) for an oscillator frequen-
cy of 2kHz.
DC mode does not have a peak hold function.
(3)
The pin 9 and 10 grid outputs are open-collector NPN
transistors. The logic is active low (the fluorescent tube
lights when the output is “L”), so connect two PNP tran-
sistors Q
circuit to drive the fluorescent tubes (see Fig. 3).
808
Audio ICs
Input block
Peak hold circuit
Grid output
1
and Q
2
as shown in the application example
1
and VR
2
) in se-
(4)
Pins 11 to 26 are the segment outputs. The output circuits
are open-collector PNP transistors. When grid 1 is “L”,
the ch1 level is output (pin 1 or 5 input level), and when
grid 2 is “L”, the ch2 level is output (pin 3 or 6 input level).
Refer to Fig. 4.
(5)
segment output timing for an oscillator frequency of 2kHz
is shown in Fig. 5.
(6)
The response characteristic for AC input signals is set by
resistor R
capacitor C
C
time is about 1sec. (same for ch2).
(7)
The resistor R
termine the oscillator frequency.
The oscillator frequency (f
are related as follows :
3
= 22 F, the attack time is about 4ms, and the release
Attack time
Release time : Time for the voltage on pins 2 and 4
T (ms) = 16 / f
Segment output block
Grid and segment output timing chart. The grid and
Attack and release times
Oscillator frequency
1
and capacitor C
4
for ch2 (pins 2 and 4). When R
26
and capacitor C
: Time for the voltage on pins 2 and 4
osc
to rise from 1V to 2.5V when the in-
put goes from no input to 2.6Vrms,
then back to no input.
to fall from 2.5V to 1V when the input
goes from 2.6Vrms to no input.
(kHz)
osc
3
) and grid output period (T)
for ch1 and resistor R
5
connected to pin 28 de-
BA6800AF
1
= 47k and
2
and