BA6820 ROHM [Rohm], BA6820 Datasheet - Page 7

• Manufacturer Part Number: BA6820
• Description: LED level meter driver, 12-point x 2 channel, VU scale, bar display
• Manufacturer: ROHM [Rohm]

(3)
The peak hold circuit momentarily holds the maximum
signal level in AC input mode. The peak hold function ap-
plies to comparator levels 5 to 12 (8 points). When the os-
cillator frequency is 4kHz, the peak hold time is two se-
conds (Typ.), and can be changed by changing the
oscillator frequency. The peak hold function can be
turned off by setting pin 8 high.
The peak hold function does not operate in DC input
mode.
(4)
The two sets of 12 LEDs for the BA6820F and
BA6822S / F are divided into 4 groups of six. A dynamic-
drive technique is used to drive the LEDs in order, and
display the input level.
Therefore, six LED drive outputs, and four display switch
terminals are provided.
The output timing chart for when all LEDs are lit is shown
in Fig. 3.
In DC input mode, only channel 2 operates.
D
for AC mode (i.e. D
for the channel 1 period.
668
Audio ICs
1
to D
Peak hold
Output block
Group 1
Channel 1 LEDs 1, 3, 5, 7, 9 and 11
(odd-numbered LEDs)
Group 2
Channel 1 LEDs 2, 4, 6, 8, 10 and 12
(even-numbered LEDs)
Group 3
Channel 2 LEDs 1, 3, 5, 7, 9 and 11
(odd-numbered LEDs)
Group 4
Channel 2 LEDs 2, 4, 6, 8, 10 and 12
(even-numbered LEDs)
4
in the timing chart operate in the same way as
1
and D
2
operate), but O
1
to O
6
are high
(1) Display switch outputs (pins 12 to 15)
To successively switch between the four LED groups,
these outputs are active low (see Fig. 4).
The outputs are pulled up by 36k resistors (between the
base and emitter of Q
sistors are not required.
BA6820F / BA6822S / BA6822F
1
to Q
4
), so leak current bypass re-