BA6820 Ver la hoja de datos (PDF) - ROHM Semiconductor

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BA6820

LED level meter driver, 12-point x 2 channel, VU scale, bar display

ROHM Semiconductor 

Audio ICs

BA6820F / BA6822S / BA6822F

(3) Peak hold

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) Output block

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.

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)

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.

D1 to D4 in the timing chart operate in the same way as

for AC mode (i.e. D1 and D2 operate), but O1 to O6 are high

for the channel 1 period.

(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 36kΩ resistors (between the

base and emitter of Q1 to Q4), so leak current bypass re-

sistors are not required.

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