Audio ICs
LED level meter driver, 12-point,
power scale, dot or bar display
The BA683A is a monolithic IC for LED power meter applications. The display level range is 9mVrms to 380mVrms (Typ.)
divided into 12 points with interval spacings of 3dB. The constant current outputs can be set using an external resistor.
Level meters for all types of audio equipment applications
1) 12-point power meter driver for bar / dot displays.
2) Fixed-current outputs that can directly drive LEDs.
3) Output current can be set using external resistors allowing different types of LEDs to be used in combination.
4) Built-in half-wave rectifier amplifier.
5) With bar-type display, by connecting four LEDs in series, power dissipation is reduced.
Block diagram
Audio ICs
FAbsolute maximum ratings (Ta = 25_C)
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 12V, and f = 1kHz)
Audio ICs
Measurement circuit
Comparator level vs. AC and DC input levels
Application example
Audio ICs
Attached components
(1) LED current setting resistor (R1)
This resistor sets the LED current value. Refer to Fig. 3
for the relationship between the value of this resistor and
the current value. The ratio of the current for outputs 1 to
8 and 9 to 12 is about 2: 1. The recommended value is
for this resistor is 27kΩ. If the LED current is set too high,
the allowable power dissipation of the package may be
exceeded, so exercise due caution.
(2) Input coupling capacitor (C1)
This capacitor connects the BA683A to external input circuits. The recommended value is 2.2µF.
(3) Input bias resistor (R2)
This resistor is the input impedance. If the value is set too
large, the DC bias voltage will increase, and the input offset will increase and have an effect on the comparators.
The recommended value is 10kΩ.
(4) Resistor and capacitor that set the LED operation
level discharge time constant (R3 and C2)
These components set the discharge time constant for
LED operation level. The recommended values are R3 =
10kΩ and C2 = 10µF.
Operation notes
(1) LED connection
Connect the LEDs as indicated in Fig. 2 (1) and Fig 2 (2).
Note that the connection methods are different for bar
and dot displays, and that in the case of bar display, pin
18 is open, while for dot display, pin 18 is connected to
For the BA683A, the ratio of the current for LEDs L1 to L8
and L9 to L12 is about 2: 1. If you want the current ratio for
some of the L1 to L8 LEDs to be 1, reduce the current by
connecting a resistance in parallel with the LED. Short
any LED that are unused. Connect the LEDs that are not
used from the lowest level LED (except when the 12th
LED is not used for display alignment).
(2) LED current adjustment
The LED current is set using R1. The relationship between the value of R1 and the typical LED current is given
in Fig. 3.
(5) Input offset adjustment resistors (R4 and VR1)
These resistors are used to adjust the input offset for the
rectifier amplifier. The recommended values are R4 =
240kΩ, and VR1 = 500Ω. If the value of VR1 is too high,
adjustment becomes difficult, and if it is too small, adjustment may not be possible.
(6) Power supply capacitor (C3)
This capacitor stabilizes the power supply line. The recommended value is 10µF. This capacitor will have no effect if its value is 1µF or less.
(3) Comparator voltage
In the case of the BA683A, the comparator voltage is the
input voltage when about half LED current setting value
(Typ.) starts flowing in an LED.
Therefore, if the LED current is set to 16mA, when the
third LED starts to light and 8mA is flowing in the LED,
this input voltage is the third comparator voltage.
(4) 0dB and input offset adjustment
First, adjust the input signal so that the 10th LED lights.
This is the 0dB input signal level. Next, lower the input
signal level to 27dB, and adjust the offset adjustment
potentiometer VR1 so that the first LED lights. Repeat the
0dB and 27dB adjustments alternately to accurately
set the levels. The input level at which an LED lights is the
comparator voltage.
(5) Earthing
The BA683A GND (pin 9) and the external component
earths should connected together at one point.
Audio ICs
Tape deck application example
External dimensions (Units: mm)