Audio ICs LED level meter driver, 5-point, linear scale BA6125 The BA6125 is a driver IC for LED linear level meters in stereo equipment and other display applications. The IC displays the input level on five LEDs. The display level range is 35mVrms to 175mVrms in five equally-spaced 35mVrms steps. The BA6125 includes a rectifier amplifier allowing direct AC input, and has constant-current outputs, so it can directly drive the LEDs without variations in LED current due to supply voltage fluctuations. Applications Battery checkers, signal meters, and other display devices. Features 1) Rectifier amplifier allows either AC or DC input. 2) Constant-current outputs for constant LED current when the supply voltage fluctuates. 3) Built-in reference voltage means that power supply voltage fluctuations do not effect the display. Absolute maximum ratings (Ta = 25c) 624 4) Wide operating power supply voltage range (3.5V to 16V) for a wide range of applications. 5) Low PCB space requirements. Comes in a compact 9-pin SIP package and requires few external components. Audio ICs BA6125 Block diagram Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 6.0V, and f = 1kHz) Measurement circuit 625 Audio ICs BA6125 Application example The response time (attack and release time) can be changed by varying the values of C1 and R1. C2 is a coupling capacitor, and the potentiometer VR varies the input level. Input the voltage level that you desire for the center point, and adjust the potentiometer so that the third LED (VC3) lights. To reduce the LED current, connect a resistor either in parallel (Fig. 3 (1)) or in series (Fig. 3 (2)) with the LED. If a resister is connected in series with the LED, the LED current will change if the supply voltage fluctuates. Note: If the power supply voltage exceeds 9V, insert a resistor in series with the LED current supply line, or connect a heat sink so that the maximum power dissipation Pd Max. is not exceeded (see Fig. 4). 626 Audio ICs BA6125 Use with DC input Use the potentiometer shown in Fig. 5 to adjust the input level. Adjust the potentiometer so that the third LED (VC3) lights for the desired input level. For large input levels, input via pin 7 is also possible. In this case, the dispersion in comparator level is less than in the case of input via pin 8. Note that, if the resistance value of the 100kΩ potentiometer shown in Fig. 6 is made too small, the discharge time constant determined by C1 and R1 will change, and the response time will vary. The maximum input level for pin 7 is 5V. External dimensions (Units: mm) 627