cascading AN6877 led driver

[adown]

cascading AN6877 led driver(sound level light bar)

Has anybody cascaded or know how to cascade an AN6877 to use as a led bar graph driver. I need 12 segment. Since the LM3914 isn't big enough I figured I'd cascade the AN6877 instead because of it's smaller size. The bar graph will be driven by car audio low level outputs for a sound level light bar with 3-5 leds on each segment. Thanks

 

[hjames]

The datasheet is a bit confusing, but from what I gather, pins 7,8 are connected to the resistor chain. On the chip responsible for the upper range, call it U1, connect U1.pin 7 to U1.pin 6(which is the internally generated 3.75V reference source). Then for the chip responsible for the lower range, U2, connect U1.pin 8 to U2.pin7, and U2.pin8 to ground.

This approach won't work for the logarithmic version(AA6878) of the chip - you'll need to add an extra resistor paralleling the lower range chip. The reason I bring up the log is that typically log indicators are used for audio indicators.

 

[Nigel Goodwin]

This approach won't work for the logarithmic version(AA6878) of the chip - you'll need to add an extra resistor paralleling the lower range chip. The reason I bring up the log is that typically log indicators are used for audio indicators.

Yes, it's really essential to use a logarithmic version!.

 

[audioguru]

You probably won't need to cascade ICs to drive 12 LEDs if you use the LM3915 logarithmic 10-LED bar-graph driver because its range is 30dB which is 31.6 times the voltage and 1000 times the power. The linear LM3914 has a range of only 20dB which is only 10 times the voltage and 100 times the power.