Low-end of the internal resistor divider. Usually tied to ground. Pin 5 (SIG): Analog input signal to be measured.
To help refine your specific design, could you share your target (e.g., phone line-level, amplifier output, sensor), your supply voltage , and whether you prefer Dot or Bar mode ?
A single LM3915 covers 30dB. For pro audio, you want 60dB. The updated calculator includes a "Cascade Mode." You tell it you want a 60dB range from 10mV to 10V. It calculates the top chip's resistors and the bottom chip's resistors, plus the coupling capacitor needed between pin 5 of the first and pin 5 of the second. lm3915 calculator updated
Let's walk through a real-world design scenario using the updated calculation method. Design Goals: Target LED Current ( ILEDcap I sub cap L cap E cap D end-sub ): (Standard brightness for typical 5mm LEDs). Target Peak Reference Voltage ( VREFcap V sub cap R cap E cap F end-sub
<!DOCTYPE html> <html> <head><title>LM3915 Resistor Calculator</title></head> <body> <h2>LM3915 Resistor Calculator</h2> Low-end of the internal resistor divider
). These same resistors simultaneously determine the current flowing through the LEDs, eliminating the need for individual current-limiting resistors for each LED. Key Technical Specifications
Where Vf_LED is the forward voltage drop of your specific LED (Red=1.8V, Green=2.1V, Blue=3.2V). The updated tool has a dropdown menu for LED colors, eliminating guesswork. To help refine your specific design, could you
based on your target LED brightness (typically 10mA to 20mA for standard LEDs).
The total voltage at Pin 7 determines the maximum input voltage ( VINcap V sub cap I cap N end-sub ) required to light the 10th LED.
The update tells you the power dissipation difference. In Dot mode, only one LED is on at a time. In Bar mode, all 10 LEDs could be on simultaneously. The new calculator calculates total system current and warns you if your 7805 regulator will overheat.