) between the REF OUT pin (Pin 7) and the REF ADJ pin (Pin 8). By connecting two external resistors, R1cap R sub 1 R2cap R sub 2
VREF=1.25×(1+R2R1)+(IADJ×R2)cap V sub cap R cap E cap F end-sub equals 1.25 cross open paren 1 plus the fraction with numerator cap R sub 2 and denominator cap R sub 1 end-fraction close paren plus open paren cap I sub cap A cap D cap J end-sub cross cap R sub 2 close paren Where: R1cap R sub 1 is the resistor connected between Pin 7 and Pin 8. R2cap R sub 2 is the resistor connected between Pin 8 and Ground. IADJcap I sub cap A cap D cap J end-sub
components = calculate_components(Vin, Vref, gain)
VREF=1.25×(1+R2R1)+(IADJ×R2)cap V sub cap R cap E cap F end-sub equals 1.25 cross open paren 1 plus the fraction with numerator cap R sub 2 and denominator cap R sub 1 end-fraction close paren plus open paren cap I sub cap A cap D cap J end-sub cross cap R sub 2 close paren Where: VREFcap V sub cap R cap E cap F end-sub is the target full-scale voltage. R1cap R sub 1 is the resistor connected between Pin 7 and Pin 8. R2cap R sub 2 is the resistor connected between Pin 8 and Ground. IADJcap I sub cap A cap D cap J end-sub is the current flowing out of Pin 8 (typically a negligible For simplified standard calculations, the IADJcap I sub cap A cap D cap J end-sub term is often omitted if R2cap R sub 2 is relatively low: lm3915 calculator updated
Under normal operation, inputs can go down to 0V and up to within 1.5V of V+cap V raised to the positive power The Mathematical Formulas
close to 3.3V–5V, or insert a power resistor in series with the LED anodes to drop excess voltage.
<div style="margin-bottom:15px;"> <h3>Calculate LED Current:</h3> <label>R1 Resistor Value (Ω): </label> <input type="number" id="resistorValue"> <button onclick="calcCurrent()">Calculate</button> <p>LED Current: <strong id="currentResult">--</strong> mA</p> </div> ) between the REF OUT pin (Pin 7)
For most standard applications, an LED current of 10mA to 20mA is ideal, meaning R1cap R sub 1 typically ranges from 3. Total Reference Current
If you are looking for an updated way to calculate resistor values ( R1cap R sub 1 R2cap R sub 2 ) for the LM3915 Logarithmic Dot/Bar Display Driver Go to product viewer dialog for this item.
3V=1200+R21200×1.25V3 V equals the fraction with numerator 1200 plus cap R sub 2 and denominator 1200 end-fraction cross 1.25 V IADJcap I sub cap A cap D cap
Before diving into the calculations, keep these critical parameters from the datasheet in mind: 3V to 25V Reference Voltage Range: 1.2V to 12V LED Current Programmability: 1 mA to 30 mA
R1=12.50.0125=1000Ω (or 1kΩ)cap R sub 1 equals 12.5 over 0.0125 end-fraction equals 1000 space cap omega (or 1 k cap omega ) Step 3: Calculate R2cap R sub 2