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ADS1115 IC Pinout Explorer Guide & Tips:
1. The ADDR (Address) Pin
Do not leave this floating. The ADS1115 uses this pin to determine its I2C address.
Connect to GND: Address is
0x48(Standard/Default).Connect to VDD: Address is
0x49.Connect to SDA: Address is
0x4A.Connect to SCL: Address is
0x4B.
Pro Tip: This allows you to connect up to four ADS1115 chips to the same Arduino using only two wires (SDA/SCL)!
2. The ALERT/RDY Pin
Leave it floating (disconnected) if not used. This pin is an "interrupt" pin. It can be programmed to trigger (go LOW) when a conversion is finished or when a voltage crosses a certain threshold.
If you don't need interrupts: Leave it alone. It does not need to be grounded.
If you use it: You usually connect it to an Arduino digital pin (like D2) and use a $10k\Omega$ pull-up resistor to VDD.
3. The Analog Input Pins (A0, A1, A2, A3)
Leave them floating if unused.
Unlike some high-speed operational amplifiers that can oscillate if inputs are floating, the ADS1115 is a sigma-delta converter and is generally stable.
Should you ground them? You can ground them to ensure they read "0" and don't pick up electromagnetic noise (ghost voltages) in your code, but it is not electrically required for the chip to operate.
Important: Never apply a voltage to these pins that is higher than VDD + 0.3V. If you are powering the chip with 3.3V, a 5V signal will damage it.
4. The VDD and GND Pins
VDD: Connect to 2.0V–5.5V.
GND: Connect to the common ground of your Arduino.
Decoupling: It is a "best practice" to place a 0.1µF capacitor between VDD and GND as close to the chip as possible to filter out power supply noise. Since you're dealing with 16-bit precision, even tiny power ripples can affect your readings!
