Overview

The ADS1115 is an ultra-small, low-power, 16-bit precision analog-to-digital converter (ADC) manufactured by Texas Instruments. It features 4 single-ended or 2 differential input channels, an onboard Programmable Gain Amplifier (PGA), a low-drift voltage reference, an internal oscillator, and a digital I2C interface.

It is widely used to add high-resolution analog measurement capabilities to microcontrollers that lack analog inputs (such as the Raspberry Pi) or require precision beyond standard 10-bit MCU ADCs.

Quick reference

Supply voltage (VDD)2.0 V to 5.5 V DC
ADC resolution16-bit (65,536 steps) / 15-bit single-ended
Input channels4 Single-Ended (A0–A3) or 2 Differential pairs
Programmable gain (PGA)23×,1×,2×,4×,8×,16×\frac{2}{3}\times, 1\times, 2\times, 4\times, 8\times, 16\times (FSR ±0.256 V\pm 0.256\text{ V} to ±6.144 V\pm 6.144\text{ V})
Programmable sample rate8 SPS to 860 SPS
Communication interfaceI2C (address selectable 0x48–0x4B)
Operating current150 µA typical (continuous mode), 0.5 µA (power-down)

Pinout

Standard ADS1115 Breakout Module Header

PinNameTypeDescription
1VDDPowerSupply voltage (+2.0 V to +5.5 V DC)
2GNDPowerGround (0 V)
3SCLDigital InputI2C Serial Clock line
4SDADigital I/OI2C Serial Data line
5ADDRDigital InputI2C Slave Address select pin
6ALRT / RDYDigital OutputActive-LOW Comparator Alert or Conversion Ready output
7A0Analog InputAnalog input channel 0
8A1Analog InputAnalog input channel 1
9A2Analog InputAnalog input channel 2
10A3Analog InputAnalog input channel 3

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVDDV_{DD}2.03.35.5VDC
Operating CurrentIDDI_{DD}—150200µAContinuous mode
Power-down CurrentIPDI_{PD}—0.52.0µAPower-down mode
Full-Scale Range (PGA = 2/3)FSRFSR—±6.144\pm 6.144—VVINV_{IN} cannot exceed VDD+0.3 VV_{DD} + 0.3\text{ V}
Full-Scale Range (PGA = 1)FSRFSR—±4.096\pm 4.096—V
Full-Scale Range (PGA = 2)FSRFSR—±2.048\pm 2.048—V
Full-Scale Range (PGA = 16)FSRFSR—±0.256\pm 0.256—VMax sensitivity: 7.8125 μV/LSB7.8125\text{ }\mu\text{V/LSB}
Sample RatefSPSf_{SPS}8—860SPSProgrammable via Config Register

I2C Addressing & PGA Settings

Hardware Address Selection (ADDR Pin)

Connection on ADDR PinI2C Slave Address (Hex)
Connect to GND0x48 (Default)
Connect to VDD0x49
Connect to SDA0x4A
Connect to SCL0x4B

PGA Gain vs Resolution Voltage (VLSBV_{LSB})

PGA GainFull-Scale Range (FSR)LSB Voltage (VLSB=FSR32768V_{LSB} = \frac{FSR}{32768})
2/3±6.144 V\pm 6.144\text{ V}187.5 μV187.5\text{ }\mu\text{V}
1±4.096 V\pm 4.096\text{ V}125.0 μV125.0\text{ }\mu\text{V}
2±2.048 V\pm 2.048\text{ V}62.5 μV62.5\text{ }\mu\text{V}
4±1.024 V\pm 1.024\text{ V}31.25 μV31.25\text{ }\mu\text{V}
8±0.512 V\pm 0.512\text{ V}15.625 μV15.625\text{ }\mu\text{V}
16±0.256 V\pm 0.256\text{ V}7.8125 μV7.8125\text{ }\mu\text{V}

Wiring

ADS1115 Module Pin→Microcontroller (Arduino / ESP32 / Raspberry Pi)
VDD5V (or 3.3V)
GNDGND
SDASDA (A4 on Uno, GPIO21 on ESP32, Pin 3 on Pi)
SCLSCL (A5 on Uno, GPIO22 on ESP32, Pin 5 on Pi)
ADDRGND (for default address 0x48)
Warning

Absolute Maximum Input Voltage Limit: Even when PGA gain is set to 2/3 (FSR=±6.144 V\text{FSR} = \pm 6.144\text{ V}), the analog input voltage on pins A0–A3 MUST NOT exceed VDD+0.3 VV_{DD} + 0.3\text{ V}. Supplying 6V to A0 while VDD=3.3 VV_{DD} = 3.3\text{ V} will damage the internal protection diodes.

Common mistakes

  • Exceeding VDDV_{DD} on analog inputs: Assuming PGA 2/3 allows measuring up to 6.144 V when powering the chip with 3.3V. Input voltages must always stay within GND−0.3 V≤VIN≤VDD+0.3 VGND - 0.3\text{ V} \le V_{IN} \le V_{DD} + 0.3\text{ V}.
  • Not handling negative values in differential mode: In differential mode (A0 vs A1), readings range from -32768 to +32767. Store results in a signed 16-bit integer (int16_t).
  • Ignoring single-ended resolution limit: In single-ended mode, negative voltages cannot be measured relative to GND. Effective single-ended resolution is 15-bit (0 to 32,767 counts).

Notes

  • Internal voltage reference accuracy is ±0.15%\pm 0.15\% typical over temperature.

Assets & downloads