Beschreibung

The ADS1113, ADS1114, and ADS1115 (ADS111x) are precision, low-power, 16-bit, I2C-compatible, analog-to-digital converters (ADCs) offered in a leadless X2QFN-10, a SOT-10 package, and a VSSOP-10 package. The ADS111x devices incorporate a low-drift voltage reference and an oscillator. The ADS1114 and ADS1115 also incorporate a programmable gain amplifier (PGA) and a digital comparator. These features, along with a wide operating supply range, are useful for power- and space-constrained, sensor measurement applications.
The ADS111x devices perform conversions at data rates of up to 860 samples per second (SPS). The PGA offers input ranges from ±256mV to ±6.144V, allowing precise large- and small-signal measurements. The ADS1115 features an input multiplexer (MUX) that allows two differential or four single-ended input measurements. Use the digital comparator in the ADS1114 and ADS1115 for undervoltage and overvoltage detection.

 

Eigenschaften

• Ultra-small packages:
– X2QFN: 2mm × 1.5mm × 0.4mm
– SOT: 2.9mm × 2.8mm × 0.6mm
• Wide supply range: 2.0V to 5.5V
• Low current consumption: 150μA (continuous-conversion mode)
• Programmable data rate: 8SPS to 860SPS
• Single-cycle settling
• Internal low-drift voltage reference
• Internal oscillator
• I²C interface: four pin-selectable addresses
• Operating temperature range:–40°C to +125°C
• Family of devices:
– ADS1113: one single-ended (SE) or differential (DE) input
– ADS1114: one single-ended or differential input with comparator and PGA
– ADS1115: four single-ended or two differential inputs with comparator and PGA

 

Anwendungen

• Portable instrumentation
• Battery voltage and current monitoring
• Temperature measurement systems
• Consumer electronics
• Factory automation and process control

 

Noise Performance

Delta-sigma (ΔΣ) analog-to-digital converters (ADCs) are based on the principle of oversampling. The input signal of a ΔΣ ADC is sampled at a high frequency (modulator frequency) and subsequently filtered and decimated in the digital domain to yield a conversion result at the respective output data rate. The ratio between modulator frequency and output data rate is called oversampling ratio (OSR). By increasing the OSR, and thus reducing the output data rate, the noise performance of the ADC can be optimized. In other words, the input-referred noise drops when reducing the output data rate because more samples of the internal modulator are averaged to yield one conversion result. Increasing the gain also reduces the input-referred noise, which is particularly useful when measuring low-level signals.

 

Übersicht

The ADS111x devices are very small, low-power, 16-bit, delta-sigma (ΔΣ) analog-to-digital converters (ADCs). The ADS111x consist of a ΔΣ ADC core with an internal voltage reference, a clock oscillator, and an I²C interface. The ADS1114 and ADS1115 also integrate a programmable gain amplifier (PGA) and a programmable digital comparator.
The ADS111x ADC core measures a differential signal, VIN, that is the difference of V(AINP) and V(AINN). The converter core consists of a differential, switched-capacitor ΔΣ modulator followed by a digital filter. This architecture results in a very strong attenuation of any common-mode signals. Input signals are compared to the internal voltage reference. The digital filter receives a high-speed bitstream from the modulator and outputs a code proportional to the input voltage.
The ADS111x have two available conversion modes: single-shot and continuous-conversion. In single-shot mode, the ADC performs one conversion of the input signal upon request, stores the conversion value to an internal conversion register, and then enters a power-down state. This mode is intended to provide significant power savings in systems that only require periodic conversions or when there are long idle periods between conversions. In continuous-conversion mode, the ADC automatically begins a conversion of the input signal as soon as the previous conversion is completed. The rate of continuous conversion is equal to the programmed data rate. Data can be read at any time and always reflect the most recent completed conversion.

 

Analoge Eingänge

The ADS111x use a switched-capacitor input stage where capacitors are continuously charged and then discharged to measure the voltage between AINP and AINN. The frequency at which the input signal is sampled is called the sampling frequency or the modulator frequency (fMOD). The ADS111x has a 1MHz internal oscillator that is further divided by a factor of 4 to generate fMOD at 250kHz. The capacitors used in this input stage are small, and to external circuitry, the average loading appears resistive.