Texas Instruments ADS7844NG4

Overview

ADS7844NG4 from Texas Instruments is a 12-bit, 8-channel SAR analog-to-digital converter with synchronous serial interface, ±1 LSB INL/DNL, 72 dB SINAD, and 200 kHz max throughput at +5 V. It supports single-ended (8-channel) or differential (4-channel) inputs, operates from 2.7 V to 5 V, and integrates an onboard multiplexer-ideal for portable multichannel data loggers requiring low-power, high-accuracy sampling.

For engineers reviewing the ADS7844NG4 datasheet, ADS7844NG4 pinout, ADS7844NG4 application, or ADS7844NG4 equivalent, key selection factors include its 20-lead SSOP package, 12-bit resolution with no missing codes, shutdown mode (<1 µW), reference voltage flexibility (100 mV to VCC), and compatibility with isolated serial acquisition systems.

Technical Context

The ADS7844NG4 implements a capacitive redistribution successive approximation register (SAR) architecture with integrated sample/hold, enabling precise digitization without external hold circuitry. Its eight-channel analog multiplexer supports configurable single-ended or differential input routing via SGL/DIF and A2–A0 control bits transmitted serially over DIN.

Digital operation relies on a 16-clock-per-conversion protocol (extendable to 15 clocks with FPGA/ASIC control), with BUSY signaling conversion status and DOUT synchronized to DCLK falling edge. Power management includes auto power-down (PD1=PD0=0) and hardware SHDN pin, both delivering sub-µA quiescent current while preserving instant wake-up and valid first-conversion timing.

Key Specifications

Pinout & Package

The ADS7844NG4 is housed in a 20-lead SSOP (Shrink Small Outline Package) with 0.65 mm lead pitch, RoHS-compliant, and rated for –40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit SAR ADC applications.

Compared with MAX147ACPP+, the ADS7844NG4 delivers superior dynamic performance (72 dB vs. 69 dB SINAD) and tighter linearity (±1 vs. ±2 LSB), making it preferable for precision data acquisition; versus ADS7841IPW, it provides full 8-channel support and COM-referenced single-ended operation essential for sensor array interfaces.

Availability

ADS7844NG4 is available at Aetrix Electronics and suitable for portable medical devices, industrial process controllers, and battery-powered test instrumentation requiring stable component supply across extended production lifecycles.

Supply support for ADS7844NG4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision data converters and low-power signal chain solutions.

The ADS7844NG4 belongs to TI's precision SAR ADC product line, designed specifically for portable, multichannel measurement systems demanding high resolution, low power, and flexible input configuration without external multiplexing.

FAQ

What is the maximum sampling rate of the ADS7844NG4 at 2.7 V supply?

The ADS7844NG4 achieves a maximum throughput rate of 125 kHz when operated at +2.7 V supply, VREF = +2.5 V, and fCLK = 2 MHz. This is specified in the SBAS100A datasheet Section "SPECIFICATION: +2.7V" and reflects reduced clock speed and settling constraints at lower supply voltage. The ADS7844NG4 maintains full 12-bit performance and ±1 LSB linearity at this rate.

Does the ADS7844NG4 support true differential input mode?

Yes, the ADS7844NG4 supports true differential input mode using four of its eight channels (e.g., CH0/CH1, CH2/CH3, etc.) as defined by Table II in the SBAS100A datasheet. When SGL/DIF = LOW and appropriate A2–A0 bits are set, the internal multiplexer routes complementary signals to +IN and –IN, enabling common-mode rejection and improved noise immunity-critical for sensor bridge or thermocouple applications.

How does the reference input current vary with sample rate on the ADS7844NG4?

The ADS7844NG4 reference input current scales linearly with sample rate: at 12.5 kHz it draws 2.5 µA, rising to ~40 µA at 125 kHz (2.7 V) and ~100 µA at 200 kHz (5 V), as shown in Figure 8 of SBAS100A. This behavior stems from charge redistribution during each bit decision in the CDAC array, and must be accounted for when selecting reference buffers or low-impedance sources.

Can the ADS7844NG4 operate with a 1.8 V reference voltage?

Yes, the ADS7844NG4 accepts VREF from 100 mV to VCC, so a 1.8 V reference is fully supported when VCC ≥ 1.8 V. With VREF = 1.8 V, the LSB size is 439 µV (1.8 V / 4096), and the device retains ±1 LSB INL/DNL. However, SNR degrades slightly due to reduced signal swing, and layout care (bypassing, grounding, noise isolation) becomes more critical to maintain effective resolution.

What is the function of the COM pin on the ADS7844NG4?

The COM pin on the ADS7844NG4 serves as the analog ground reference for single-ended input mode. When SGL/DIF = HIGH, each selected channel (CH0–CH7) is measured relative to COM, which should be connected to a clean system AGND or a stable bias voltage. In differential mode, COM is unused. Its proper connection directly impacts offset accuracy and zero-code stability-floating COM causes unpredictable baseline shifts in digitized outputs.