Texas Instruments ADS7844N

Overview

ADS7844N from Texas Instruments is a 12-bit, 8-channel SAR analog-to-digital converter with synchronous serial interface, single-supply operation (2.7V–5V), ±1 LSB INL/DNL, and up to 200kHz throughput at +5V - used in portable data loggers, battery-powered test equipment, and multichannel industrial sensing systems.

For engineers reviewing the ADS7844N datasheet, ADS7844N pinout, ADS7844N application, or ADS7844N equivalent, key selection criteria include its 20-lead SSOP package, differential/single-ended input flexibility, 72dB SINAD at 10kHz, shutdown mode (<1µW), and compatibility with isolated serial interfaces in remote acquisition.

Technical Context

The ADS7844N implements a capacitive redistribution SAR architecture with integrated sample/hold, requiring an external reference (100mV to VCC) and external clock (fCLK = 16 × fSAMPLE). Its eight-channel analog multiplexer supports both single-ended (8 channels referenced to COM) and differential (4 channel pairs) configurations via SGL/DIF and A2–A0 control bits.

Digital interface uses CMOS-level serial protocol with 24-clock (standard) or 16-clock (overlapped) conversion cycles; BUSY and DOUT are high-impedance when CS is high. Power management includes auto power-down (PD1=PD0=0) and hardware shutdown (SHDN low), enabling sub-µW standby without wake-up latency.

Key Specifications

Pinout & Package

ADS7844N is housed in a 20-lead SSOP (DB) package with 0.65mm lead pitch, optimized for compact PCB layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS7844E and MAX147ACPP, the ADS7844N provides identical performance in a space-saving SSOP package with dedicated SHDN pin for deterministic ultra-low-power states - making it optimal for new designs prioritizing board area and battery efficiency.

Availability

ADS7844N is available at Aetrix Electronics and suitable for portable instrumentation, industrial data loggers, and battery-powered test equipment requiring stable component supply across extended production lifecycles.

Supply support for ADS7844N 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, embedded processing, and connectivity technologies with broad industrial and automotive design expertise.

The ADS7844N belongs to TI's precision data acquisition portfolio, engineered for low-power, multichannel measurement in portable and distributed sensing applications where size, accuracy, and energy efficiency are critical.

FAQ

What is the maximum sampling rate of the ADS7844N and under what conditions?

The ADS7844N achieves up to 200kHz throughput when operated at +5V supply, VREF = +5V, and fCLK = 3.2MHz (16 × fSAMPLE). At +2.7V supply with VREF = +2.5V, the maximum rate drops to 125kHz. These rates assume standard 24-clock conversion cycles; overlapping 16-clock mode maintains timing but does not increase absolute throughput beyond datasheet limits. The ADS7844N specification defines these values under –40°C to +85°C ambient conditions.

Does the ADS7844N support differential input mode, and how is it configured?

Yes, the ADS7844N supports differential input mode using four of its eight channels (e.g., CH0–CH1, CH2–CH3, etc.) as paired inputs. Configuration is done via the SGL/DIF control bit in the serial command byte: when SGL/DIF = LOW, the A2–A0 bits select one of four differential pairs. The ADS7844N datasheet Table II defines exact channel mapping. In this mode, COM is unused, and the input range becomes ±VREF/2 relative to the selected –IN channel.

What is the purpose of the COM pin on the ADS7844N, and how should it be connected?

The COM pin serves as the analog ground reference for single-ended input mode on the ADS7844N. It sets the zero-code voltage - when COM is grounded, CH0–CH7 measure 0V to VREF. If COM is biased to a non-zero voltage (e.g., 0.5V), the input range shifts accordingly (e.g., 0.5V to VREF + 0.5V). In differential mode, COM is not used and may be left unconnected. For best accuracy, COM must be tied to a low-impedance, noise-free ground point separate from digital ground.

How does the ADS7844N handle power management, and what are the differences between SHDN and PD1/PD0 modes?

The ADS7844N provides two independent power control mechanisms: hardware SHDN (pin 10) forces immediate sub-1µW shutdown regardless of serial state, while PD1/PD0 bits in the control byte enable auto power-down between conversions (PD1=PD0=0). SHDN overrides all other states; PD1/PD0 only affects operation when CS is active. The ADS7844N resumes full operation instantly after SHDN release or PD1/PD0 transition - no wake-up delay or invalid first conversion occurs.

Can the ADS7844N operate with a reference voltage lower than 1V, and what impact does that have on performance?

Yes, the ADS7844N accepts VREF as low as 100mV, but LSB size scales linearly (e.g., 24µV at 100mV), exposing internal noise and increasing effective INL/DNL in LSB units. Offset and gain errors remain fixed in volts but appear larger numerically. The ADS7844N datasheet warns that below ~500mV, noise dominates, requiring oversampling or digital filtering. Stable low-noise layout, clean bypassing, and low-ripple supplies become essential - the ADS7844N itself remains functional but system-level SNR degrades.