Analog Devices Inc. LTC1861IS8#TRPBF

Overview

LTC1861IS8#TRPBF from Analog Devices (formerly Linear Technology) is a 12-bit, 250ksps, 2-channel software-selectable multiplexed successive approximation ADC in an 8-lead SOIC package, operating on a single 5V supply with 850µA typical supply current and auto-shutdown to 1nA between conversions. It features SPI/MICROWIRE-compatible serial I/O, adjustable reference input, and high-impedance analog inputs enabling direct connection to signal sources in portable instrumentation.

For engineers reviewing the LTC1861IS8#TRPBF datasheet, LTC1861IS8#TRPBF pinout, LTC1861IS8#TRPBF application, or LTC1861IS8#TRPBF equivalent, key selection criteria include its 2-channel MUX capability in SO-8 form factor, guaranteed operation from –40°C to +85°C, differential/single-ended input flexibility, and compatibility with external references down to 1V full-scale.

Technical Context

The LTC1861IS8#TRPBF implements a switched-capacitor SAR architecture with integrated sample-and-hold, supporting both differential and single-ended acquisition modes via a 2-bit configuration word shifted into SDI. Its internal MUX allows channel selection between CH0/CH1 with configurable polarity, enabling four distinct input configurations per conversion cycle.

It uses a 3-wire serial interface (SCK, SDO, SDI) with CONV-controlled timing: rising edge initiates conversion, falling edge enables data readout, and sustained high CONV forces auto-shutdown. In the SO-8 variant, VREF is internally tied to VCC, fixing the full-scale span to VCC, unlike the MSOP version which supports external reference voltages from 1V to VCC.

Key Specifications

Pinout & Package

Package: 8-lead plastic SOIC (narrow, 0.150-inch width), JEDEC MS-012, with θJA = 175°C/W 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, serial-interface ADC applications.

Compared with LTC1861IS8#TRPBF, LTC1864CS8#PBF trades channel count for resolution and requires external reference design, while ADS7822U reduces complexity and power at the expense of sampling speed and input flexibility-making LTC1861IS8#TRPBF optimal for dual-sensor, SO-8 constrained, industrial-temp applications requiring software-configurable acquisition.

Availability

LTC1861IS8#TRPBF is available at Aetrix Electronics and suitable for portable instrumentation, industrial sensor interfaces, and isolated remote monitoring requiring stable component supply, extended temperature operation, and compact SOIC packaging.

Supply support for LTC1861IS8#TRPBF 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

Analog Devices acquired Linear Technology in 2017 and maintains its high-performance analog IC portfolio, emphasizing precision, power efficiency, and robustness in signal conditioning and data conversion.

The LTC1861IS8#TRPBF belongs to Linear's µPower SAR ADC family, designed specifically for battery-operated and space-constrained systems needing high-speed, low-power, multi-channel digitization without sacrificing DC accuracy or AC performance.

FAQ

What is the maximum sampling rate of the LTC1861IS8#TRPBF across its full operating temperature range?

The LTC1861IS8#TRPBF guarantees a maximum sampling rate of 250ksps from –40°C to +85°C. This is confirmed in the Recommended Operating Conditions table under fSMPL(MAX) with H-grade specification, and supported by timing characteristics showing tCONV ≤ 3.3µs and minimum tCYC compatible with 250kHz cycles. The LTC1861IS8#TRPBF maintains this rate without derating in industrial environments.

Does the LTC1861IS8#TRPBF require an external reference voltage, or is it internally generated?

The LTC1861IS8#TRPBF does not require an external reference voltage because its SO-8 package internally ties VREF to VCC. As stated in the Applications Information section, "The reference input of the LTC1861 SO-8 package is internally tied to VCC," making the full-scale span equal to the supply voltage (4.75V–5.25V). Therefore, no external reference component is needed for the LTC1861IS8#TRPBF.

How many analog input channels does the LTC1861IS8#TRPBF support, and how is channel selection performed?

The LTC1861IS8#TRPBF supports two analog input channels (CH0 and CH1) with software-selectable multiplexing. Channel selection is performed by shifting a 2-bit configuration word into the SDI pin during the CONV-low period before data readout. As shown in Table 1, these bits define four combinations: single-ended CH0/GND, CH1/GND, or differential CH0–CH1 and CH1–CH0. This functionality is intrinsic to the LTC1861IS8#TRPBF and does not require external MUX hardware.

What is the supply current consumption of the LTC1861IS8#TRPBF during active conversion versus standby mode?

The LTC1861IS8#TRPBF draws 850µA typical supply current during active 250ksps conversion, and automatically powers down to 1nA typical between conversions when CONV remains high. This auto-shutdown behavior is explicitly documented in the Features list and verified in the Supply Current vs Sampling Frequency graph (Figure G01), where current drops below 0.01µA at frequencies <1Hz. This dual-state current profile is a core feature of the LTC1861IS8#TRPBF.

Is the LTC1861IS8#TRPBF pin-compatible with other members of the LTC1860/LTC1861 family, such as the LTC1860IS8#TRPBF?

No, the LTC1861IS8#TRPBF is not pin-compatible with the LTC1860IS8#TRPBF. While both use the same 8-lead SOIC package, their pinouts differ: LTC1861IS8#TRPBF uses Pins 2–3 for CH0/CH1 and Pin 5 for SDI, whereas LTC1860IS8#TRPBF uses Pins 2–3 for IN+/IN– and has no SDI pin. The functional block diagram and Pin Functions section confirm this distinction, making direct substitution impossible without PCB redesign for the LTC1861IS8#TRPBF.