Analog Devices Inc. LTC1726IS8-2.5#TRPBF

Overview

LTC1726IS8-2.5#TRPBF from Analog Devices (formerly Linear Technology) is a triple supply monitor and microprocessor supervisory IC designed for systems requiring simultaneous monitoring of 2.5V, 3.3V, and an adjustable voltage rail. It features ±1.5% threshold accuracy over temperature, adjustable reset timeout (via RT pin capacitor), adjustable watchdog timeout (via WT pin capacitor), and guaranteed RST assertion down to VCC3 ≥ 1V or VCC25 ≥ 1V. It is used in notebook computers and portable battery-powered equipment where reliable power-up sequencing and brownout detection are critical.

For engineers reviewing the LTC1726IS8-2.5#TRPBF datasheet, LTC1726IS8-2.5#TRPBF pinout, LTC1726IS8-2.5#TRPBF application, or LTC1726IS8-2.5#TRPBF equivalent, key selection criteria include its 2.5V/3.3V/ADJ triple-monitor capability, 16µA typical supply current, open-drain active-low RST output with weak internal pull-up to VCC3, and compatibility with SO-8 packaging for legacy board designs.

Technical Context

The LTC1726IS8-2.5#TRPBF implements three independent voltage comparators with precision bandgap references to monitor VCC25 (2.5V rail), VCC3 (3.3V rail), and VCCA (adjustable rail, nominal 1V trip). Its reset logic asserts RST low when any monitored supply falls below its specified threshold - VRT25 = 2.337V (±1.5%), VRT3 = 3.085V (±1.5%), VRTA = 1.000V (±1.5%) - and holds RST asserted until all supplies recover and the external CRT capacitor on RT completes its timing cycle.

Watchdog functionality is implemented via a charge/discharge timer on the WT pin, where tWT = 21.8 × CWT (CWT in pF → tWT in µs); a WDI edge resets the timer, and timeout triggers RST assertion. The device derives operating power from whichever of VCC25 or VCC3 reaches ≥1V first, ensuring deterministic RST behavior during asymmetric power-up sequences.

Key Specifications

Pinout & Package

Package: 8-Lead Plastic SO (Small Outline, Narrow 0.150-inch body), RoHS-compliant, lead-free finish, rated for –40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triple-supply monitoring applications.

Compared with LTC1726IS8-2.5#TRPBF, LTC1326-2.5 offers superior threshold precision at the cost of higher quiescent current, while LTC1727-2.5 provides rail-specific reset signaling but increases PCB routing complexity - making LTC1726IS8-2.5#TRPBF optimal for cost-sensitive, space-constrained designs needing balanced accuracy and power efficiency.

Availability

LTC1726IS8-2.5#TRPBF is available at Aetrix Electronics and suitable for notebook computers, intelligent instruments, and portable battery-powered equipment requiring stable component supply across extended product lifecycles.

Supply support for LTC1726IS8-2.5#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 full technical and manufacturing continuity for legacy Linear products including the LTC1726 family.

The LTC1726 series was designed specifically for high-reliability embedded systems requiring simultaneous multi-rail monitoring, adjustable timing, and guaranteed reset behavior under brownout - targeting computing, instrumentation, and portable electronics markets.

FAQ

What is the exact supply voltage monitoring configuration supported by the LTC1726IS8-2.5#TRPBF?

The LTC1726IS8-2.5#TRPBF is factory-configured to monitor three specific rails: VCC25 (2.5V nominal, threshold 2.337V ±1.5%), VCC3 (3.3V nominal, threshold 3.085V ±1.5%), and VCCA (adjustable rail, threshold 1.000V ±1.5%). It does not support 5V monitoring - that function is exclusive to the LTC1726-5 variants. The part automatically selects VCC25 or VCC3 as its power source based on which reaches ≥1V first.

How do I calculate the reset timeout period for the LTC1726IS8-2.5#TRPBF using the RT pin capacitor?

The reset timeout period tRT for the LTC1726IS8-2.5#TRPBF is calculated as tRT = 3.30 × CRT, where CRT is the capacitance (in pF) connected between Pin 8 (RT) and GND, and tRT is in µs. For example, a 47nF (47,000pF) capacitor yields tRT = 3.30 × 47,000 = 155,100µs ≈ 155ms. Ceramic capacitors are recommended due to low leakage; avoid electrolytics or high-DF types.

Can the watchdog timer in the LTC1726IS8-2.5#TRPBF be disabled, and how?

Yes, the watchdog timer in the LTC1726IS8-2.5#TRPBF can be disabled by connecting both Pin 5 (WDI) and Pin 7 (WT) directly to GND. This configuration forces the watchdog circuit into a permanently cleared state, allowing the LTC1726IS8-2.5#TRPBF to operate strictly as a triple-supply monitor with adjustable reset timing. No external components beyond the RT capacitor are required in this mode.

What is the minimum operating voltage required for the RST output to remain valid on the LTC1726IS8-2.5#TRPBF?

The RST output of the LTC1726IS8-2.5#TRPBF is guaranteed to maintain correct logic state (low when asserted, high-impedance when deasserted) for VCC3 ≥ 1V or VCC25 ≥ 1V. Below 1V on both VCC3 and VCC25, the internal circuitry cannot sustain proper biasing, and RST behavior becomes undefined. This 1V guarantee ensures fail-safe reset assertion during deep brownout conditions common in battery-powered systems.

Does the LTC1726IS8-2.5#TRPBF support monitoring a 1.8V rail, and if so, how?

Yes, the LTC1726IS8-2.5#TRPBF supports monitoring a 1.8V rail using the VCCA pin (Pin 3) with an external resistor divider. Since VCCA has a fixed 1.000V ±1.5% threshold, a resistive divider (e.g., R1 = 1.07MΩ, R2 = 105kΩ) scales the 1.8V rail down to ~1.000V at VCCA. The datasheet provides design equations and layout guidance for maintaining ±1.5% overall accuracy, including tolerance stack-up and leakage considerations.