Analog Devices Inc. LTC1726IS8-5#PBF

Overview

LTC1726IS8-5#PBF from Analog Devices (formerly Linear Technology) is a triple supply monitor and microprocessor supervisory IC with adjustable reset timeout, adjustable watchdog timer, and active-low open-drain RST output. It monitors 5V, 3.3V, and an adjustable input (VCCA) with ±1.5% threshold accuracy over temperature, 16µA typical supply current, and guaranteed RST assertion down to VCC3 ≥ 1V or VCC5 ≥ 1V - ideal for reliable power-up sequencing in desktop and notebook computers.

For engineers reviewing the LTC1726IS8-5#PBF datasheet, LTC1726IS8-5#PBF pinout, LTC1726IS8-5#PBF application, or LTC1726IS8-5#PBF equivalent, key selection criteria include its triple-supply monitoring capability with independent VCC5/VCC3/VCCA thresholds, capacitor-adjustable reset and watchdog periods (tRT = 3.30·CRT, tWT = 21.8·CWT), glitch immunity, and SO-8 package compatibility with industrial temperature range (–40°C to +85°C).

Technical Context

The LTC1726IS8-5#PBF implements three independent voltage comparators with precision bandgap references, each feeding into a common reset logic block. Its internal power-detect circuit selects either VCC3 or VCC5 as the supply rail based on relative voltage magnitude, ensuring RST remains valid down to 1V on either rail.

Reset assertion is triggered when any monitored supply falls below its trip point (VRT5 = 4.675V typ, VRT3 = 3.085V typ, VRTA = 1.000V typ); deassertion occurs only after all supplies exceed thresholds and the external RT capacitor times out. The watchdog function clears on WDI edge transitions and asserts RST if no transition occurs within the CWT-defined period.

Key Specifications

Pinout & Package

Package: 8-Lead Plastic Small Outline (SO-8), narrow body (0.150"), RoHS-compliant lead-free finish, operating temperature range –40°C to +85°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1727-5 and LTC1326-5, the LTC1726IS8-5#PBF uniquely balances adjustable timing, integrated watchdog, and industrial temperature rating in an SO-8 package - making it optimal for cost-sensitive, space-constrained systems requiring both supervision and software liveness assurance.

Availability

LTC1726IS8-5#PBF is available at Aetrix Electronics and suitable for desktop computers, notebook computers, and intelligent instruments requiring stable component supply with guaranteed long-term availability and consistent parametric performance.

Supply support for LTC1726IS8-5#PBF 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 product support, datasheet documentation, and manufacturing continuity for legacy Linear parts including the LTC1726 family.

The LTC1726 belongs to Linear's precision power supervision product line, designed specifically for reliable multi-rail monitoring and watchdog protection in computing, instrumentation, and communications infrastructure equipment.

FAQ

What is the operating temperature range for the LTC1726IS8-5#PBF?

The LTC1726IS8-5#PBF is rated for operation from –40°C to +85°C, matching the Industrial temperature grade ('I' suffix). This range is validated across all electrical specifications including threshold accuracy, supply current, and timing parameters - ensuring robust performance in demanding environments like network server chassis or portable test equipment where ambient temperatures fluctuate widely.

How do I configure the LTC1726IS8-5#PBF to monitor only two supplies instead of three?

The LTC1726IS8-5#PBF can be configured for dual-supply monitoring by tying the unused VCCA pin (Pin 3) to either VCC3 or VCC5. For example, to monitor only 5V and 3.3V, connect VCCA to VCC3 - this disables the adjustable threshold function while preserving full accuracy on the two active rails. The part's internal logic automatically ignores VCCA when its voltage matches VCC3 within ±25mV.

What capacitor values are recommended for a 155ms reset timeout and 1s watchdog timeout with the LTC1726IS8-5#PBF?

Using the formulas tRT = 3.30·CRT and tWT = 21.8·CWT (with t in µs and C in pF), a 155ms reset timeout requires CRT = 155,000 / 3.30 ≈ 47,000pF (47nF), and a 1s watchdog timeout requires CWT = 1,000,000 / 21.8 ≈ 45,870pF (47nF). Ceramic capacitors are recommended for both due to low leakage; X7R or C0G dielectrics ensure stable timing across temperature and voltage.

Does the LTC1726IS8-5#PBF support manual reset functionality?

Yes - the LTC1726IS8-5#PBF supports manual reset via an external push-button switch connected between WDI (Pin 5) and GND (Pin 4), as shown in Typical Application TA09. Pressing the button pulls WDI low, which triggers the watchdog timer and forces RST assertion. No additional components are required beyond the switch and optional series resistor for ESD protection.

Can the LTC1726IS8-5#PBF be used with a 2.5V main supply instead of 5V?

No - the LTC1726IS8-5#PBF is specifically configured for 5V/3.3V/ADJ monitoring (indicated by the '-5' suffix). For 2.5V systems, the pin-compatible LTC1726IS8-2.5#PBF must be used, which has different internal thresholds (VRT25 = 2.337V typ) and disables the VCC5 input. Using the -5 version with 2.5V on VCC5 will prevent proper power-up sequencing and may cause persistent RST assertion.