Analog Devices Inc. LTC1726ES8-5#PBF

Overview

LTC1726ES8-5#PBF from Analog Devices (formerly Linear Technology) is a triple supply monitor and microprocessor supervisory IC with adjustable reset and watchdog timer functions, designed for systems requiring simultaneous monitoring of 5V, 3.3V, and an adjustable voltage rail. It features ±1.5% threshold accuracy over temperature, 16µA typical supply current, and guaranteed RST assertion down to VCC3 ≥ 1V or VCC5 ≥ 1V - enabling reliable power-up sequencing in desktop computers and network servers.

For engineers reviewing the LTC1726ES8-5#PBF datasheet, LTC1726ES8-5#PBF pinout, LTC1726ES8-5#PBF application, or LTC1726ES8-5#PBF equivalent, key selection considerations include its dual-supply override capability (VCC5 disabled when within ±25mV of VCC3 below 4.15V), open-drain active-low RST output with weak internal pull-up to VCC3, and capacitor-adjustable reset/watchdog timeouts (tRT = 3.30·CRT, tWT = 21.8·CWT).

Technical Context

The LTC1726ES8-5#PBF implements three independent voltage comparators with precision bandgap references to monitor VCC5 (4.675V typ), VCC3 (3.085V typ), and VCCA (1.000V typ) thresholds. Its internal power-detect logic selects either VCC5 or VCC3 as the primary supply source depending on relative voltage levels, ensuring RST remains asserted until both reach ≥1V.

Reset timing is governed by an external capacitor on RT (tRT = 3.30·CRT, e.g., 47nF → 155ms), while watchdog timeout is set via WT capacitor (tWT = 21.8·CWT, e.g., 47nF → 1s). The WDI input requires periodic edge transitions to prevent timeout-induced reset, and the part supports watchdog disable by grounding WDI and WT.

Key Specifications

Pinout & Package

Package: 8-Lead Plastic SO (S8), 0.150-inch narrow body, 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#PBF, LTC1726ES8-5#PBF reduces pin count and routing complexity via shared RST, while compared with LTC1326-5#PBF it trades minor accuracy degradation for integrated watchdog and dynamic rail selection - making it optimal for general-purpose embedded systems requiring balanced performance and integration.

Availability

LTC1726ES8-5#PBF is available at Aetrix Electronics and suitable for desktop computers, notebook computers, and network servers requiring stable component supply with guaranteed long-term availability and full traceability.

Supply support for LTC1726ES8-5#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, manufacturing, and documentation for legacy Linear parts including the LTC1726 series.

The LTC1726 belongs to Linear's precision power supervision product line, engineered for high-reliability computing and communications systems where deterministic reset behavior and multi-rail coordination are critical.

FAQ

What is the function of the VCCA pin on the LTC1726ES8-5#PBF?

The VCCA pin on the LTC1726ES8-5#PBF is a high-impedance 1V nominal input used to monitor an adjustable voltage rail - commonly configured with a resistor divider to supervise voltages like 1.8V or 2.5V. It can be tied directly to VCC3 or VCC5 if unused, and its threshold is guaranteed accurate to ±1.5% over temperature. The LTC1726ES8-5#PBF uses this pin alongside VCC5 and VCC3 to provide true triple-supply monitoring capability.

How does the VCC5 override feature work in the LTC1726ES8-5#PBF?

The LTC1726ES8-5#PBF disables its 5V monitoring function when VCC5 is within ±25mV of VCC3 and below approximately 4.15V, effectively converting the device into a 3.3V + adjustable rail monitor. This prevents spurious RST deassertion during slow 5V ramp-up through the 3.1V–4.15V region. The LTC1726ES8-5#PBF resumes full 5V monitoring once VCC5 exceeds 4.15V or deviates >±25mV from VCC3.

What capacitor values are needed to achieve a 155ms reset timeout and 1s watchdog timeout on the LTC1726ES8-5#PBF?

To achieve a 155ms reset timeout, connect a 47nF capacitor between RT (Pin 8) and GND, since tRT = 3.30·CRT yields 155ms for CRT = 47nF. For a 1s watchdog timeout, use a 47nF capacitor between WT (Pin 7) and GND, as tWT = 21.8·CWT gives ~1s for CWT = 47nF. The LTC1726ES8-5#PBF datasheet confirms these values in Typical Application TA01 and TA02.

Can the LTC1726ES8-5#PBF operate with only two supply rails active?

Yes, the LTC1726ES8-5#PBF can monitor one or two rails instead of all three - for example, using only VCC5 and VCC3 while tying VCCA to VCC3, or disabling the watchdog by grounding WDI and WT. The LTC1726ES8-5#PBF maintains full reset supervision functionality in these configurations, with RST asserted whenever any active monitored rail falls below its threshold.

What is the minimum supply voltage required for the LTC1726ES8-5#PBF to guarantee correct RST logic state?

The LTC1726ES8-5#PBF guarantees correct RST logic state (low during undervoltage, high after timeout) for VCC3 ≥ 1V or VCC5 ≥ 1V. Below 1V on both VCC3 and VCC5, RST behavior is not specified. This 1V minimum ensures robust reset assertion during brownout conditions, and the LTC1726ES8-5#PBF continues to monitor all inputs down to this level.