Analog Devices Inc. LTC1985ES5-1.8#TRPBF

Overview

LTC1985ES5-1.8 from Analog Devices (formerly Linear Technology) is a micropower precision triple supply monitor IC for systems requiring simultaneous monitoring of 3V, 1.8V, and an adjustable voltage rail. It delivers ±1.5% threshold accuracy over temperature, 10µA typical supply current, and a guaranteed 200ms reset delay. It serves as a system-level power-on reset supervisor in portable battery-powered equipment and notebook computers.

For engineers reviewing the LTC1985ES5-1.8 datasheet, LTC1985ES5-1.8 pinout, LTC1985ES5-1.8 application, or LTC1985ES5-1.8 equivalent, key selection criteria include its dual-supply powering capability (VCC3 or VCC18), push-pull RST output with guaranteed logic state down to 1V, and configurable three-input or reduced-input monitoring modes.

Technical Context

The LTC1985ES5-1.8 integrates three independent voltage comparators referenced to a stable internal bandgap, each with dedicated trip thresholds: 2.805V (VCC3), 1.683V (VCC18), and 1.000V (VCCA). Its 200ms reset pulse generator ensures glitch-immune assertion only after all monitored supplies remain valid for the full delay period.

Power is autonomously drawn from whichever of VCC3 or VCC18 is at higher potential, enabling reliable reset assertion during brownout on either rail. The push-pull RST output drives low until all inputs exceed their thresholds and remains low for ≥200ms after recovery - with VOL ≤ 0.4V at 2.5mA sink and VOH ≥ 0.8×VCC3 when sourcing 200µA.

Key Specifications

Pinout & Package

Package: 5-lead SOT-23 (S5), 2.80–3.00 mm × 1.90 mm × 1.10–1.30 mm, SC-74A compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1728-1.8 and LTC1326, the LTC1985ES5-1.8 uniquely combines push-pull reset drive, 1.8V/3V-specific thresholds, and sub-10µA quiescent current - making it optimal for space-constrained, battery-sensitive designs where rail compatibility and output drive strength are jointly critical.

Availability

LTC1985ES5-1.8 is available at Aetrix Electronics and suitable for notebook computers, portable battery-powered equipment, and intelligent instruments requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance.

Supply support for LTC1985ES5-1.8 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 precision analog and power management product lines with full datasheet, reliability, and support continuity.

The LTC1985ES5-1.8 belongs to Linear's micropower supply monitor family, engineered specifically for multi-rail embedded systems where accuracy, ultra-low current, and autonomous dual-supply operation are essential for robust power sequencing.

FAQ

What is the primary function of the LTC1985ES5-1.8 in a power management system?

The LTC1985ES5-1.8 functions as a precision triple-supply monitor that asserts an active-low reset signal only after all three monitored rails - VCC3 (3V), VCC18 (1.8V), and VCCA (adjustable) - remain above their respective thresholds for a guaranteed 200ms. Its push-pull RST output ensures deterministic logic levels without external components, and its dual-supply powering architecture guarantees reset initiation as soon as either VCC3 or VCC18 reaches 1V - a key capability for brownout resilience in the LTC1985ES5-1.8.

Can the LTC1985ES5-1.8 monitor fewer than three supplies, and how is this configured?

Yes, the LTC1985ES5-1.8 supports flexible configuration: VCCA (Pin 3) can be tied to VCC3 or VCC18 to disable its monitoring function, enabling dual-rail (3V + 1.8V) or single-rail operation. Tying VCC18 to VCC3 is also permissible, but VCC3 must always be used - connecting only VCC18 while leaving VCC3 unpowered will cause continuous RST assertion. This configurability is explicitly supported in the LTC1985ES5-1.8 datasheet and verified in typical application circuits TA02–TA04.

What is the minimum supply voltage at which the LTC1985ES5-1.8 guarantees correct RST logic state?

The LTC1985ES5-1.8 guarantees correct RST logic state - i.e., valid high or low output - for VCC3 ≥ 1V or VCC18 ≥ 1V, per Absolute Maximum Ratings and Electrical Characteristics tables. Below 1V, RST sink capability degrades significantly; however, a 100kΩ pull-down resistor (as shown in Figure 1 of the LTC1985ES5-1.8 datasheet) ensures RST remains low down to 0V, preserving system safety in deep brownout conditions.

How does the LTC1985ES5-1.8 achieve ±1.5% threshold accuracy over temperature?

The LTC1985ES5-1.8 achieves ±1.5% threshold accuracy across –40°C to +85°C through laser-trimmed internal voltage references and matched comparator input stages, all referenced to a stable bandgap core. This specification is guaranteed over temperature (denoted by "G" in the Electrical Characteristics table), with measured VRT3, VRT18, and VRTA parameters showing ≤30mV total deviation across the full range - confirmed in Figures G04–G06 of the LTC1985ES5-1.8 datasheet.

Is the LTC1985ES5-1.8 pin-compatible with other members of the LTC1985 family, such as the LTC1985ES5-2.5 or LTC1985ES5-3.3?

No - the LTC1985ES5-1.8 is not pin-compatible with other variants like LTC1985ES5-2.5 or LTC1985ES5-3.3 because they feature different fixed thresholds (e.g., 2.5V or 3.3V on VCC3) and distinct internal reference architectures. While all share the same 5-lead SOT-23 package and pinout mapping, the VCC3 and VCC18 threshold voltages are factory-set and non-interchangeable; substituting variants risks incorrect reset timing or failure to assert under valid operating conditions. Always verify threshold values against the specific LTC1985ES5-1.8 datasheet.