Analog Devices Inc. LTC2939CMS#PBF

Overview

LTC2939CMS#PBF from Analog Devices (formerly Linear Technology) is a configurable six-supply voltage monitor IC with integrated watchdog timer, reset output, and programmable threshold selection via external resistive divider. It monitors up to six independent supply rails-including 5V, 3.3V, 2.5V, 1.8V, 1.5V, 1.2V, and ±adjustable inputs-with ±1.5% threshold accuracy over temperature, 80μA typical supply current, and guaranteed RST operation down to VCC = 1V. It is used in multivoltage server power systems requiring reliable brownout detection and microprocessor supervision.

For engineers reviewing the LTC2939CMS#PBF datasheet, LTC2939CMS#PBF pinout, LTC2939CMS#PBF application, or LTC2939CMS#PBF equivalent, key selection criteria include its 16-pin MSOP package, six independent comparator inputs with ADJ/–ADJ modes, externally adjustable reset and watchdog timeout periods (via CRT/CWT capacitors), and guaranteed glitch-immune reset assertion during power-up/down/brownout events.

Technical Context

The LTC2939CMS#PBF implements six high-impedance voltage comparators referenced to either fixed thresholds (±1.5% accuracy) or a 0.5V internal reference for adjustable monitoring. Its configuration logic samples VPG at power-up to select one of sixteen preset voltage combinations, enabling flexible system-level supply monitoring without firmware involvement.

It features dual timing paths: a reset timeout generator (tRST = 2ms/nF on CRT) and a watchdog timeout generator (tWD = 20ms/nF on CWT), both driven by precision 2μA charging currents. The RST and WDO outputs each have weak 6μA pull-ups to V2, with external pull-up support required when V2 ≤ 2.5V to meet downstream VIH requirements.

Key Specifications

Pinout & Package

Package: 16-Lead Plastic MSOP (3mm × 4.9mm, 0.65mm pitch), exposed pad optional for thermal enhancement.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6816ESE+ and TPS3808G33DBVR, the LTC2939CMS#PBF delivers integrated six-rail supervision, user-selectable thresholds, and hardware watchdog in a single 16-pin MSOP-reducing component count by ≥5× and eliminating inter-device timing skew in safety-critical power sequencing.

Availability

LTC2939CMS#PBF is available at Aetrix Electronics and suitable for desktop computers, telecom equipment, and network servers requiring stable component supply with guaranteed long-term manufacturability and consistent parametric performance.

Supply support for LTC2939CMS#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors for precision instrumentation, industrial automation, and communications infrastructure.

The LTC2939 belongs to Linear's precision power supervision product line, designed specifically for multivoltage systems in computing, networking, and automotive domains where deterministic reset behavior, low power, and configurability are mandatory.

FAQ

What is the maximum number of supply rails the LTC2939CMS#PBF can monitor simultaneously?

The LTC2939CMS#PBF can monitor up to six independent supply rails (V1 through V6) simultaneously. This includes combinations of fixed thresholds (5V, 3.3V, 2.5V, 1.8V, 1.5V, 1.2V) and adjustable inputs (ADJ and –ADJ modes). The LTC2938 variant supports only four rails; the LTC2939CMS#PBF is the six-input version in 16-lead MSOP packaging.

How does the LTC2939CMS#PBF achieve ±1.5% threshold accuracy over temperature?

The LTC2939CMS#PBF achieves ±1.5% threshold accuracy using trimmed bandgap-referenced comparators and factory-calibrated resistor networks internal to the die. This specification is guaranteed across the full operating temperature range (0°C to 70°C for the CMS grade) and applies to all fixed thresholds (e.g., VRT33 = 3.086V typ) and the 0.5V ADJ reference. No external calibration is required.

Can the LTC2939CMS#PBF monitor negative supply voltages?

Yes - the LTC2939CMS#PBF supports negative rail monitoring via its –ADJ mode on the V4 input. In this configuration, VREF (1.210V) serves as a level-shift reference: an external resistive divider between the negative supply and VREF connects to V4, enabling accurate trip-point setting for rails such as –5V or –12V without external op-amps or level shifters.

What happens to the RST output when VCC drops below 1V?

When VCC drops below 1V, the LTC2939CMS#PBF no longer guarantees correct RST logic state - the output may float or become indeterminate. However, down to 1V, RST is guaranteed to remain in the correct asserted (low) state. This ensures clean reset hold-through during controlled brownout, but system designers must ensure V1/V2 do not collapse below 1V before critical logic loses functionality.

Is the LTC2939CMS#PBF pin-compatible with other members of the LTC2938/LTC2939 family?

No - the LTC2939CMS#PBF uses a 16-lead MSOP package, while the LTC2938 variants use 12-lead packages (DFN or MSOP). Although functionally related, they are not pin-compatible. Direct substitution requires PCB layout revision. The LTC2939IMS#PBF and LTC2939HMS#PBF share the same 16-lead MSOP footprint but differ in temperature grade and marking.