Analog Devices Inc. LTC2938CMS#TRPBF

Overview

LTC2938CMS#TRPBF from Analog Devices (formerly Linear Technology) is a configurable 4-supply voltage monitor IC with integrated watchdog timer, reset output, and programmable threshold selection via external resistive divider. It monitors up to four independent supply rails (e.g., 5V, 3.3V, 2.5V, 1.8V), provides ±1.5% threshold accuracy over temperature, supports adjustable reset (2–4 ms/nF) and watchdog (20–40 ms/nF) timeouts, and operates down to VCC = 1V - enabling reliable power-on reset in multivoltage embedded systems.

For engineers reviewing the LTC2938CMS#TRPBF datasheet, LTC2938CMS#TRPBF pinout, LTC2938CMS#TRPBF application, or LTC2938CMS#TRPBF equivalent, key selection criteria include its 12-lead MSOP package, guaranteed RST assertion at VCC ≥ 1V, ±1.5% voltage threshold accuracy, 80μA typical supply current, and support for both positive and negative adjustable thresholds on V3/V4 inputs.

Technical Context

The LTC2938CMS#TRPBF implements six high-impedance comparator inputs (V1–V4) with factory-preset and user-programmable thresholds (5V/3.3V/2.5V/1.8V/1.5V/1.2V + ADJ/–ADJ), where V1 and V2 serve as internal supply (VCC) and define the pull-up rail for RST/WDO outputs. Its configuration logic samples VPG during a 150μs power-up window to select one of sixteen voltage combinations using a 1% resistive divider referenced to the 1.210V buffered VREF.

Reset timing is set by an external capacitor on CRT (2ms/nF scaling), while watchdog timeout is controlled by CWT (20ms/nF scaling); both timers feature glitch immunity and operate independently. The device guarantees correct RST state down to VCC = 1V and includes bandgap-referenced comparators with 150μs undervoltage detection latency and 6μA internal pull-ups to V2.

Key Specifications

Pinout & Package

Package: 12-Lead Plastic MSOP (MS Package), 3mm × 4.9mm body, exposed pad optional, rated for 0°C to 70°C operating temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6369ESA+ and TPS3808G33DBVR, the LTC2938CMS#TRPBF delivers unique value through hardware-programmable rail combinations, ±ADJ threshold flexibility, and integrated watchdog - reducing component count and enabling robust supervision of complex multivoltage systems without firmware intervention.

Availability

LTC2938CMS#TRPBF is available at Aetrix Electronics and suitable for desktop computers, telecom equipment, and multivoltage embedded systems requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance across commercial temperature range.

Supply support for LTC2938CMS#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.

The LTC2938CMS#TRPBF belongs to Linear's precision power monitoring product line, designed specifically for reliable, low-power, multi-rail supervision in computing, communications, and industrial control systems where voltage accuracy and watchdog reliability are critical.

FAQ

What is the minimum VCC voltage that guarantees correct RST output behavior for LTC2938CMS#TRPBF?

The LTC2938CMS#TRPBF guarantees correct RST logic state down to VCC = 1V. This means the reset output remains valid and asserted low during brownout conditions until both V1 and V2 drop below 1V, ensuring fail-safe system initialization even under severe supply sag. This specification is explicitly tested and guaranteed across the full 0°C to 70°C operating range.

How does the VPG pin configure the voltage monitoring thresholds on LTC2938CMS#TRPBF?

The VPG pin on LTC2938CMS#TRPBF accepts a voltage divider ratio between VREF (1.210V) and GND to select one of sixteen predefined monitoring combinations. During a 150μs power-up window, the device samples VPG and configures V1–V4 thresholds accordingly - for example, 0.094×VREF selects Mode 1 (5V/3.3V/ADJ/–ADJ). No capacitance may be added to VPG to avoid sampling errors.

Can LTC2938CMS#TRPBF monitor negative supply voltages, and if so, how?

Yes, LTC2938CMS#TRPBF supports negative voltage monitoring on the V4 input using the –ADJ mode, which sets the comparator reference to ±18mV around ground. To monitor a –5V rail, connect a resistive divider between –5V and VREF (1.210V), then feed the tap point to V4. The trip point is calculated as VTRIP = –(R3/R4) × 1.210V, enabling accurate detection of negative undervoltage events.

What are the recommended capacitor types and tolerances for CRT and CWT on LTC2938CMS#TRPBF?

For CRT (reset timeout) and CWT (watchdog timeout), LTC2938CMS#TRPBF recommends low-leakage ceramic capacitors with ±10% tolerance or better. Leakage current directly impacts timing accuracy since the internal 2μA charging current integrates across the capacitor. X7R or C0G dielectrics are preferred; electrolytic or tantalum capacitors are unsuitable due to high leakage and aging effects.

Does LTC2938CMS#TRPBF require external pull-up resistors on RST and WDO, and when?

Yes - external pull-up resistors are required on RST and WDO when V2 is configured to monitor 2.5V or lower supplies (e.g., 1.8V, 1.5V, 1.2V). The internal 6μA pull-up to V2 cannot guarantee VOH > VIH of downstream logic (typically 2.0V for 3.3V interfaces). An external resistor to the host logic supply (e.g., 3.3V or 5V) ensures proper high-level signaling and avoids interface failures.