Analog Devices Inc. LTC2938CDE#TRPBF

Overview

LTC2938CDE#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 supplies (e.g., 5V, 3.3V, 2.5V, 1.8V), provides ±1.5% threshold accuracy over temperature, supports adjustable reset and watchdog timeout periods using external capacitors, and operates down to VCC = 1V - used in multivoltage embedded systems requiring reliable power-on reset and software supervision.

For engineers reviewing the LTC2938CDE#TRPBF datasheet, LTC2938CDE#TRPBF pinout, LTC2938CDE#TRPBF application, or LTC2938CDE#TRPBF equivalent, key selection criteria include guaranteed RST assertion at VCC ≥ 1V, 80μA typical supply current, 12-pin 4mm × 3mm DFN package, ±1.5% voltage threshold accuracy, and support for both positive and negative adjustable thresholds on V3/V4 inputs.

Technical Context

The LTC2938CDE#TRPBF implements six high-impedance comparator inputs (V1–V4) with internal reference-based thresholds, where V1 and V2 serve as dual supply inputs and determine VCC (the greater of the two). Its configuration logic samples VPG during a 150μs power-up window to select one of sixteen preset voltage combinations or ADJ/–ADJ modes.

Reset timing is controlled by CRT (2ms/nF scaling), watchdog timeout by CWT (20ms/nF), and both outputs (RST, WDO) feature weak 6μA pull-ups to V2 - requiring external pull-ups when V2 ≤ 2.5V to meet VOH requirements of downstream logic. Glitch immunity is built into all comparators, and the bandgap reference (1.210V ±18mV) powers VREF and enables negative-adjust mode via level-shifting.

Key Specifications

Pinout & Package

Package: 12-lead (4mm × 3mm) plastic DFN (DE package) with optional exposed pad connected to GND. Pin count and layout match MSOP variant but offer lower thermal resistance (θJA = 43°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3808G33DBVR and MAX6369KA+T, the LTC2938CDE#TRPBF uniquely combines 16 programmable voltage combinations, ±1.5% accuracy, ADJ/–ADJ flexibility, and capacitor-adjustable timing - making it optimal for complex multivoltage systems requiring hardware-configurable, high-fidelity supervision without firmware overhead.

Availability

LTC2938CDE#TRPBF is available at Aetrix Electronics and suitable for desktop computers, telecom equipment, and network servers requiring stable component supply with guaranteed commercial-temperature performance and long-term sourcing continuity.

Supply support for LTC2938CDE#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 acquired Linear Technology in 2017 and maintains its precision analog and power management portfolio with rigorous qualification and long-term product support.

The LTC2938 belongs to Linear's high-accuracy power supply monitoring IC family, designed specifically for multivoltage digital systems needing deterministic reset behavior, watchdog supervision, and hardware-programmable flexibility without microcontroller intervention.

FAQ

What is the function of the VPG pin on the LTC2938CDE#TRPBF?

The VPG pin on the LTC2938CDE#TRPBF is the threshold configuration input. During a 150μs power-up window, it samples a voltage divider between VREF and GND to select one of sixteen predefined voltage monitoring combinations (e.g., 5V/3.3V/2.5V/1.8V) or ADJ/–ADJ modes. The LTC2938CDE#TRPBF uses this sampled value to configure its internal comparators without firmware involvement.

Can the LTC2938CDE#TRPBF monitor negative supply voltages?

Yes - the LTC2938CDE#TRPBF supports negative rail monitoring via its V4 input in –ADJ mode. In this mode, VREF (1.210V) serves as a level-shift reference: an external resistor divider connects between the negative supply and VREF, and the tap point feeds V4. The LTC2938CDE#TRPBF then detects when the negative voltage crosses its threshold relative to ground, enabling supervision of rails like –1.8V or –5V.

How does the LTC2938CDE#TRPBF ensure reliable reset during brownout conditions?

The LTC2938CDE#TRPBF guarantees RST remains asserted (low) for VCC down to 1V, ensuring reset continuity even as input supplies collapse. Its internal comparators maintain glitch immunity, and the reset timeout (tRST) is capacitor-programmable to enforce minimum hold time after all rails recover. This behavior is fully specified and tested across 0°C to 70°C for the LTC2938CDE#TRPBF.

What are the recommended capacitor types for CRT and CWT on the LTC2938CDE#TRPBF?

Low-leakage ceramic capacitors are recommended for both CRT (reset timeout) and CWT (watchdog timeout) on the LTC2938CDE#TRPBF. These minimize timing error caused by leakage current (nominal charging current is 2μA). Avoid high-leakage types like electrolytic or tantalum. For example, a 47nF X7R ceramic yields tRST ≈ 94ms and tWD ≈ 940ms - values confirmed in the LTC2938CDE#TRPBF typical application circuit.

Does the LTC2938CDE#TRPBF require external pull-up resistors on RST and WDO?

Yes - when V2 is configured to monitor 2.5V or lower (e.g., 1.8V, 1.5V, 1.2V), external pull-up resistors are required on both RST and WDO to ensure VOH exceeds the VIH threshold of downstream logic. The LTC2938CDE#TRPBF's internal 6μA pull-up to V2 is insufficient for reliable high-level signaling at those voltages; pulling to a higher interface supply (e.g., 3.3V) resolves this per the LTC2938CDE#TRPBF datasheet guidance.