Analog Devices Inc. LTC2938HDE#PBF

Overview

LTC2938HDE#PBF from Analog Devices (formerly Linear Technology) is a high-accuracy, configurable 4-supply voltage monitor IC with integrated watchdog timer and reset output. It supports up to four user-selectable supply thresholds (e.g., 5V/3.3V/2.5V/1.8V), ±1.5% threshold accuracy over temperature, 80μA typical supply current, and operates from –40°C to 125°C. It is used in multivoltage embedded systems requiring reliable power-on reset and software supervision.

For engineers reviewing the LTC2938HDE#PBF datasheet, LTC2938HDE#PBF pinout, LTC2938HDE#PBF application, or LTC2938HDE#PBF equivalent, key selection criteria include guaranteed RST operation down to VCC = 1V, adjustable reset/watchdog timeouts via external capacitors (CRT/CWT), 12-pin DFN package compatibility, and support for both positive and negative adjustable thresholds on V3–V4 inputs.

Technical Context

The LTC2938HDE#PBF implements six independent comparators - four for voltage monitoring (V1–V4), one for watchdog input (WDI) edge detection, and one for internal reference regulation - all referenced to a buffered 1.210V bandgap (VREF). Its configuration logic samples VPG at power-up to select one of sixteen preset voltage combinations using an external resistive divider.

Reset assertion is synchronized across all monitored supplies: RST pulls low if any input falls below its configured threshold and remains low for the CRT-set timeout after all supplies recover. The watchdog timer starts only when RST goes high and requires periodic WDI transitions; expiration forces WDO low and triggers a full reset pulse via RST.

Key Specifications

Pinout & Package

Package: 12-lead (4mm × 3mm) plastic DFN with exposed pad (DE package), RoHS-compliant, moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6361KA29+T and TPS3808G33DBVR, the LTC2938HDE#PBF uniquely delivers four independently configurable supply thresholds, ±1.5% accuracy over extended temperature, and integrated watchdog/reset co-timing - making it the sole option for high-reliability multivoltage systems requiring both power integrity and firmware health assurance.

Availability

LTC2938HDE#PBF is available at Aetrix Electronics and suitable for automotive control units, telecom line cards, and industrial servers requiring stable component supply with guaranteed long-term availability and extended temperature support.

Supply support for LTC2938HDE#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 power management semiconductors.

The LTC2938HDE#PBF belongs to the Linear Technology LTC® supervisor family, designed specifically for high-accuracy, multi-rail power monitoring in mission-critical embedded systems where reliability, temperature resilience, and design flexibility are paramount.

FAQ

What is the operating temperature range of the LTC2938HDE#PBF?

The LTC2938HDE#PBF is rated for operation from –40°C to +125°C junction temperature, matching the H-grade specification. This makes it suitable for under-hood automotive applications, industrial motor drives, and base station equipment where ambient temperatures exceed standard commercial or industrial grades. The device maintains ±1.5% threshold accuracy across this full range, as verified in the Electrical Characteristics table (LTC2938/LTC2939 datasheet Rev. F, page 3).

How does the VPG pin configure the LTC2938HDE#PBF for different voltage thresholds?

The VPG pin accepts a voltage divider tap between VREF (1.210V) and GND to select one of sixteen preset combinations for V1–V4 thresholds. For example, applying 0.115V to VPG selects Mode 1 (5V/3.3V/ADJ/–ADJ). The LTC2938HDE#PBF samples VPG during a 150μs power-up window and locks the configuration. Resistor values for each mode are specified in Table 1 of the datasheet, with ±1% tolerance recommended for accuracy.

Can the LTC2938HDE#PBF monitor negative supply voltages?

Yes - the V4 input supports –ADJ mode, allowing direct monitoring of negative rails such as –12V or –5V. In this mode, VREF (1.210V) serves as the reference offset: a resistive divider connects the negative supply to VREF, and the tap feeds V4. The trip point is calculated as VTRIP = –(R3/R4) × VREF. Table 3 in the datasheet provides validated 1% resistor pairs for common negative rails.

What is the minimum VCC required for the LTC2938HDE#PBF to assert a valid RST output?

The LTC2938HDE#PBF guarantees correct RST logic state (low) for VCC ≥ 1V, as stated in the Absolute Maximum Ratings and Electrical Characteristics tables. This ensures fail-safe reset assertion even during severe brownout conditions where V1 or V2 drops below typical regulator dropout levels. Internal circuitry remains functional down to this threshold, unlike many supervisors that require ≥2.0V for reliable operation.

How do CRT and CWT capacitors affect timing in the LTC2938HDE#PBF?

CRT sets the reset timeout period at 2ms per nanofarad (e.g., 47nF → 94ms), while CWT sets the watchdog timeout at 20ms per nanofarad (e.g., 47nF → 940ms). Both capacitors charge via internal 2μA current sources, so low-leakage ceramic types are recommended. Leaving either pin unconnected yields ~20μs (CRT) or ~200μs (CWT) minimum timeouts, but parasitic capacitance may cause variation.