Analog Devices Inc. LTC2935ITS8-2#TRPBF

Product Summary LTC2935ITS8-2#TRPBF Monitoring IC

In battery-powered and portable systems, ensuring reliable supply voltage monitoring is crucial to avoid erratic operation and safeguard data integrity. The Analog Devices LTC2935ITS8-2#TRPBF, a member of the LTC2935 family, is a single-channel voltage supervisor specifically optimized for ultra-low quiescent current applications. Housed in an 8-lead TSOT-23 package, this supervisor offers a combination of precision, configurability, and low power consumption, making it suitable for both space- and power-sensitive designs.

Highlights of the LTC2935ITS8-2#TRPBF

The LTC2935ITS8-2#TRPBF offers a feature set that addresses common challenges in reliable system startup and shutdown:

Extremely low quiescent current, consuming only 500nA, maximizing battery life in portable applications.

High precision with a maximum ±1.5% reset threshold accuracy across temperature variations ensures robust supply monitoring.

Eight pin-selectable reset thresholds (covering 1.6V to 3.45V) and eight corresponding power-fail thresholds via three digital selection pins allow rapid adaptation across different voltage rails and battery chemistries, offering board-level flexibility.

Power-fail (PFO) output provides an early warning at a voltage above the reset threshold, enabling controlled shutdown routines prior to undervoltage-induced resets.

Reliable timing with a fixed 200ms reset timeout, supporting processor and system initialization.

Integrated manual reset (MR) input allows external system-level reset control, facilitating robust user/maintenance interactions.

Compact dimensions (2mm x 2mm DFN and TSOT-23-8 packages) make the device suitable for dense PCB layouts in portable or miniaturized products.

Pin Layout and Functional Block Overview

The LTC2935ITS8-2#TRPBF leverages an organized pinout to deliver versatile supervisory functionality:

S2, S1, S0: These digital inputs set one of eight different internal monitoring thresholds by a simple binary addressing method, eliminating the need for additional passive components and enabling easy re-configuration or product family reuse.

MR (Manual Reset): This pin, typically driven by a pushbutton switch, allows a user or system to impose a hardware reset; an internal pull-up resistor ensures default high-state operation.

PFO (Power-Fail Output): Pulls low to signal impending supply fault, usually wired to a processor Non-Maskable Interrupt (NMI) or similar pre-shutdown alert system.

RST (Reset Output): Active low reset, released after the voltage rises above the reset threshold with a 5% hysteresis margin and expiration of the internal 200ms reset timer.

VCC: Monitored voltage input as well as device supply; a decoupling capacitor (e.g., 0.1μF) is recommended for noise immunity.

GND and Exposed Pad: Provide electrical and thermal return paths; the exposed pad (on DFN) can be left floating or connected to ground.

The functional block diagram integrates precision attenuators, comparators with programmable reference voltages, an early warning circuit, standard reset logic, and timing circuitry, all targeting robust, glitch-immune voltage detection.

Electrical and Thermal Specifications of the LTC2935ITS8-2#TRPBF

Reliability in power supervision applications hinges on well-defined, predictable electrical performance:

Input supply range: Up to 6V absolute maximum.

Power-fail and reset outputs (in this -2 variant): Actively pulled up to VCC, ensuring logic-level compatibility without the need for external pull-up resistors.

Input and output current handling: PFO and RST outputs tolerate ±5mA, providing flexibility for interfacing with various logic families.

Temperature range: Rated for industrial operation between -40°C and +85°C; the device itself can handle up to 125°C junction temperature for design margin.

Thermal resistance: For TSOT-23-8, junction-to-ambient (θJA) is 195°C/W, which, combined with the device’s low power dissipation, permits use in high-density layouts.

Application Recommendations and Common Use Scenarios

The LTC2935ITS8-2#TRPBF is engineered for scenarios where integrity during system power-up, operation, and shutdown is essential:

Portable and battery-powered equipment: Its 500nA quiescent current adds negligible load on batteries. In coin cell-powered IoT devices, for instance, the device minimizes leakage yet guarantees system-level reset and early warning.

Security and wireless systems: The supervisor can issue early power-fail notifications, affording time to store state or trigger controlled system shutdowns, protecting data and system firmware.

Point-of-sale (POS) terminals and portable instrumentation: Known for frequent power cycling, these designs benefit from the supervisor's glitch-immune reset generation and hysteresis, preventing spurious resets in noisy environments.

Typical application example: Monitoring multi-cell alkaline stacks for undervoltage; configured thresholds track battery chemistries, output signals drive microcontroller reset and status.

Output Logic Modes and Threshold Configuration for the LTC2935ITS8-2#TRPBF

This supervisor family provides two main options for logic interfacing:

The LTC2935ITS8-2#TRPBF features active pull-up logic outputs, with both RST and PFO pulled up to VCC—particularly attractive where external pull-ups are undesirable or PCB area is constrained.

Alternatively, open-drain output options are available within the LTC2935 series for other application scenarios, such as level translation.

Threshold configuration is granular: three select pins (S2, S1, S0) define one of eight reset thresholds, accommodating a broad palette of supply voltages and enabling simple reuse across varying product lines.

Power-fail thresholds are set at a fixed offset above reset—150mV for the -2 variant—ensuring predictability in early-warning design.

LTC2935ITS8-2#TRPBF Package Details and PCB Design Guidelines

Compact integration is made possible by industry-standard packages:

8-lead TSOT-23 (the ‘ITS8’ suffix): 2.9mm x 3mm footprint, with minimal height, suits handheld and ultra-compact designs.

Proper layout recommendations: The monitored VCC pin should be bypassed with at least a 0.01μF capacitor to GND to address noise susceptibility.

The exposed pad on DFN variants can aid in heat dissipation and may optionally be connected to system GND for enhanced grounding if used.

Possible Alternative/Replacement ICs for the LTC2935ITS8-2#TRPBF

When designing with the LTC2935ITS8-2#TRPBF, consider the following models for alternative configurations or second-source selection:

LTC2935-1 and LTC2935-3: These variants offer open-drain outputs, suitable for interfacing with higher supply rails or when additional logic level translation is needed.

LTC2935ITS8-4: This family member provides a different power-fail threshold offset (120mV above reset) with active pull-up outputs, matching applications needing tighter pre-warning margins.

For cross-referencing among manufacturers, review pin-compatible supervisors from the Analog Devices product lineup, ensuring reset threshold accuracy, power-fail configuration, and quiescent current specifications align with your system requirements.

Conclusion

The Analog Devices LTC2935ITS8-2#TRPBF provides a strong solution for engineers seeking a low-power, precision voltage supervisor with flexible threshold and output configuration. Its extremely low quiescent current, wide selection of reset and power-fail thresholds, and ease of configuration position it as an optimal choice for modern portable, battery-powered, and low-voltage systems. Informed selection of output logic style and threshold settings provides system designers with a high degree of adaptability, while compact packaging and straightforward PCB integration streamline realization in even the most space-constrained platforms. For engineers committed to reducing power draw and maximizing reliability, the LTC2935ITS8-2#TRPBF is a compelling addition to the supervisor landscape.