Analog Devices Inc. LTC694IS8#TRPBF

Overview

LTC694IS8#TRPBF from Analog Devices (formerly Linear Technology) is an industrial-grade microprocessor supervisory circuit in 8-lead SOIC package, providing guaranteed reset assertion down to VCC = 1V, 4.65V precision power supply monitoring, 140ms minimum reset active time, and integrated battery switchover for CMOS RAM backup. It serves as a single-chip solution for power-fail warning, watchdog timing, and memory write protection in embedded controllers.

For engineers reviewing the LTC694IS8#TRPBF datasheet, LTC694IS8#TRPBF pinout, LTC694IS8#TRPBF application, or LTC694IS8#TRPBF equivalent, key selection criteria include guaranteed low-VCC reset behavior, battery-backed VOUT output with 1µA standby current, adjustable reset timing via OSC SEL, PFI/PFO comparator for early power-fail detection, and industrial temperature range (–40°C to +85°C) operation.

Technical Context

The LTC694IS8#TRPBF integrates a precision 4.65V voltage monitor with 40mV hysteresis, a 140ms minimum reset pulse generator (vs. 35ms for LTC690), and a dual-mode oscillator-internal (1.6s/100ms watchdog timeout) or external clock/capacitor configurable via OSC SEL. Its charge-pumped NMOS VOUT switch delivers up to 50mA at <5Ω on-resistance during main power, while a 125Ω PMOS switch enables ultra-low-dropout battery backup.

It features three independent comparators: C1 (VCC vs. 4.65V reference) driving RESET/LOWLINE, C2 (VCC–VBATT threshold detection) controlling battery switchover and BATT ON, and C3 (PFI vs. 1.3V reference) generating PFO. All outputs are actively driven with defined sink/source capability, and WDI accepts three-level logic (high/low/floating) to enable/disable the watchdog timer.

Key Specifications

Pinout & Package

Package: 8-lead plastic SOIC (S8), JEDEC MS-012AC, 3.9mm × 4.9mm body, 1.27mm pitch. RoHS-compliant, Pb-free finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisory applications.

Compared with MAX692AESA+ and TPS3823-46DBVR, the LTC694IS8#TRPBF uniquely integrates reset, watchdog, power-fail warning, *and* battery-backed VOUT in one 8-pin SOIC-reducing BOM count, PCB area, and design complexity for systems requiring full power management autonomy.

Availability

LTC694IS8#TRPBF is available at Aetrix Electronics and suitable for industrial automation, automotive electronics, medical portable devices, and smart metering applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LTC694IS8#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 LTC694IS8#TRPBF belongs to the LTC690 family of microprocessor supervisory ICs, designed specifically for robust power monitoring, battery backup, and fail-safe system recovery in harsh environments.

FAQ

What is the guaranteed minimum reset active time for LTC694IS8#TRPBF?

The LTC694IS8#TRPBF guarantees a minimum reset active time of 140ms after VCC rises above the 4.65V threshold, with a typical value of 200ms. This extended duration-double that of the LTC690-ensures reliable microprocessor initialization during slow-rising or noisy power supplies. The LTC694IS8#TRPBF achieves this using its internal oscillator configuration, and the timing can be adjusted further using an external clock or capacitor on the OSC IN pin when OSC SEL is pulled low.

Does LTC694IS8#TRPBF support battery backup for external RAM, and how does it work?

Yes, the LTC694IS8#TRPBF supports battery backup via its VBATT and VOUT pins. When VCC drops below VBATT minus 50mV, an internal PMOS switch connects VBATT to VOUT, delivering up to 250µA at ultra-low dropout. In normal operation, an NMOS switch supplies VOUT from VCC with ≤5Ω resistance and up to 50mA. The LTC694IS8#TRPBF also provides BATT ON-a logic output that goes high during battery mode-to drive external PNP transistors for higher backup current.

Can LTC694IS8#TRPBF generate an early warning before system reset occurs?

Yes, the LTC694IS8#TRPBF provides early power-fail warning through its PFI/PFO circuitry. By connecting a resistor divider from VCC to GND at the PFI pin, the internal 1.3V comparator triggers PFO low milliseconds before VCC crosses the 4.65V reset threshold. This allows the microprocessor to execute critical shutdown routines-such as saving state or logging faults-before RESET forces a hard halt. The LTC694IS8#TRPBF's PFO response time is under 8µs with pull-up, enabling timely intervention.

What is the lowest VCC voltage at which LTC694IS8#TRPBF still asserts RESET correctly?

The LTC694IS8#TRPBF guarantees RESET remains logic low down to VCC = 1V, a key differentiator versus most supervisors that release reset above 2.5V. This ensures the microprocessor stays in a known, halted state even during deep brownouts or battery depletion. Internally, the RESET driver uses a dedicated low-voltage bias network, and the specification is tested and guaranteed across the full –40°C to +85°C industrial temperature range-not just at room temperature.

How does the watchdog timer function in LTC694IS8#TRPBF, and what are its timeout options?

The LTC694IS8#TRPBF watchdog timer monitors the WDI pin: any transition resets the timeout counter, while a sustained high or low state longer than the programmed period forces both RESET and WDO low. It offers two internal timeout modes-1.6s (long) and 100ms (short)-selected by OSC IN logic level. An external clock or RC network on OSC IN enables fully customizable timeouts. The LTC694IS8#TRPBF watchdog is disabled when WDI is left floating, simplifying integration in systems that don't require runtime supervision.