Analog Devices Inc. LTC699IN8#PBF

Overview

LTC699IN8#PBF from Analog Devices (formerly Linear Technology) is a precision microprocessor supervisory circuit with integrated watchdog timer and guaranteed reset assertion down to VCC = 1V. It monitors +5V supply lines, provides 4.65V threshold detection with 40mV hysteresis, delivers 200ms reset pulse, and supports watchdog timeout at 1.6s. Used in automotive control units and industrial embedded systems requiring robust power-on reset and firmware fault recovery.

For engineers reviewing the LTC699IN8#PBF datasheet, LTC699IN8#PBF pinout, LTC699IN8#PBF application, or LTC699IN8#PBF equivalent, key selection criteria include guaranteed low-VCC reset hold, open-drain RESET output compatibility with 3.3V/5V µPs, SO-8/DIP-8 package options, and watchdog input transition sensitivity - all validated over –40°C to +85°C.

Technical Context

The LTC699IN8#PBF integrates a bandgap voltage reference and precision comparator to monitor VCC against a 4.65V threshold with 40mV hysteresis, ensuring immunity to supply transients. Its open-drain RESET output remains logic-low down to VCC = 1V, enabling stable processor shutdown during brownout.

A dedicated three-level WDI input enables watchdog functionality: transitions restart the 1.6s timeout period, static high/low forces reset, and floating disables the timer. The internal reset pulse generator guarantees ≥140ms active-low duration after power-up or timeout events.

Key Specifications

Pinout & Package

Package: N8 - 8-lead plastic DIP, through-hole mounting, 0.300" wide body, 0.100" lead pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX699CSA+ and TPS3823-46DBVR, the LTC699IN8#PBF uniquely combines guaranteed 1V reset hold, integrated watchdog, and industrial temperature range in a through-hole DIP package - making it irreplaceable for safety-critical brownout recovery where both reset integrity and firmware liveness must be enforced.

Availability

LTC699IN8#PBF is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLC modules, medical infusion pump controllers, and railway signaling interface boards requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for LTC699IN8#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 digital signal processing semiconductors.

The LTC699IN8#PBF belongs to Linear's legacy µP supervisory product line, designed specifically for robust power monitoring and fault recovery in mission-critical embedded systems operating under harsh electrical and thermal conditions.

FAQ

What is the guaranteed minimum VCC level at which LTC699IN8#PBF maintains active RESET?

The LTC699IN8#PBF guarantees RESET remains active low down to VCC = 1V, ensuring the microprocessor stays held in reset during severe brownout conditions. This behavior is explicitly tested and specified in the Absolute Maximum Ratings and Electrical Characteristics tables. The internal circuitry sustains logic-low output even as supply voltage collapses, preventing undefined processor states. This feature is critical for automotive and industrial applications where supply instability is common. The LTC699IN8#PBF achieves this via dedicated low-voltage biasing networks not found in standard reset ICs.

Does LTC699IN8#PBF require external components to operate as a basic reset supervisor?

No, the LTC699IN8#PBF requires only an external pull-up resistor on the RESET pin and a 0.1µF ceramic bypass capacitor on VCC - no timing resistors or external references are needed. Its internal bandgap reference, precision comparator, and reset pulse generator eliminate external component dependencies. This minimal BOM reduces cost, board area, and qualification effort. The LTC699IN8#PBF is fully functional out-of-the-box for power-on reset and brownout detection. Watchdog operation adds no additional passive components beyond those already required.

How does the WDI input function on LTC699IN8#PBF, and what happens if it's left unconnected?

The WDI input on LTC699IN8#PBF is a three-level interface: transitions (high-to-low or low-to-high) reset the 1.6s watchdog timer; static high or low asserts RESET; and floating (high-impedance) disables the watchdog entirely. When left unconnected, the internal weak pull-down ensures WDI defaults to logic low - which *does* activate RESET continuously. To disable watchdog, WDI must be actively floated using a switch or tri-state driver. The LTC699IN8#PBF datasheet explicitly warns against leaving WDI open. Proper disabling requires deliberate circuit design, not omission.

What is the significance of multiple VCC and GND pins on LTC699IN8#PBF?

The LTC699IN8#PBF features two VCC pins (pins 2 and 3) and three GND pins (pins 4, 5, and 7) to minimize supply impedance and ground bounce during RESET assertion. This layout reduces voltage drop across bond wires and PCB traces, ensuring accurate threshold detection and clean reset pulse edges - especially critical under dynamic load conditions. The dual VCC pins lower effective series inductance, while multiple GND paths provide low-impedance return paths for both analog reference and digital output stages. This architecture directly supports the LTC699IN8#PBF's 10µs response time and 40mV hysteresis specification.

Is LTC699IN8#PBF pin-compatible with MAX699 variants?

No, LTC699IN8#PBF is not pin-compatible with MAX699 variants. While both are supervisory ICs with 4.65V thresholds, the LTC699IN8#PBF includes a dedicated WDI pin (pin 1) and NC pin (pin 6), whereas MAX699 uses different pin assignments (e.g., WDI absent, different GND distribution). The LTC699IN8#PBF's 8-pin DIP layout places WDI at pin 1 and RESET at pin 8, while MAX699CSA+ assigns RESET to pin 1 and lacks WDI entirely. Direct replacement would require PCB redesign. The LTC699IN8#PBF is positioned as a functional *upgrade*, not a drop-in replacement.