Analog Devices Inc. LTC694CN8-3.3#PBF

Overview

LTC694CN8-3.3#PBF from Analog Devices (formerly Linear Technology) is an 8-pin PDIP-packaged 3.3V microprocessor supervisory circuit integrating power-on reset, battery back-up switching, RAM write protection, power-fail warning, and watchdog timing. It asserts RESET below 2.90V threshold, guarantees logic-low RESET down to VCC = 1V, delivers up to 50mA from VOUT via charge-pumped NMOS switch, and consumes only 0.6mW typical operating power - used in battery-backed embedded controllers requiring reliable low-voltage reset and memory retention.

For engineers reviewing the LTC694CN8-3.3#PBF datasheet, LTC694CN8-3.3#PBF pinout, LTC694CN8-3.3#PBF application, or LTC694CN8-3.3#PBF equivalent, key selection criteria include guaranteed reset assertion at 1V supply, 2.90V precision voltage monitor with 40mV hysteresis, fast 30ns CE gating for RAM write protection, 1μA max standby current in battery-backup mode, and compatibility with 3.3V systems requiring minimal external components.

Technical Context

The LTC694CN8-3.3#PBF implements a dual-comparator architecture: C1 monitors VCC against a 2.90V bandgap reference to generate RESET/LOW_LINE, while C3 compares PFI to a 1.3V internal reference for power-fail detection. Its charge-pumped NMOS VOUT switch enables low-dropout (VCC – VOUT ≈ 100mV @ 1mA), low-quiescent-current operation, and seamless switchover between VCC and VBATT with 70mV/50mV thresholds and 20mV hysteresis.

It integrates a programmable watchdog timer with internal oscillator (100ms/1.6s timeout options selected via OSC SEL), supports external clock input on WDI, and provides CE IN/CE OUT gating with 30ns propagation delay to protect CMOS RAM during brownout. All outputs - RESET, PFO, WDO, LOW_LINE - are push-pull capable of sinking ≥400μA with defined voltage levels across temperature.

Key Specifications

Pinout & Package

Package: 8-lead PDIP (N8), 0°C to 70°C operating range, θJA = 130°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACPA+ and TPS3808G33DBVR, the LTC694CN8-3.3#PBF uniquely integrates battery switchover, CE gating, and PFI/PFO in an 8-pin PDIP package - making it the only option for space-constrained 3.3V systems requiring full supervisory functionality without external components.

Availability

LTC694CN8-3.3#PBF is available at Aetrix Electronics and suitable for industrial data loggers, medical patient monitors, automotive telematics units, and smart energy meters requiring stable component supply with long-term lifecycle support.

Supply support for LTC694CN8-3.3#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 LTC694-3.3 family was designed specifically for 3.3V microprocessor systems needing integrated power supervision, battery backup, and memory protection - addressing reliability gaps in earlier 5V-focused supervisors.

FAQ

What is the minimum VCC voltage at which LTC694CN8-3.3#PBF guarantees RESET remains active low?

The LTC694CN8-3.3#PBF guarantees RESET output remains logic-low down to VCC = 1V with ISINK = 10μA. This ensures the microprocessor stays in a controlled reset state during deep brownout conditions where other supervisors may release reset prematurely, preventing undefined behavior or memory corruption in the LTC694CN8-3.3#PBF-equipped system.

Does LTC694CN8-3.3#PBF support battery-backed RAM write protection, and how is it implemented?

Yes, the LTC694CN8-3.3#PBF supports RAM write protection via its CE IN and CE OUT pins. When VCC falls below 2.90V or VBATT, CE OUT is forced high independently of CE IN, disabling RAM chip enable. This function is implemented with a 30ns propagation delay and works without external logic, making the LTC694CN8-3.3#PBF ideal for protecting static CMOS RAM in battery-backed applications.

What is the maximum continuous output current capability of the VOUT pin on LTC694CN8-3.3#PBF?

The VOUT pin of the LTC694CN8-3.3#PBF delivers up to 50mA continuously from VCC through its charge-pumped NMOS switch, with a typical on-resistance of 5Ω. Short-circuit current is internally limited to ~200mA, and thermal shutdown activates at ~155°C. In battery-backup mode (VCC = 0V), VOUT supplies up to 250μA from VBATT with ≤100mV dropout - confirming the LTC694CN8-3.3#PBF's suitability for low-power RAM retention.

Can LTC694CN8-3.3#PBF generate an early warning signal before main supply failure?

Yes, the LTC694CN8-3.3#PBF provides early power-fail warning via its PFI/PFO circuit. The PFI pin accepts a user-defined voltage divider input; when that voltage drops below the internal 1.30V reference, PFO goes low. With proper resistor selection (e.g., 51k/16k divider), PFO can assert 15ms before VCC reaches the 2.90V reset threshold - giving the host system time to save critical data before the LTC694CN8-3.3#PBF asserts RESET.

What are the operating temperature limits and package type for LTC694CN8-3.3#PBF?

The LTC694CN8-3.3#PBF is specified for 0°C to 70°C operation and housed in an 8-lead plastic DIP (PDIP) package with lead-free finish (#PBF). Its thermal resistance is θJA = 130°C/W, and absolute maximum ratings include VCC and VBATT up to 6V. This makes the LTC694CN8-3.3#PBF suitable for commercial-grade embedded systems where through-hole mounting and moderate ambient temperatures are required.