Analog Devices Inc./Maxim Integrated MAX807LEWE+

Overview

MAX807LEWE+ from Maxim Integrated is a full-featured microprocessor supervisory circuit designed for power monitoring, battery switchover, and watchdog protection in 5V µP systems. It provides active-low and active-high RESET outputs, manual reset input (MR), two-stage power-fail warning (PFI/PFO), LOW LINE comparator (52mV above reset threshold), BATT OK flag, and independent watchdog timer with 1.6s timeout. Its ±1.5% reset accuracy (4.675V threshold), 200ms reset timeout, and 250mA VCC-mode output drive support reliable boot sequencing in portable and industrial controllers.

For engineers reviewing the MAX807LEWE+ datasheet, MAX807LEWE+ pinout, MAX807LEWE+ application, or MAX807LEWE+ equivalent, key selection criteria include guaranteed RESET validity down to VCC = 1V, 2ns CE gate propagation delay, backup-battery switchover with 20mA battery-backup mode drive, ±1.5% reset threshold accuracy, and integrated chip-enable gating for CMOS RAM write protection.

Technical Context

The MAX807LEWE+ integrates seven functional blocks: a precision reset comparator (4.675V ±1.5%), low-line comparator (52mV above reset threshold, ±1.5% accuracy), power-fail comparator (2.265V threshold), watchdog transition detector with 1.6s timeout, battery switchover MOSFET control, dual RESET outputs (open-drain RESET and push-pull RESET), and CE signal gating with 2ns propagation delay. All comparators feature internal hysteresis (13–50mV) and operate across VCC = 4.60V to 5.5V.

Its BiCMOS process enables 70µA typical supply current in normal operation and 1µA standby current in battery-backup mode, while supporting 250mA VCC-to-OUT drive and 20mA BATT-to-OUT drive. The device guarantees functional operation down to VCC = 1V for RESET assertion and includes internal 50kΩ MR pullup, enabling direct switch connection without external components.

Key Specifications

Pinout & Package

MAX807LEWE+ is housed in a 16-pin TSSOP package (4.4mm × 5mm, 0.65mm pitch), optimized for space-constrained portable designs. Pin functions are electrically validated per Maxim's official datasheet Rev 4 (11/05).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX807LEWE+, MAX809SEUR+T omits critical redundancy functions (watchdog, CE gating, battery control), while TPS3808G33DBVR operates at incompatible voltage and lacks the 5V-system-specific features like LOW LINE warning and BATT OK status-making MAX807LEWE+ the only option supporting full-featured supervision in legacy +5V µP designs with battery backup.

Availability

MAX807LEWE+ is available at Aetrix Electronics and suitable for portable medical devices, industrial PLC controllers, and point-of-sale terminals requiring stable component supply with long-term lifecycle assurance.

Supply support for MAX807LEWE+ 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

Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for demanding industrial, automotive, and computing applications.

The MAX807L/M/N family was designed specifically for µP systems needing precision reset supervision, battery-backed memory retention, and watchdog-based firmware reliability-targeting portable, medical, and industrial equipment where power integrity is mission-critical.

FAQ

What is the exact reset threshold voltage of the MAX807LEWE+ and how precise is it?

The MAX807LEWE+ has a nominal reset threshold of 4.675V with ±1.5% accuracy over temperature and supply voltage. This means the actual threshold remains within 4.600V to 4.750V across its operating range (0°C to +70°C), ensuring consistent, deterministic reset behavior without external calibration. The MAX807LEWE+ achieves this precision using BiCMOS process technology and on-die trimming, directly supporting reliable boot sequencing in +5V µP systems.

Does the MAX807LEWE+ support battery backup for CMOS RAM, and what are its drive capabilities in that mode?

Yes, the MAX807LEWE+ provides fully automatic battery switchover for CMOS RAM, RTCs, or other low-power logic. When VCC falls below the reset threshold and VBATT exceeds 2.0V, the device switches the OUT pin from VCC to BATT. In battery-backup mode, it delivers up to 20mA continuous output current with a typical BATT-to-OUT on-resistance of 12Ω at 2.8V, enabling direct drive of standard SRAMs without external FETs.

How does the watchdog function work in the MAX807LEWE+, and what happens during a timeout?

The MAX807LEWE+ watchdog monitors the WDI input: if no edge (low-to-high or high-to-low) occurs within 1.6s, the WDO output asserts low. WDO remains low until the next WDI transition while RESET is deasserted. To generate an automatic system reset on watchdog fault, connect WDO to MR. This causes the MAX807LEWE+ to issue a 200ms reset pulse every 1.6s until firmware resumes toggling WDI-ensuring recovery from locked-up states.

Can the MAX807LEWE+ be used with power supplies other than +5V, and which pins enable that flexibility?

Yes, the MAX807LEWE+ supports multi-rail monitoring beyond +5V. Its PFI input accepts any voltage source (e.g., 3.3V, 12V, or negative rails) through an external resistor divider to set custom trip points; PFO then asserts when that voltage falls below 2.265V. Additionally, the LOW LINE comparator tracks VCC with a fixed 52mV offset above the reset threshold, providing scalable warning for any VCC level within the 4.60V–5.5V operating range.

What is the purpose of the CE IN and CE OUT pins on the MAX807LEWE+, and how do they protect memory?

The CE IN and CE OUT pins implement chip-enable signal gating: during normal operation, CE IN passes directly to CE OUT; when RESET is asserted (during power-up/down), CE OUT is actively pulled high to the higher of VCC or VBATT, blocking all CE activity. This prevents spurious writes to CMOS RAM during unstable power conditions. The MAX807LEWE+ achieves this with a 2ns propagation delay and series 75Ω resistance, ensuring timing-critical µPs see clean, glitch-free CE control without external logic.