Analog Devices Inc./Maxim Integrated MAX690ACPA+

Overview

The MAX690ACPA+ from Maxim Integrated is a microprocessor supervisory circuit providing precision 4.65V reset threshold detection, 200ms reset pulse width, 1.6s watchdog timeout, battery-backup switchover, and 1.25V power-fail comparator for +5V systems. It monitors VCC during power-up/down/brownout, asserts active-low RESET to initialize μPs, switches CMOS RAM to VBATT on failure, and supports lithium battery backup in industrial controllers and intelligent instruments.

For engineers reviewing the MAX690ACPA+ datasheet, MAX690ACPA+ pinout, MAX690ACPA+ application, or MAX690ACPA+ equivalent, this page delivers verified electrical parameters, package mapping, functional role in μP reset sequencing, battery switchover behavior, and validated alternative parts for embedded power monitoring designs.

Technical Context

The MAX690ACPA+ integrates four independent functions: a precision bandgap-based reset generator with hysteresis (40mV), a monostable watchdog timer cleared by WDI edges or RESET assertion, a dual-path power switch (5Ω PMOS for VCC→VOUT, 80Ω PMOS for VBATT→VOUT), and a rail-to-rail PFI comparator referenced to 1.25V ±1%. All logic thresholds are internally generated and temperature-compensated.

Its reset assertion is guaranteed down to VCC = 1.0V, and RESET remains low for ≥200ms after VCC rises above 4.65V. In battery-backup mode (VCC < 4.65V and VBATT > VCC + 20mV), supply current drops to ≤5.0µA over temperature, while VOUT regulation maintains ≤80mV dropout at 250µA load.

Key Specifications

Pinout & Package

MAX690ACPA+ is housed in an 8-pin plastic DIP (dual in-line package) with 0.300" wide body, lead-free finish (RoHS-compliant), and JEDEC MS-001AC outline. Pin spacing is 0.100", and thermal resistance θ_JA is 109°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX802LCPA+, the MAX690ACPA+ adds watchdog supervision without increasing footprint or cost; versus MAX705CPA+, it delivers lower supply current and deeper reset assertion, making it optimal for long-life battery-backed systems requiring both reliability and efficiency.

Availability

MAX690ACPA+ is available at Aetrix Electronics and suitable for battery-powered controllers, intelligent instrumentation, critical μP power monitoring, industrial data loggers, and remote telemetry systems requiring stable component supply and long-term lifecycle support.

Supply support for MAX690ACPA+ 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 analog, mixed-signal, and power-management ICs for industrial, communications, and computing markets.

The MAX690A family was designed specifically for robust, low-power microprocessor supervision in harsh environments-delivering guaranteed reset behavior, battery switchover, and fault detection in compact 8-pin packages.

FAQ

What is the guaranteed minimum VCC level at which MAX690ACPA+ asserts RESET?

The MAX690ACPA+ guarantees RESET assertion down to VCC = 1.0V across the 0°C to +70°C operating range. This ensures deterministic reset initiation even during severe brownout events where supply voltage collapses gradually. The internal reset generator remains functional and drives the open-drain RESET output low until VCC recovers above 4.65V and the 200ms timer expires. This behavior is explicitly tested and specified in the Absolute Maximum Ratings and Electrical Characteristics tables of the official MAX690A datasheet.

Does MAX690ACPA+ support active-high reset outputs?

No, the MAX690ACPA+ provides only an active-low RESET output. The active-high variant is the MAX805L series (e.g., MAX805LCPA+), which substitutes RESET for RESET. The MAX690ACPA+ pin 7 is strictly RESET (active-low, open-drain). Attempting to use it as an active-high signal will result in incorrect μP initialization. For Intel 80C51 or other active-high-reset μPs, MAX805LCPA+ is the functionally matched replacement with identical reset threshold and timing.

How does the battery switchover mechanism work in MAX690ACPA+?

In the MAX690ACPA+, battery switchover activates only when VCC falls below 4.65V AND VBATT exceeds VCC by at least 20mV. At that point, the internal 80Ω PMOS switch connects VBATT to VOUT, powering CMOS RAM. When VCC rises above VBATT + 20mV, the 5Ω PMOS reconnects VCC to VOUT. This 40mV hysteresis prevents oscillation during slow VCC recovery. Unlike earlier MAX690 versions, the MAX690ACPA+ does not connect VBATT to VOUT unless both conditions are met, eliminating unnecessary battery drain.

Can MAX690ACPA+ monitor negative supply rails?

Yes, the MAX690ACPA+ power-fail comparator (PFI/PFO) can monitor negative voltages using an external resistor network as shown in Figure 7 of the datasheet. By referencing PFI to ground and applying the negative rail through a voltage divider, the comparator detects when the magnitude of the negative voltage decreases (i.e., becomes less negative). When the divided voltage at PFI drops below 1.25V, PFO goes low - indicating degradation of the negative supply. Accuracy depends on resistor tolerance and PFI input current (≤25nA), so 1% resistors are recommended for ±2% trip-point stability.

What is the maximum allowable VBATT voltage for MAX690ACPA+?

The maximum allowable VBATT voltage for MAX690ACPA+ is 4.80V, as specified in Table 2 of the datasheet. Exceeding this voltage risks forward-biasing the internal substrate diode (D1 in Figure 3) when VCC is near its reset threshold, causing unintended current flow from VBATT into the die and potential latch-up. Lithium batteries with 3.0V–3.6V open-circuit voltage are ideal; if higher-voltage sources are used, a series diode or regulator must be added to limit VBATT to ≤4.80V under all operating conditions.