Analog Devices Inc./Maxim Integrated MAX791EPE+

Overview

MAX791EPE+ from Maxim Integrated is a microprocessor supervisory circuit providing precision 4.65V reset monitoring, 200ms reset timeout, independent watchdog timer (preset 1.6s or adjustable via external capacitor), battery switchover (250mA VCC mode / 25mA battery mode), and chip-enable gating with 6ns propagation delay - used in portable/battery-powered equipment to ensure reliable µP startup, brownout recovery, and fail-safe memory write completion.

For engineers reviewing the MAX791EPE+ datasheet, MAX791EPE+ pinout, MAX791EPE+ application, or MAX791EPE+ equivalent, key selection considerations include guaranteed RESET validity down to VCC = 1V, dual-stage power-fail warning (PFI/LOWLINE), software-monitored backup-battery voltage, and CMOS RAM write protection during supply transitions.

Technical Context

The MAX791EPE+ integrates a precision 4.65V reset comparator with 15mV hysteresis, a separate low-line comparator thresholded 150mV above reset, and an uncommitted 1.25V PFI comparator for flexible power-fail detection. Its watchdog timer supports both fixed 1.6s timeout (SWT tied to VOUT) and user-adjustable timeout (4.7–100nF capacitor from SWT to GND).

Battery switchover uses internal PMOS switches: VCC-to-VOUT on-resistance is 1.2Ω (typ), VBATT-to-VOUT is 17Ω (typ); BATT ON output signals switchover event. Chip-enable gating operates with 75Ω series resistance and 6ns propagation delay (50Ω source, 50pF load), disabling CE OUT during reset to prevent memory corruption.

Key Specifications

Pinout & Package

MAX791EPE+ is housed in a 16-pin plastic DIP package (0.300" wide), RoHS-compliant and lead-free (denoted by '+' suffix). Pin layout follows standard DIP numbering with 0.1" pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX692EPA+ and TPS3823-46DBVR, MAX791EPE+ uniquely combines precision reset, dual-stage power-fail warning, adjustable watchdog, battery switchover, and CE gating in one 16-pin DIP - making it the only option for applications requiring coordinated memory protection and fail-safe backup operation.

Availability

MAX791EPE+ is available at Aetrix Electronics and suitable for portable/battery-powered equipment, critical µP power monitoring, intelligent instruments, computers, and controllers requiring stable component supply across industrial temperature ranges (-40°C to +85°C).

Supply support for MAX791EPE+ 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) designs precision analog, mixed-signal, and power management ICs for demanding industrial, automotive, and computing applications.

The MAX791EPE+ belongs to Maxim's microprocessor supervisory product line, engineered specifically for robust power sequencing, fail-safe memory protection, and battery-backed system operation in harsh environments.

FAQ

What is the operating temperature range for MAX791EPE+?

The MAX791EPE+ is rated for operation from -40°C to +85°C, as confirmed by its ordering code suffix 'E' and the Electrical Characteristics tables covering TMIN to TMAX. This extended industrial temperature range supports deployment in automotive under-hood modules, outdoor instrumentation, and factory automation equipment where ambient temperatures exceed commercial-grade limits. The MAX791EPE+ maintains full specification compliance-including 4.65V reset threshold accuracy and 200ms timeout-across this entire range.

Does MAX791EPE+ support battery-backed CMOS RAM operation?

Yes, MAX791EPE+ fully supports battery-backed CMOS RAM operation through integrated battery switchover functionality. When VCC falls below the 4.65V reset threshold and VBATT exceeds VCC, the internal PMOS switch connects VBATT to VOUT, sustaining power to RAM and RTC circuits. The BATT ON output signals this transition, and the 25mA battery-mode output current is sufficient for typical low-power SRAM and real-time clocks. The MAX791EPE+ also provides software-accessible battery voltage monitoring via the PFI comparator.

How does the watchdog timer function in MAX791EPE+?

The MAX791EPE+ watchdog timer monitors the WDI input for transitions: if WDI remains static (high or low) beyond the timeout period-1.6s by default or user-adjustable via SWT capacitor-the WDPO output pulses low for ≥1ms, followed 70ns later by WDO going low. WDO stays low until the next WDI transition. The timer is disabled when VCC is below reset threshold, during battery-backup mode, or when WDI is left floating (internally biased to ~1.6V). This behavior is documented in the Watchdog Function section and timing diagrams of the MAX791EPE+ datasheet.

Can MAX791EPE+ be used with non-5V power supplies?

Yes, MAX791EPE+ supports non-5V monitoring via its dedicated PFI input, which has a fixed 1.25V threshold and operates independently of VCC. By connecting PFI to a resistor divider from a 3.3V, 12V, or negative supply, designers can generate power-fail alerts for auxiliary rails. Additionally, the LOWLINE comparator tracks VCC with a 150mV offset above the 4.65V reset point, enabling early warning for any VCC level. However, VCC itself must remain within 4.75V–5.5V for proper internal operation per Absolute Maximum Ratings.

What is the purpose of the CE IN and CE OUT pins on MAX791EPE+?

The CE IN and CE OUT pins implement chip-enable signal gating to prevent memory corruption during power faults. CE IN accepts the system's chip-enable signal; CE OUT delivers a gated version that is automatically disabled (driven high) whenever RESET is asserted. This blocks spurious memory writes during power-up, brownout, or reset sequences. With 6ns propagation delay and 75Ω series resistance, the path preserves timing integrity in high-speed systems. The feature is explicitly described in the "Chip-Enable Signal Gating" section and Figure 1 block diagram of the MAX791EPE+ datasheet.