Analog Devices Inc./Maxim Integrated MAX7391CMTP

Overview

MAX7391CMTP from Maxim Integrated is a speed-switching clock generator with integrated power-fail and reset supervision for microcontrollers in 3.3V/5V systems. It delivers factory-trimmed 8MHz clock output (±4% accuracy over –40°C to +125°C), open-drain RST output, 4.38V POR threshold, ±10mA CLOCK drive, and operates from 2.7V to 5.5V supply. It replaces crystals/resonators in white goods and appliance control boards requiring robust timing and brownout protection.

For engineers reviewing the MAX7391CMTP datasheet, MAX7391CMTP pinout, MAX7391CMTP application, or MAX7391CMTP equivalent, this device serves as a single-chip clock + reset + power-fail monitor with programmable speed switching, VCC/internal PFI monitoring, and high-temperature reliability up to +125°C - critical for industrial MCU systems where EMI resistance and flash-safe power-fail response are required.

Technical Context

The MAX7391CMTP integrates a BiCMOS oscillator core, power-on reset (POR) comparator with 4.38V rising threshold (VTH+), and dual-mode power-fail detection - configurable via PFI pin for either internal VCC monitoring (VITH = 4.38V) or external voltage sensing (VETH = 1.1V). Its SPEED input enables dynamic clock halving during power-fail events when tied to PFO.

It features push-pull CLOCK output with 45–55% duty cycle, 310ps RMS jitter (20s observation), 2.5–7.0ns rise/fall times (10pF load), and reset timeout tRST = 135µs (typ). The RST/RST output is open-drain, valid down to 1.1V VCCR, and asserts on VCC falling below VTH− = 0.98 × VTH+.

Key Specifications

Pinout & Package

MAX7391CMTP is housed in an 8-pin µMAX® package (U8-1 outline, 3mm × 3mm, 0.5mm pitch), surface-mount, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar clock + reset + power-fail monitoring applications.

Compared with MAX7390MTP+, MAX7391CMTP adds configurable external PFI monitoring and retains identical 8MHz clock and 4.38V reset; versus TPS3808G33DBVR, MAX7391CMTP integrates timing and supervision in one package - reducing component count, layout complexity, and qualification effort for new MCU designs.

Availability

MAX7391CMTP is available at Aetrix Electronics and suitable for white goods control, appliance MCU systems, and portable equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX7391CMTP 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 industrial, computing, and consumer applications.

The MAX7391CMTP belongs to Maxim's supervisory clock generator family, engineered to replace discrete timing and reset solutions in microcontroller-based systems demanding high reliability, EMI resilience, and extended temperature operation.

FAQ

What is the factory-programmed clock frequency of the MAX7391CMTP?

The MAX7391CMTP is factory-programmed to 8MHz, as indicated by the "TP" suffix in its part number per Maxim's Selector Guide. This frequency is trimmed to ±4% accuracy over –40°C to +125°C and requires no external load capacitors. The MAX7391CMTP clock output drives MCU clock inputs directly in push-pull CMOS format.

Does the MAX7391CMTP support external voltage monitoring for power-fail detection?

Yes, the MAX7391CMTP supports external voltage monitoring via the PFI pin. When VPFI < 0.65 × VCC, it enters external detection mode and triggers PFO when the applied voltage falls below 1.1V (VETH). This allows monitoring of auxiliary rails like 3.3V or 2.5V supplies using a simple resistive divider - a capability confirmed in the MAX7391CMTP Electrical Characteristics table and Functional Diagram.

What is the reset threshold voltage for the MAX7391CMTP, and how is it configured?

The MAX7391CMTP has a fixed 4.38V power-on reset (POR) threshold (VTH+), denoted by the "r" code "J" in Table 1. This value is factory-trimmed and non-adjustable. The reset output remains asserted until VCC rises above 4.38V and then holds for 135µs (tRST), ensuring reliable MCU initialization. The MAX7391CMTP datasheet specifies ±2.5% tolerance over temperature.

Can the MAX7391CMTP operate from a 3.3V supply, and what are the implications?

Yes, the MAX7391CMTP operates from 2.7V to 5.5V, fully supporting 3.3V systems. At 3.3V, its CLOCK output maintains rail-to-rail swing (VOHC = VCC – 0.3V, VOLC = 0.3V), and reset remains valid down to 1.1V VCCR. However, internal VCC monitoring uses a fixed 4.38V threshold, so PFI must be used in external mode with a resistor divider to monitor the 3.3V rail - a configuration validated in the MAX7391CMTP Typical Application Circuit.

How does the SPEED pin function in the MAX7391CMTP, and what design benefit does it provide?

The SPEED pin on the MAX7391CMTP selects between full-speed (SPEED = high) and half-speed (SPEED = low) clock output. When tied to PFO, it automatically reduces clock frequency during power-fail events - extending the time available for critical tasks like flash writes before shutdown. This behavior is explicitly documented in the MAX7391CMTP General Description and Figure 1 timing diagram.