Analog Devices Inc./Maxim Integrated MAX6391KA17

Overview

MAX6391KA17 from Maxim Integrated is a dual-voltage microprocessor supervisory circuit with sequenced open-drain reset outputs, factory-set VCC reset threshold of 1.67V (min), guaranteed reset validity down to VCC = 1.0V, and fixed 140ms (min) RESET1 timeout. It monitors master supply VCC and adjustable secondary supply RESET IN2 (down to 625mV) for power sequencing in multivoltage embedded systems.

For engineers reviewing the MAX6391KA17 datasheet, MAX6391KA17 pinout, MAX6391KA17 application, or MAX6391KA17 equivalent, this device supports precise power-up ordering between primary and secondary subsystems, offers internal 47kΩ pullup resistors on both RESET1 and RESET2, and delivers low 15µA typical supply current in an 8-pin SOT23 package.

Technical Context

The MAX6391KA17 implements two independent voltage monitoring paths: a factory-trimmed bandgap-based comparator for VCC (threshold = 1.67V) and a high-impedance 625mV reference comparator for RESET IN2. RESET1 asserts only on VCC undervoltage and deasserts after a fixed 140ms minimum timeout; RESET2 asserts if either VCC or RESET IN2 falls below its respective threshold and deasserts after 140ms (min) or a capacitor-adjustable delay via CSRT.

Its sequenced behavior is deterministic: during power-up, RESET2 deasserts strictly after RESET1; during power-down, RESET2 asserts before RESET1. The device guarantees valid reset assertion even at VCC = 1.0V and features immunity to short negative VCC transients (≤100ns at 100mV overdrive).

Key Specifications

Pinout & Package

MAX6391KA17 is housed in an 8-pin SOT23 package (JEDEC MO-178 compliant, 1.95mm × 2.80mm × 1.30mm body), rated for -40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-voltage supervisory applications.

Compared with MAX6392KA17, MAX6391KA17 eliminates MR complexity and retains dual internal pullups; compared with TPS3808G17DBVR, it uniquely provides dual-supply monitoring and guaranteed reset sequencing-critical for multivoltage SoC and FPGA platforms.

Availability

MAX6391KA17 is available at Aetrix Electronics and suitable for industrial PLC controllers, embedded multicore SoC systems, and battery-backed data loggers requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to +85°C operation.

Supply support for MAX6391KA17 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, medical, and communications applications.

The MAX6391/MAX6392 product line delivers dual-voltage supervisory circuits with deterministic reset sequencing-engineered specifically for reliable power-up/down control in multirail embedded systems.

FAQ

What is the factory-set VCC reset threshold voltage for MAX6391KA17?

The MAX6391KA17 has a factory-trimmed VCC reset threshold of 1.67V (typical), with a guaranteed range of 1.62V to 1.71V across temperature. This value is laser-trimmed during production and cannot be adjusted. The threshold applies exclusively to the VCC supply monitored at Pin 2 and directly determines when RESET1 asserts during brownout or power-down events. MAX6391KA17 uses this fixed threshold to ensure consistent, repeatable reset behavior without external components.

How does MAX6391KA17 generate sequenced reset outputs during power-up?

During power-up, MAX6391KA17 asserts RESET1 first when VCC rises above its 1.67V threshold, then holds it asserted for ≥140ms before deassertion. RESET2 remains asserted until both VCC exceeds 1.67V and RESET IN2 exceeds 625mV, and only deasserts after the CSRT-configured delay (140ms min or capacitor-adjustable). This enforces strict RESET1-before-RESET2 release order. MAX6391KA17 achieves this via separate internal timing chains and comparator latches, guaranteeing sequencing without software or external logic.

Can MAX6391KA17 monitor a 2.5V supply as the secondary voltage (RESET IN2)?

Yes - MAX6391KA17 can monitor a 2.5V supply on RESET IN2 using an external resistor divider. With its internal 625mV reference, a divider ratio of R3/R4 = (2.5V / 0.625V) − 1 = 3.0 sets the correct threshold. For example, using R4 = 500kΩ yields R3 = 1.5MΩ. The high-impedance input draws only 50nA, minimizing divider current. MAX6391KA17's RESET IN2 pin accepts any voltage up to VCC+0.3V, making it compatible with common rail voltages while maintaining accurate threshold scaling.

What is the purpose of the R1 and R2 pins on MAX6391KA17?

R1 (Pin 8) and R2 (Pin 6) provide internal 47kΩ pullup resistors connected to RESET1 and RESET2 outputs respectively. These allow designers to tie R1/R2 to any desired VOH rail (e.g., 3.3V or 5V) independent of VCC, enabling level-shifted reset signaling without external resistors. Unlike open-drain-only supervisors, MAX6391KA17 integrates these pullups to reduce BOM count and layout area. MAX6391KA17 requires no external pullups unless a different resistance value or voltage is needed.

Does MAX6391KA17 support operation below 1.2V VCC?

No - MAX6391KA17 specifies a minimum operating VCC of 1.2V across the full -40°C to +85°C range, though its reset outputs remain valid down to VCC = 1.0V. Below 1.2V, internal circuitry (including comparators and timing blocks) may not function reliably. The 1.0V reset validity ensures that once VCC drops below 1.2V, the device continues asserting RESET1/RESET2 correctly until VCC reaches 1.0V, providing extended brownout coverage. MAX6391KA17 is not characterized or guaranteed for continuous operation below 1.2V.