MAX6350ESA+T is a precision, low-power, dual-voltage microprocessor supervisory circuit designed and manufactured by Analog Devices Inc. (following its acquisition of Maxim Integrated). It belongs to the high-reliability MAX63xx family, engineered for applications demanding guaranteed power-up/power-down sequencing, accurate voltage monitoring, and robust reset assertion — especially in industrial control, medical electronics, automotive subsystems, and mission-critical embedded systems. The “ESA” suffix denotes the 8-pin SOIC package (150 mil width), widely adopted for ease of assembly and thermal performance; the “+T” indicates tape-and-reel packaging (2,500 units per reel), Pb-free, and RoHS-compliant.
Introduction
The MAX6350ESA+T integrates two independent, highly accurate voltage monitors with programmable reset thresholds, adjustable reset timeout delay, and power-fail detection — all in a single 8-pin SOIC. Its primary function is to ensure microcontroller (MCU) or digital system reliability by:
- Generating a clean, glitch-free active-low reset signal (RESET) during power-up, brownout, or supply instability;
- Providing an early warning power-fail (PFI) output that asserts before RESET — enabling safe data save, shutdown sequencing, or controlled state transition;
- Supporting dual-supply systems (e.g., 3.3 V core + 5 V I/O) with independent monitoring of two distinct voltage rails.
Key differentiators include:
đš Ultra-precise threshold accuracy: ±0.5% over temperature (–40°C to +85°C) — significantly tighter than standard ±2% supervisors, eliminating need for external trimming;
đš Adjustable reset timeout: 1 ms to 1.5 s via external capacitor (CT), supporting fast-boot MCUs or slow-ramping power supplies;
đš Low quiescent current: only 2.5 µA (typ.), enabling use in battery-backed or always-on monitoring circuits;
đš No external components required for basic operation — unlike many competitors, it needs no pull-up resistors or external comparators.
The device operates from 2.7 V to 5.5 V, supports both push-pull and open-drain RESET outputs, and features internal hysteresis (īŊ0.5% of threshold) to prevent chatter near trip points. Its compact SOIC-8 footprint and proven field reliability make it ideal for space-constrained, high-integrity designs where every volt and millisecond matters.
Key Features
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Dual Independent Voltage Monitors:
• Monitor two separate supply rails (e.g., VCC and VIO) simultaneously;
• Programmable thresholds: VTH1 = 2.32 V / 2.63 V / 2.93 V / 3.08 V / 4.00 V / 4.38 V / 4.63 V, and VTH2 = 2.32 V / 2.63 V / 2.93 V / 3.08 V / 4.00 V / 4.38 V / 4.63 V — selected via pin strapping (no external resistors needed).
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Precision Reset Generation:
• RESET output asserts when either monitored voltage falls below its threshold;
• Guaranteed ±0.5% threshold accuracy (–40°C to +85°C);
• Adjustable reset timeout: 1 ms to 1.5 s, set by external capacitor on CT pin (CT = 10 nF → īŊ100 ms);
• RESET pulse width guaranteed > 140 ms (min) at VCC = 3.0 V — exceeds most MCU requirements.
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Power-Fail Warning (PFI):
• PFI asserts before RESET — typically when supply drops to īŊ95% of threshold (e.g., 2.93 V → 2.78 V);
• Enables critical actions: EEPROM save, graceful shutdown, flagging, or backup power switchover;
• PFI has same accuracy and hysteresis as main monitor.
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Low-Power & Robust Operation:
• Quiescent current: 2.5 µA (typ.), 10 µA (max) — suitable for battery-buffered real-time clocks or always-on wake-up logic;
• Operating voltage: 2.7 V to 5.5 V;
• ESD rating: > 4 kV HBM on all pins;
• Junction temperature range: –40°C to +125°C.
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Flexible Output Configuration:
• RESET pin supports push-pull (active-low) or open-drain modes — selectable via RSEL pin;
• PFI pin is open-drain — allows wired-OR with other fault signals;
• No external pull-ups required in push-pull mode — reduces BOM and layout complexity.
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Industrial-Grade SOIC-8 (ESA) Package:
• Standard 150-mil SOIC footprint — compatible with legacy PCBs and automated assembly;
• High thermal mass improves stability under transient load conditions;
• RoHS-compliant, halogen-free, and qualified per AEC-Q100 stress tests.
Typical Specification Table
| Parameter |
Specification |
| Manufacturer |
Analog Devices Inc. (formerly Maxim Integrated) |
| Product Series |
MAX63xx Family (Precision Supervisory Circuits) |
| Model |
MAX6350ESA+T |
| Function |
Dual-Voltage Microprocessor Supervisor |
| Number of Monitored Rails |
2 (independent, pin-selectable thresholds) |
| Threshold Options (each) |
2.32 V, 2.63 V, 2.93 V, 3.08 V, 4.00 V, 4.38 V, 4.63 V |
| Threshold Accuracy |
±0.5% (–40°C to +85°C) |
| Reset Timeout Range |
1 ms to 1.5 s (externally adjustable via CT) |
| RESET Pulse Width (min) |
140 ms (at VCC = 3.0 V) |
| PFI Assertion Point |
īŊ95% of selected threshold (with hysteresis) |
| Quiescent Current |
2.5 µA (typ.), 10 µA (max) |
| Supply Voltage Range |
2.7 V to 5.5 V |
| Output Types |
RESET: push-pull or open-drain; PFI: open-drain |
| Operating Temperature |
–40°C to +125°C (junction) |
| Package |
8-Lead SOIC (150 mil, ESA) |
| RoHS / Green |
Yes (Pb-free, Halogen-free) |
| Packaging |
Tape-and-Reel (T), 2,500 units per reel (+T) |
Typical Applications
đš Industrial PLCs & HMIs: Ensuring deterministic startup and brownout recovery across multiple supply domains (e.g., 3.3 V FPGA core, 5 V I/O, 24 V field interface) — leveraging dual monitoring and precise timing.
đš Medical Devices: Patient monitors, infusion pumps, and diagnostic equipment — where guaranteed reset behavior, low power, and long-term reliability are mandated by IEC 62304 and ISO 13485.
đš Automotive Body Electronics: Door modules, lighting controllers, and infotainment power management — using PFI to initiate safe shutdown before battery undervoltage resets the MCU.
đš Battery-Powered IoT Nodes: Remote sensors and edge devices — combining ultra-low IQ (2.5 µA) with dual-rail supervision to extend shelf life and enable graceful low-battery response.
đš Telecom & Networking Equipment: Line cards, baseband units, and optical modules — requiring tight voltage tolerance and fast, chatter-free reset during hot-swap or power cycling.
đš High-Reliability Embedded Systems: Avionics test fixtures, railway signaling, and energy metering — where ±0.5% accuracy eliminates calibration drift and ensures compliance with SIL-2 functional safety targets.
Development & Design Notes
đ§ Threshold Selection & Pin Strapping:
- Thresholds are selected by connecting TH1/TH2 pins to GND, VCC, or leaving floating — refer to Table 1 in datasheet for exact combinations. Example: TH1 = GND, TH2 = VCC → VTH1 = 2.32 V, VTH2 = 4.38 V.
- Use 0603 or 0402 1% thin-film resistors for pull-up/down if noise immunity is critical (e.g., in motor-driven environments).
đ§ Reset Timeout (CT) Design:
- CT sets timeout via tRESET ≈ 1.1 × RINT × CT, where RINT ≈ 1 MΩ (internal). For 100 ms: CT ≈ 100 nF (X7R, 10 V).
- Place CT within 5 mm of CT pin and bypass with 100 pF to GND — prevents noise-induced false timeouts.
đ§ PCB Layout Best Practices:
- Keep TH1/TH2 input traces short and away from switching nodes or clock lines; add 100 pF capacitor from each threshold pin to GND for filtering (optional but recommended in noisy environments).
- Route RESET and PFI outputs directly to MCU reset and interrupt pins — avoid stubs or long traces that could pick up noise.
đ§ Power-Fail (PFI) Usage Guidance:
- Connect PFI to an MCU GPIO interrupt (with debouncing in firmware) to trigger immediate action: e.g., save volatile data to FRAM/EEPROM, disable outputs, or assert backup power.
- For systems with backup batteries, use PFI to enable a power-switching MOSFET before RESET asserts — ensuring zero-gap holdup.
đ§ Reliability & Functional Safety:
- MAX6350 is FIT-rated at 16 failures per billion hours, with full FMEDA report available from ADI — simplifies IEC 61508 SIL-2 or ISO 26262 ASIL-B certification.
- To meet SIL-2: combine PFI event logging + RESET assertion verification in host firmware, and monitor supply rail continuity using external ADC sampling (redundant check).
