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Analog Devices Inc./Maxim Integrated MAX6391KA44
- Part No.:
- MAX6391KA44
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- SOT-23-8
- Datasheet:
-
MAX6391KA44.pdf
- Description:
- IC SUPERVISOR 2 CHANNEL SOT23-8
- Quantity:
- Payment:
- Shipping:
Inventory:953
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Product details
Overview
MAX6391KA44 from Maxim Integrated is a dual-voltage microprocessor supervisory circuit with sequenced reset outputs for multi-rail systems. It monitors VCC (master supply) at 4.38V threshold and RESET IN2 (adjustable secondary supply), asserts RESET1 and RESET2 in controlled sequence, and guarantees valid reset operation down to VCC = 1V - used in industrial controllers and multivoltage servers requiring precise power-up sequencing.
For engineers reviewing the MAX6391KA44 datasheet, MAX6391KA44 pinout, MAX6391KA44 application, or MAX6391KA44 equivalent, this device delivers factory-trimmed 4.38V VCC monitoring, user-configurable RESET2 timeout via CSRT capacitor, open-drain RESET1/RESET2 with internal 47kΩ pullups, and guaranteed operation across -40°C to +85°C in SOT23-8.
Technical Context
The MAX6391KA44 implements two independent voltage comparators: one fixed-threshold (4.38V) comparator on VCC driving RESET1, and a 625mV reference comparator on RESET IN2 enabling external resistive-divider monitoring of secondary supplies as low as 625mV. RESET1 deasserts 140ms (min) after VCC exceeds 4.38V, while RESET2 deasserts either 140ms (min) after both VCC and RESET IN2 exceed thresholds (CSRT tied to VCC) or after a capacitor-adjustable delay (CSRT to ground).
RESET2 always deasserts after RESET1 during power-up and asserts before RESET1 during power-down, enforcing strict sequencing. The device uses BiCMOS process (810 transistors), draws only 15µA typical supply current, and remains functional with VCC as low as 1.0V - critical for brownout resilience in embedded control systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Reset Threshold | 4.38V (factory-trimmed, ±0.13V tolerance) - sets precise master supply brownout detection point |
| RESET IN2 Threshold | 625mV (internal reference) - enables monitoring of secondary supplies down to 625mV via external resistor divider |
| RESET1 Timeout | 140ms minimum - ensures stable µP reset hold time after VCC recovery, no external components needed |
| RESET2 Timeout | 140ms minimum (CSRT = VCC) or capacitor-adjustable (CSRT = C to GND) - supports flexible sequencing for slave processors or peripherals |
| Supply Current | 15µA typical - enables use in battery-backed or ultra-low-power systems without compromising supervision integrity |
| Operating Voltage Range | 1.2V to 5.5V - guarantees full functionality across wide input range, including 1.8V, 3.3V, and 5V rails |
| Reset Valid Down To | VCC = 1.0V - maintains reliable reset assertion during deep brownout conditions before system collapse |
Pinout & Package
MAX6391KA44 is housed in an 8-pin SOT23 package (3.00mm × 1.75mm × 1.30mm body, 0.65mm pitch), rated for -40°C to +85°C operation, with lead-free option available (+T suffix).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - RESET IN2 | Secondary supply monitor input | High-impedance node for external resistive divider; sets RESET2 activation threshold via 625mV internal reference |
| 2 - VCC | Main supply and master reset monitor | Power source and primary voltage sense input; triggers both RESET1 and RESET2 when below 4.38V |
| 3 - CSRT | RESET2 timeout configuration terminal | Connect to VCC for fixed 140ms RESET2 delay; connect to capacitor-to-GND for user-adjustable delay (tRP2 = 2.08×10⁶ × CCSRT) |
| 4 - GND | Analog/digital ground reference | Common return path for all internal comparators, references, and output drivers |
| 5 - RESET2 | Secondary active-low reset output | Open-drain output asserted when VCC < 4.38V OR RESET IN2 < 625mV; deasserts only after both recover and RESET1 is released |
| 6 - R2 | Internal pullup connection for RESET2 | 47kΩ resistor internally connected to RESET2; tie to external VOH (e.g., 3.3V or 5V) for level-shifted high-state drive |
| 7 - RESET1 | Primary active-low reset output | Open-drain output asserted solely on VCC < 4.38V; deasserts 140ms (min) after VCC recovery, independent of RESET IN2 |
| 8 - R1 | Internal pullup connection for RESET1 | 47kΩ resistor internally connected to RESET1; tie to external VOH for independent high-level pullup voltage |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent voltage monitoring | Simultaneous 4.38V VCC and 625mV RESET IN2 sensing enables robust dual-rail supervision without external comparators |
| Sequenced reset timing control | Guaranteed RESET2 assertion before RESET1 on power-down and RESET1 release before RESET2 on power-up enforces safe boot order |
| Capacitor-adjustable RESET2 timeout | CSRT pin accepts external capacitor (e.g., 1500pF → 3.1ms) or VCC tie (→ 140ms min) - eliminates need for discrete RC timing networks |
| Internal 47kΩ pullup resistors | R1/R2 pins allow direct connection to any external VOH rail (1.8V/3.3V/5V), eliminating external pullup components and enabling mixed-voltage reset signaling |
| Brownout immunity down to 1.0V | Valid reset assertion maintained even as VCC collapses to 1.0V - prevents spurious release during severe undervoltage events |
Applications
| Industrial Controllers | Servers / Workstations |
|---|---|
|
Use Scenario: PLCs and motion controllers with separate 5V logic and 3.3V I/O rails requiring coordinated power-up. IC Role / Device Role / Timing Role: Master supervisor enforcing RESET1 (5V rail) before RESET2 (3.3V I/O) to prevent bus contention during boot. Use Value: Eliminates risk of I/O peripherals powering up before CPU initialization by guaranteeing 140ms+ delay between RESET1 and RESET2 deassertion. |
Use Scenario: Dual-CPU server boards with independent core and memory voltage domains (e.g., 1.2V CPU, 1.5V DDR). IC Role / Device Role / Timing Role: Monitors VCC (1.2V) and RESET IN2 (1.5V via divider) to sequence CPU reset before memory controller reset. Use Value: Prevents memory access violations by ensuring CPU is fully initialized before DDR PHY training begins. |
| Set-Top Boxes | Printers |
|
Use Scenario: Consumer STBs with 3.3V SoC and 1.8V tuner ICs needing glitch-immune reset coordination. IC Role / Device Role / Timing Role: Uses CSRT capacitor to extend RESET2 timeout for slower tuner startup, while RESET1 releases quickly for SoC boot. Use Value: Avoids tuner lock failure by delaying peripheral reset until after SoC firmware loads required configuration registers. |
Use Scenario: Multifunction printers with motor drivers, sensors, and USB host controller powered from different rails. IC Role / Device Role / Timing Role: Monitors main 24V DC-DC output (via divider on RESET IN2) and 3.3V logic rail (VCC) to assert resets in mechanical vs. digital subsystem order. Use Value: Ensures stepper motor drivers are held in reset until logic firmware verifies sensor readiness, preventing unintended motion. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-voltage supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX6392KA44 | Includes active-low manual reset (MR) input and push-pull RESET1; lacks R1 pin (replaced by MR); same VCC threshold and RESET IN2 architecture | Required where field-service reset or debug-triggered reboot is needed; not suitable if R1 pullup flexibility is mandatory | Select MAX6392KA44 only when manual reset functionality is essential and push-pull RESET1 is acceptable |
| TPS3808G33 | Single-supply supervisor (3.3V fixed threshold); no secondary supply monitor or sequenced dual-reset outputs; requires external components for dual-rail support | Applicable only for single-rail systems; cannot replace MAX6391KA44 in dual-voltage sequencing applications without redesign | Choose TPS3808G33 only for cost-sensitive, single-rail designs where RESET2 sequencing is unnecessary |
Compared with MAX6392KA44, the MAX6391KA44 provides dedicated R1/R2 pullup pins for independent VOH control but lacks manual reset; compared with TPS3808G33, it delivers integrated dual-supply monitoring and guaranteed sequencing - making it irreplaceable in multivoltage systems requiring deterministic reset ordering.
Availability
MAX6391KA44 is available at Aetrix Electronics and suitable for industrial controllers, servers/workstations, and set-top boxes requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to +85°C performance.
Supply support for MAX6391KA44 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, computing, and communications applications.
The MAX6391/MAX6392 product line was engineered specifically for dual-rail microprocessor systems requiring deterministic, sequenced reset generation - eliminating discrete supervision circuits and reducing board space and BOM count.
FAQ
What is the exact VCC reset threshold voltage for MAX6391KA44?
The MAX6391KA44 has a factory-trimmed VCC reset threshold of 4.38V, with a guaranteed range of 4.25V to 4.50V across temperature (-40°C to +85°C). This value is laser-trimmed during production and specified in the Electrical Characteristics table under "VCC Reset Threshold (VTH1)" for the "MAX639_UA44" variant. The top-mark "AAHK" on the SOT23-8 package confirms this threshold version.
Can MAX6391KA44 monitor a 1.2V supply as the secondary voltage?
Yes - the MAX6391KA44 can monitor a 1.2V supply on RESET IN2 using an external resistive divider. With its internal 625mV reference, a divider ratio of R3/R4 = (1.2V / 0.625V) − 1 ≈ 0.92 allows precise 1.2V threshold detection. For example, using R4 = 500kΩ yields R3 ≈ 460kΩ. The MAX6391KA44's high-impedance RESET IN2 input (50nA max leakage) ensures minimal loading on the divider network.
How is the RESET2 timeout period configured on MAX6391KA44?
The RESET2 timeout on MAX6391KA44 is configured via the CSRT pin: tying CSRT to VCC selects a fixed 140ms (minimum) timeout, while connecting CSRT to an external capacitor (CCSRT) to ground enables user adjustment per tRP2 = 2.08 × 10⁶ × CCSRT seconds. For instance, a 1500pF capacitor yields ~3.1ms. The MAX6391KA44's internal 600nA current source and 1.25V reference implement this timing without external resistors or op-amps.
Does MAX6391KA44 support operation below 1.8V VCC?
Yes - the MAX6391KA44 operates over VCC = 1.2V to 5.5V and guarantees valid reset assertion down to VCC = 1.0V. Its BiCMOS process enables functional reset behavior even as VCC drops below typical logic thresholds, ensuring reliable brownout detection in ultra-low-voltage systems such as battery-powered IoT edge nodes or energy-harvesting devices where VCC may sag to 1.1V during peak load.
What is the purpose of the R1 and R2 pins on MAX6391KA44?
The R1 and R2 pins on MAX6391KA44 provide dedicated connections to internal 47kΩ pullup resistors for RESET1 and RESET2, respectively. Unlike standard open-drain supervisors, these pins allow designers to tie R1/R2 to any external voltage rail (e.g., 1.8V, 3.3V, or 5V) - enabling level-shifted reset signaling across mixed-voltage domains without adding external pullup resistors or level translators. This feature is unique to the MAX6391 variant and absent in MAX6392.
MAX6391KA44 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- SOT-23-8
- Packaging:
- Bulk
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Multi-Voltage Supervisor
- Number of Voltages Monitored:
- 2
- Voltage - Threshold:
- 4.63V, Adj
- Output:
- Open Drain or Open Collector
- Reset:
- Active Low
- Reset Timeout:
- 140ms/Adjustable Minimum
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-8
MAX6391KA44 FAQ
1.How can I place an order for MAX6391KA44 through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX6391KA44 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for MAX6391KA44 reliable?
The price and inventory of MAX6391KA44 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX6391KA44 is usually 5 days.
3.What payment methods are accepted for MAX6391KA44?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX6391KA44 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX6391KA44?
MAX6391KA44 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX6391KA44 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for MAX6391KA44?
For technical support, including MAX6391KA44 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX6391KA44 requirements.
6.How does Aetrix verify that MAX6391KA44 is sourced from the original manufacturer or authorized distributors?
All MAX6391KA44 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MAX6391KA44 meets industry standards.
7.What is the process for return or replacement of MAX6391KA44?
All MAX6391KA44 units undergo pre-shipment inspection (PSI). If there is an issue with MAX6391KA44, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The MAX6391KA44 part is unused and in its original packaging.
Return procedure for MAX6391KA44:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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