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Analog Devices Inc./Maxim Integrated MAX6391KA29+
- Part No.:
- MAX6391KA29+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- SOT-23-8
- Datasheet:
-
MAX6391KA29+.pdf
- Description:
- MAX6391 DUAL-VOLTAGE MICROPROCES
- Quantity:
- Payment:
- Shipping:
Inventory:313
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Product details
Overview
MAX6391KA29+ from Maxim Integrated is a dual-voltage microprocessor supervisory circuit with sequenced open-drain reset outputs, monitoring VCC (2.93V factory-fixed threshold) and an adjustable secondary supply (RESET IN2), delivering guaranteed reset validity down to VCC = 1V and 15µA typical supply current for multi-rail power-up sequencing in industrial controllers and embedded systems.
For engineers reviewing the MAX6391KA29+ datasheet, MAX6391KA29+ pinout, MAX6391KA29+ application, or MAX6391KA29+ equivalent, this page delivers verified timing behavior (140ms min RESET1 timeout, CSRT-configurable RESET2 delay), true dual-supply monitoring architecture, SOT23-8 package constraints, and real-world sequencing requirements for dual-voltage µP systems.
Technical Context
The MAX6391KA29+ implements two independent voltage comparators: one fixed at 2.93V for VCC (master supply), and one referenced to 625mV for RESET IN2 (slave supply), enabling precise dual-threshold supervision. RESET1 asserts only on VCC undervoltage and deasserts after a fixed 140ms minimum timeout; RESET2 asserts if either supply falls below its threshold and deasserts after a fixed 140ms minimum or capacitor-adjustable delay via CSRT.
Its sequenced reset logic ensures RESET2 always deasserts after RESET1 during power-up and asserts before RESET1 during power-down - a deterministic timing relationship critical for safe multi-component turn-on/off. Internal 47kΩ pullup resistors on RESET1 and RESET2 support flexible VOH level selection without external components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Reset Threshold | 2.93V (factory-fixed; ensures reliable reset assertion when primary supply drops below nominal 3.3V rail) |
| RESET IN2 Threshold | 625mV (internal reference; enables monitoring of secondary supplies as low as ~0.625V via external resistor divider) |
| RESET1 Timeout Period | 140ms min (fixed internal timer; guarantees minimum reset hold time after VCC recovery for stable µP initialization) |
| RESET2 Timeout Period | 140ms min (fixed) or user-adjustable (via CSRT capacitor); provides flexibility for slave processor wake-up coordination |
| Supply Current | 15µA typical (enables use in battery-backed or ultra-low-power systems without compromising supervision integrity) |
| Reset Valid Down To | VCC = 1V (ensures functional reset assertion even during deep brownout conditions) |
| Operating Temperature | -40°C to +85°C (supports deployment in industrial and extended-environment embedded applications) |
Pinout & Package
MAX6391KA29+ is housed in an 8-pin SOT23 package (JEDEC MO-178 compliant, 1.95mm × 2.80mm footprint, 1.30mm height), optimized for space-constrained PCB layouts while maintaining thermal and electrical performance across -40°C to +85°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - RESET IN2 | Secondary supply monitor input | High-impedance comparator input referenced to 625mV; accepts voltage from external resistor divider to set custom reset threshold |
| 2 - VCC | Main supply input & power rail | Primary monitored supply (2.93V threshold) and device power source; all resets assert when VCC falls below threshold |
| 3 - CSRT | RESET2 timeout configuration node | Connect to VCC for fixed 140ms RESET2 delay; connect to capacitor for user-adjustable delay (tRP2 = 2.08×10⁶ × CCSRT) |
| 4 - GND | Analog/digital ground reference | Common return path for all internal comparators, timers, and output drivers; must be low-impedance for noise immunity |
| 5 - RESET2 | Secondary active-low open-drain reset output | Asserts LOW when VCC or RESET IN2 falls below threshold; deasserts after fixed or capacitor-timed delay; requires external pullup |
| 6 - R2 | Internal pullup connection for RESET2 | 47kΩ resistor tied internally to RESET2; connect to desired VOH rail (e.g., 3.3V or 5V) to set output high level without discrete resistor |
| 7 - RESET1 | Primary active-low open-drain reset output | Asserts LOW only on VCC undervoltage; deasserts 140ms min after VCC recovery; timing independent of RESET IN2 |
| 8 - R1 | Internal pullup connection for RESET1 | 47kΩ resistor tied internally to RESET1; connect to target VOH rail to define high-state voltage independently of RESET2 |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent voltage monitors | One fixed 2.93V VCC monitor + one 625mV-referenced RESET IN2 monitor enable simultaneous supervision of master/slave rails with no shared timing dependency |
| Guaranteed reset operation down to VCC = 1V | Ensures functional reset assertion during severe brownout or battery sag, preventing undefined µP states in low-VCC conditions |
| Sequenced reset timing control | RESET2 always deasserts after RESET1 on power-up and asserts before RESET1 on power-down - enforcing strict turn-on/turn-off order for multi-IC systems |
| Integrated 47kΩ pullup resistors | Eliminates need for external pullups on both RESET outputs; allows independent VOH level selection by connecting R1/R2 to different supply rails |
| Immunity to short negative VCC transients | Rejects glitches ≤100ns at ≥10mV overdrive, preventing spurious resets from EMI or switching noise on the main supply rail |
Applications
| Industrial PLC Controllers | Multi-Rail Embedded Systems |
|---|---|
|
Use Scenario: Powering FPGA, MCU, and I/O peripherals from separate 3.3V, 1.8V, and 5V rails with strict startup ordering. IC Role / Device Role / Timing Role: Supervisory sequencer ensuring FPGA config memory initializes before MCU firmware execution and I/O drivers power up last. Use Value: Prevents bus contention and latch-up by enforcing RESET1 (FPGA) → RESET2 (MCU/I/O) deassertion sequence, validated across -40°C to +85°C. |
Use Scenario: Dual-core SoC with independent core and I/O power domains requiring staggered reset release. IC Role / Device Role / Timing Role: Primary reset (RESET1) controls core domain; secondary reset (RESET2) controls I/O domain, delayed via CSRT capacitor to meet SoC boot timing spec. Use Value: Enables compliance with SoC vendor's 200ms minimum core-to-I/O reset separation requirement using single IC and one external capacitor. |
| Network Equipment Power Management | Medical Diagnostic Instrumentation |
|
Use Scenario: 48V-to-12V/5V/3.3V DC-DC conversion chain powering switch ASIC, PHY, and management MCU. IC Role / Device Role / Timing Role: Monitors 12V intermediate rail (VCC) and 3.3V management rail (RESET IN2); RESET1 enables switch ASIC, RESET2 enables management MCU after ASIC stabilization. Use Value: Eliminates need for discrete RC timers and dual supervisors, reducing BOM count and layout area while guaranteeing 140ms+ reset hold on both rails. |
Use Scenario: Portable ultrasound device with battery-backed real-time clock, analog front-end, and display controller requiring fail-safe power sequencing. IC Role / Device Role / Timing Role: VCC (3.3V system rail) triggers primary reset; RESET IN2 monitors 1.8V AFE rail; RESET2 delays display controller enable until analog signal chain stabilizes. Use Value: Ensures diagnostic image integrity by preventing display initialization before ADC reference settles - enforced by deterministic RESET2 delay and 1V reset validity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-voltage supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX6392KA29+ | Includes active-low manual reset (MR) input and push-pull RESET1; lacks R1 pullup (replaced by MR); same VCC threshold and RESET IN2 architecture | Required where field-service reset or system-level watchdog-triggered restart is needed; not drop-in due to pin function change (Pin 8 = MR, not R1) | Select MAX6392KA29+ when manual reset capability is mandatory; otherwise MAX6391KA29+ offers simpler pinout and dedicated R1 pullup |
| TPS3808G33DBVR | Single-supply supervisor (3.3V fixed threshold); no secondary supply monitor or sequenced dual-reset outputs; 200ms fixed reset timeout | Suitable only for single-rail systems; cannot replace dual-monitoring or sequencing functionality of MAX6391KA29+ | Use TPS3808G33DBVR only for cost-sensitive single-supply applications; it does not satisfy dual-voltage sequencing requirements |
Compared with MAX6392KA29+, the MAX6391KA29+ provides dedicated R1/R2 pullup terminals for independent VOH control but omits manual reset - making it optimal for fixed-configuration embedded systems. Compared with TPS3808G33DBVR, MAX6391KA29+ adds essential dual-supply monitoring and deterministic reset sequencing absent in single-threshold alternatives.
Availability
MAX6391KA29+ is available at Aetrix Electronics and suitable for industrial PLC controllers, multi-rail embedded systems, network equipment power management, medical diagnostic instrumentation, and portable test equipment requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.
Supply support for MAX6391KA29+ 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, automotive, communications, and computing applications.
The MAX6391/MAX6392 product line delivers dual-voltage µP supervisory circuits with sequenced reset outputs, targeting systems requiring deterministic power-up/down sequencing across multiple supply rails in space- and power-constrained environments.
FAQ
What is the factory-set VCC reset threshold voltage for MAX6391KA29+?
The MAX6391KA29+ has a factory-set VCC reset threshold of 2.93V (minimum 2.85V, maximum 3.00V per datasheet). This value is laser-trimmed during production and applies specifically to the KA29 variant - confirmed in the Selector Guide and Electrical Characteristics table. The MAX6391KA29+ uses this fixed threshold to assert RESET1 whenever VCC drops below 2.93V, ensuring compatibility with standard 3.3V supply rails.
Does MAX6391KA29+ support adjustable RESET2 timeout, and how is it configured?
Yes, MAX6391KA29+ supports user-adjustable RESET2 timeout via the CSRT pin. Connecting an external capacitor from CSRT to ground sets the delay using tRP2 = 2.08 × 10⁶ × CCSRT (e.g., 1500pF yields ~3.1ms). Alternatively, tying CSRT to VCC selects a fixed 140ms minimum timeout. This dual-mode configuration is exclusive to the MAX6391KA29+ and is implemented via an internal 600nA current source and 1.25V reference comparator.
What is the purpose of pins R1 and R2 on MAX6391KA29+?
Pins R1 (Pin 8) and R2 (Pin 6) are internal 47kΩ pullup resistors connected to RESET1 and RESET2 outputs respectively. They allow designers to set independent high-level output voltages (VOH) by connecting each pin to its target rail (e.g., R1 to 5V, R2 to 3.3V), eliminating external pullup resistors. This feature is unique to the MAX6391KA29+ series and is documented in the Pin Description and Applications Information sections.
How does MAX6391KA29+ ensure correct reset sequencing during power-up and power-down?
MAX6391KA29+ enforces strict sequencing: during power-up, RESET2 deasserts only after RESET1 has deasserted (140ms min delay); during power-down, RESET2 asserts before RESET1. This behavior is hardwired in the internal logic and verified across -40°C to +85°C. The timing diagram (Figure 2) and Detailed Description section confirm that tRD2 < tRD1 ensures RESET2 leads RESET1 on falling VCC, preventing race conditions in multi-IC systems.
Is MAX6391KA29+ compatible with 1.8V or 2.5V supply rails for RESET IN2 monitoring?
Yes, MAX6391KA29+ can monitor 1.8V or 2.5V rails via RESET IN2 using an external resistor divider. With a fixed 625mV internal reference, a 1.8V rail requires R3/R4 ≈ 1.88 (e.g., R4 = 500kΩ, R3 = 940kΩ); a 2.5V rail requires R3/R4 ≈ 3.0 (e.g., R4 = 500kΩ, R3 = 1.5MΩ). This calculation method is explicitly provided in the Applications Information section and validated for all temperature ranges.
MAX6391KA29+ 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:
- 2.93V, Adj
- Output:
- Open Drain or Open Collector
- Reset:
- Active Low
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-8
MAX6391KA29+ FAQ
1.How can I place an order for MAX6391KA29+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX6391KA29+ 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 MAX6391KA29+ reliable?
The price and inventory of MAX6391KA29+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX6391KA29+ is usually 5 days.
3.What payment methods are accepted for MAX6391KA29+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX6391KA29+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX6391KA29+?
MAX6391KA29+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX6391KA29+ 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 MAX6391KA29+?
For technical support, including MAX6391KA29+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX6391KA29+ requirements.
6.How does Aetrix verify that MAX6391KA29+ is sourced from the original manufacturer or authorized distributors?
All MAX6391KA29+ 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 MAX6391KA29+ meets industry standards.
7.What is the process for return or replacement of MAX6391KA29+?
All MAX6391KA29+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX6391KA29+, 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 MAX6391KA29+ part is unused and in its original packaging.
Return procedure for MAX6391KA29+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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