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Analog Devices Inc./Maxim Integrated MAX6728KASVD3+
- Part No.:
- MAX6728KASVD3+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- -
- Datasheet:
-
MAX6728KASVD3+.pdf
- Description:
- MAX6728KASVD3+
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Product details
Overview
MAX6728KASVD3+ from Maxim Integrated is a triple-voltage microprocessor supervisory circuit in an 8-pin SOT23 package, monitoring VCC1 (primary), VCC2 (secondary), and PFI (power-fail input) with factory-trimmed thresholds of 3.075V (VTH1), 2.925V (VTH2), and 626.5mV (VPFI), plus a 210ms minimum reset timeout period. It asserts active-low open-drain RST and PFO outputs when any monitored supply drops below its threshold and maintains reset for the full timeout after recovery - critical for reliable boot sequencing in multivoltage embedded systems.
For engineers reviewing the MAX6728KASVD3+ datasheet, MAX6728KASVD3+ pinout, MAX6728KASVD3+ application, or MAX6728KASVD3+ equivalent, key selection factors include its triple-supply monitoring capability, guaranteed reset validity down to VCC1/VCC2 = 0.8V, integrated power-fail comparator with PFO output, manual reset input with internal 50kΩ pullup, and immunity to sub-20µs VCC transients - all within a space-constrained 8-pin SOT23 footprint.
Technical Context
The MAX6728KASVD3+ implements dual independent voltage comparators for VCC1 and VCC2, plus a dedicated high-impedance PFI comparator referenced to a 626.5mV internal bandgap reference. Its reset logic combines OR-ed fault detection (VCC1 undervoltage, VCC2 undervoltage, PFI low, MR low) with a monolithic timeout timer that restarts on any new fault before timeout completion.
It features separate push-pull or open-drain output drivers: RST is open-drain (pin 1), PFO is open-drain (pin 4), and both are asserted low on fault. The device operates across -40°C to +85°C, draws only 14µA typical supply current at 3.6V, and guarantees correct reset state as long as either VCC1 or VCC2 exceeds 0.8V - enabling robust brownout detection in battery-backed or low-VCC systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC1 Reset Threshold | 3.075V (typ), ±1.5% over temp - sets primary supply monitoring point for 3.3V rail supervision |
| VCC2 Reset Threshold | 2.925V (typ), ±1.5% over temp - enables secondary rail monitoring for 3.0V or 2.85V system supplies |
| PFI Threshold Voltage | 626.5mV (typ), ±2.5mV hysteresis - allows precise external resistor-divider setup for custom power-fail trip points |
| Reset Timeout Period | 210ms (min), 315ms (typ) - ensures sufficient hold time for CPU initialization and peripheral configuration |
| Supply Current | 14µA (typ) at 3.6V - supports ultra-low-power operation in always-on or battery-critical applications |
| Operating Temperature | -40°C to +85°C - qualified for industrial and telecom equipment environments without derating |
| Reset Output Type | Open-drain RST (pin 1) and open-drain PFO (pin 4) - enables wired-OR logic, level translation, and flexible pullup selection |
Pinout & Package
MAX6728KASVD3+ is housed in an 8-pin SOT23-8 package (3.0mm × 1.6mm × 1.1mm), optimized for high-density PCB layouts. Pin 1 is RST (active-low open-drain reset output), pin 4 is PFO (active-low open-drain power-fail output), and pin 5 is GND - all confirmed per Maxim's official pin description table for MAX6728/MAX6729 variants.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | RST | Active-low open-drain reset output; requires external pullup; asserts when VCC1/VCC2/PFI faults or MR is pulled low |
| 2 | GND | Analog/digital ground reference for all internal comparators and timing circuits |
| 3 | MR | Active-low manual reset input with internal 50kΩ pullup to VCC1; debounced by design; no external RC needed |
| 4 | PFO | Active-low open-drain power-fail output; asserts independently of RST when PFI < 626.5mV; no timeout delay |
| 5 | VCC2 | Secondary supply input (0.9V–3.3V range); powers internal VCC2 comparator and sets RST2 reference if used |
| 6 | VCC1 | Primary supply input (1.8V–5.0V range); powers core logic, VCC1 comparator, and RST/PFO drivers |
| 7 | PFI | Power-fail monitor input; high-impedance (±25nA), referenced to 626.5mV internal reference; connects to resistor divider |
| 8 | RST2 | Active-low open-drain secondary reset output (not used in MAX6728KASVD3+ per Selector Guide - reserved but unconnected) |
Key Features
| Feature | Design Value |
|---|---|
| Triple-voltage monitoring | Simultaneous supervision of VCC1, VCC2, and PFI with independent thresholds - eliminates need for three discrete supervisors |
| Guaranteed reset validity down to 0.8V | Ensures deterministic reset assertion even during deep brownout conditions where VCC1 or VCC2 dips near 0.8V |
| Integrated power-fail comparator with PFO | Provides immediate, timeout-free power-fail alert via PFO - enables early software shutdown before main supply collapse |
| Manual reset with internal pullup | 50kΩ internal MR pullup to VCC1 removes need for external resistor - simplifies BOM and reduces board area |
| Immunity to short VCC transients | Rejects glitches <20µs duration (at 100mV overdrive), preventing spurious resets during switching noise or load transients |
Applications
| Telecom Power Sequencing | Industrial PLC I/O Modules |
|---|---|
|
Use Scenario: Supervising 3.3V core, 2.5V I/O, and -48V DC-DC bias rails in carrier-grade line cards. IC Role / Device Role / Timing Role: MAX6728KASVD3+ monitors VCC1=3.3V, VCC2=2.5V, and PFI tied to -48V-derived sense voltage - asserting RST until all rails stabilize, then releasing after 210ms. Use Value: Prevents FPGA configuration corruption by ensuring all voltage domains meet spec before release, while PFO triggers graceful firmware shutdown if -48V sags. |
Use Scenario: Ensuring safe startup and fault response in DIN-rail mounted programmable logic controllers with isolated 24V field power. IC Role / Device Role / Timing Role: MAX6728KASVD3+ uses VCC1=3.3V (logic), VCC2=2.4V (isolated sensor supply), and PFI monitoring 24V bus - holding RST during cold start and pulsing PFO on brownout. Use Value: Eliminates need for external PFI resistor network and discrete reset IC, reducing component count by 2–3 parts while meeting IEC 61000-4-4 surge immunity requirements. |
| Medical Diagnostic Imaging | Network Edge Router |
|
Use Scenario: Managing power-up sequence for multi-rail imaging subsystems (1.2V FPGA core, 1.8V memory, 5V analog front-end). IC Role / Device Role / Timing Role: MAX6728KASVD3+ configures VCC1=1.2V, VCC2=1.8V, and PFI on 5V rail - asserting RST until all three are valid, with PFO interrupting MCU on 5V sag. Use Value: Enables single-chip supervision of three critical rails, reducing risk of partial initialization and improving FDA Class II compliance traceability. |
Use Scenario: Securing boot integrity in fanless edge routers with 12V PoE input, 5V intermediate, and 3.3V CPU rails. IC Role / Device Role / Timing Role: MAX6728KASVD3+ monitors VCC1=3.3V (CPU), VCC2=5V (PHY), and PFI on 12V PoE input - using PFO to trigger hardware watchdog reset if PoE drops before graceful shutdown. Use Value: Provides deterministic 210ms reset hold for ARM Cortex-A53 boot ROM execution while delivering independent PoE health signaling - no software polling required. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-voltage supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX6729KASVD3+ | Same pinout and thresholds, but push-pull PFO output instead of open-drain | Requires no external PFO pullup; incompatible with wired-OR PFO bus topologies | Select MAX6729KASVD3+ only when driving a dedicated PFO load with known VCC1-referenced logic levels |
| TPS3808G33DBVR | Dual-supply monitor (VDD/VDD2) only; no PFI/PFO function; fixed 3.3V/3.0V thresholds; 200ms timeout | Lacks third-voltage monitoring and independent power-fail signaling - requires external comparator for PFI-equivalent function | Choose TPS3808G33DBVR only for cost-sensitive dual-rail designs where PFI is unnecessary and layout space permits added discretes |
Compared with MAX6728KASVD3+, MAX6729KASVD3+ offers identical supervision logic but replaces open-drain PFO with push-pull for simpler interfacing, while TPS3808G33DBVR reduces functionality to dual monitoring only - making MAX6728KASVD3+ the sole option supporting true triple-voltage supervision with independent PFO signaling in an 8-pin SOT23.
Availability
MAX6728KASVD3+ is available at Aetrix Electronics and suitable for telecom power sequencing, industrial PLC I/O modules, medical diagnostic imaging, and network edge router designs requiring stable component supply, guaranteed long-term availability, and full traceability from wafer to shipment.
Supply support for MAX6728KASVD3+ 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and computing markets.
The MAX6715–MAX6729 family was designed specifically for space-constrained multivoltage systems needing reliable, low-quiescent-current supervision with flexible threshold and timeout options - targeting applications where discrete solutions increase BOM cost and PCB area.
FAQ
What is the exact reset threshold voltage for VCC1 on the MAX6728KASVD3+?
The MAX6728KASVD3+ has a factory-trimmed VCC1 reset threshold of 3.075V (typical), with a guaranteed range of 3.000V to 3.150V over temperature and process variation. This value is set by the "S" suffix in the part number per Maxim's Reset Voltage Threshold Suffix Guide and applies directly to the primary supply monitoring function of the MAX6728KASVD3+.
Does the MAX6728KASVD3+ support monitoring a negative supply voltage?
Yes - the MAX6728KASVD3+ can monitor negative supplies using the PFI input with an appropriate resistor-divider network, as shown in Figure 3b of the datasheet. When a negative rail drops, PFI falls below 626.5mV and PFO asserts high (since it is active-low open-drain and pulled up externally), providing direct indication of negative supply failure - a verified capability of the MAX6728KASVD3+.
Is the PFO output of the MAX6728KASVD3+ subject to the same reset timeout period as RST?
No - the PFO output of the MAX6728KASVD3+ deasserts immediately when PFI rises above 626.5mV and asserts immediately when PFI falls below that threshold, with no timeout delay. Unlike RST, which holds low for 210ms (min) after fault clearance, PFO provides instantaneous power-fail status - a confirmed behavior documented in the Electrical Characteristics table for MAX6728KASVD3+.
What is the maximum allowable VCC transient duration that will not trigger a reset on the MAX6728KASVD3+?
The MAX6728KASVD3+ rejects negative-going VCC transients up to 20µs in duration when the overdrive is 100mV below the reset threshold, as specified in the Typical Operating Characteristics graph "Maximum VCC Transient Duration vs. Reset Threshold Overdrives". This immunity is inherent to the MAX6728KASVD3+'s internal comparator architecture and requires no external filtering.
Can the MAX6728KASVD3+ be used without connecting the RST2 pin?
Yes - the RST2 pin (pin 8) on the MAX6728KASVD3+ is unused per the Selector Guide and Pin Description table; it is reserved for other variants (e.g., MAX6727) but left unconnected in MAX6728KASVD3+. Leaving RST2 floating or tying it to GND has no effect on MAX6728KASVD3+ operation - a confirmed configuration supported by Maxim's official documentation for this specific part number.
MAX6728KASVD3+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- -
- Number of Voltages Monitored:
- -
- Voltage - Threshold:
- -
- Output:
- -
- Reset:
- -
- Reset Timeout:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
MAX6728KASVD3+ FAQ
1.How can I place an order for MAX6728KASVD3+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX6728KASVD3+ 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 MAX6728KASVD3+ reliable?
The price and inventory of MAX6728KASVD3+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX6728KASVD3+ is usually 5 days.
3.What payment methods are accepted for MAX6728KASVD3+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX6728KASVD3+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX6728KASVD3+?
MAX6728KASVD3+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX6728KASVD3+ 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 MAX6728KASVD3+?
For technical support, including MAX6728KASVD3+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX6728KASVD3+ requirements.
6.How does Aetrix verify that MAX6728KASVD3+ is sourced from the original manufacturer or authorized distributors?
All MAX6728KASVD3+ 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 MAX6728KASVD3+ meets industry standards.
7.What is the process for return or replacement of MAX6728KASVD3+?
All MAX6728KASVD3+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX6728KASVD3+, 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 MAX6728KASVD3+ part is unused and in its original packaging.
Return procedure for MAX6728KASVD3+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
MAX6728KASVD3+ Tags
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MIC826SYMT-TR
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APX803L20-29SA-7
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