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Analog Devices Inc./Maxim Integrated MAX687CUA
- Part No.:
- MAX687CUA
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
MAX687CUA.pdf
- Description:
- IC REG LINEAR LDO
- Quantity:
- Payment:
- Shipping:
Inventory:3,024
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Product details
Overview
The MAX687CUA from Maxim Integrated is a precision 3.3V fixed-output, low-dropout linear regulator that uses an external PNP pass transistor to deliver >1A output current with dropout as low as 40mV at 200mA (FZT749). It features automatic latched shutdown below 2.96V output, power-fail monitoring (PFO), and 10mA base-drive capability. It is designed for battery-powered portable telephones and memory backup supplies where deep-discharge protection is critical.
For engineers reviewing the MAX687CUA datasheet, MAX687CUA pinout, MAX687CUA application, or MAX687CUA equivalent, this page delivers verified technical context-including latched shutdown behavior, PFO comparator thresholds, µMAX-8 package constraints, and base-current limiting via RB-essential for reliable low-voltage battery system design.
Technical Context
The MAX687CUA implements a precision bandgap reference and dual comparators: one monitors VOUT for power-fail warning (trip at 3.13V nominal −170mV = 2.96V), and another triggers latched shutdown when VOUT falls to 2.96V. Its ON input requires a high pulse to initiate startup and must remain asserted until VOUT exceeds the shutdown threshold.
Base drive is delivered through the BASE pin with current limited by a resistor (RB) between BASE and BLIM, enabling programmable output current limiting without collector-sense resistors. The PFO output actively sources and sinks current (not open-drain), distinguishing it from MAX688/MAX689 variants.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±2% over temperature and load; ensures stable logic supply for CMOS RAM and microcontrollers. |
| Dropout Voltage | 40mV at 200mA (FZT749); enables regulation down to VIN ≈ 3.34V, critical for single-cell Li-ion or 3-cell NiMH systems. |
| Shutdown Threshold | 2.96V (latched); prevents battery damage by disabling output before cell reversal occurs in portable instruments. |
| PFO Trip Point | 170mV below nominal VOUT (i.e., 3.13V → trips at 2.96V); provides early warning before shutdown, allowing host MCU time to save state. |
| Supply Current | 150µA operating / <1µA shutdown; minimizes quiescent drain during standby in battery-critical applications. |
| Input Voltage Range | 2.7V to 11.0V; supports wide-input battery chemistries including depleted alkaline, NiCd, and Li-ion packs. |
| Base Drive Capability | ≥10mA sink current; sufficient to drive high-β PNP transistors (e.g., FZT749, β > 100) for >1A output loads. |
Pinout & Package
MAX687CUA is housed in an 8-pin µMAX package (3.05mm × 3.05mm, 0.65mm pitch), optimized for space-constrained portable designs. Pin 1 is IN; pin 8 is CC; pin 4 is GND; pin 5 is OUT; pin 2 is ON (active-high, latching control).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 IN | Positive input supply | Accepts 2.7V–11.0V; bypass capacitor (C1) must be placed directly between IN and GND for stability. |
| 2 ON | Startup enable input | Active-high pulse required to exit latch-off state; must remain high until VOUT > 2.96V to sustain regulation. |
| 3 PFO | Power-fail open-collector output | Sources/sinks current; asserts low at 2.96V to signal impending shutdown-enables graceful system shutdown. |
| 4 GND | Analog and power ground | Common return for all internal circuitry and external capacitors; must be low-impedance connection to minimize noise. |
| 5 OUT | Regulated 3.3V output | Drives external load via PNP emitter; output capacitor (C2 ≥68µF @ 500mA) required for transient stability. |
| 6 BLIM | Base current limit sense | Forms voltage divider with RB to set max base current: IBASE ≤ 0.1V/(RB + 5Ω); enables programmable current limiting. |
| 7 BASE | PNP transistor base driver | Sinks ≥10mA; connects to PNP base; internal 5Ω series resistor ensures safe current limiting even if BLIM is shorted. |
| 8 CC | Compensation node | Connects 10nF non-polarized capacitor to GND; stabilizes loop response and suppresses power-on overshoot. |
Key Features
| Feature | Design Value |
|---|---|
| Latched automatic shutdown | Prevents battery deep discharge by holding OFF until ON is pulsed-no external reset circuit needed. |
| Integrated PFO comparator | Provides precise 2.96V trip point with 7mV hysteresis, enabling deterministic low-VOUT detection without external components. |
| Programmable base-current limiting | RB resistor between BASE and BLIM sets max IBASE without sacrificing dropout voltage-no collector-sense penalty. |
| Low-quiescent 150µA operation | Extends battery life in always-on portable instruments while maintaining fast wake-up response via ON pin. |
| µMAX-8 package | 3.05mm × 3.05mm footprint with exposed pad option (not specified for CUA grade); enables high-density PCB layouts. |
Applications
| Portable Telephones | Battery-Powered Memory Backup |
|---|---|
Use Scenario: Powering RF front-end and baseband ICs in GSM/CDMA handsets during battery depletion. IC Role / Device Role / Timing Role: Primary 3.3V LDO regulator with latched shutdown to prevent cell reversal during low-battery operation. Use Value: Eliminates need for external voltage supervisor; PFO alert allows firmware to trigger emergency save before shutdown. |
Use Scenario: Maintaining SRAM/CMOS RAM voltage during main power loss in PDAs and handheld terminals. IC Role / Device Role / Timing Role: Standby regulator delivering clean 3.3V from backup coin cell or supercapacitor. Use Value: <1µA shutdown current preserves backup energy; 2.96V cutoff avoids data corruption from marginal VDD. |
| Portable Instruments | High-Efficiency Linear Regulator Systems |
Use Scenario: Supplying analog front-end and ADC in handheld multimeters and gas detectors. IC Role / Device Role / Timing Role: Precision 3.3V source with <±2% accuracy and low noise (105µVRMS) for measurement integrity. Use Value: Output accuracy and line/load regulation (0.4mV/V, 45mV) ensure consistent sensor biasing across battery discharge curve. |
Use Scenario: Configuring high-current (>1A) LDO using FZT749 or TIP42 PNP pass transistors. IC Role / Device Role / Timing Role: Controller IC providing base drive, current limiting, and fault signaling-not standalone regulator. Use Value: Enables ultra-low dropout (40mV) and scalable output current without custom IC redesign or layout changes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar low-dropout linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX688CUA | Same 3.3V output, but uses SHDN (not ON) and lacks automatic shutdown; PFO is open-drain only. | Requires external shutdown control logic; no latched protection-unsuitable for self-backup memory systems. | Select MAX688CUA only when precise external timing of shutdown is needed and battery protection is handled elsewhere. |
| LT1129CS8-3.3 | Monolithic 3.3V LDO (no external transistor); 600mA max; 350mV dropout at 600mA; no PFO or latched shutdown. | Lower BOM count but cannot scale beyond 600mA or achieve sub-50mV dropout; no power-fail signaling. | Choose LT1129CS8-3.3 for simpler, lower-current designs where external PNP complexity is undesirable. |
Compared with MAX688CUA and LT1129CS8-3.3, the MAX687CUA uniquely combines latched low-VOUT shutdown, active PFO signaling, and external PNP scalability-making it irreplaceable in battery-critical portable systems requiring >1A and deep-discharge prevention.
Availability
MAX687CUA is available at Aetrix Electronics and suitable for portable telephones, battery-powered memory backup systems, and portable instrumentation requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for MAX687CUA 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 consumer applications.
The MAX687CUA belongs to Maxim's precision low-dropout linear regulator family, engineered specifically for battery-powered equipment requiring accurate voltage regulation, intelligent power-fail detection, and robust deep-discharge protection.
FAQ
What is the function of the ON pin on the MAX687CUA?
The ON pin on the MAX687CUA is an active-high, latching enable input. A high pulse initiates startup, and the pin must remain high until the output voltage exceeds 2.96V to maintain regulation. Once latched off due to low VOUT, only another ON pulse can restore operation-ensuring MAX687CUA remains disabled until conditions improve.
Does the MAX687CUA include built-in power-fail detection?
Yes, the MAX687CUA integrates a dedicated power-fail comparator that drives the PFO pin low when VOUT drops to 2.96V (170mV below nominal 3.3V). Unlike MAX688/MAX689, the MAX687CUA's PFO actively sources and sinks current, enabling direct interface with microcontroller interrupt inputs without pull-up resistors.
What external components are mandatory for stable operation of the MAX687CUA?
Four external components are mandatory: (1) an external PNP pass transistor (e.g., FZT749), (2) a bypass capacitor (C1 ≥2.2µF) from IN to GND, (3) an output capacitor (C2 ≥68µF for 500mA load), and (4) a compensation capacitor (C3 = 10nF) from CC to GND. The BASE–BLIM resistor (RB) is optional but required for current limiting.
How does the MAX687CUA implement output current limiting?
The MAX687CUA limits output current by controlling base drive to the external PNP transistor. A resistor (RB) between BASE and BLIM sets maximum base current as IBASE ≤ 0.1V/(RB + 5Ω). With RB = 12Ω, IBASE is limited to ~6mA-enabling ~600mA output with FZT749 (β ≈ 100). This method avoids dropout penalties from collector-sense resistors.
Is the MAX687CUA pin-compatible with other members of the MAX687/MAX688/MAX689 family?
Yes, the MAX687CUA shares identical pinout and µMAX-8 package with MAX688CUA and MAX689CUA. However, functional differences exist: MAX687CUA uses ON for latched startup/shutdown, while MAX688/MAX689 use SHDN; PFO is push-pull in MAX687CUA but open-drain in others-requiring schematic review before substitution.
MAX687CUA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Output Configuration:
- Positive
- Output Type:
- Fixed
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 11V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Voltage Dropout (Max):
- -
- Current - Output:
- 1A
- Current - Quiescent (Iq):
- 250 µA
- Current - Supply (Max):
- -
- PSRR:
- -
- Control Features:
- Current Limit, Enable, Power Fail
- Protection Features:
- Over Current
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-µMAX
MAX687CUA FAQ
1.How can I place an order for MAX687CUA through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX687CUA 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 MAX687CUA reliable?
The price and inventory of MAX687CUA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX687CUA is usually 5 days.
3.What payment methods are accepted for MAX687CUA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX687CUA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX687CUA?
MAX687CUA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX687CUA 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 MAX687CUA?
For technical support, including MAX687CUA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX687CUA requirements.
6.How does Aetrix verify that MAX687CUA is sourced from the original manufacturer or authorized distributors?
All MAX687CUA 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 MAX687CUA meets industry standards.
7.What is the process for return or replacement of MAX687CUA?
All MAX687CUA units undergo pre-shipment inspection (PSI). If there is an issue with MAX687CUA, 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 MAX687CUA part is unused and in its original packaging.
Return procedure for MAX687CUA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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