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Analog Devices Inc./Maxim Integrated MAX688CUA+
- Part No.:
- MAX688CUA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
MAX688CUA+.pdf
- Description:
- IC REG LINEAR 3.3V 1A 8UMAX
- Quantity:
- Payment:
- Shipping:
Inventory:2,809
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Product details
Overview
The MAX688CUA+ from Maxim Integrated is a precision 3.3V fixed-output, low-dropout linear regulator that drives an external PNP pass transistor to deliver >1A output current with dropout as low as 40mV at 200mA. It features active-low shutdown control (SHDN), power-fail monitoring (PFO), and operates from 2.7V to 11.0V input. Used in portable telephones and battery-powered instrumentation where regulated 3.3V supply with precise shutdown threshold and low quiescent current is required.
For engineers reviewing the MAX688CUA+ datasheet, MAX688CUA+ pinout, MAX688CUA+ application, or MAX688CUA+ equivalent, this page delivers verified technical context, exact pin functions, real-world design meaning of specifications, and confirmed alternative parts for 3.3V LDO systems requiring external PNP drive and precision voltage monitoring.
Technical Context
The MAX688CUA+ implements a three-level SHDN interface: fully on above 1.25V, standby (<25µA) below 1.2V, and full shutdown (<1µA) below 0.2V. Its PFO is open-drain and trips 170mV below nominal VOUT (3.3V), with 7mV hysteresis.
Base drive is actively limited via the BLIM–BASE resistor network (IBASE ≤ 0.1V/(RB + 5Ω)), enabling accurate current limiting without collector-sense resistors. Dropout voltage is determined solely by the external PNP's VCE(SAT), not internal circuitry.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±2% - ensures stable logic supply for 3.3V microcontrollers and memory without external feedback. |
| Dropout Voltage | 40mV at 200mA (FZT749) - enables regulation down to VIN = 3.34V, critical for single-cell Li-ion or multi-cell alkaline systems. |
| Supply Current | 150µA operating / <1µA shutdown - minimizes battery drain during sleep modes in portable devices. |
| SHDN Thresholds | VON = 1.25V, VSTBY = 1.2V, VSD = 0.2V - allows precise, hysteresis-controlled power sequencing using simple resistor dividers. |
| PFO Trip Point | VPFT = 3.13V (170mV below 3.3V) with 7mV hysteresis - provides early warning before output falls out of regulation, enabling graceful system shutdown. |
| Input Voltage Range | 2.7V to 11.0V - supports wide battery chemistries (Li-ion, NiMH, alkaline) and unregulated wall adapters. |
| Base Drive Capability | ≥10mA minimum - drives high-β PNP transistors (e.g., FZT749, β > 100) to sustain >1A load current. |
Pinout & Package
MAX688CUA+ is housed in an 8-pin µMAX package (3.05mm × 3.05mm, 0.65mm pitch), optimized for space-constrained portable designs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 IN | Positive input supply | Accepts 2.7V–11.0V; bypass capacitor must be placed directly between IN and GND for stability. |
| 2 SHDN | Active-low shutdown control | Three-level input: >1.25V = on, <1.2V = standby, <0.2V = full shutdown; PFO forced low when SHDN < 0.2V. |
| 3 PFO | Open-drain power-fail output | Sinks current when VOUT < 3.13V; requires external pull-up; used for system reset or low-VOUT interrupt. |
| 4 GND | Circuit ground reference | Common return for IN, OUT, CC, and all internal comparators; must be low-impedance connection. |
| 5 OUT | Regulated 3.3V output node | Drives external PNP emitter; connects to load and output capacitor C2 (min 10µF, low ESR). |
| 6 BLIM | Base current limit sense | Forms voltage divider with BASE pin; sets max base current via RB resistor (e.g., 12Ω → ~6mA limit). |
| 7 BASE | PNP transistor base driver | Sources ≥10mA; connects to PNP base; current limited by BLIM-BASE resistor network. |
| 8 CC | Compensation capacitor terminal | Connects 10nF–100nF non-polarized capacitor to GND; stabilizes loop and suppresses power-on overshoot. |
Key Features
| Feature | Design Value |
|---|---|
| External PNP drive architecture | Enables scalable output current (>1A) and ultra-low dropout (set by transistor VCE(SAT), not IC), avoiding thermal limitations of monolithic LDOs. |
| Three-level SHDN control | Supports sequenced power management: full operation → low-IQ standby → zero-IQ shutdown, with precise thresholds for deterministic state transitions. |
| Open-drain PFO with hysteresis | Provides noise-immune early-warning signal (3.13V trip) for host processor or supervisor IC, eliminating need for external comparator circuits. |
| Base-current limiting via BLIM/BASE | Eliminates need for collector-sense resistor; maintains accuracy across temperature while preventing excessive base drive during dropout. |
| Low-noise 150µA quiescent current | Extends battery life in always-on monitoring applications (e.g., RTC backup, sensor wake-up circuits) without sacrificing regulation accuracy. |
Applications
| Portable Telephones | Battery-Powered Instruments |
|---|---|
Use Scenario: Powering RF front-end and baseband ICs in GSM/CDMA handsets with single Li-ion cell (3.0V–4.2V). IC Role / Device Role / Timing Role: Primary 3.3V LDO delivering up to 1A with fast transient response and precise PFO-triggered brownout protection. Use Value: Prevents data corruption during battery sag by asserting PFO at 3.13V, allowing host MCU to save state before shutdown. | Use Scenario: Supplying ADCs, op-amps, and microcontrollers in handheld multimeters or gas detectors. IC Role / Device Role / Timing Role: High-accuracy 3.3V reference source with <±2% output tolerance and low 105µVRMS noise. Use Value: Ensures measurement integrity by maintaining stable rail under varying load and temperature (±0.5mV drift over –40°C to +85°C). |
| Power Backup for SRAM | Portable Medical Devices |
Use Scenario: Maintaining CMOS SRAM voltage during main power loss in data loggers or POS terminals. IC Role / Device Role / Timing Role: Low-quiescent-current (150µA) regulator with latched shutdown disabled - stays active until VIN drops below 2.7V. Use Value: Extends backup time from coin cell or supercapacitor by minimizing IQ, while PFO signals imminent failure to initiate RAM save. | Use Scenario: Regulating power for low-power Bluetooth LE modules and biosensor analog front-ends in wearable patches. IC Role / Device Role / Timing Role: Compact µMAX-packaged 3.3V LDO enabling PCB area reduction without sacrificing shutdown control or PFO monitoring. Use Value: Enables small form factor (3.05mm × 3.05mm) while supporting medical-grade reliability via guaranteed 0°C to +70°C operation and <1µA shutdown current. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3.3V external-PNP LDO applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX687CUA+ | Includes automatic latched shutdown at VOUT < 2.96V and ON pin; PFO sources/sinks current. | Used where self-protecting battery discharge prevention is mandatory (e.g., embedded RAM backup). | Select MAX687CUA+ only if automatic shutdown and bidirectional PFO are required; MAX688CUA+ offers superior controllability via SHDN. |
| LT1528CS8#PBF | Monolithic 3.3V LDO (no external transistor); 350mV dropout at 3A; no PFO or SHDN pin. | Used where board space permits larger package and external pass device is undesirable. | Choose LT1528CS8#PBF for simplicity and higher current; MAX688CUA+ for lower dropout, lower IQ, and programmable shutdown. |
Compared with MAX687CUA+, MAX688CUA+ replaces latched auto-shutdown with flexible three-level SHDN control and open-drain PFO - enabling precise power sequencing in multi-rail systems. Versus LT1528CS8#PBF, it trades monolithic integration for lower dropout, lower quiescent current, and external current scalability.
Availability
MAX688CUA+ is available at Aetrix Electronics and suitable for portable telephones, battery-powered instruments, and portable medical devices requiring stable component supply with guaranteed 0°C to +70°C operation and µMAX footprint compatibility.
Supply support for MAX688CUA+ 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 and mixed-signal ICs for power management, sensing, and communications.
The MAX687/MAX688/MAX689 family was engineered specifically for high-accuracy, low-dropout regulation in battery-critical applications using external PNP transistors - balancing efficiency, size, and intelligent monitoring.
FAQ
What is the function of the BLIM pin on the MAX688CUA+?
The BLIM pin on the MAX688CUA+ serves as the base-current limit sense node. When connected to the BASE pin via a resistor (RB), it forms a precision current-limiting network: IBASE ≤ 0.1V / (RB + 5Ω). This prevents excessive base drive during dropout or overload, protecting both the external PNP transistor and the MAX688CUA+ itself. For example, with RB = 12Ω, maximum base current is ~6mA - sufficient to drive high-β transistors like the FZT749 while maintaining regulation at >1A load.
Does the MAX688CUA+ have built-in short-circuit protection?
The MAX688CUA+ does not provide direct short-circuit protection on its OUT pin. Instead, it limits output current indirectly by capping base drive to the external PNP transistor via the BLIM–BASE resistor network. If the load shorts, the PNP saturates and dissipates power; protection relies on the PNP's SOA rating and thermal design. The MAX688CUA+'s primary safety mechanism is its PFO output, which alerts the system at VOUT = 3.13V - well before catastrophic failure - allowing host firmware to disable the rail via SHDN before damage occurs.
Can the MAX688CUA+ operate with a 2.5V input supply?
No, the MAX688CUA+ cannot regulate at 2.5V input. Its absolute minimum input voltage is 2.7V per the Absolute Maximum Ratings table, and functional regulation requires VIN ≥ VOUT + dropout - i.e., ≥3.3V + 40mV = 3.34V at 200mA. At 2.5V, the device remains powered but cannot maintain 3.3V output; the PFO will assert low, and SHDN will remain inactive unless pulled externally. For sub-3.3V inputs, a boost converter or different LDO architecture is required.
What is the purpose of the CC pin on the MAX688CUA+?
The CC pin on the MAX688CUA+ is the compensation capacitor terminal. A 10nF to 100nF non-polarized capacitor (e.g., ceramic or polyester) must be connected from CC to GND to stabilize the control loop and prevent oscillation. This capacitor directly affects startup behavior: 10nF yields fast turn-on with minor overshoot, while 100nF eliminates overshoot at the cost of longer start-up time (~300µs vs. ~100µs). Electrolytic capacitors are prohibited due to leakage current (>25nA), which shifts output voltage and PFO thresholds.
How does the PFO output behave during shutdown of the MAX688CUA+?
During shutdown of the MAX688CUA+, the PFO output is forced low regardless of the actual VOUT level. Specifically, when SHDN falls below 0.2V, the device enters full shutdown mode (<1µA supply current), and PFO becomes a strong sink - pulling the output node to near-GND. This behavior is intentional: it provides a reliable "power-fail" signal to downstream logic even when the regulator is disabled, ensuring consistent system-level fault indication. The PFO remains low until SHDN rises above 1.25V and regulation resumes.
MAX688CUA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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):
- 0.04V @ 200mA (Typ)
- Current - Output:
- 1A
- Current - Quiescent (Iq):
- 25 µA
- Current - Supply (Max):
- 250 µA
- PSRR:
- -
- Control Features:
- Current Limit, Enable, Power Fail
- Protection Features:
- -
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-uMAX/uSOP
MAX688CUA+ FAQ
1.How can I place an order for MAX688CUA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX688CUA+ 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 MAX688CUA+ reliable?
The price and inventory of MAX688CUA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX688CUA+ is usually 5 days.
3.What payment methods are accepted for MAX688CUA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX688CUA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX688CUA+?
MAX688CUA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX688CUA+ 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 MAX688CUA+?
For technical support, including MAX688CUA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX688CUA+ requirements.
6.How does Aetrix verify that MAX688CUA+ is sourced from the original manufacturer or authorized distributors?
All MAX688CUA+ 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 MAX688CUA+ meets industry standards.
7.What is the process for return or replacement of MAX688CUA+?
All MAX688CUA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX688CUA+, 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 MAX688CUA+ part is unused and in its original packaging.
Return procedure for MAX688CUA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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