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Analog Devices Inc./Maxim Integrated MAX688CSA+
- Part No.:
- MAX688CSA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX688CSA+.pdf
- Description:
- IC REG LINEAR 3.3V 1A 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,302
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Product details
Overview
MAX688CSA+ from Maxim Integrated is a precision 3.3V fixed-output, low-dropout linear regulator requiring an external PNP pass transistor; it delivers up to 1A output current with 40mV dropout at 200mA (FZT749), features active-low SHDN control, power-fail monitoring (PFO), and operates from 2.7V to 11.0V input - used in portable telephones and battery-powered memory backup supplies.
For engineers reviewing the MAX688CSA+ datasheet, MAX688CSA+ pinout, MAX688CSA+ application, or MAX688CSA+ equivalent, this page provides verified technical context, real-world design meaning of specifications, validated pin functions, confirmed alternatives, and supply-chain support for industrial and portable electronics design.
Technical Context
The MAX688CSA+ implements a precision bandgap reference and high-gain error amplifier to regulate 3.3V output via external PNP base drive; its BLIM-BASE interface enables programmable base-current limiting using an external resistor (RB), directly controlling output current without collector-sense penalty. It integrates dual comparators: one for PFO (trip at 170mV below nominal VOUT) and another for SHDN threshold detection (1.25V ON / 1.2V standby entry).
SHDN operates as a three-level control: >1.25V = full operation, <1.2V = standby (<25µA supply), <0.2V = full shutdown (<1µA); PFO is open-drain and sinks current only. Unlike MAX687, MAX688CSA+ lacks automatic latched shutdown - output disable is fully controlled by SHDN voltage level and timing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±2% - ensures stable logic supply for 3.3V microcontrollers and SRAM without external feedback. |
| Dropout Voltage | 40mV at 200mA (FZT749) - enables regulation down to VIN = 3.34V, critical for extending battery runtime in single-cell Li-ion or 3-cell alkaline systems. |
| Supply Current | 150µA operating / <1µA shutdown - minimizes quiescent drain during sleep modes in portable instrumentation. |
| Input Voltage Range | 2.7V to 11.0V - supports wide-input battery stacks (e.g., 3×AA, Li-ion + LDO pre-regulation) and unregulated wall adapters. |
| PFO Threshold | 170mV below nominal VOUT (3.13V typ) - provides early warning before output collapse, enabling graceful system shutdown or data save. |
| SHDN Thresholds | VON = 1.25V ±2%, VSTBY = 1.2V, VSD = 0.2V - allows precise, hysteresis-stabilized (70mV) power sequencing using resistive dividers from VIN. |
| Base Drive | ≥10mA min - drives high-β PNP transistors (e.g., FZT749, β > 100) to sustain >1A load while maintaining low dropout. |
Pinout & Package
MAX688CSA+ is housed in an 8-pin SO (Small Outline) package, 150 mil width, RoHS-compliant, with gull-wing leads and standard JEDEC MS-012AC footprint.
| 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 SHDN | Active-low shutdown control | Three-level input: >1.25V = on, <1.2V = standby, <0.2V = full shutdown; open-drain PFO asserts low when SHDN < 0.2V. |
| 3 PFO | Power-fail open-drain output | Sinks current when VOUT drops ≤170mV below 3.3V; requires external pull-up; disabled (low) during shutdown. |
| 4 GND | Circuit ground reference | Common return for IN, OUT, CC, BASE, BLIM; must be low-impedance plane for noise immunity and transient response. |
| 5 OUT | Regulated 3.3V output node | Connects to emitter of external PNP; output capacitor C2 ≥10µF (68µF typical for 500mA) required for stability. |
| 6 BLIM | Base-current limit sense | Forms voltage divider with RB to set max base current: IBASE ≤ 0.1V/(RB + 5Ω); short to BASE for ~20mA limit. |
| 7 BASE | PNP transistor base driver | Sources ≥10mA; connects to base of external PNP; current-limited via BLIM resistor to prevent saturation loss in dropout. |
| 8 CC | Compensation capacitor node | Connects 10nF non-polarized capacitor (ceramic/polyester) to GND; stabilizes loop; leakage <25nA required. |
Key Features
| Feature | Design Value |
|---|---|
| External PNP drive | Direct 10mA+ base drive enables use of discrete high-β, high-power PNP transistors (e.g., FZT749, TIP42) for scalable output current beyond IC limits. |
| Programmable current limit | Resistor-based BLIM-BASE interface sets precise base-current ceiling without added dropout voltage or collector sensing components. |
| Early power-fail warning | PFO trips 170mV before output collapse - gives system time to save state or switch to backup supply before brownout. |
| Three-level SHDN control | Enables sequenced power management: full-on → low-IQ standby → ultra-low-IQ shutdown - ideal for multi-mode portable devices. |
| Low-noise regulation | <2mV line transient (3.4V–3.6V input step) and 105µVRMS output noise ensure clean supply for analog sensors and RF sections. |
Applications
| Portable Telephones | Battery-Powered Memory Backup |
|---|---|
|
Use Scenario: Powering baseband processor and RF transceiver in GSM/CDMA handsets with single Li-ion cell (2.7V–4.2V). IC Role / Device Role / Timing Role: Primary 3.3V LDO regulator; interfaces with external FZT749 PNP to sustain peak transmit currents >500mA. Use Value: 40mV dropout at 200mA extends usable battery range by ~150mV, delaying brownout shutdown and improving talk time. |
Use Scenario: Maintaining CMOS SRAM voltage during main power loss in PDAs or medical loggers. IC Role / Device Role / Timing Role: Standby regulator with PFO-triggered interrupt; SHDN held high until backup battery engages. Use Value: <1µA shutdown current prevents backup battery depletion over months; PFO alert enables deterministic RAM save before VOUT collapse. |
| Portable Instruments | High-Efficiency Linear Regulation |
|
Use Scenario: Supplying precision ADCs, op-amps, and microcontrollers in handheld multimeters and gas analyzers. IC Role / Device Role / Timing Role: Low-noise, high-accuracy 3.3V source; CC compensation ensures stability with ceramic output caps. Use Value: ±2% output accuracy and <2mV line transient rejection preserve measurement integrity across varying battery states. |
Use Scenario: Replacing inefficient switching regulators where EMI sensitivity prohibits inductors (e.g., audio front-ends, sensor signal chains). IC Role / Device Role / Timing Role: External-PNP LDO architecture decouples thermal dissipation (in transistor) from IC die, enabling higher power density. Use Value: Dropout limited only by PNP VCE(SAT) - e.g., 0.8V at 4A with TIP42 - achieves better efficiency than monolithic LDOs at high current. |
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 |
|---|---|---|---|
| LT1528CS8#PBF | Monolithic 3.3V LDO (no external PNP); 350mV dropout at 3A; integrated current limit; no PFO or SHDN hysteresis. | Eliminates external transistor but cannot match MAX688CSA+'s sub-100mV dropout at moderate loads; no early power-fail warning. | Select when board space is constrained and 350mV dropout is acceptable; avoid when battery runtime or PFO sequencing is critical. |
| TPS76333DBVR | Monolithic 3.3V LDO; 120mV dropout at 150mA; 1µA shutdown; active-high EN; no PFO; fixed 3.3V ±2%. | Lacks PFO and programmable current limiting; simpler interface but no early-warning capability or external current scaling. | Choose for cost-sensitive, low-complexity designs where PFO and external PNP flexibility are unnecessary. |
Compared with LT1528CS8#PBF and TPS76333DBVR, MAX688CSA+ uniquely combines ultra-low dropout (40mV), open-drain PFO with precise trip threshold, and externally scalable current via PNP - making it optimal for battery-critical, high-reliability portable systems requiring both efficiency and intelligent power monitoring.
Availability
MAX688CSA+ is available at Aetrix Electronics and suitable for portable telephones, battery-powered memory backup systems, and portable instrumentation requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for MAX688CSA+ 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power-management ICs for industrial, automotive, and communications markets.
The MAX687/MAX688/MAX689 family was designed specifically for high-accuracy, low-dropout regulation in battery-constrained portable equipment - emphasizing minimal dropout, intelligent power-fail signaling, and flexible external pass-element control.
FAQ
What is the maximum output current achievable with MAX688CSA+?
The MAX688CSA+ itself does not deliver output current directly - it drives an external PNP transistor. With a high-β device like the FZT749 (β > 100), the MAX688CSA+ can sustain >1A output. At 4A, a pseudo-Darlington configuration (e.g., TIP42 + 2N4403) is recommended per Figure 3. The actual limit depends on PNP selection, heatsinking, and RB resistor value setting base current.
Does MAX688CSA+ have automatic shutdown like MAX687?
No. MAX688CSA+ does not feature automatic latched shutdown on output undervoltage. Instead, it uses the SHDN pin for explicit, user-controlled enable/disable. When SHDN falls below 0.2V, MAX688CSA+ enters full shutdown (<1µA); unlike MAX687, it does not self-shutdown if VOUT drops - that function requires external monitoring and SHDN assertion.
What is the purpose of the CC pin on MAX688CSA+?
The CC pin on MAX688CSA+ connects to a 10nF non-polarized capacitor (e.g., ceramic or polyester) to GND. This capacitor stabilizes the internal control loop, suppresses power-on overshoot, and ensures phase margin across load and input conditions. Aluminum or tantalum electrolytics are unsuitable due to leakage current (>25nA), which shifts output voltage and PFO thresholds.
Can MAX688CSA+ be used with a P-channel MOSFET instead of a PNP transistor?
No. MAX688CSA+ is designed exclusively for NPN-driven PNP pass transistors - its BASE pin sources current and expects a bipolar junction. A P-channel MOSFET requires gate-drive voltage relative to source (not emitter), lacks inherent current gain, and would not interface correctly with the BLIM/BASE current-limiting architecture. Use only specified PNP types (e.g., FZT749, 2N2907A).
What is the minimum output capacitance required for stable operation of MAX688CSA+?
Per the datasheet, the minimum output capacitance (C2) for MAX688CSA+ is 10µF for loads ≤100mA. For higher loads, use 1µF per 10mA (e.g., 68µF for 500mA). Capacitor ESR must be ≤1% of load resistance - low-ESR types (e.g., Sanyo OS-CON, polymer aluminum) are strongly recommended. Ceramic capacitors may be used if ESR is adequately damped.
MAX688CSA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm 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-SOIC
MAX688CSA+ FAQ
1.How can I place an order for MAX688CSA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX688CSA+ 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 MAX688CSA+ reliable?
The price and inventory of MAX688CSA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX688CSA+ is usually 5 days.
3.What payment methods are accepted for MAX688CSA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX688CSA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX688CSA+?
MAX688CSA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX688CSA+ 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 MAX688CSA+?
For technical support, including MAX688CSA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX688CSA+ requirements.
6.How does Aetrix verify that MAX688CSA+ is sourced from the original manufacturer or authorized distributors?
All MAX688CSA+ 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 MAX688CSA+ meets industry standards.
7.What is the process for return or replacement of MAX688CSA+?
All MAX688CSA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX688CSA+, 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 MAX688CSA+ part is unused and in its original packaging.
Return procedure for MAX688CSA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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