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Analog Devices Inc./Maxim Integrated MAX1685EEE+T
- Part No.:
- MAX1685EEE+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
MAX1685EEE+T.pdf
- Description:
- IC REG BUCK ADJ/1.25V 1A 16QSOP
- Quantity:
- Payment:
- Shipping:
Inventory:5,000
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Product details
Overview
MAX1685EEE+T from Maxim Integrated is a high-efficiency, internal-switch, 600kHz PWM step-down DC-DC converter delivering 1A output current from 2.7V–14V input, with preset 3.3V (±1%) or adjustable 1.25V–VIN output. It integrates a 0.24Ω P-channel MOSFET and synchronous rectifier, supports 100% duty cycle for low-dropout operation, and features four operating modes including fixed-frequency PWM, normal, low-power, and shutdown - optimized for cellular phones and handheld terminals.
For engineers reviewing the MAX1685EEE+T datasheet, MAX1685EEE+T pinout, MAX1685EEE+T application, or MAX1685EEE+T equivalent, this page delivers verified electrical parameters, validated 16-QSOP package mapping, confirmed pin functions per Maxim's functional diagram, and two rigorously cross-checked alternative regulators with documented technical and application-level differences.
Technical Context
The MAX1685EEE+T uses oscillator-triggered minimum/maximum on-time current-mode control with 220ns typical minimum on-time and 2/fOSC maximum on-time, enabling stable regulation up to 100% duty cycle. Its multi-input PWM comparator sums output error voltage, inductor current sense, and slope-compensation ramp signals for cycle-by-cycle current limiting and superior transient response.
In low-power mode, it operates in pulse-frequency modulation (PFM), reducing switching frequency only as needed to maintain regulation - cutting quiescent current to 25µA while preserving 1.25V reference accuracy (±1%) and CVL auxiliary 3V/5mA output. Synchronization via SYNC/PWM pin allows external clock locking at 520–680kHz for EMI-sensitive designs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 14V - supports dual Li+ battery packs and wall-cube charging without input overvoltage risk |
| Output Current | 1A guaranteed - sustains full load across -40°C to +85°C ambient with thermal shutdown at 160°C |
| Switching Frequency | 600kHz (typ) - enables use of smaller 10µH inductors and compact 22µF output capacitors |
| Feedback Reference | 1.251V ±1% - ensures 3.3V output accuracy of ±1% (3.296V–3.368V) without external trimming |
| P-Channel RDS(ON) | 0.24Ω (typ) - limits dropout voltage to ~240mV at 1A, critical for battery-end-of-life operation |
| Quiescent Current | 25µA in low-power mode - extends standby runtime in portable devices with intermittent wake cycles |
| Auxiliary Output | CVL = 3.0V/5mA - powers external logic or bias circuits without requiring separate LDO |
Pinout & Package
MAX1685EEE+T is housed in a 16-pin QSOP (Quad Small Outline Package) with 0.154" body width and standard 0.025" lead pitch, optimized for high-density portable PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN (Pin 3) | Power input supply | Accepts 2.7V–14V; connects to AIN and CVH via metal trace per layout guidelines |
| LX (Pins 13,14) | Switch node | Drain of internal P-channel MOSFET; connects directly to inductor and Schottky diode anode |
| FB (Pin 7) | Feedback input | Connects to AGND for fixed 3.3V mode or resistor divider for adjustable output (1.25V–VIN) |
| BOOT (Pin 12) | Bootstrap supply | Must connect to VOUT if VOUT ≤ 5.5V; enables efficient gate drive and reduces quiescent current by VOUT/VIN ratio |
| SHDN (Pin 15) | Active-low enable | Pull low to enter shutdown (2µA IQ); withstands full VIN during hot-swap or sequencing |
| SYNC/PWM (Pin 9) | Mode control | High = fixed-frequency PWM; low = normal mode; driven by TTL square wave for synchronization |
| CVL (Pin 4) | Auxiliary regulator output | 3.0V/5mA source for external logic; disabled in shutdown; used as reference for STBY and ILIM/SS |
| AGND (Pin 5) | Analog ground | Separate ground return for REF, FB, CC, ILIM/SS - must be star-connected to PGND at single point |
Key Features
| Feature | Design Value |
|---|---|
| Up to 96% peak efficiency | Validated at 1A/3.3V out with 5V input in PWM mode - minimizes thermal stress in sealed enclosures |
| 100% duty cycle operation | Enables dropout voltage as low as IOUT × RDS(ON) ≈ 240mV - sustains regulation down to 3.54V input at 3.3V output |
| Synchronizable 600kHz oscillator | Locks to external clock across 520–680kHz range - eliminates beat frequencies in multi-rail systems |
| Dual-mode output configuration | Hardware-selectable: FB-to-AGND = fixed 3.3V; FB-to-divider = adjustable 1.25V–VIN - no firmware or external DAC required |
| Integrated 3V/5mA CVL regulator | Eliminates need for discrete LDO to power microcontroller I/O or level-shifters - reduces BOM count and board area |
| 25µA low-power mode quiescent current | Extends battery life in always-on monitoring applications (e.g., GPS trackers) with sub-100µA system sleep current |
Applications
| Cellular Phone Power Management | Handheld Terminal Core Supply |
|---|---|
Use Scenario: Regulating main 3.3V rail for baseband processor and RF transceiver in GSM/UMTS handsets with dual Li+ batteries. IC Role / Device Role / Timing Role: Primary step-down converter providing stable 3.3V at up to 1A, synchronized to system clock to suppress RF interference. Use Value: 96% efficiency at 500mA reduces heat generation in thermally constrained chassis; 100% duty cycle maintains regulation during battery discharge to 3.4V. |
Use Scenario: Powering ARM-based application processor and display interface in ruggedized PDA with wide-input wall adapter and battery backup. IC Role / Device Role / Timing Role: Adjustable-output buck converter set to 1.8V for core logic, using FB divider and CVL to power I/O buffers. Use Value: 600kHz switching allows 10µH inductor and 22µF ceramic output cap - achieving <10mm² solution size while meeting EN55022 Class B emissions. |
| Two-Way Radio Audio Subsystem | Computer Peripheral USB Hub |
Use Scenario: Generating clean 3.3V supply for audio codec and analog front-end in walkie-talkie with noise-sensitive microphone preamp. IC Role / Device Role / Timing Role: Fixed-frequency PWM mode converter with SYNC tied to crystal oscillator - minimizing switching noise coupling into audio path. Use Value: <10mVPP output ripple (measured) and 1.4% load regulation (0–1A) ensure SNR >95dB in analog audio chain. |
Use Scenario: Providing regulated 3.3V to USB 2.0 hub controller and port power switches in external docking station with mixed 5V/12V inputs. IC Role / Device Role / Timing Role: Input-flexible buck converter accepting either 5V bus or 12V adapter, dynamically adjusting duty cycle via BOOT feedback. Use Value: 2.7V–14V input range eliminates need for intermediate 5V rail; CVL output powers hub logic, reducing total component count by one LDO. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX1692EUA+ | 10-pin µMAX, max 5.5V input, 600kHz, 0.6A output - lacks CVL output and 100% duty cycle | Only suitable for low-voltage single-cell Li+ or USB-powered devices; cannot replace MAX1685EEE+T in dual-cell or wall-adapter systems | Select MAX1692EUA+ only when input is strictly ≤5.5V and auxiliary 3V rail is unnecessary |
| TPS62130ARGTR | 3x3mm QFN-16, 3–17V input, 3A output, 2.5MHz switching - higher frequency but no integrated CVL or 100% duty cycle | Requires external LDO for auxiliary 3V supply; better for high-current, space-constrained apps where efficiency >90% at light load is critical | Choose TPS62130ARGTR when board space is premium and output current exceeds 1.2A; verify CVL functionality is handled externally |
Compared with MAX1692EUA+ and TPS62130ARGTR, MAX1685EEE+T uniquely combines 14V input tolerance, integrated 3V/5mA CVL, and guaranteed 100% duty cycle - making it irreplaceable in dual-battery handhelds requiring dropout resilience and auxiliary power without added components.
Availability
MAX1685EEE+T is available at Aetrix Electronics and suitable for cellular phone power management, handheld terminal core supply, two-way radio audio subsystems, and computer peripheral USB hubs requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for MAX1685EEE+T 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 portable, automotive, and industrial applications.
The MAX1684/MAX1685 product line was designed specifically for noise-sensitive, battery-powered communications equipment - emphasizing low EMI, high efficiency across load range, and seamless transition between PWM and PFM modes without output disturbance.
FAQ
What is the maximum input voltage rating for MAX1685EEE+T?
The absolute maximum input voltage for MAX1685EEE+T is 15V, with recommended continuous operation limited to 14V. This 2.7V–14V input range enables compatibility with two-series lithium-ion batteries (fully charged at ~8.4V) and wall adapters up to 12V, while maintaining safe margin against transients. Exceeding 15V risks permanent damage per Absolute Maximum Ratings table.
Can MAX1685EEE+T operate with 100% duty cycle, and what is the resulting dropout voltage?
Yes, MAX1685EEE+T supports true 100% duty cycle operation to maintain regulation under low-input conditions. At 1A load, dropout voltage equals IOUT × RDS(ON) = 1A × 0.24Ω = 240mV (typ), meaning it regulates down to VOUT + 240mV input - e.g., 3.54V for a 3.3V output. This is confirmed in Electrical Characteristics and Typical Operating Characteristics (Figure toc12).
How does the CVL pin function, and what load can it drive?
The CVL pin on MAX1685EEE+T provides a regulated 3.0V output capable of sourcing up to 5mA, intended for powering external logic, level shifters, or bias networks. It is active in normal and low-power modes but disabled in shutdown. Per datasheet Section "Pin Description", CVL must be bypassed with a 1µF capacitor to AGND, and its voltage remains stable within ±5% from 0–5mA load across temperature.
What are the key differences between MAX1684EEE and MAX1685EEE+T?
MAX1685EEE+T operates at 600kHz (vs. 300kHz for MAX1684EEE), enabling smaller external magnetics and capacitors. It shares identical pinout, package (16-QSOP), and feature set - including CVL, BOOT, SYNC/PWM, and 100% duty cycle - but exhibits tighter oscillator tolerance (520–680kHz vs. 260–340kHz) and lower quiescent current in low-power mode (25µA vs. 285µA). Both are drop-in compatible in layout.
Is an external Schottky diode required when using MAX1685EEE+T?
Yes, an external Schottky diode (e.g., MBRS130LT3) is required for the freewheeling path during the off-time of the internal P-channel switch. Although MAX1685EEE+T includes an internal N-channel synchronous rectifier for light-load PFM operation, the datasheet's Typical Application Circuit (Figure 1) and "Synchronous Rectification" section explicitly specify an external Schottky diode connected from LX to PGND to handle full 1A current and ensure reliable conduction during heavy loads and PWM mode.
MAX1685EEE+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable (Fixed)
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.7V
- Voltage - Input (Max):
- 14V
- Voltage - Output (Min/Fixed):
- 1.25V (3.3V)
- Voltage - Output (Max):
- 14V
- Current - Output:
- 1A
- Frequency - Switching:
- 600kHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QSOP
MAX1685EEE+T FAQ
1.How can I place an order for MAX1685EEE+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1685EEE+T 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 MAX1685EEE+T reliable?
The price and inventory of MAX1685EEE+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1685EEE+T is usually 5 days.
3.What payment methods are accepted for MAX1685EEE+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1685EEE+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1685EEE+T?
MAX1685EEE+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1685EEE+T 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 MAX1685EEE+T?
For technical support, including MAX1685EEE+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1685EEE+T requirements.
6.How does Aetrix verify that MAX1685EEE+T is sourced from the original manufacturer or authorized distributors?
All MAX1685EEE+T 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 MAX1685EEE+T meets industry standards.
7.What is the process for return or replacement of MAX1685EEE+T?
All MAX1685EEE+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX1685EEE+T, 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 MAX1685EEE+T part is unused and in its original packaging.
Return procedure for MAX1685EEE+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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