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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:4,411
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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, used in cellular phones and handheld terminals requiring low-noise power regulation.
For engineers reviewing the MAX1685EEE-T datasheet, MAX1685EEE-T pinout, MAX1685EEE-T application, or MAX1685EEE-T equivalent, this page provides verified technical context, validated pin functions, confirmed operating modes (PWM/normal/low-power/shutdown), exact efficiency curves (up to 96%), and real-world design meaning for dropout, quiescent current, and synchronous rectification.
Technical Context
The MAX1685EEE-T uses oscillator-triggered minimum/maximum on-time current-mode control with 220ns typical minimum on-time and 100% duty-cycle capability for ultra-low dropout operation. Its internal P-channel high-side switch (0.24Ω) and N-channel synchronous rectifier enable high efficiency across load ranges.
It supports five distinct operating modes-fixed-frequency PWM (600kHz), normal (PFM at light loads), low-power (standby), shutdown, and synchronized-PWM-each with defined quiescent currents (25µA low-power, 2µA shutdown) and current limits (ILIM = 1.2–2.3A, ILIMLP = 285–475mA).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 14V - supports dual Li+ battery input and wall-cube charging without external LDO. |
| Output Current | 1A guaranteed - sustains full load under worst-case thermal and voltage conditions per datasheet test conditions. |
| Switching Frequency | 600kHz - enables use of smaller external inductors (e.g., 10µH vs. 22µH for MAX1684) and reduces output filter size. |
| Efficiency | Up to 96% - achieved via low RDS(on) P-channel switch (0.24Ω) and integrated synchronous rectifier. |
| Feedback Reference | 1.251V ±0.013V - enables precise output adjustment; 1% accuracy ensures stable 3.3V output (3.296–3.368V) across temperature. |
| Quiescent Current | 25µA in low-power mode - extends battery life during standby in portable devices without compromising wake-up response. |
| Duty Cycle Range | 0–100% - maintains regulation down to VIN = VOUT + IOUT×RDS(on) ≈ 3.65V at 1A, critical for battery end-of-discharge operation. |
Pinout & Package
MAX1685EEE-T is housed in a 16-pin QSOP package (5.3mm × 10.2mm, 0.65mm pitch), optimized for space-constrained portable designs. Thermal performance supports continuous 1A operation at -40°C to +85°C ambient with standard PCB copper area.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN | Power input supply | Accepts 2.7V–14V; powers internal regulators and high-side switch; absolute max 15V. |
| LX (13,14) | Switch node | Drain of internal P-channel MOSFET; connects to inductor; handles peak currents up to 2.3A. |
| PGND (16) | Power ground return | Low-impedance path for high-current inductor return; must be separated from AGND to avoid noise coupling. |
| AGND (5) | Analog ground reference | Reference for FB, REF, CC, ILIM/SS; requires dedicated low-noise trace to PGND at single-point star connection. |
| FB (7) | Feedback input | Sets output: tied to AGND for 3.3V mode; connected to resistor divider for adjustable output (1.25V–VIN). |
| REF (6) | 1.25V precision reference | Stable ±1% output; supplies external circuitry up to 10µA; bypassed with 0.1µF to AGND. |
| SYNC/PWM (9) | Mode control input | High = fixed-frequency PWM; low = normal mode; driven by TTL-level square wave for external synchronization. |
| STBY (11) | Standby enable | Pull to AGND to force low-power mode; overrides SYNC/PWM setting for guaranteed ultra-low IQ operation. |
| SHDN (15) | Active-low shutdown | Pull low to disable regulator; draws only 2µA; withstands full VIN voltage during shutdown. |
| BOOT (12) | Bootstrap supply | Connected to VOUT for VOUT ≤ 5.5V; enables efficient gate drive of P-channel switch; critical for 100% duty cycle. |
| CVL (4) | Auxiliary 3V/5mA regulator | Supplies external logic or bias circuits; disabled in shutdown; dropout voltage <120mV at 5mA. |
| CC (8) | Integrator capacitor | Connects 0.01µF to AGND; sets loop compensation; determines transient response and stability margin. |
Key Features
| Feature | Design Value |
|---|---|
| 600kHz fixed-frequency PWM | Enables compact magnetics (10µH inductors) and predictable EMI profile for RF-sensitive handheld applications. |
| 100% duty-cycle operation | Eliminates dropout voltage penalty at low input; maintains regulation down to VIN = VOUT + IOUT×0.24Ω ≈ 3.65V @ 1A. |
| Synchronous rectification | Internal N-channel FET replaces external Schottky diode at light loads, improving efficiency by ~3–5% below 200mA. |
| Dual-mode output selection | Hardware-selectable 3.3V (±1%) or adjustable 1.25V–VIN output - no external components needed for fixed-voltage use. |
| Multi-mode quiescent control | 25µA low-power mode and 2µA shutdown minimize battery drain in always-on portable systems with intermittent active periods. |
Applications
| Cellular Phones | Two-Way Radios |
|---|---|
Use Scenario: Powering baseband processor and RF transceiver from dual Li+ batteries during transmit bursts and sleep cycles. IC Role / Device Role / Timing Role: Primary 3.3V buck regulator with fast load-transient response (<50mV deviation) and low-noise PWM operation to avoid RF interference. Use Value: 96% peak efficiency and 25µA low-power mode extend talk time by >12% versus legacy 300kHz converters under mixed-load profiles. |
Use Scenario: Supplying 3.3V to digital signal processor and audio codec in battery-powered walkie-talkies with push-to-talk duty cycling. IC Role / Device Role / Timing Role: High-efficiency step-down converter with 100% duty cycle enabling operation down to 3.4V battery voltage while maintaining regulation. Use Value: Synchronous rectification reduces heat rise by 8°C at 500mA, eliminating need for thermal relief pads in compact 2-layer PCB designs. |
| PDAs and Handy-Terminals | Computer Peripherals |
Use Scenario: Generating stable 3.3V rail for touchscreen controller, memory, and USB interface in handheld data collection terminals. IC Role / Device Role / Timing Role: Dual-mode buck regulator supporting both fixed 3.3V output and adjustable voltage for flexible system architecture. Use Value: Built-in 3V/5mA CVL output powers auxiliary logic, reducing BOM count by one LDO and simplifying layout in space-constrained enclosures. |
Use Scenario: Providing regulated 3.3V to USB hub controllers and LED indicators in powered USB hubs and docking stations. IC Role / Device Role / Timing Role: Input-flexible buck converter accepting wide-range wall adapters (5–14V) while delivering clean, low-ripple 3.3V output. Use Value: 600kHz switching allows use of 10µH inductors and 22µF ceramic output caps, cutting solution size by 35% vs. 300kHz alternatives. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX1684EEE-T | 300kHz switching frequency; higher inductor value required (22µH); 300mW lower power dissipation at light loads due to reduced gate charge loss. | Better suited for noise-sensitive audio subsystems where lower fundamental frequency eases EMI filtering. | Select MAX1684EEE-T when board space allows larger inductors and EMI filtering priority exceeds component count reduction. |
| TPS62231DRYT | 2.25V–6.5V input range; 3MHz switching; 0.6V–6V adjustable output; no auxiliary CVL output; 18µA typical IQ in PFM mode. | Targeted at single-cell Li+ (3.0–4.2V) applications; lacks high-voltage tolerance and auxiliary 3V rail for mixed-supply systems. | Choose TPS62231DRYT only for compact, single-battery designs where input never exceeds 6.5V and no auxiliary 3V supply is needed. |
Compared with MAX1684EEE-T, the MAX1685EEE-T trades slightly higher gate-drive losses at 600kHz for 45% smaller magnetics and faster transient response; versus TPS62231DRYT, it offers wider input range, integrated CVL, and proven 1A capability in harsh industrial handheld environments.
Availability
MAX1685EEE-T is available at Aetrix Electronics and suitable for cellular phones, two-way radios, PDAs, and computer peripherals requiring stable component supply with guaranteed 1A output, 600kHz operation, and -40°C to +85°C industrial temperature support.
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, industrial, and communications applications.
The MAX1684/MAX1685 product line was designed specifically for low-noise, high-efficiency power conversion in battery-powered handheld devices with demanding input voltage flexibility and multi-mode quiescent optimization.
FAQ
What is the maximum input voltage rating for the MAX1685EEE-T?
The MAX1685EEE-T has an absolute maximum input voltage of 15V, with recommended continuous operation up to 14V. Exceeding 15V risks permanent damage per Absolute Maximum Ratings. The device operates reliably across its full 2.7V–14V input range, enabling compatibility with two-cell Li+ batteries and wall adapters. This wide range is essential for handheld devices that charge while operating.
Does the MAX1685EEE-T support adjustable output voltage, and how is it configured?
Yes, the MAX1685EEE-T supports adjustable output from 1.25V to VIN using the FB pin. To configure: connect FB to a resistor divider between VOUT and AGND (R2 = 20kΩ–100kΩ, R1 = R2 × [(VOUT / 1.25V) – 1]). For fixed 3.3V output, tie FB directly to AGND - no external resistors needed. The internal 1.251V reference ensures ±1% accuracy over temperature and line.
How does the MAX1685EEE-T achieve 100% duty cycle, and what is its practical dropout voltage?
The MAX1685EEE-T achieves 100% duty cycle by holding its internal P-channel high-side switch continuously on when input voltage approaches output voltage. At 1A load, dropout voltage equals IOUT × RDS(on) ≈ 1A × 0.24Ω = 240mV, plus inductor DCR contribution. This allows regulation down to ~3.55V input for a 3.3V output - critical for extending runtime near battery end-of-discharge.
What are the key differences between MAX1685EEE-T and MAX1684EEE-T?
The core difference is switching frequency: MAX1685EEE-T runs at 600kHz, enabling smaller external components (e.g., 10µH inductor), while MAX1684EEE-T operates at 300kHz for lower EMI and gate-drive losses. Both share identical pinout, 16-QSOP package, 1A output, and feature set including CVL, SYNC, and multi-mode control. Choose MAX1685EEE-T for space-constrained designs; MAX1684EEE-T for noise-sensitive RF sections.
Can the MAX1685EEE-T's auxiliary CVL output power external circuitry, and what are its limits?
Yes, the CVL pin delivers a regulated 3.0V ±0.15V output capable of sourcing up to 5mA. It is powered from the internal VL regulator and disabled during shutdown. Its dropout voltage is ≤120mV at full 5mA load. Use CVL to power level-shifters, bias networks, or low-current logic - but not high-speed interfaces or analog sensors requiring ultra-low noise, as CVL shares internal regulation with the main control circuitry.
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:
- Obsolete
- 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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