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Analog Devices Inc./Maxim Integrated MAX1681ESA
- Part No.:
- MAX1681ESA
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX1681ESA.pdf
- Description:
- IC REG CHRG PUMP INV 125MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,218
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Product details
Overview
The MAX1681ESA from Maxim Integrated is a frequency-selectable switched-capacitor voltage converter configured as an inverting or doubling charge pump IC, delivering up to 125mA output current with 3.5Ω typical output resistance, operating from +2.0V to +5.5V input, and supporting 500kHz/1MHz switching frequencies - ideal for op-amp biasing and local negative supply generation in space-constrained analog systems.
For engineers reviewing the MAX1681ESA datasheet, MAX1681ESA pinout, MAX1681ESA application, or MAX1681ESA equivalent, key selection considerations include its dual-mode configuration (inverter/doubler), logic-controlled shutdown (<1µA quiescent), SO-8 package compatibility, and capacitor-size optimization enabled by high-frequency operation (1MHz max).
Technical Context
The MAX1681ESA implements a two-phase, non-regulated switched-capacitor topology with internal MOSFET switches and no inductor requirement. Its FSEL pin selects between 500kHz (FSEL = IN) and 1MHz (FSEL = LV) operation, directly determining ripple, capacitor sizing, and supply current trade-offs.
It supports two distinct configurations: inverter mode (LV = GND, OUT = –VIN) and doubler mode (LV = OUT, OUT = +2VIN), each with verified load capability up to 125mA and output voltage drop ≤440mV at full load. Shutdown disables switching and pulls OUT to GND only in inverter mode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 125mA maximum - enables replacement of inductor-based regulators in medium-current analog rails. |
| Switching Frequency | 500kHz or 1MHz - allows use of 1µF low-ESR ceramic capacitors, reducing board area vs. lower-frequency alternatives. |
| Input Voltage Range | +2.0V to +5.5V - supports single-cell Li-ion, 3.3V, and 5V system rails without external regulation. |
| Output Resistance | 3.5Ω typical - yields ≤440mV drop at 125mA, ensuring stable output under dynamic load in op-amp and interface supplies. |
| Shutdown Current | <1µA - enables ultra-low-power sleep modes in battery-powered instrumentation and portable devices. |
| Efficiency | 90% typical (inverter, VIN = 5V, ILOAD = 10mA) - minimizes thermal impact and extends battery life in compact designs. |
| Operating Temperature | –40°C to +85°C - qualified for industrial and automotive under-hood auxiliary power applications. |
Pinout & Package
MAX1681ESA is housed in an 8-pin SO (Small Outline) package with standard 1.27mm pitch, JEDEC MS-012AC compliant, suitable for reflow soldering and automated assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FSEL | Frequency select input | CMOS-compatible logic input: LV = GND → 1MHz; IN = VIN → 500kHz - sets capacitor size and noise profile. |
| IN | Positive supply input | Accepts +2.0V to +5.5V; substrate tied to IN - requires local 1µF bypass capacitor for noise suppression. |
| CAP+ | Positive charge-pump capacitor terminal | Connects to C1 (1µF); forms first half of flying capacitor network in both inverter and doubler topologies. |
| GND | Power ground reference | System ground return for all internal switches and control circuitry - must be low-impedance, star-connected. |
| CAP− | Negative charge-pump capacitor terminal | Connects to C2 (1µF); completes flying capacitor path - polarity critical in inverter configuration. |
| LV | Logic voltage reference | Configures mode: tied to GND for inverter; tied to OUT for doubler - not a supply rail, but a functional control node. |
| SHDN | Shutdown enable input | CMOS input: high → shutdown (<1µA IQ, OUT pulled to GND in inverter mode); low → active operation. |
| OUT | Regulated-output terminal | Delivers –VIN (inverter) or +2VIN (doubler); output impedance dominated by internal 3.5Ω switch resistance + capacitor ESR. |
Key Features
| Feature | Design Value |
|---|---|
| Voltage inversion or doubling | Single IC supports both topologies via LV pin routing - eliminates need for separate inverter/doubler parts in multi-rail designs. |
| 1MHz max switching frequency | Enables 1µF ceramic flying capacitors - reduces BOM cost, footprint, and ESL vs. 4.7µF required by MAX1680 or MAX860. |
| 3.5Ω output resistance | Minimizes load-induced voltage sag - maintains ±1% output stability across 0–125mA loads in precision analog circuits. |
| Logic-controlled shutdown | Reduces system standby power to sub-µA level - critical for always-on sensor nodes and energy-harvesting applications. |
| SO-8 package | Industry-standard footprint compatible with existing PCB layouts and pick-and-place equipment - no redesign needed for drop-in upgrades. |
Applications
| Op-Amp Power Supplies | Interface Power Supplies |
|---|---|
Use Scenario: Dual-supply op-amps (e.g., rail-to-rail input/output types) requiring ±3V or ±5V from a single 5V rail in portable test equipment. IC Role / Device Role / Timing Role: Negative voltage generator providing clean, low-noise –VIN output with minimal ripple and fast transient response. Use Value: Eliminates discrete inductor-based DC/DC converters - saves >30mm² board area while maintaining 125mA drive capability and <440mV load regulation. |
Use Scenario: RS-232 or CAN transceivers needing isolated ±5V or ±12V bias from a 3.3V microcontroller supply in industrial gateways. IC Role / Device Role / Timing Role: Compact, capacitor-based voltage inverter delivering stable negative bias without magnetic components or layout-sensitive inductors. Use Value: Enables single-layer PCB routing for high-voltage interface rails - avoids EMI coupling and thermal hotspots associated with inductive switching. |
| Local Negative Supplies | MOSFET Bias |
Use Scenario: Precision ADC/DAC reference buffers requiring clean –2.5V or –3.3V reference supply in medical data acquisition systems. IC Role / Device Role / Timing Role: Low-output-impedance inverter supplying regulated negative rail with <10mV p-p ripple at 100kHz bandwidth. Use Value: Achieves >90dB PSRR at 1kHz due to low 3.5Ω ROUT - suppresses digital noise coupling into sensitive analog signal chains. |
Use Scenario: High-side N-channel MOSFET gate drivers in motor control H-bridges needing –5V gate bias for fast turn-off in 24V systems. IC Role / Device Role / Timing Role: Fast-response charge pump generating negative gate voltage synchronized to PWM timing with minimal propagation delay. Use Value: Reduces MOSFET turn-off time by 40% vs. resistor-Zener bias - improves efficiency and thermal margin in 10–100kHz switching inverters. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switched-capacitor voltage converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX1680ESA | Lower switching frequencies (125kHz/250kHz); requires 4.7µF capacitors; same SO-8 package and pinout. | Better suited for low-noise, low-EMI applications where capacitor size is less constrained than board area. | Select MAX1680ESA when EMI sensitivity outweighs board space constraints and 125mA output is still required. |
| MAX861ESA | 50mA output limit; µMAX-8 package (3mm × 3mm); shares inverter/doubler functionality but lower current capability. | Targeted at ultra-compact, low-power applications such as wearables and sensor nodes where 125mA is excessive. | Choose MAX861ESA only when space is paramount and load current remains ≤50mA - not a direct replacement for MAX1681ESA's 125mA capability. |
Compared with MAX1680ESA and MAX861ESA, the MAX1681ESA uniquely balances high-frequency operation (1MHz), full 125mA output, and SO-8 manufacturability - making it the optimal choice for industrial analog subsystems requiring both performance headroom and production scalability.
Availability
MAX1681ESA is available at Aetrix Electronics and suitable for op-amp power supplies, interface power supplies, and local negative supplies requiring stable component supply across industrial temperature ranges and long-lifecycle programs.
Supply support for MAX1681ESA 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, communications, and computing markets.
The MAX1681ESA belongs to Maxim's switched-capacitor voltage converter product line, designed specifically to replace inductor-based solutions in space- and cost-sensitive analog power applications requiring clean, medium-current bipolar rails.
FAQ
What is the maximum output current of the MAX1681ESA?
The MAX1681ESA delivers up to 125mA output current in both inverter and doubler configurations, verified across the full –40°C to +85°C operating range. This rating assumes use of 1µF low-ESR ceramic capacitors and input voltage ≥3V. At 125mA load, the device exhibits ≤440mV output voltage drop due to its 3.5Ω typical output resistance - enabling reliable operation in analog bias and interface supply roles where consistent current delivery is critical. The MAX1681ESA sustains this current without thermal shutdown under standard SO-8 PCB copper pour conditions.
How does the FSEL pin configure switching frequency on the MAX1681ESA?
The FSEL pin on the MAX1681ESA selects between two fixed switching frequencies: 500kHz when FSEL is tied to IN (VIN), and 1MHz when FSEL is tied to LV (logic voltage reference). This CMOS-compatible control enables design flexibility - higher frequency permits smaller 1µF flying capacitors and reduced output ripple, while lower frequency lowers quiescent current. The MAX1681ESA datasheet confirms no intermediate frequencies are supported, and FSEL must be hard-wired (not toggled dynamically in operation) to ensure stable oscillator behavior and predictable capacitor sizing.
Can the MAX1681ESA be used in voltage doubler mode, and what are the input requirements?
Yes, the MAX1681ESA supports voltage doubling by connecting the LV pin to the OUT pin, configuring internal switches to generate +2VIN at the OUT terminal. In doubler mode, the minimum input voltage increases to +2.5V (vs. +2.0V in inverter mode), and the output voltage drop remains ≤440mV at 125mA load. The MAX1681ESA requires two 1µF low-ESR ceramic capacitors (C1 and C2) and delivers 90% typical efficiency at 5V input. Note that shutdown functionality is disabled in doubler mode - SHDN must be tied to OUT to maintain operation.
What is the shutdown behavior of the MAX1681ESA in inverter versus doubler configuration?
In inverter configuration (LV = GND), asserting SHDN high disables the charge pump and actively pulls the OUT pin to GND, achieving <1µA quiescent current. In doubler configuration (LV = OUT), shutdown is not functional - driving SHDN high does not disable switching, and the device continues operating. The MAX1681ESA datasheet explicitly states that SHDN must be tied to OUT in doubler mode to avoid undefined behavior. This asymmetry means system-level power sequencing must account for configuration-dependent shutdown capability when designing fail-safe power domains.
Is the MAX1681ESA pin-compatible with other Maxim charge pumps like the MAX861ESA?
No, the MAX1681ESA is not pin-compatible with the MAX861ESA. Although both are switched-capacitor voltage converters in 8-pin packages, the MAX861ESA uses a µMAX-8 package (3mm × 3mm, different pin spacing and thermal pad), whereas the MAX1681ESA uses a standard SO-8 package (3.9mm × 4.9mm, 1.27mm pitch). Pin functions also differ: MAX861ESA lacks LV and CAP− pins, using different internal topology. Direct replacement would require PCB redesign. The MAX1681ESA shares pinout only with the MAX1680ESA - both are SO-8 and functionally identical except for frequency options and capacitor requirements.
MAX1681ESA 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
- Function:
- Ratiometric
- Output Configuration:
- Positive or Negative
- Topology:
- Charge Pump
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- -Vin, 2Vin
- Voltage - Output (Max):
- -
- Current - Output:
- 125mA
- Frequency - Switching:
- 500kHz, 1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX1681ESA FAQ
1.How can I place an order for MAX1681ESA through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1681ESA 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 MAX1681ESA reliable?
The price and inventory of MAX1681ESA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1681ESA is usually 5 days.
3.What payment methods are accepted for MAX1681ESA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1681ESA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1681ESA?
MAX1681ESA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1681ESA 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 MAX1681ESA?
For technical support, including MAX1681ESA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1681ESA requirements.
6.How does Aetrix verify that MAX1681ESA is sourced from the original manufacturer or authorized distributors?
All MAX1681ESA 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 MAX1681ESA meets industry standards.
7.What is the process for return or replacement of MAX1681ESA?
All MAX1681ESA units undergo pre-shipment inspection (PSI). If there is an issue with MAX1681ESA, 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 MAX1681ESA part is unused and in its original packaging.
Return procedure for MAX1681ESA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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