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Analog Devices Inc./Maxim Integrated MAX861ISA+T
- Part No.:
- MAX861ISA+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX861ISA+T.pdf
- Description:
- IC REG CHARG PUMP INV 50MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,505
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Product details
Overview
MAX861ISA+T from Maxim Integrated is a frequency-selectable, 50mA switched-capacitor voltage inverter/doubler IC that converts +1.5V to +5.5V inputs to inverted (–VIN) or doubled (+2VIN) outputs. It operates at selectable switching frequencies of 13kHz, 100kHz, or 250kHz, delivers 87% efficiency at 50mA load, and features 12Ω output resistance and 1µA shutdown current. It is used in portable medical instruments requiring compact, inductorless negative rail generation.
For engineers reviewing the MAX861ISA+T datasheet, MAX861ISA+T pinout, MAX861ISA+T application, or MAX861ISA+T equivalent, key selection criteria include its SO-8 package compatibility, LV pin configuration for mode selection, FC pin-driven frequency trade-offs between capacitor size and quiescent current, and its suitability as a drop-in upgrade over ICL7660 in space-constrained battery-powered systems.
Technical Context
The MAX861ISA+T implements a BiCMOS charge-pump architecture with internal flying-capacitor switching controlled by an oscillator whose fundamental frequency is directly set via the FC pin-no internal division is applied. Its LV pin selects inverter mode (LV = GND) or doubler mode (LV = OUT), defining input voltage range (+1.5V–+5.5V vs. +2.5V–+5.5V) and functional behavior.
Shutdown is active-low on the SHDN pin, reducing supply current to <1µA while preserving pin-state integrity. Output regulation is unregulated but highly predictable: output voltage droop follows VOUT = –VIN – IOUT × ROUT, where ROUT = 12Ω typical (including 0.2Ω test capacitor ESR), enabling stable biasing for op-amps and analog front-ends without feedback loops.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 50mA max continuous - supports rail-splitting for dual-supply op-amps without external inductors |
| Switching Frequencies | 13kHz / 100kHz / 250kHz - selectable via FC pin to optimize capacitor size (2.2µF–68µF) and EMI profile |
| Input Voltage Range | +1.5V to +5.5V (inverter), +2.5V to +5.5V (doubler) - enables single-cell Li-ion or 3.3V/5V system rail usage |
| Efficiency | 87% at 50mA load - minimizes thermal rise in sealed handheld enclosures |
| Output Resistance | 12Ω typical - defines predictable voltage droop (e.g., –4.4V at 50mA from +5V input) |
| Quiescent Current | 200µA typical - extends battery life in always-on sensor nodes |
| Shutdown Current | <1µA - meets ultra-low-power sleep-mode requirements for portable diagnostics |
Pinout & Package
MAX861ISA+T is housed in an 8-pin SO (Small Outline) package, 3.9mm × 4.9mm, 1.75mm height, RoHS-compliant, with standard gull-wing leads and 1.27mm pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FC (Pin 1) | Frequency control input | Selects oscillator frequency: FC = VDD → 13kHz, FC = GND → 100kHz, FC = OUT → 250kHz |
| C1+ (Pin 2) | Flying capacitor positive terminal | Connects to one side of external flying capacitor C1; carries full switching current |
| GND (Pin 3) | Ground reference | Common return for all internal circuitry and external capacitors; must be low-impedance |
| C1– (Pin 4) | Flying capacitor negative terminal | Connects to other side of C1; phase-inverted node relative to C1+ |
| OUT (Pin 5) | Inverted or doubled output | Delivers –VIN (LV = GND) or +2VIN (LV = OUT); requires external reservoir capacitor C2 |
| LV (Pin 6) | Mode selection input | LV = GND → inverter; LV = OUT → doubler; floating not recommended |
| SHDN (Pin 7) | Active-low shutdown enable | Pull low to disable charge pump; pull high (VDD) to enable; open-circuit disables device |
| VDD (Pin 8) | Positive supply input | Accepts +1.5V to +5.5V; supplies internal logic and pump switches; bypass with 0.1µF ceramic |
Key Features
| Feature | Design Value |
|---|---|
| Invert or double supply voltage | Single IC replaces discrete inverter/doubler circuits; eliminates need for separate DC-DC modules |
| Three selectable switching frequencies | Enables EMI-sensitive designs (e.g., ECG front-end) to avoid critical bands like 10–100kHz |
| 12Ω output resistance | Provides predictable load regulation without closed-loop compensation - simplifies layout and BOM |
| 1µA shutdown current | Meets IEC 62304 Class C power budget constraints for battery-powered medical devices |
| SO-8 package compatibility | Direct PCB footprint reuse from legacy ICL7660/MAX660 designs with only SHDN pin rewiring |
Applications
| Portable Medical Sensors | Handheld Test Equipment |
|---|---|
Use Scenario: Battery-powered pulse oximeter requiring –5V rail for analog signal conditioning and ADC biasing. IC Role / Device Role / Timing Role: Voltage inverter generating stable negative supply from single 3.7V Li-ion cell. Use Value: Eliminates bulky inductive DC-DC converter; 87% efficiency preserves runtime; 12Ω output resistance ensures ±2% VOUT accuracy across 1–50mA load range. | Use Scenario: Pocket-sized multimeter needing dual ±3.3V rails for precision op-amp front-end and display driver. IC Role / Device Role / Timing Role: Paired MAX861ISA+T devices-one in inverter mode (–3.3V), one in doubler mode (+6.6V)-feeding linear regulators. Use Value: SO-8 footprint allows compact two-rail generation; FC pin tuning avoids 32.768kHz crystal interference; 1µA shutdown enables auto-off without leakage concerns. |
| Operational-Amplifier Power Supplies | Interface Power Supplies |
Use Scenario: Low-noise instrumentation amplifier in wireless sensor node requiring symmetric ±2.5V supplies. IC Role / Device Role / Timing Role: Inverter generating –2.5V from regulated 2.5V LDO output; LV = GND, FC = GND for 100kHz operation. Use Value: 100kHz switching enables use of 4.7µF ceramic C1/C2 - reduces board area by 60% vs. 10µF electrolytics; 200µA quiescent current aligns with µA-level system sleep budgets. | Use Scenario: RS-232 transceiver IC requiring ±5V supplies in a USB-powered diagnostic dongle. IC Role / Device Role / Timing Role: Dual-rail generator: one MAX861ISA+T in inverter mode (–5V), second in doubler mode (+10V), both fed from +5V USB rail. Use Value: 250kHz high-frequency mode permits 2.2µF flying caps - cuts total capacitance volume by 75%; SO-8 package fits 10mm × 10mm dongle PCB constraint. |
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 |
|---|---|---|---|
| MAX860ISA+T | Same SO-8 package and pinout; offers 6kHz/50kHz/130kHz frequencies instead of 13kHz/100kHz/250kHz | Better suited for ultra-low-noise audio biasing where sub-20kHz switching avoids audible artifacts | Select MAX860ISA+T when lower fundamental switching frequency is required to avoid sensitive analog bands |
| ICL7660CPA+ | Legacy 8-pin PDIP/SO; fixed ~10kHz frequency; 10mA output; 55Ω output resistance; no FC or LV pins | Limited to low-current, non-critical applications; incompatible with modern high-density layouts due to larger footprint and lower efficiency | Choose ICL7660CPA+ only for legacy repair or cost-sensitive, non-battery applications with <10mA load |
Compared with MAX860ISA+T, the MAX861ISA+T provides higher-frequency options enabling smaller external capacitors and better noise floor control, while versus ICL7660CPA+, it delivers 5× higher output current, 4.6× lower output resistance, and programmable frequency - making it suitable for next-generation portable instrumentation where size, efficiency, and precision are critical.
Availability
MAX861ISA+T is available at Aetrix Electronics and suitable for portable medical sensors, handheld test equipment, operational-amplifier power supplies, interface power supplies, and battery-powered instrumentation requiring stable component supply with long-term manufacturability.
Supply support for MAX861ISA+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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power-management ICs for industrial, medical, and communications applications.
The MAX860/MAX861 product line was designed specifically to replace legacy charge pumps like the ICL7660 in space-constrained, battery-operated systems-delivering higher current, lower output resistance, and frequency flexibility without inductors.
FAQ
What is the maximum continuous output current specification for MAX861ISA+T?
The MAX861ISA+T is rated for 50mA continuous output current under specified thermal conditions (TA ≤ +85°C, SO package). Absolute maximum rating is 60mA, but sustained operation above 50mA may exceed junction temperature limits or degrade output regulation. Derating is required above +70°C ambient per the 5.88mW/°C SO package power dissipation curve. This 50mA capability enables direct powering of multiple op-amps or low-power ADCs without additional regulation stages.
How does the LV pin affect the operating mode and input voltage range of MAX861ISA+T?
The LV pin on the MAX861ISA+T determines functional mode: when tied to GND, the device operates as a voltage inverter supporting +1.5V to +5.5V input; when tied to OUT, it functions as a voltage doubler requiring +2.5V to +5.5V input. The LV pin must not be left floating - incorrect connection causes undefined behavior or failure to start. This dual-mode capability allows one MAX861ISA+T design to serve both negative-rail and boosted-positive-rail needs across different subsystems in the same product family.
Can MAX861ISA+T be used as a direct replacement for ICL7660 in existing SO-8 footprints?
Yes, the MAX861ISA+T is pin-compatible with the ICL7660 in SO-8 packages, but requires one wiring change: the ICL7660's OSC pin (Pin 1) maps to MAX861ISA+T's FC pin, and the ICL7660's unused Pin 7 maps to MAX861ISA+T's SHDN pin, which must be pulled high (to VDD) for normal operation. All other pins match functionally. No PCB redesign is needed - only jumpering SHDN to VDD and optionally configuring FC for desired frequency yields immediate performance gains including 5× higher current and 4.6× lower output resistance.
What are the recommended capacitor values for MAX861ISA+T when operating in high-frequency mode (FC = OUT)?
When FC = OUT (250kHz mode), the MAX861ISA+T datasheet recommends 2.2µF for both flying capacitor C1 and reservoir capacitor C2 using low-ESR types (e.g., ceramic or polymer tantalum). This value balances minimal capacitor size against output resistance and ripple: smaller values increase ROUT and VRIPPLE, while larger values yield diminishing returns. At 250kHz, 2.2µF achieves ~12Ω ROUT and <20mVpp ripple at 50mA load with 0.2Ω ESR capacitors - enabling compact, high-density layouts in handheld medical devices.
Does MAX861ISA+T require external feedback or regulation circuitry to maintain output voltage accuracy?
No, the MAX861ISA+T is an unregulated charge-pump converter and does not require external feedback. Its output voltage follows predictable droop: VOUT = –VIN – IOUT × ROUT (inverter) or VOUT = +2VIN – IOUT × ROUT (doubler), where ROUT = 12Ω typical. Designers select input voltage, load current, and capacitor ESR to meet accuracy targets - e.g., with +5V input and 10mA load, inverter output is –4.88V (±0.1V). This open-loop behavior simplifies design, eliminates compensation networks, and improves reliability in safety-critical portable systems.
MAX861ISA+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Ratiometric
- Output Configuration:
- Positive or Negative
- Topology:
- Charge Pump
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 1.5V, 2.5V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- -Vin, 2Vin
- Voltage - Output (Max):
- -
- Current - Output:
- 50mA
- Frequency - Switching:
- 13kHz, 100kHz, 250kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -25°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX861ISA+T FAQ
1.How can I place an order for MAX861ISA+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX861ISA+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 MAX861ISA+T reliable?
The price and inventory of MAX861ISA+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX861ISA+T is usually 5 days.
3.What payment methods are accepted for MAX861ISA+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX861ISA+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX861ISA+T?
MAX861ISA+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX861ISA+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 MAX861ISA+T?
For technical support, including MAX861ISA+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX861ISA+T requirements.
6.How does Aetrix verify that MAX861ISA+T is sourced from the original manufacturer or authorized distributors?
All MAX861ISA+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 MAX861ISA+T meets industry standards.
7.What is the process for return or replacement of MAX861ISA+T?
All MAX861ISA+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX861ISA+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 MAX861ISA+T part is unused and in its original packaging.
Return procedure for MAX861ISA+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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