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Texas Instruments LM2661MX/NOPB
- Part No.:
- LM2661MX/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM2661MX/NOPB.pdf
- Description:
- IC REG CHRG PUMP INV 100MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,921
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Product details
Overview
LM2661MX/NOPB from Texas Instruments is a CMOS switched-capacitor voltage inverter/doubler IC operating from 1.5 V to 5.5 V input, delivering up to 100 mA output current with 88% typical conversion efficiency at full load and 6.5 Ω typical output resistance. It supports dual-mode operation (inverting or doubling), selectable 10 kHz/80 kHz oscillator frequency via FC pin, and features low 120 µA quiescent current - ideal for space-constrained, battery-powered operational amplifier and interface power supplies.
For engineers reviewing the LM2661MX/NOPB datasheet, LM2661MX/NOPB pinout, LM2661MX/NOPB application, or LM2661MX/NOPB equivalent, key selection criteria include its unregulated charge-pump architecture, LV pin configuration dependency on input voltage (<3.5 V vs ≥3.5 V), OSC pin limitations in doubler mode, and SOIC-8 package thermal performance (RθJA = 170 °C/W).
Technical Context
The LM2661MX/NOPB implements a four-switch CMOS charge-pump topology that alternately charges and transfers energy between two external capacitors to generate inverted or doubled output voltages. Its internal oscillator drives synchronous switching at fSW = fOSC/2, where fOSC is selected by FC pin state (open = 10 kHz typ, V+ = 80 kHz typ) or externally programmable via OSC pin capacitance or clock input (up to 150 kHz, inverter mode only).
Functional modes are determined by external pin connections: inverter mode uses V+ as input and OUT as negative output with LV floating or grounded depending on supply voltage; doubler mode reassigns GND as input and V+ as positive output, requiring LV tied to OUT and disabling external OSC drive. Output resistance (6.5 Ω typ) reflects combined contributions of internal switch RON, capacitor ESR, and switching frequency.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1.5 V to 5.5 V - supports single-cell Li-ion, alkaline, and regulated 3.3 V/5 V rails without external regulation. |
| Output Current | 100 mA - sufficient for dual-rail op-amp biasing or RS-232 interface generation with minimal voltage drop. |
| Oscillator Frequency | 10 kHz / 80 kHz (FC-selectable) - lower frequency reduces quiescent current (0.12 mA); higher frequency enables smaller external capacitors. |
| Conversion Efficiency | 88% at 100 mA - minimizes heat rise and extends battery life in portable instrumentation. |
| Output Resistance | 6.5 Ω typical - defines load regulation error (e.g., 650 mV drop at 100 mA), critical for stable analog supply design. |
| Quiescent Current | 120 µA - enables always-on bias generation in low-power sensor nodes without significant standby drain. |
| Operating Temperature | –40°C to +85°C - qualified for industrial and medical equipment environments. |
Pinout & Package
LM2661MX/NOPB is housed in an 8-pin SOIC (D) package measuring 4.90 mm × 3.91 mm, with standard 1.27 mm pitch and surface-mount compatibility. Thermal resistance is 170 °C/W (junction-to-ambient), supporting continuous 100 mA operation at ≤60°C ambient with minimal heatsinking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 FC | Frequency control input | Selects internal oscillator frequency: open = 10 kHz, connected to V+ = 80 kHz; no effect when OSC driven externally. |
| 2 CAP+ | Flying capacitor positive terminal | Connects to positive lead of charge-pump capacitor C1; carries bidirectional switching current during charge-transfer cycles. |
| 3 GND | Power ground reference | Primary return path for input supply, internal logic, and capacitor discharge currents; must be low-impedance for ripple control. |
| 4 CAP− | Flying capacitor negative terminal | Connects to negative lead of C1; forms half of charge-transfer loop with CAP+ and internal switch array. |
| 5 OUT | Inverter output / Doubler ground | In inverter mode: negative output rail; in doubler mode: tied to system ground - pin function changes with configuration. |
| 6 LV | Low-voltage enable input | Tie to GND for V+ < 3.5 V to bypass internal regulator; leave open or tie to GND for V+ ≥ 3.5 V; must be GND when driving OSC externally. |
| 7 OSC | Oscillator control | Accepts external capacitor to reduce frequency or external CMOS clock (≤150 kHz) in inverter mode only; disabled in doubler mode. |
| 8 V+ | Positive supply input / Doubler output | In inverter mode: main input rail; in doubler mode: positive output rail - pin role reverses based on external wiring. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-mode topology (inverter/doubler) | Single IC replaces separate negative and positive boost rails - reduces BOM count and PCB area in dual-supply systems. |
| Configurable oscillator (10/80 kHz) | Enables trade-off between low-noise/low-quiescent operation (10 kHz) and compact capacitor sizing (80 kHz) without redesign. |
| Parallel operation support | Multiple LM2661MX/NOPB units can share one output capacitor while using individual flying capacitors, lowering composite output resistance. |
| Low 120 µA quiescent current | Permits use in always-on auxiliary supplies for microcontroller reset circuits or sensor biasing without compromising battery runtime. |
| SOIC-8 thermal performance | RθJA = 170 °C/W allows 100 mA continuous output at ambient ≤60°C - eliminates need for thermal vias or copper pours in cost-sensitive designs. |
Applications
| Operational Amplifier Power Supplies | Interface Power Supplies |
|---|---|
|
Use Scenario: Generating ±5 V dual rails for precision op-amps in handheld test equipment powered by a single 5 V USB source. IC Role / Device Role / Timing Role: LM2661MX/NOPB operates in inverter mode to produce –5 V from +5 V input, with FC pin open for low-noise 10 kHz switching. Use Value: Eliminates need for inductor-based DC/DC converters, reducing EMI and board area while maintaining 88% efficiency at 50 mA load. |
Use Scenario: Providing –12 V bias for RS-232 transceivers in portable medical data loggers using a 3.3 V LDO supply. IC Role / Device Role / Timing Role: LM2661MX/NOPB configured as inverter with LV tied to GND (V+ = 3.3 V < 3.5 V), enabling reliable start-up and regulation. Use Value: Achieves –3.3 V output with 6.5 Ω output resistance, ensuring stable line driver operation without external LDO post-regulation. |
| Laptop Peripheral Power | Handheld Instrumentation |
|
Use Scenario: Supplying isolated –3.3 V for analog front-end ADC drivers in ultraportable laptop docking stations. IC Role / Device Role / Timing Role: LM2661MX/NOPB used in parallel configuration (two units) to halve effective output resistance and support 150 mA peak current. Use Value: Delivers low-ripple –3.3 V with <150 mV load regulation error across 0–100 mA, meeting SNR requirements for 16-bit ADCs. |
Use Scenario: Creating +5 V from a 3 V coin-cell battery in pocket-sized pH meters requiring analog signal conditioning. IC Role / Device Role / Timing Role: LM2661MX/NOPB operated in doubler mode (GND = input, V+ = output), with LV tied to OUT and OSC open. Use Value: Produces regulated +5 V output using only two external capacitors and a Schottky diode, extending battery life beyond 100 hours. |
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 |
|---|---|---|---|
| LM2660M/NOPB | Same core architecture and pinout; differs only in SOIC packaging (tube vs tape-and-reel) and orderable part marking (LM2660M vs LM2661MX/NOPB). | No functional difference - identical electrical specs, thermal performance, and mode configuration. | Select LM2660M/NOPB for tube-based prototyping; LM2661MX/NOPB for automated SMT assembly with 2500-unit tape-and-reel reels. |
| MAX680CPA+ | Higher 125 mA output current but fixed 10 kHz oscillator; no FC pin or external OSC option; requires different capacitor values (10 µF vs 150 µF). | Better suited for high-current, fixed-frequency applications where layout simplicity outweighs configurability needs. | Choose MAX680CPA+ when output current >100 mA is required and oscillator flexibility is not needed; verify capacitor ESR impact on ripple. |
Compared with LM2660M/NOPB, LM2661MX/NOPB offers identical functionality in tape-and-reel packaging optimized for production, while MAX680CPA+ trades configurability for higher current and simpler layout - making LM2661MX/NOPB optimal for volume-manufactured portable instruments needing flexible frequency tuning and reliable low-power inversion.
Availability
LM2661MX/NOPB is available at Aetrix Electronics and suitable for operational amplifier power supplies, interface power supplies, laptop peripheral power, and handheld instrumentation requiring stable component supply, consistent tape-and-reel delivery, and long-term industrial lifecycle support.
Supply support for LM2661MX/NOPB 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
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and digital signal solutions, with over 90 years of innovation in power management and precision analog ICs.
The LM2661MX/NOPB belongs to TI's switched-capacitor voltage converter product line, engineered specifically for low-EMI, inductorless DC/DC conversion in battery-powered portable and medical electronics where size, efficiency, and reliability are critical.
FAQ
What is the primary function of the LM2661MX/NOPB?
The LM2661MX/NOPB is a CMOS switched-capacitor voltage converter that functions as either an inverter (generating negative output from positive input) or a doubler (generating doubled positive output). Its core purpose is to provide compact, inductorless DC/DC conversion for dual-rail analog circuits and interface ICs. The LM2661MX/NOPB achieves this using only two external capacitors and delivers up to 100 mA with 88% efficiency, making it especially valuable in space- and noise-sensitive portable designs.
Can the LM2661MX/NOPB operate from a 1.8 V supply?
Yes, the LM2661MX/NOPB supports input voltages as low as 1.5 V in inverter mode when the LV pin is tied to GND. At 1.8 V input, it reliably generates –1.8 V output with appropriate external capacitors and maintains 120 µA quiescent current. However, output current capability decreases proportionally with input voltage due to reduced charge transfer per cycle - at 1.8 V, maximum usable output current is approximately 40–50 mA before excessive voltage drop occurs. The LM2661MX/NOPB datasheet specifies 1.5 V minimum for inverter operation with LV = GND.
How does the FC pin affect LM2661MX/NOPB performance?
The FC (Frequency Control) pin on the LM2661MX/NOPB selects the internal oscillator frequency: open circuit yields 10 kHz (typ), while connection to V+ raises it to 80 kHz (typ). This directly impacts design trade-offs - 10 kHz operation minimizes quiescent current (0.12 mA) and EMI but requires larger external capacitors for low output resistance; 80 kHz allows smaller capacitors and lower ripple but increases supply current to ~1 mA. The LM2661MX/NOPB's FC pin has no effect when OSC is driven by an external clock.
Is the LM2661MX/NOPB pin-compatible with the LMC7660?
No, the LM2661MX/NOPB is not pin-compatible with the LMC7660. While both are CMOS charge-pump inverters, the LM2661MX/NOPB uses an 8-pin SOIC package with dedicated CAP+, CAP−, FC, LV, and OSC pins for enhanced configurability, whereas the LMC7660 uses an 8-pin SOIC with different pin assignments (e.g., no separate FC or LV pins). Direct replacement would require PCB layout modification. The LM2661MX/NOPB datasheet notes that leaving LV open simplifies substitution *in certain cases*, but full pin compatibility is not claimed.
What are the thermal limitations of the LM2661MX/NOPB in SOIC-8 package?
The LM2661MX/NOPB in SOIC-8 package has a junction-to-ambient thermal resistance (RθJA) of 170 °C/W. At 100 mA output into a –5 V rail (5 V input), power dissipation is ~100 mW, resulting in ~17°C junction-to-ambient rise. With 25°C ambient, junction temperature reaches ~42°C - well within the –40°C to +85°C operating range. Derating is required above 60°C ambient; full 100 mA output is not recommended above 85°C case temperature. The LM2661MX/NOPB's thermal specification assumes standard JEDEC 2-layer board conditions.
LM2661MX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Ratiometric
- Output Configuration:
- Positive or Negative
- Topology:
- Charge Pump
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 1.5V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- -Vin, 2Vin, Vin/2
- Voltage - Output (Max):
- -
- Current - Output:
- 100mA
- Frequency - Switching:
- 5kHz, 40kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
LM2661MX/NOPB FAQ
1.How can I place an order for LM2661MX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2661MX/NOPB 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 LM2661MX/NOPB reliable?
The price and inventory of LM2661MX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2661MX/NOPB is usually 5 days.
3.What payment methods are accepted for LM2661MX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2661MX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2661MX/NOPB?
LM2661MX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2661MX/NOPB 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 LM2661MX/NOPB?
For technical support, including LM2661MX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2661MX/NOPB requirements.
6.How does Aetrix verify that LM2661MX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM2661MX/NOPB 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 LM2661MX/NOPB meets industry standards.
7.What is the process for return or replacement of LM2661MX/NOPB?
All LM2661MX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM2661MX/NOPB, 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 LM2661MX/NOPB part is unused and in its original packaging.
Return procedure for LM2661MX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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