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Texas Instruments LM2611BMFX
- Part No.:
- LM2611BMFX
- Manufacturer:
- Texas Instruments
- Package:
- SC-74A, SOT-753
- Datasheet:
-
LM2611BMFX.pdf
- Description:
- IC REG CUK ADJ 900MA SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:3,143
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Product details
Overview
LM2611BMFX from Texas Instruments is a current-mode PWM Cuk converter IC with integrated DMOS FET, designed for high-efficiency negative voltage generation. It operates from 2.7 V to 14 V input, delivers −5 V at 300 mA from 5-V input, features 1.4-MHz fixed switching frequency, 0.7-Ω RDS(ON), and −1.23-V internal feedback reference. It is used in precision bias supplies for CCDs, LCDs, and GaAs FETs where low output ripple and compact size are critical.
For engineers reviewing the LM2611BMFX datasheet, LM2611BMFX pinout, LM2611BMFX application, or LM2611BMFX equivalent, this page provides verified technical context, validated pin functions, confirmed Cuk topology implementation details, real-world efficiency curves, and two rigorously cross-checked alternative parts for negative-output DC/DC design.
Technical Context
The LM2611BMFX implements a fixed-frequency (1.4 MHz), current-mode controlled Cuk topology with integrated 0.7-Ω DMOS switch and internal slope compensation. Its dual-inductor architecture (L1 and L2) enables continuous input/output current waveforms, minimizing RMS ripple on both sides-unlike buck-boost or flyback topologies.
It uses an internal −1.23-V reference connected to the NFB pin via external resistor divider for output voltage setting, supports pulse-skipping mode at light loads, and includes thermal shutdown (163°C trip, 155°C recovery) and cycle-by-cycle current limiting (0.9-A typical limit for Grade B).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Cuk inverting converter - enables simultaneous low-input-ripple and low-output-ripple operation without transformer isolation. |
| Switching frequency | 1.4 MHz (±0.4 MHz over temp) - allows use of sub-3-mm inductors and <22 µF ceramic capacitors for space-constrained designs. |
| RDS(ON) | 0.7 Ω (Grade B, TJ = 25°C) - reduces conduction loss at 300-mA load, enabling >85% efficiency at 5-V input to −5-V output. |
| Current limit | 0.9 A (Grade B, TJ = −40°C to +85°C) - sets maximum peak switch current; constrains max output current based on VIN, VOUT, and inductor values. |
| Feedback reference | −1.23 V (±25 mV over temp) - defines output voltage as VOUT = −1.23 × (1 + RFB1/RFB2); enables precise −5-V regulation with 29.4k/10k divider. |
| Shutdown current | <1 µA - preserves battery life in portable systems during standby; activated by grounding SHDN pin. |
| Package | SOT-23 (DBV), 5-pin, 1.60 mm × 2.90 mm - surface-mount compatible with standard reflow profiles; θJA = 163.5°C/W. |
Pinout & Package
SOT-23 (DBV) 5-pin package: ultra-compact footprint (1.60 mm × 2.90 mm), thermally enhanced plastic body with exposed pad not present; rated for −40°C to +125°C operating junction temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - SW | Switch drain node | Connects internally to DMOS FET drain; externally ties to input inductor (L1) and Cuk capacitor (CCUK) - carries full switch current and high dv/dt. |
| 2 - GND | Analog & power ground | Common return for internal error amplifier, current sense, and power stage; must be low-impedance copper pour tied to input/output capacitor grounds. |
| 3 - NFB | Negative feedback input | Accepts resistor divider from VOUT; compares against −1.23-V internal reference to regulate output voltage; bias current ≤6.7 µA. |
| 4 - SHDN | Shutdown control | Logic-level input: ≥1.5 V = enabled, ≤0.5 V = disabled; draws ≤1 µA in shutdown; no pull-up required. |
| 5 - VIN | Power input | Supplies internal circuitry and switch; requires local 0.1-µF ceramic bypass within 5 mm; absolute max 14.5 V. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Cuk controller + DMOS FET | Eliminates need for external MOSFET driver and gate resistor; simplifies layout and reduces BOM count for inverting converters. |
| 1.4-MHz fixed-frequency operation | Enables use of 10–22 µH inductors and 10–22 µF ceramic output capacitors - cuts solution size by >40% vs lower-frequency alternatives. |
| Internal current-mode compensation | Removes need for external compensation network; supports stable operation with L1 = L2 = 15 µH to 22 µH per TI-recommended range. |
| Pulse-skipping at light load | Maintains regulation down to ~10 mA while reducing quiescent current to <1 µA in shutdown - extends battery runtime in always-on bias rails. |
| Thermal shutdown with hysteresis | Deactivates switch at 163°C junction; resumes operation at 155°C - prevents permanent damage during sustained overload or poor heatsinking. |
Applications
| Digital Camera CCD Bias | LCD Panel Bias Supply |
|---|---|
|
Use Scenario: Providing stable −5 V to CCD image sensor analog front-end during exposure and readout cycles. IC Role / Device Role / Timing Role: Inverting DC/DC regulator generating clean negative rail; operates in PWM mode under full load, switches to pulse-skipping during idle frames. Use Value: 1-mVp-p output ripple ensures minimal clock feedthrough into analog signal path, preserving SNR and dynamic range. |
Use Scenario: Powering TFT-LCD source/gate driver ICs requiring precise −5 V gate turn-off voltage. IC Role / Device Role / Timing Role: Primary negative voltage generator; regulated via NFB pin with 1% tolerance resistors to hold VOUT within ±30 mV. Use Value: Dual-inductor Cuk topology minimizes conducted EMI into display timing circuits, reducing visual artifacts and frame jitter. |
| GaAs FET RF Bias | MR Head Preamp Bias |
|
Use Scenario: Delivering low-noise −5 V to GaAs pHEMT amplifier stages in portable wireless transceivers. IC Role / Device Role / Timing Role: Compact, high-frequency inverter supplying bias voltage; SHDN pin synchronized to transmit/receive state machine. Use Value: 0.7-Ω RDS(ON) and 1.4-MHz switching reduce thermal rise in tight RF module layouts, maintaining gain stability over temperature. |
Use Scenario: Generating −5 V for magnetoresistive (MR) head preamplifiers in HDD read channels. IC Role / Device Role / Timing Role: Low-ripple negative supply referenced to system ground; operates continuously during disk access with <100-ns transient response. Use Value: Feed-forward capacitor (CFF = 330 pF) optimizes loop bandwidth, limiting output deviation to <50 mV during 100-mA step load changes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar inverting DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2611AMFX | Grade A variant: 1.2-A current limit, 0.5-Ω RDS(ON), same pinout and topology. | Supports up to 375 mA at −5 V from 5-V input (vs. 300 mA for LM2611BMFX); higher efficiency at full load. | Select LM2611AMFX when output current exceeds 300 mA or when lower conduction loss is prioritized over cost. |
| MAX764CSA+ | Fixed-frequency (125 kHz) inverting controller; external MOSFET required; no integrated switch. | Requires additional FET, driver, and compensation components; larger solution size but supports wider VIN (2.7–16.5 V) and higher IOUT. | Choose MAX764CSA+ only if >500 mA output current or programmable frequency is required - not a drop-in replacement. |
Compared with LM2611AMFX, the LM2611BMFX trades 0.3-A peak current headroom and 0.2-Ω higher RDS(ON) for lower unit cost and sufficient margin in 300-mA bias applications; versus MAX764CSA+, it offers full integration and smaller footprint but less flexibility in output current scaling.
Availability
LM2611BMFX is available at Aetrix Electronics and suitable for digital camera CCD bias, LCD panel bias, GaAs FET RF bias, and MR head preamp bias applications requiring stable component supply, long-term manufacturability, and guaranteed SOT-23 packaging consistency.
Supply support for LM2611BMFX 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 company specializing in analog, embedded processing, and power management ICs, with leadership in high-reliability, high-performance power conversion solutions.
The LM2611 product line delivers integrated Cuk converter ICs optimized for compact, low-noise negative voltage generation in portable imaging, display, and RF systems - targeting applications where board space, EMI, and output ripple are critical constraints.
FAQ
What is the maximum output current capability of the LM2611BMFX at −5 V from a 5-V input?
The LM2611BMFX delivers up to 300 mA at −5 V when supplied from 5 V, as confirmed in the TI SNOS965J datasheet Figure 23 and Typical Application section. This rating assumes L1 = L2 = 15 µH (SUMIDA CR32-150/CR32-470), CIN/COUT = 22 µF X5R ceramics, and ambient temperature ≤85°C. Exceeding this current risks thermal shutdown due to its 0.9-A current limit and 163.5°C/W thermal resistance.
Does the LM2611BMFX require external compensation components?
No, the LM2611BMFX features fully internal type II/III compensation optimized for 10–22 µH inductors, eliminating the need for external compensation networks. However, a feed-forward capacitor (CFF) across RFB1 is optional and recommended to improve transient response - 330 pF is validated for the 5-V-to−5-V design in the datasheet's Figure 24.
Can the LM2611BMFX generate output voltages other than −5 V?
Yes, the LM2611BMFX supports adjustable negative outputs via the NFB pin. With its −1.23-V internal reference, VOUT = −1.23 × (1 + RFB1/RFB2). For example, using RFB1 = 29.4 kΩ and RFB2 = 10 kΩ yields −5.00 V; changing RFB2 to 15 kΩ sets VOUT ≈ −6.15 V. Resistor values must stay ≤50 kΩ to minimize NFB pin leakage error.
What is the purpose of the CCUK capacitor in the LM2611BMFX Cuk topology?
The CCUK capacitor (e.g., 1 µF or 2.2 µF X5R ceramic) forms the energy-transfer element between input and output inductors in the Cuk topology. It enables continuous current on both input and output sides, reducing RMS ripple by >50% compared to buck-boost. Its value directly impacts voltage stress on SW pin and must be rated for ≥16 V DC plus AC ripple.
How does the LM2611BMFX behave under very light load conditions?
Below ~10 mA, the LM2611BMFX enters pulse-skipping (hysteretic) mode to maintain regulation while minimizing quiescent current. Output ripple increases slightly (still <20 mVp-p), but efficiency remains >70%. Shutdown mode (via SHDN pin) reduces total current to <1 µA - ideal for battery-powered standby states.
LM2611BMFX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- SC-74A, SOT-753
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Negative
- Topology:
- Cuk
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.7V
- Voltage - Input (Max):
- 14V
- Voltage - Output (Min/Fixed):
- -1.23V
- Voltage - Output (Max):
- -32V
- Current - Output:
- 900mA
- Frequency - Switching:
- 1.4MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-5
LM2611BMFX FAQ
1.How can I place an order for LM2611BMFX through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2611BMFX 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 LM2611BMFX reliable?
The price and inventory of LM2611BMFX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2611BMFX is usually 5 days.
3.What payment methods are accepted for LM2611BMFX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2611BMFX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2611BMFX?
LM2611BMFX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2611BMFX 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 LM2611BMFX?
For technical support, including LM2611BMFX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2611BMFX requirements.
6.How does Aetrix verify that LM2611BMFX is sourced from the original manufacturer or authorized distributors?
All LM2611BMFX 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 LM2611BMFX meets industry standards.
7.What is the process for return or replacement of LM2611BMFX?
All LM2611BMFX units undergo pre-shipment inspection (PSI). If there is an issue with LM2611BMFX, 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 LM2611BMFX part is unused and in its original packaging.
Return procedure for LM2611BMFX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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