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Texas Instruments LM2687MM
- Part No.:
- LM2687MM
- Manufacturer:
- Texas Instruments
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LM2687MM.pdf
- Description:
- IC REG CHRG PUMP ADJ 10MA 8VSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,209
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Product details
Overview
LM2687MM from Texas Instruments (formerly National Semiconductor) is a low-noise, regulated switched-capacitor voltage inverter IC that generates an adjustable negative output voltage from a +2.7V to +5.5V input. It delivers up to 10mA output current with 1mV typical ripple, 91% typical charge-pump efficiency at 10mA, and operates at 100kHz switching frequency. It is used for GaAsFET power amplifier biasing in cellular handsets.
For engineers reviewing the LM2687MM datasheet, LM2687MM pinout, LM2687MM application, or LM2687MM equivalent, key selection criteria include its regulated negative output range (−1.5V to −5.2V), shutdown quiescent current (0.05µA typ.), MSOP-8 package footprint, feedback-based output adjustment via VFB, and low-noise performance critical for RF bias supplies.
Technical Context
The LM2687MM integrates a fixed-frequency (100kHz typ.) switched-capacitor inverter stage followed by a low-dropout linear regulator. The charge-pump generates unregulated negative voltage at VNEG, which is then filtered and regulated at VOUT using internal LDO architecture with −1.20V feedback reference.
It employs CMOS process technology, supports logic-level active-low shutdown (SD), and requires only four external capacitors - C1 (flyback), C2 (output smoothing), C3 (LDO bypass), and optional C4 (VADJ decoupling). Its PSRR attenuates charge-pump ripple before final regulation, enabling 1mVpp output noise.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | +2.7V to +5.5V - compatible with single-cell Li-ion, 3.3V, and 5V logic rails. |
| Output Voltage Range | −1.5V to −5.2V - adjustable via external resistor divider on VFB pin. |
| Max Output Current | 10mA - sufficient for GaAsFET gate bias and low-power analog circuitry. |
| Output Ripple | 1mV typical - enables clean biasing of sensitive RF power amplifiers. |
| Shutdown Current | 0.05µA typical - preserves battery life during idle or sleep modes. |
| Switching Frequency | 100kHz typical - balances EMI, capacitor size, and output resistance. |
| Charge-Pump Efficiency | 91% at 10mA - minimizes thermal load and extends battery runtime. |
Pinout & Package
The LM2687MM is housed in an 8-pin MSOP (Mini Small Outline Package) with exposed die attach pad connected internally to GND - no external connection required. Package dimensions: 3.0mm × 3.0mm × 1.0mm height, 0.65mm lead pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - Cap+ | Flyback capacitor positive terminal | Connects to positive plate of C1; forms charge-transfer path with Cap−. |
| 2 - GND | Analog and power ground reference | Common return for VIN, VFB, SD, and internal regulators; must be low-impedance. |
| 3 - Cap− | Flyback capacitor negative terminal | Connects to negative plate of C1; alternates polarity with Cap+ during switching cycle. |
| 4 - SD | Active-low shutdown control input | Pull low to disable device and reduce IQ to 0.05µA; high-Z when open or pulled high ≥2.2V. |
| 5 - VNEG | Unregulated negative charge-pump output | Provides raw inverted voltage to LDO stage; not intended for direct load connection. |
| 6 - VFB | Feedback input for output regulation | Senses −1.20V reference; connects to resistor divider between VOUT and VADJ (GND or VIN). |
| 7 - VOUT | Regulated negative output voltage | Final stable output; supplies bias to RF amplifiers and analog circuits requiring low-noise negative rail. |
| 8 - VIN | Positive input supply | Accepts 2.7–5.5V; powers both charge-pump and LDO stages. |
Key Features
| Feature | Design Value |
|---|---|
| Regulated negative output | Adjustable from −1.5V to −5.2V via external resistors - eliminates need for discrete LDO post-regulation. |
| Low-output-noise architecture | 1mVpp ripple + high PSRR LDO - meets stringent RF bias noise requirements without additional filtering. |
| Ultra-low shutdown current | 0.05µA typical - enables >1-year battery shelf life in portable devices with periodic wake-up cycles. |
| High-efficiency charge pump | 91% efficiency at 10mA - reduces heat generation and extends battery runtime in space-constrained handsets. |
| Minimal external components | Only four capacitors required - simplifies BOM, layout, and qualification for high-volume consumer designs. |
Applications
| Cellular Phone Power Amplifier Biasing | Wireless Communication Systems |
|---|---|
Use Scenario: Providing stable, low-noise negative gate bias to GaAsFET power amplifiers in GSM/UMTS/LTE handset front-ends. IC Role / Device Role / Timing Role: Regulated negative voltage source with fast transient response and minimal spectral contamination. Use Value: Enables consistent PA linearity and efficiency across battery discharge profile while avoiding RF desense from supply noise. |
Use Scenario: Generating clean auxiliary negative rails for RF transceivers, IF mixers, and baseband ADC/DAC biasing in Wi-Fi, Bluetooth, and Zigbee modules. IC Role / Device Role / Timing Role: Dedicated low-noise inverting regulator supporting multi-rail analog signal chains. Use Value: Reduces system-level EMI and improves SNR in receiver paths by eliminating switching noise coupling through shared ground planes. |
| Interface Power Supplies | Handheld Instrumentation |
Use Scenario: Supplying negative voltage for RS-232 transceivers, op-amp dual-rail operation, and LCD contrast control in embedded controllers. IC Role / Device Role / Timing Role: Compact, efficient inverter replacing bulky inductor-based solutions in space-limited industrial interfaces. Use Value: Eliminates magnetic components and associated EMI, enabling conformal coating and compact PCB stacking in sealed enclosures. |
Use Scenario: Powering precision analog front-ends, sensor excitation circuits, and display drivers in portable multimeters, gas detectors, and handheld oscilloscopes. IC Role / Device Role / Timing Role: Low-quiescent, regulated negative rail generator supporting battery-operated measurement accuracy. Use Value: Maintains calibration stability over temperature and battery voltage drift due to tight line/load regulation (1mV/V, 5mV/mA). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar regulated negative voltage inverter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX680ESA+ | Unregulated inverter; no LDO stage; fixed −2×VIN output; higher ripple (10mVpp); no VFB pin. | Suitable only where regulation tolerance >±5% and noise <10mVpp is acceptable. | Select MAX680ESA+ only if cost sensitivity outweighs regulation precision and noise performance. |
| TPS60403DBVR | Regulated inverter with −1.5V to −5.5V range; 1.5MHz switching; higher IQ (1.2mA); requires different capacitor values. | Better transient response but higher EMI; less suitable for RF-bias-critical layouts near antennas. | Choose TPS60403DBVR when faster startup (<50µs) and smaller capacitors are prioritized over ultra-low noise. |
Compared with MAX680ESA+ and TPS60403DBVR, the LM2687MM uniquely combines sub-mV ripple, 0.05µA shutdown, and 100kHz switching in an MSOP-8 package - making it optimal for battery-powered RF bias where noise, quiescent power, and board area are co-constrained.
Availability
LM2687MM is available at Aetrix Electronics and suitable for cellular phone power amplifier biasing, wireless communication systems, and handheld instrumentation requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM2687MM 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 (TI) is a global semiconductor leader delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and personal electronics markets.
The LM2687MM belongs to TI's legacy power management portfolio originally developed by National Semiconductor, targeting low-noise, capacitor-based DC/DC conversion for portable RF and precision analog applications.
FAQ
What is the function of the VFB pin on the LM2687MM?
The VFB pin on the LM2687MM is the feedback input for the internal LDO regulator and is held at a precise −1.20V reference. It connects to a resistor divider between VOUT and VADJ (typically GND or VIN) to set the regulated output voltage within −1.5V to −5.2V. The LM2687MM uses this pin to maintain output accuracy across load and temperature variations, with feedback current limited to 10nA–100nA to minimize resistor-divider error.
Can the LM2687MM operate from a 2.5V input supply?
No, the LM2687MM cannot reliably operate from a 2.5V input supply. Its specified operating input voltage range is +2.7V to +5.5V per Absolute Maximum Ratings and Electrical Characteristics tables. At 2.5V, the internal charge pump may fail to start or sustain regulation, and output voltage accuracy and ripple performance are not guaranteed. For 2.5V-compatible alternatives, consider the TPS60400 series.
What is the purpose of the Cap+ and Cap− pins on the LM2687MM?
The Cap+ and Cap− pins on the LM2687MM form the terminals of the flying capacitor (C1) used in the switched-capacitor inverter stage. During each switching cycle, charge is transferred between these pins to invert the input voltage and generate the unregulated negative voltage at VNEG. Their correct connection to a low-ESR ceramic capacitor (≥1µF) is essential for achieving rated output current, efficiency, and ripple performance in the LM2687MM.
Does the LM2687MM require an external resistor divider for basic operation?
Yes, the LM2687MM requires an external resistor divider connected to the VFB pin to establish regulation - it does not have a fixed-output variant. The divider sets the output voltage using the relationship VOUT = −1.2V × (1 + R1/R2), where R2 connects between VFB and VADJ (usually GND). Leaving VFB unconnected will result in loss of regulation and unstable VOUT in the LM2687MM.
How does shutdown affect the VOUT and VNEG pins of the LM2687MM?
When the SD pin of the LM2687MM is pulled low, the device enters shutdown mode: internal switches disable, reducing supply current to 0.05µA typical, and both VOUT and VNEG are actively discharged to GND. This prevents backfeeding or floating outputs in battery-powered systems. Upon exit from shutdown, the LM2687MM requires ~120–600µs to re-establish regulation at VOUT.
LM2687MM Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Negative
- Topology:
- Charge Pump
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.7V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- -1.5V
- Voltage - Output (Max):
- -5.2V
- Current - Output:
- 10mA
- Frequency - Switching:
- 110kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-VSSOP
LM2687MM FAQ
1.How can I place an order for LM2687MM through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2687MM 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 LM2687MM reliable?
The price and inventory of LM2687MM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2687MM is usually 5 days.
3.What payment methods are accepted for LM2687MM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2687MM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2687MM?
LM2687MM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2687MM 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 LM2687MM?
For technical support, including LM2687MM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2687MM requirements.
6.How does Aetrix verify that LM2687MM is sourced from the original manufacturer or authorized distributors?
All LM2687MM 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 LM2687MM meets industry standards.
7.What is the process for return or replacement of LM2687MM?
All LM2687MM units undergo pre-shipment inspection (PSI). If there is an issue with LM2687MM, 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 LM2687MM part is unused and in its original packaging.
Return procedure for LM2687MM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM2687MM Tags
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