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Texas Instruments LM2687LD/NOPB
- Part No.:
- LM2687LD/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-WFDFN Exposed Pad
- Datasheet:
-
LM2687LD/NOPB.pdf
- Description:
- IC REG CHARG PUMP ADJ 10MA 8WSON
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LM2687LD/NOPB from Texas Instruments is a low-noise, regulated switched-capacitor voltage inverter IC that generates an adjustable negative output (−1.5V to −5.2V) from a +2.7V to +5.5V input supply. It delivers up to 10mA output current with 1mV typical output 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 LM2687LD/NOPB datasheet, LM2687LD/NOPB pinout, LM2687LD/NOPB application, or LM2687LD/NOPB equivalent, key selection criteria include regulated negative output adjustability, ultra-low shutdown current (0.05µA), MSOP-8/LLP-8 package compatibility, low-noise performance for RF bias, and feedback-based output voltage programming via external resistors.
Technical Context
The LM2687LD/NOPB integrates a fixed-frequency (100kHz typ.) switched-capacitor inverter stage followed by a low-dropout linear regulator to suppress charge-pump ripple. Its feedback pin (VFB) maintains a precise −1.20V reference, enabling programmable VOUT via resistor divider between VOUT, VFB, and VADJ (0V to VIN).
It features active-low logic-level shutdown (SD), grounding both VOUT and VNEG when asserted, reducing quiescent current to 0.05µA. The DAP (die attach pad) in the LLP-8 package must be connected to VNEG for thermal and electrical integrity - a critical layout requirement not shared with the MSOP-8 variant.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | +2.7V to +5.5V - supports single-cell Li-ion, 3.3V, and 5V rail systems without external regulation. |
| Output Voltage Range | −1.5V to −5.2V - adjustable via external resistor divider; enables precise GaAsFET gate bias tuning. |
| Max Output Current | 10mA - sufficient for RF power amplifier bias circuits in portable wireless transceivers. |
| Output Ripple | 1mV (typ.) - achieved via PSRR of integrated LDO; critical for minimizing AM noise in PA stages. |
| Shutdown Current | 0.05µA (typ.) - enables battery-sensitive applications to disable bias supply during sleep modes. |
| Switching Frequency | 100kHz (typ.) - balances capacitor size, ESR sensitivity, and EMI; avoids audible band and simplifies filtering. |
| Feedback Reference | −1.20V (typ.) - stable internal reference allows accurate output setting independent of load or temperature drift. |
Pinout & Package
The LM2687LD/NOPB is packaged in an 8-pin Leadless Leadframe Package (LLP-8), marked "L050B", with exposed die attach pad (DAP) requiring connection to VNEG for thermal conduction and signal reference integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - Cap+ | Charge pump flying capacitor positive terminal | Connects to C1+; internal switch node for charge transfer phase 1. |
| 2 - GND | Ground reference | Primary return path for input supply, feedback network, and regulator control circuitry. |
| 3 - Cap− | Charge pump flying capacitor negative terminal | Connects to C1−; internal switch node for charge transfer phase 2. |
| 4 - SD | Active-low shutdown control | Logic-low (≤0.5V) disables oscillator and grounds VOUT/VNEG; high-impedance input draws <100nA. |
| 5 - VNEG | Unregulated negative charge-pump output | Raw inverted voltage node; connects to DAP and C2/C3; supplies LDO input. |
| 6 - VFB | Regulator feedback input | Senses output via resistor divider; internal −1.20V reference sets VOUT = −1.20V × (1 + R1/R2). |
| 7 - VOUT | Regulated negative output | Final clean output; LDO-filtered version of VNEG; drives load directly. |
| 8 - VIN | Positive input supply | Accepts 2.7–5.5V; powers oscillator, logic, and charge-pump switches. |
| DAP | Die attach pad (LLP only) | Must be soldered to VNEG plane; improves thermal resistance (θJA = 250°C/W) and reduces noise coupling. |
Key Features
| Feature | Design Value |
|---|---|
| Regulated negative output generation | Delivers stable, ripple-suppressed VOUT (−1.5V to −5.2V) without inductors - ideal for space-constrained RF modules. |
| Integrated LDO post-regulation | Reduces charge-pump ripple to 1mV (typ.) via high-PSRR linear stage - eliminates need for external LC filters in PA bias paths. |
| Programmable output via resistor divider | VFB reference (−1.20V) enables precise, load-independent output setting using standard 1% SMD resistors. |
| Ultra-low shutdown current | 0.05µA (typ.) shutdown draw extends battery life in intermittent-use portable devices like cellular handsets. |
| LLP-8 package with thermal DAP | Exposed pad tied to VNEG improves thermal dissipation and reduces ground bounce in high-frequency bias applications. |
Applications
| Cellular Phone Power Amplifier Biasing | Wireless Communication Systems |
|---|---|
Use Scenario: Biasing GaAsFET power amplifiers in GSM/UMTS/LTE handset front-ends where low-noise negative gate voltage is required. IC Role / Device Role / Timing Role: Provides regulated, low-ripple −2.5V to −3.8V gate bias to control PA gain and linearity while minimizing AM-to-PM distortion. Use Value: 1mV ripple ensures minimal noise injection into RF signal path; 10mA drive capability supports multi-stage PA bias networks. |
Use Scenario: Generating clean negative supply for analog front-end components (mixers, IF amplifiers, ADC drivers) in portable baseband radios. IC Role / Device Role / Timing Role: Supplies isolated, low-noise VNEG to sensitive analog blocks without magnetic coupling or PCB area penalty of inductive converters. Use Value: 91% charge-pump efficiency at 10mA preserves battery runtime; shutdown mode enables dynamic power gating per channel. |
| Interface Power Supplies | Handheld Instrumentation |
Use Scenario: Providing negative rail for RS-232 transceivers, op-amp dual supplies, or LCD bias in compact embedded interfaces. IC Role / Device Role / Timing Role: Replaces discrete charge-pump + LDO solutions with single-chip, capacitor-only design meeting ±5% output accuracy over temp. Use Value: Adjustable output allows compliance with legacy interface standards (e.g., ±3V, ±5V, ±12V derived); no inductor simplifies EMC certification. |
Use Scenario: Supplying precision negative bias to sensor signal conditioning circuits (e.g., bridge amplifiers, photodiode TIA) in battery-powered test meters. IC Role / Device Role / Timing Role: Delivers stable, low-drift VOUT for offset nulling and reference generation where supply noise directly impacts measurement resolution. Use Value: −1.20V VFB reference enables sub-10mV output error across −40°C to +85°C; 500µA no-load IQ minimizes standby drain. |
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 (~10mV); no VFB pin. | Suitable only where output regulation and ultra-low ripple are not required (e.g., non-critical digital logic bias). | Select MAX680ESA+ only if cost and BOM count are prioritized over noise performance and output adjustability. |
| TPS60403DBVR | Regulated inverter with 3.3V fixed output; no adjustable VOUT; 250kHz switching; 60mA output; SOT-23-6 package. | Designed for fixed −3.3V rails in microcontroller I/O bias; lacks programmability and low-noise optimization for RF. | Choose TPS60403DBVR for higher-current, fixed-output needs where board space is extremely limited and RF-grade noise is not critical. |
Compared with MAX680ESA+ and TPS60403DBVR, the LM2687LD/NOPB uniquely combines adjustable regulated output, 1mV ripple, and LLP-8 thermal performance - making it the only option qualified for GaAsFET PA bias in production cellular handsets.
Availability
LM2687LD/NOPB is available at Aetrix Electronics and suitable for cellular phone power amplifier biasing, handheld instrumentation, and wireless communication system design requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM2687LD/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 company headquartered in Dallas, Texas, delivering analog, embedded processing, and connectivity technologies for industrial, automotive, and consumer markets.
The LM2687LD/NOPB belongs to TI's precision power management portfolio, specifically engineered to replace inductive DC/DC inverters in noise-sensitive RF and portable analog applications with capacitor-based simplicity and LDO-grade cleanliness.
FAQ
What is the function of the DAP (die attach pad) on the LM2687LD/NOPB?
The DAP on the LM2687LD/NOPB is an exposed thermal pad on the underside of the LLP-8 package. It must be soldered to a VNEG copper pour to ensure proper thermal dissipation and low-impedance return path for the charge-pump and LDO stages. Leaving it unconnected degrades thermal performance and may increase output noise. This requirement is specific to the LM2687LD/NOPB and does not apply to the MSOP-8 variant.
Can the LM2687LD/NOPB generate −5.0V from a 3.3V input?
Yes, the LM2687LD/NOPB can generate −5.0V from a 3.3V input. Its output range is −1.5V to −5.2V, and the minimum input voltage for −5.0V output is VIN ≥ 3.0V (per Electrical Characteristics table). Using the VFB reference of −1.20V and a resistor divider (e.g., R1 = 249kΩ, R2 = 60.4kΩ), the LM2687LD/NOPB achieves precise −5.0V output with ≤1% error under 2.5mA load.
How does the LM2687LD/NOPB achieve 1mV output ripple?
The LM2687LD/NOPB achieves 1mV typical output ripple by combining a 100kHz switched-capacitor inverter with a post-regulating low-dropout linear stage. The LDO's high PSRR attenuates charge-pump ripple, and the −1.20V VFB reference ensures tight regulation. Measured ripple assumes 1µF ceramic C1/C2 and 10µF low-ESR C3; increasing C3 further reduces residual ripple at LM2687LD/NOPB VOUT.
What happens to VOUT and VNEG during shutdown of the LM2687LD/NOPB?
When the SD pin is pulled low, the LM2687LD/NOPB disables its internal oscillator and actively pulls both VOUT and VNEG to GND through internal switches. This prevents floating outputs and ensures controlled discharge of external capacitors. The shutdown current drops to 0.05µA (typ.), but VOUT and VNEG remain grounded until SD is returned high, at which point the LM2687LD/NOPB resumes normal operation with ~120µs startup time.
Is the LM2687LD/NOPB pin-compatible with the LM2687MM/NOPB?
No, the LM2687LD/NOPB is not pin-compatible with the LM2687MM/NOPB. While both share identical pin functions (Cap+, GND, Cap−, SD, VNEG, VFB, VOUT, VIN), the LM2687LD/NOPB uses an LLP-8 package with an exposed DAP requiring connection to VNEG, whereas the LM2687MM/NOPB uses an MSOP-8 package without a DAP. PCB layouts, thermal pads, and solder stencil designs differ - direct substitution requires board revision.
LM2687LD/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-WFDFN Exposed Pad
- 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-WSON (3x3)
LM2687LD/NOPB FAQ
1.How can I place an order for LM2687LD/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2687LD/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 LM2687LD/NOPB reliable?
The price and inventory of LM2687LD/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2687LD/NOPB is usually 5 days.
3.What payment methods are accepted for LM2687LD/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2687LD/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2687LD/NOPB?
LM2687LD/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2687LD/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 LM2687LD/NOPB?
For technical support, including LM2687LD/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2687LD/NOPB requirements.
6.How does Aetrix verify that LM2687LD/NOPB is sourced from the original manufacturer or authorized distributors?
All LM2687LD/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 LM2687LD/NOPB meets industry standards.
7.What is the process for return or replacement of LM2687LD/NOPB?
All LM2687LD/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM2687LD/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 LM2687LD/NOPB part is unused and in its original packaging.
Return procedure for LM2687LD/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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