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Analog Devices Inc. LTC1550LCMS8#PBF
- Part No.:
- LTC1550LCMS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LTC1550LCMS8#PBF.pdf
- Description:
- IC REG CHARG PUMP ADJ 20MA 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,256
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Product details
Overview
LTC1550LCMS8#PBF from Analog Devices (formerly Linear Technology) is a low-noise, switched-capacitor regulated negative voltage inverter with integrated linear post-regulator, delivering –2V output at up to 20mA load current, <1mVP-P ripple, and 900kHz charge pump frequency. It operates from a single 2.7V–5.25V supply and features active-low TTL-compatible shutdown (SHDN), making it suitable for GaAs FET bias generation in portable RF transmitters.
For engineers reviewing the LTC1550LCMS8#PBF datasheet, LTC1550LCMS8#PBF pinout, LTC1550LCMS8#PBF application, or LTC1550LCMS8#PBF equivalent, key selection criteria include guaranteed ±2.5% output regulation over line/load/temperature, minimal external component count (four capacitors), MSOP-8 package compatibility, and verified performance in battery-powered cellular front-end biasing.
Technical Context
The LTC1550LCMS8#PBF integrates a 900kHz inverting charge pump stage followed by a negative linear regulator with N-channel MOSFET pass device and internal 1.225V reference. Its architecture minimizes switching artifacts via fast transient response and ESR-dependent loop stabilization, requiring ≥4.7µF output capacitance with moderate ESR.
It uses two 0.1µF flying capacitors (C1+, C1–) and a 0.1µF CPOUT storage capacitor to generate a negative rail, then regulates that rail to a precise –2V output. The REG pin provides open-drain power-valid indication when VOUT is within ±5% of target, sinking up to 4mA at 5V supply.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed –2.0V (±2.5% over line/load/temperature); enables direct GaAs FET gate bias without external feedback. |
| Output Ripple | <1mVP-P typical (at 0–10mA, 10µF + 0.1µF output cap); meets low-noise RF bias requirements. |
| Charge Pump Frequency | 900kHz fixed; avoids IF bands (400–600kHz), reduces capacitor size, and eases EMI filtering. |
| Supply Range | 2.7V to 5.25V; supports Li-ion (3.0–4.2V) and 3.3V/5V systems with headroom for –2V output. |
| Shutdown Current | 0.2µA typical (active-low SHDN); extends battery life in portable standby modes. |
| Max Output Current | 20mA (at VCC ≥ 3.75V); sufficient for biasing multiple GaAs FETs or low-power analog circuitry. |
| Regulation Accuracy | ±2.5% over full temperature range (0°C to 70°C); ensures stable FET operating point across environments. |
Pinout & Package
Package: 8-lead MSOP (MS8), 3.0mm × 3.0mm × 0.85mm body, 0.65mm lead pitch, exposed pad not electrically connected.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (REG) | Open-drain power-good indicator | Pulls low when VOUT is within ±5% of –2V; requires external pull-up to VCC or higher (≤6V) for logic-high assertion. |
| 2 (CPOUT) | Negative charge pump output | Intermediate node between flying capacitor and linear regulator; requires 0.1µF capacitor to GND with star-ground connection to minimize ripple. |
| 3 (GND) | Analog/power ground reference | Single-pin ground for 8-lead MSOP; must connect to low-impedance PCB ground plane to avoid regulation error. |
| 4 (C1–) | Flying capacitor negative terminal | Connects to one side of 0.1µF flying capacitor (C1); forms charge transfer path with C1+ during clock phases. |
| 5 (SHDN) | Active-low shutdown control | TTL-compatible input; pulls low to disable charge pump and reduce IQ to 0.2µA; no internal pull-up-requires external resistor. |
| 6 (VCC) | Positive input supply | Accepts 2.7–5.25V; must be bypassed with ≥2.2µF ceramic capacitor close to pin to prevent supply droop during charge pumping. |
| 7 (C1+) | Flying capacitor positive terminal | Connects to other side of 0.1µF flying capacitor (C1); alternately charged/discharged at 900kHz to generate negative voltage. |
| 8 (VOUT) | Regulated negative output | Delivers stable –2V; requires ≥10µF output capacitor (moderate ESR) plus 0.1µF ceramic in parallel for <1mVP-P ripple. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated linear post-regulator | Reduces charge pump ripple to <1mVP-P without external LDO, enabling clean bias for noise-sensitive RF stages. |
| 900kHz fixed-frequency oscillator | Enables use of small 0.1µF ceramic flying capacitors and avoids interference with common IF bands in cellular receivers. |
| Four-component solution | Requires only input bypass (2.2µF), two flying caps (0.1µF each), and output filter (10µF + 0.1µF)-no inductors or diodes. |
| Guaranteed –2V output accuracy | ±2.5% regulation over 0°C–70°C, 2.7V–5.25V VCC, and 0–20mA load ensures predictable FET gate voltage in production designs. |
| Low-quiescent-current shutdown | 0.2µA typical IQ in shutdown mode extends battery runtime in intermittent-transmit applications like GSM burst transmission. |
Applications
| GaAs FET Transmitter Bias | Portable RF Front-End Power |
|---|---|
Use Scenario: Generating stable negative gate bias for GaAs pHEMT power amplifiers in 2G/3G cellular handsets. IC Role / Device Role / Timing Role: Regulated –2V voltage inverter providing precise, low-noise DC bias to amplifier gate terminals. Use Value: Enables consistent amplifier gain and efficiency across battery discharge and temperature, with <1mVP-P ripple preventing AM-to-PM distortion. |
Use Scenario: Supplying isolated negative rail for RF switch drivers and mixer bias in compact Bluetooth/WiFi modules. IC Role / Device Role / Timing Role: Compact, capacitor-based negative voltage generator replacing discrete charge pumps and LDOs. Use Value: Reduces BOM count by four components versus discrete solutions while maintaining RF-grade noise performance in space-constrained layouts. |
| Battery-Powered Instrumentation | Single-Supply Signal Conditioning |
Use Scenario: Providing negative reference for precision op-amp circuits in handheld test equipment powered by single Li-ion cells. IC Role / Device Role / Timing Role: Low-noise, regulated negative supply enabling rail-to-rail input/output operation of instrumentation amplifiers. Use Value: Eliminates need for dual supplies while preserving DC accuracy and dynamic range, with ±2.5% regulation ensuring measurement repeatability. |
Use Scenario: Biasing analog switches and level translators in industrial sensor interfaces where only +3.3V or +5V is available. IC Role / Device Role / Timing Role: Fixed-output inverter generating –2V for threshold referencing and signal inversion in mixed-signal ASICs. Use Value: Simplifies layout and improves noise immunity compared to resistor-divider or Zener-based negative rails, especially under varying load conditions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar negative voltage inverter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1550LCS8-2 | Same IC die, SO-8 package (5.0mm × 4.0mm vs MSOP-8's 3.0mm × 3.0mm); identical electrical specs and pinout mapping. | Preferred where board real estate allows larger footprint and hand-soldering is required; same thermal resistance (θJA = 135°C/W). | Select LTC1550LCMS8#PBF for high-density portable designs; choose LTC1550LCS8-2 for legacy SO-8 compatibility or cost-sensitive non-portable applications. |
| LTC1261LCS8 | Adjustable output (–1.5V to –5V), lower max IOUT (15mA), higher ripple (2mVP-P), 125kHz charge pump frequency. | Suitable for general-purpose negative rails where adjustable voltage and lower EMI priority outweigh ripple and current needs. | Choose LTC1550LCMS8#PBF when fixed –2V, <1mVP-P ripple, and 20mA drive are mandatory; select LTC1261LCS8 only if voltage flexibility and reduced EMI are primary. |
Compared with LTC1550LCS8-2, LTC1550LCMS8#PBF offers identical performance in a 44% smaller footprint; versus LTC1261LCS8, it delivers tighter regulation, lower noise, and higher output current at the cost of fixed output voltage.
Availability
LTC1550LCMS8#PBF is available at Aetrix Electronics and suitable for GaAs FET biasing, portable RF power management, and single-supply instrumentation requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LTC1550LCMS8#PBF 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
Analog Devices acquired Linear Technology in 2017 and maintains its precision analog and power management product lines with full datasheet, simulation model, and application support.
The LTC1550L series was designed specifically for low-noise, capacitor-based negative voltage generation in battery-powered RF systems-emphasizing minimal external components, tight regulation, and sub-millivolt ripple performance.
FAQ
What is the output voltage tolerance of the LTC1550LCMS8#PBF over temperature and load?
The LTC1550LCMS8#PBF guarantees ±2.5% output regulation over the commercial temperature range (0°C to 70°C), full supply range (2.7V–5.25V), and load current (0–20mA). At 25°C with 5V supply and 5mA load, typical deviation is ±0.5%, but design margin must account for worst-case ±2.5% to ensure GaAs FET gate voltage remains within safe operating limits across all conditions. This specification is explicitly confirmed in the Electrical Characteristics table for the LTC1550L-2 variant.
Can the LTC1550LCMS8#PBF be used with a 3.0V supply to generate –2V?
Yes-the LTC1550LCMS8#PBF supports VCC as low as 2.7V for –2V output. At 3.0V supply, it delivers full 20mA only above 3.75V per the "Minimum Required VCC vs VOUT and IOUT" graph; however, at 5mA load, 3.0V is sufficient. The datasheet confirms operation down to 2.7V with guaranteed regulation, making LTC1550LCMS8#PBF compatible with partially discharged Li-ion cells (3.0–3.3V) in portable RF bias applications.
What is the purpose of the REG pin on the LTC1550LCMS8#PBF, and how should it be connected?
The REG pin on the LTC1550LCMS8#PBF is an open-drain output that sinks current when VOUT is within ±5% of –2V. It requires an external pull-up resistor (typically 10kΩ to VCC or another logic supply ≤6V) to assert HIGH. When pulled up, REG goes LOW to indicate valid output; this signal can enable downstream circuitry or trigger system power sequencing. The LTC1550LCMS8#PBF datasheet specifies REG sinks up to 4mA at 5V, confirming its use as a robust power-good flag in battery-powered systems.
Why does the LTC1550LCMS8#PBF require a 0.1µF ceramic capacitor in parallel with the main output capacitor?
The LTC1550LCMS8#PBF requires a 0.1µF ceramic capacitor in parallel with the main output capacitor (≥10µF) to suppress high-frequency switching spikes (~900kHz harmonics) that remain after linear regulation. These spikes-visible as sharp peaks in scope waveforms-can exceed several millivolts peak-to-peak even when RMS noise is low. The ceramic capacitor's low impedance at MHz frequencies shunts these spikes, reducing total ripple to <1mVP-P, as validated in Figure 6 of the LTC1550L/LTC1551L datasheet for LTC1550LCMS8#PBF.
Is the LTC1550LCMS8#PBF pin-compatible with the LTC1551LCMS8#PBF?
No-the LTC1550LCMS8#PBF and LTC1551LCMS8#PBF share identical pinout and package but differ in shutdown polarity: LTC1550LCMS8#PBF has active-low SHDN, while LTC1551LCMS8#PBF has active-high SHDN. Swapping them without adjusting the control logic will invert shutdown behavior. Both parts are drop-in replacements electrically except for this single functional difference, which must be verified in system firmware or hardware control paths before substitution.
LTC1550LCMS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up/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):
- -1.225V
- Voltage - Output (Max):
- -4.8V
- Current - Output:
- 20mA
- Frequency - Switching:
- 900kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP
LTC1550LCMS8#PBF FAQ
1.How can I place an order for LTC1550LCMS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1550LCMS8#PBF 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 LTC1550LCMS8#PBF reliable?
The price and inventory of LTC1550LCMS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1550LCMS8#PBF is usually 5 days.
3.What payment methods are accepted for LTC1550LCMS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1550LCMS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1550LCMS8#PBF?
LTC1550LCMS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1550LCMS8#PBF 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 LTC1550LCMS8#PBF?
For technical support, including LTC1550LCMS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1550LCMS8#PBF requirements.
6.How does Aetrix verify that LTC1550LCMS8#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1550LCMS8#PBF 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 LTC1550LCMS8#PBF meets industry standards.
7.What is the process for return or replacement of LTC1550LCMS8#PBF?
All LTC1550LCMS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1550LCMS8#PBF, 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 LTC1550LCMS8#PBF part is unused and in its original packaging.
Return procedure for LTC1550LCMS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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