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Analog Devices Inc. LTC1550LCS8#PBF
- Part No.:
- LTC1550LCS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1550LCS8#PBF.pdf
- Description:
- IC REG CHARGE PUMP ADJ 20MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,430
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Product details
Overview
LTC1550LCS8#PBF from Analog Devices (formerly Linear Technology) is a low-noise, switched-capacitor regulated negative voltage inverter with integrated linear post-regulator, delivering a fixed –2V output at up to 20mA load current. It operates from a single 2.7V–5.25V supply, achieves <1mVP-P output ripple, and features an active-low TTL-compatible shutdown pin (SHDN). It is optimized for GaAs FET bias generation in portable RF and cellular telephone transmitters.
For engineers reviewing the LTC1550LCS8#PBF datasheet, LTC1550LCS8#PBF pinout, LTC1550LCS8#PBF application, or LTC1550LCS8#PBF equivalent, key selection criteria include guaranteed ±2.5% output regulation over line/load/temperature, 900kHz charge pump frequency enabling compact 0.1µF external capacitors, shutdown current <1µA, and SO-8 package compatibility with space-constrained portable designs.
Technical Context
The LTC1550LCS8#PBF integrates a 900kHz inverting charge pump stage followed by a negative linear regulator using an N-channel MOSFET pass device and internal 1.225V reference. Its feedback loop is optimized for fast transient response to suppress switching artifacts from CPOUT, achieving ultra-low ripple without requiring high-ESR output capacitors beyond standard design guidance.
It employs star-ground layout for VCC bypass, CPOUT, and VOUT capacitors to minimize AC current path impedance. The SHDN pin has no internal pull-up (LTC1550L variant), requiring external pull-up for default operation, and drives quiescent current to 0.2µA typical in shutdown mode while collapsing VOUT to 0V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed –2.0V, regulated to ±2.5% over line, load (0–20mA), and temperature (0°C to 70°C) |
| Output Ripple | <1mVP-P typical with 10µF + 0.1µF ceramic output capacitor; enables clean bias for sensitive RF FETs |
| Supply Range | 2.7V to 5.25V input; minimum VCC = 3.75V required for full 20mA output at –2V |
| Quiescent Current | 3.65mA typical at 5V supply; drops to 0.2µA in shutdown mode (SHDN = low) |
| Charge Pump Freq | 900kHz fixed internal oscillator; avoids IF bands (400–600kHz) and permits use of 0.1µF ceramic flying capacitors |
| Shutdown Control | Active-low TTL-compatible SHDN pin; no internal pull-up - requires external resistor for default-on operation |
| Package | 8-lead narrow SO (S8), RoHS-compliant, lead-free #PBF suffix |
Pinout & Package
Package: 8-lead narrow SO (S8), 0.150" body width, RoHS-compliant, lead-free (Pb-free).
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 (REG) | Power Good Output | Open-drain flag pulled low when VOUT is within ±5% of –2V; requires external pull-up to VCC or higher (≤6V); sinks 4mA max |
| 2 (CPOUT) | Negative Charge Pump Output | Intermediate node supplying negative voltage to linear regulator; requires 0.1µF capacitor to GND with star-ground connection to minimize ripple |
| 3 (GND) | Analog Ground | Low-impedance return for regulator feedback and internal circuitry; must connect directly to PCB ground plane |
| 4 (C1–) | Flying Capacitor Negative Terminal | Connects to negative side of 0.1µF flying capacitor (C1); forms charge transfer path with C1+ during pump cycle |
| 5 (SHDN) | Shutdown Input | Active-low TTL-compatible control; pulls device into shutdown (IQ ≈ 0.2µA) when driven low; no internal pull-up |
| 6 (VCC) | Positive Supply Input | 2.7V–5.25V input; requires ≥2.2µF low-ESR ceramic bypass capacitor placed adjacent to pin and GND |
| 7 (C1+) | Flying Capacitor Positive Terminal | Connects to positive side of 0.1µF flying capacitor (C1); alternately charged/discharged at 900kHz to generate negative voltage |
| 8 (VOUT) | Regulated Negative Output | –2V regulated output; requires ≥10µF output capacitor (tantalum or polymer) + 0.1µF ceramic in parallel for stability and <1mVP-P ripple |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Linear Post-Regulator | Eliminates need for external LDO; provides fast transient response and <1mVP-P ripple without complex filtering |
| 900kHz Switching Frequency | Enables use of small, low-cost 0.1µF ceramic flying capacitors and avoids interference with common RF IF bands |
| Ultra-Low Shutdown Current | 0.2µA typical shutdown IQ extends battery life in portable RF systems where GaAs FET bias is intermittently required |
| Guaranteed Regulation Margin | ±2.5% output accuracy maintained across full 0–20mA load range and 0°C–70°C ambient, simplifying system-level tolerance analysis |
| SO-8 Footprint Compatibility | Standard narrow SO-8 package supports drop-in replacement in legacy designs and automated assembly with existing pick-and-place workflows |
Applications
| GaAs FET Transmitter Bias | Negative Rail Generation |
|---|---|
|
Use Scenario: Providing stable gate bias voltage for GaAs power amplifier FETs in GSM/EDGE/WCDMA handset front-end modules. IC Role / Device Role / Timing Role: Regulated –2V bias generator with ultra-low noise and fast turn-on (<5ms) to support burst-mode transmission. Use Value: Enables consistent FET conduction threshold control, minimizing AM-to-PM distortion and improving EVM in RF power amplifiers. |
Use Scenario: Generating isolated negative supply for op-amp input stages or ADC reference buffers in single-supply data acquisition systems. IC Role / Device Role / Timing Role: Compact, capacitor-based negative rail source replacing discrete inductor-based solutions in space-constrained industrial sensors. Use Value: Eliminates magnetic components and EMI concerns while maintaining <1mVP-P ripple for high-resolution analog signal conditioning. |
| Battery-Powered Portable RF | Single-Supply Signal Chain |
|
Use Scenario: Powering low-noise LNAs and mixer bias networks in Bluetooth/Wi-Fi IoT edge devices operating from coin-cell or Li-ion sources. IC Role / Device Role / Timing Role: Low-quiescent-current (3.65mA) inverter with shutdown capability for duty-cycled RF subsystems. Use Value: Extends operational lifetime by >30% versus non-shutdown alternatives, while maintaining RF performance integrity during active periods. |
Use Scenario: Supplying dual-rail power to precision instrumentation amplifiers in handheld test equipment powered from USB or single-cell batteries. IC Role / Device Role / Timing Role: Fixed-output negative supply with guaranteed regulation across varying input voltage (2.7–5.25V) as battery discharges. Use Value: Maintains amplifier CMRR and offset stability without recalibration, even as main supply drops from 4.2V to 3.0V. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar negative voltage inverter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1550LCMS8#PBF | Same IC die, but in 8-lead MSOP package (3mm × 3mm vs SO-8's 4.9mm × 3.9mm); identical electrical specs and pinout mapping | Preferred for ultra-dense PCB layouts where board area is constrained; requires rework of footprint and stencil | Select when size reduction justifies MSOP assembly complexity and cost premium over SO-8. |
| LTC1261LCS8#PBF | Lower output current (15mA max), higher ripple (2mVP-P typ), no REG pin, same SO-8 package and pin compatibility | Suitable for less demanding bias applications where ±3% regulation and moderate noise are acceptable | Choose for cost-sensitive designs where full 20mA drive and power-good signaling are unnecessary. |
Compared with LTC1550LCS8#PBF, the LTC1550LCMS8#PBF offers identical performance in a smaller footprint but demands tighter assembly tolerances, while the LTC1261LCS8#PBF trades regulation accuracy and noise performance for lower unit cost in non-critical bias roles.
Availability
LTC1550LCS8#PBF is available at Aetrix Electronics and suitable for GaAs FET bias generation, portable RF transmitter power, and single-supply signal chain negative rail applications requiring stable component supply and long-term manufacturability.
Supply support for LTC1550LCS8#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 full product support, documentation, and manufacturing continuity for all Linear-branded parts including LTC series.
The LTC1550LCS8#PBF belongs to Linear's precision switched-capacitor DC/DC converter family, designed specifically for low-noise, low-power negative voltage generation in portable wireless infrastructure and battery-operated RF systems.
FAQ
What is the minimum input voltage required for LTC1550LCS8#PBF to deliver 20mA at –2V output?
The LTC1550LCS8#PBF requires a minimum VCC of 3.75V to sustain 20mA output current at –2V, as specified in the Electrical Characteristics table under "VOUT Output Regulation" for the –2V version at 3.75V ≤ VCC ≤ 5.25V, 0 ≤ IOUT ≤ 20mA. Below this, regulation degrades or current capability falls.
Does LTC1550LCS8#PBF require external resistors to set its output voltage?
No. The LTC1550LCS8#PBF is the fixed –2V version of the LTC1550L family and contains internal resistor dividers; no external resistors are needed. Only adjustable variants (e.g., LTC1550LCS8#TRPBF) require ADJ pin connections with external R1/R2.
Can LTC1550LCS8#PBF be used with ceramic output capacitors only?
Yes, but with caution: LTC1550LCS8#PBF requires ≥10µF total output capacitance, and recommends pairing a bulk capacitor (e.g., 10µF tantalum or polymer) with a 0.1µF ceramic in parallel. Using only low-ESR ceramic capacitors risks loop instability and oscillation due to missing ESR-induced phase lead.
What is the function of the REG pin on LTC1550LCS8#PBF?
The REG pin on LTC1550LCS8#PBF is an open-drain power-good indicator that pulls low when VOUT is within ±5% of –2V. It sinks up to 4mA and must be externally pulled up to VCC (or up to 6V) to generate a valid logic-high signal for system monitoring or sequencing control.
Is LTC1550LCS8#PBF pin-compatible with LTC1551LCS8#PBF?
No. While both share the same SO-8 package and pin numbering, LTC1550LCS8#PBF has an active-low SHDN pin (pin 5), whereas LTC1551LCS8#PBF has an active-high SHDN pin with internal 5µA pull-down. Interchanging them without circuit modification will invert shutdown behavior.
LTC1550LCS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm 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-SO
LTC1550LCS8#PBF FAQ
1.How can I place an order for LTC1550LCS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1550LCS8#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 LTC1550LCS8#PBF reliable?
The price and inventory of LTC1550LCS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1550LCS8#PBF is usually 5 days.
3.What payment methods are accepted for LTC1550LCS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1550LCS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1550LCS8#PBF?
LTC1550LCS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1550LCS8#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 LTC1550LCS8#PBF?
For technical support, including LTC1550LCS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1550LCS8#PBF requirements.
6.How does Aetrix verify that LTC1550LCS8#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1550LCS8#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 LTC1550LCS8#PBF meets industry standards.
7.What is the process for return or replacement of LTC1550LCS8#PBF?
All LTC1550LCS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1550LCS8#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 LTC1550LCS8#PBF part is unused and in its original packaging.
Return procedure for LTC1550LCS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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