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Analog Devices Inc. LTC1550LCS8-2.5#PBF
- Part No.:
- LTC1550LCS8-2.5#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1550LCS8-2.5#PBF.pdf
- Description:
- IC REG CHARG PUMP -2.5V 20MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:171
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Product details
Overview
LTC1550LCS8-2.5#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 –2.5V output at up to 20mA load current, <1mVP-P ripple, and 900kHz charge pump frequency. It operates from a single 3.05V–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 LTC1550LCS8-2.5#PBF datasheet, LTC1550LCS8-2.5#PBF pinout, LTC1550LCS8-2.5#PBF application, or LTC1550LCS8-2.5#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 RF biasing circuits.
Technical Context
The LTC1550LCS8-2.5#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, enabling stable regulation under dynamic load conditions.
It requires no inductors and uses only ceramic capacitors: two 0.1µF charge pump caps (C1+, C1–), one 0.1µF CPOUT capacitor, and ≥10µF output filter (VOUT-to-GND) with moderate ESR for loop stability. The SHDN pin defaults to high-impedance input with no internal pull-up, requiring external pull-up for normal operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed –2.5V, regulated to ±2.5% over line, load, and temperature (3.05V ≤ VCC ≤ 5.25V, 0–20mA). |
| Output Ripple | <1mVP-P typical with 10µF + 0.1µF output capacitor; enables clean bias for noise-sensitive GaAs FETs. |
| Charge Pump Frequency | 900kHz internal oscillator - avoids IF bands (400–600kHz) and permits use of small 0.1µF ceramic flying capacitors. |
| Supply Current | 3.65mA typical at 5V VCC; drops to 0.2µA in shutdown mode (SHDN = low), supporting ultra-low-power standby. |
| Input Voltage Range | 3.05V to 5.25V minimum required for –2.5V output - ensures compatibility with Li-ion (3.0–4.2V) and regulated 3.3V/5V rails. |
| Shutdown Interface | TTL-compatible active-low SHDN pin - compatible with standard logic outputs without level-shifting. |
| Regulation Accuracy | ±2.5% over full operating range (0°C to 70°C commercial grade) - meets tight bias voltage tolerance for RF power amplifier linearity. |
Pinout & Package
Package: 8-lead SO (Small Outline, narrow 0.150"), RoHS-compliant, lead-free (#PBF). Pin pitch: 1.27mm. Body dimensions: 4.90mm × 3.90mm × 1.75mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (REG) | Power Good Output | Open-drain signal pulled low when VOUT is within ±5% of –2.5V; requires external pull-up to monitor regulation status. |
| 2 (CPOUT) | Negative Charge Pump Output | Intermediate node supplying negative voltage to linear regulator; requires 0.1µF capacitor to GND with star-ground connection. |
| 3 (GND) | Ground Reference | Common analog/power ground return for all internal blocks and external capacitors; must connect to low-impedance 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 clock phases. |
| 5 (SHDN) | Active-Low Shutdown Control | Drives internal charge pump and regulator into ultra-low-current state (<1µA) when pulled low; high-impedance input, no internal pull-up. |
| 6 (VCC) | Positive Input Supply | Accepts 3.05–5.25V input; requires ≥2.2µF bypass capacitor placed adjacent to pin for stable charge pump operation. |
| 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 | Delivers –2.5V output; requires ≥10µF output capacitor (moderate ESR) plus 0.1µF ceramic for ripple suppression and loop stability. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Linear Post-Regulator | Eliminates need for external LDO; reduces output ripple to <1mVP-P while maintaining fast transient response for RF bias stability. |
| 900kHz Switching Frequency | Enables use of compact 0.1µF ceramic flying capacitors and avoids interference with common IF bands in cellular/RF systems. |
| Four-Capacitor Solution | Requires only CIN (2.2µF), C1 (0.1µF), CCP (0.1µF), and COUT (10µF + 0.1µF) - simplifies layout and reduces BOM count vs inductor-based solutions. |
| Guaranteed ±2.5% Regulation | Validated across line (3.05–5.25V), load (0–20mA), and temperature (0°C–70°C) - ensures consistent GaAs FET gate bias under real-world conditions. |
| Active-Low TTL-Compatible SHDN | Direct interface with microcontroller GPIO or logic-level control signals; supports rapid power cycling without external level shifters. |
Applications
| GaAs FET Transmitter Bias | Portable RF Power Amplifier Supply |
|---|---|
Use Scenario: Generating stable negative gate bias for GaAs FETs in handheld cellular transmitters operating from single-cell Li-ion batteries. IC Role / Device Role / Timing Role: Regulated –2.5V inverter providing precise, low-noise DC bias to control RF output power and linearity. Use Value: Enables >20dB gain flatness and <–45dBc harmonic distortion by eliminating ripple-induced modulation on the FET gate. |
Use Scenario: Supplying clean negative rail to RF front-end ICs in Bluetooth/WiFi modules where space and EMI are critical constraints. IC Role / Device Role / Timing Role: Compact, inductorless negative voltage source replacing discrete charge pumps and LDOs in miniaturized RF subsystems. Use Value: Reduces PCB area by >40% vs inductor-based solutions while meeting FCC radiated emission limits due to absence of magnetic fields. |
| Battery-Powered Instrumentation | Single-Supply Signal Conditioning |
Use Scenario: Providing isolated negative supply for op-amp biasing in portable medical sensors powered by 3.3V coin cells or rechargeable packs. IC Role / Device Role / Timing Role: Low-quiescent-current (3.65mA) inverter enabling extended battery life while maintaining precision analog signal integrity. Use Value: Supports >100-hour runtime in continuous monitoring devices by minimizing idle current and eliminating inductor losses. |
Use Scenario: Creating dual-rail supplies for rail-to-rail op-amps in industrial data acquisition systems using only a 3.3V or 5V main rail. IC Role / Device Role / Timing Role: Fixed-output negative generator enabling true bipolar operation without external regulators or transformers. Use Value: Eliminates need for split-rail wall adapters or isolated DC/DC converters, reducing system cost and complexity in field-deployable equipment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar negative voltage inverter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1550LCMS8-2.5#PBF | Same electrical specs and functionality, but in 8-lead MSOP package (3.0mm × 3.0mm) instead of SO (4.9mm × 3.9mm). | Preferred for space-constrained layouts; MSOP offers better thermal performance (θJA = 135°C/W vs SO's 200°C/W). | Select when board area is limited or thermal dissipation is critical; pinout identical, direct footprint replacement possible with layout revision. |
| LTC1551LCS8-2.5#PBF | Identical except active-high SHDN pin (vs active-low on LTC1550LCS8-2.5#PBF); otherwise same regulation, ripple, and package. | Suitable where host MCU GPIO defaults high or lacks open-drain capability; eliminates need for external inverter logic. | Choose when system-level control logic favors active-high enable; not pin-compatible due to opposite SHDN polarity - requires schematic update. |
Compared with LTC1550LCMS8-2.5#PBF, the LTC1550LCS8-2.5#PBF offers identical regulation and noise performance in a larger SO package with higher thermal resistance, while LTC1551LCS8-2.5#PBF provides identical functionality with inverted shutdown logic - both require careful review of mechanical and control-signal compatibility before substitution.
Availability
LTC1550LCS8-2.5#PBF is available at Aetrix Electronics and suitable for GaAs FET biasing, portable RF power amplifiers, and battery-powered instrumentation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LTC1550LCS8-2.5#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 technical documentation, application support, and long-term manufacturing commitment.
The LTC1550L series belongs to Linear Technology's low-noise switched-capacitor voltage inverter family, designed specifically for RF bias generation and noise-sensitive analog systems where inductor-free, ultra-low-ripple negative supplies are essential.
FAQ
What is the minimum input voltage required for the LTC1550LCS8-2.5#PBF to regulate –2.5V output?
The LTC1550LCS8-2.5#PBF requires a minimum VCC of 3.05V to guarantee –2.5V output regulation across temperature and load (0–20mA). Below this, regulation degrades; at 3.05V/20mA, output remains within ±2.5% (–2.562V to –2.438V). This makes LTC1550LCS8-2.5#PBF compatible with fully charged Li-ion (≥3.0V) and regulated 3.3V supplies.
Can the LTC1550LCS8-2.5#PBF be used with ceramic output capacitors only?
Yes, but with strict ESR requirements: LTC1550LCS8-2.5#PBF needs ≥10µF total output capacitance with moderate ESR (e.g., 10–100mΩ) for loop stability. A 10µF tantalum in parallel with 0.1µF ceramic is recommended; using only very-low-ESR ceramics (e.g., X7R/X5R <5mΩ) risks oscillation. The 0.1µF ceramic must remain in parallel to suppress high-frequency spikes.
Does the LTC1550LCS8-2.5#PBF have built-in short-circuit protection?
No. The LTC1550LCS8-2.5#PBF does not include current-limiting or thermal shutdown circuitry. Its absolute maximum rating allows 30 seconds of continuous short-circuit (VOUT = 0V) at VCC = 5.25V, with typical short-circuit current of 80–200mA. External current limiting or fuse protection is required for sustained fault conditions.
How does the REG pin function on the LTC1550LCS8-2.5#PBF?
The REG pin on LTC1550LCS8-2.5#PBF is an open-drain output that pulls low when VOUT is within ±5% of –2.5V (i.e., –2.625V to –2.375V). It sinks up to 4mA at 5V VCC and requires an external pull-up resistor (typically 10–100kΩ) to VCC or another logic rail. REG provides power-good indication for system sequencing or fault monitoring.
Is the LTC1550LCS8-2.5#PBF pin-compatible with other members of the LTC1550L/LTC1551L family in SO-8?
Yes - all SO-8 variants (LTC1550LCS8-x and LTC1551LCS8-x) share identical pinout and footprint. However, LTC1550LCS8-2.5#PBF (active-low SHDN) is not functionally interchangeable with LTC1551LCS8-2.5#PBF (active-high SHDN) without modifying the control signal logic; both are mechanically compatible but electrically distinct.
LTC1550LCS8-2.5#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:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.05V
- Voltage - Input (Max):
- 5.25V
- Voltage - Output (Min/Fixed):
- -2.5V
- Voltage - Output (Max):
- -
- 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
LTC1550LCS8-2.5#PBF FAQ
1.How can I place an order for LTC1550LCS8-2.5#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1550LCS8-2.5#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 LTC1550LCS8-2.5#PBF reliable?
The price and inventory of LTC1550LCS8-2.5#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1550LCS8-2.5#PBF is usually 5 days.
3.What payment methods are accepted for LTC1550LCS8-2.5#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1550LCS8-2.5#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1550LCS8-2.5#PBF?
LTC1550LCS8-2.5#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1550LCS8-2.5#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 LTC1550LCS8-2.5#PBF?
For technical support, including LTC1550LCS8-2.5#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1550LCS8-2.5#PBF requirements.
6.How does Aetrix verify that LTC1550LCS8-2.5#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1550LCS8-2.5#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 LTC1550LCS8-2.5#PBF meets industry standards.
7.What is the process for return or replacement of LTC1550LCS8-2.5#PBF?
All LTC1550LCS8-2.5#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1550LCS8-2.5#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 LTC1550LCS8-2.5#PBF part is unused and in its original packaging.
Return procedure for LTC1550LCS8-2.5#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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