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Analog Devices Inc. LTC1551LCMS8-4.1#TRPBF
- Part No.:
- LTC1551LCMS8-4.1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LTC1551LCMS8-4.1#TRPBF.pdf
- Description:
- IC REG CHARGE PUMP -4.1V 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,454
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Product details
Overview
LTC1551LCMS8-4.1#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output, switched-capacitor negative voltage inverter with integrated linear post-regulator, delivering –4.1V at up to 20mA load current with <1mVP-P output ripple, operating from 4.5V–5.25V input supply, and featuring active-high TTL-compatible shutdown. It serves as a low-noise GaAs FET bias generator in portable RF transmitters.
For engineers reviewing the LTC1551LCMS8-4.1#TRPBF datasheet, LTC1551LCMS8-4.1#TRPBF pinout, LTC1551LCMS8-4.1#TRPBF application, or LTC1551LCMS8-4.1#TRPBF equivalent, key selection criteria include guaranteed ±2.5% output regulation over line/load/temperature, 900kHz charge pump frequency, MSOP-8 package compatibility, and shutdown quiescent current <1µA - critical for battery-powered RF front-end designs.
Technical Context
The LTC1551LCMS8-4.1#TRPBF 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 GaAs FET bias loads.
Unlike adjustable variants, this fixed –4.1V version uses internal resistor divider networks; its SHDN pin is active high (logic high = normal operation), distinguishing it from the LTC1550L series. The device requires only four external capacitors: two 0.1µF charge pump caps (C1+, C1–), one 0.1µF CPOUT cap, and ≥10µF VOUT filter capacitor with moderate ESR for loop stability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | –4.1V ±2.5% over line, load, and temperature - ensures stable GaAs FET gate bias across battery discharge and ambient variation. |
| Max Output Current | 20mA at VCC ≥4.75V - sufficient for biasing multiple GaAs FETs in cellular handset power amplifiers. |
| Output Ripple | <1mVP-P typical with 10µF + 0.1µF ceramic output capacitor - meets stringent noise requirements for RF signal integrity. |
| Charge Pump Frequency | 900kHz - avoids IF bands (400–600kHz) in portable radios and enables use of small 0.1µF ceramic flying capacitors. |
| Shutdown Current | 0.2µA typical - extends battery life in standby mode without requiring external power gating circuitry. |
| Input Voltage Range | 4.5V to 5.25V - matches Li-ion battery full-charge voltage and regulated 5V rail systems. |
| Regulation Accuracy | ±2.5% over 0°C to 70°C - guarantees consistent FET transconductance and amplifier gain stability. |
Pinout & Package
Package: 8-lead MSOP (MS8), 3mm × 3mm, 0.65mm pitch, exposed pad not electrically connected.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 (REG) | Power Good Open-Drain Output | Pulls low when VOUT is within ±5% of –4.1V; requires external pull-up to monitor regulation status in real time. |
| 2 (CPOUT) | Negative Charge Pump Output | Intermediate node supplying input to linear regulator; must be bypassed with 0.1µF capacitor directly to GND pin to minimize AC current path and ripple. |
| 3 (GND) | Analog Ground Reference | Low-impedance return for regulator feedback and charge pump; star-ground connection required with CPOUT and VOUT capacitors. |
| 4 (C1–) | Flying Capacitor Negative Terminal | Connects to negative side of 0.1µF flying capacitor (C1); forms charge transfer path with C1+ during clock phase reversal. |
| 5 (SHDN) | Active-High Shutdown Control | Logic high (≥2V) enables operation; logic low disables charge pump and drops IQ to 0.2µA - no internal pull-down, requires external logic drive. |
| 6 (VCC) | Positive Input Supply | Accepts 4.5–5.25V; requires ≥2.2µF low-ESR ceramic bypass capacitor placed adjacent to pin to prevent supply droop during charge pump switching. |
| 7 (C1+) | Flying Capacitor Positive Terminal | Connects to positive side of 0.1µF flying capacitor (C1); alternately charged to VCC and discharged to generate negative voltage at CPOUT. |
| 8 (VOUT) | Regulated Negative Output | Delivers –4.1V; requires ≥10µF output capacitor with moderate ESR to ensure loop stability and <1mVP-P ripple performance. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Linear Post-Regulator | Reduces charge pump ripple to <1mVP-P while maintaining fast transient response for GaAs FET gate drive stability. |
| 900kHz Switching Frequency | Enables use of compact 0.1µF ceramic flying capacitors and avoids interference with common RF IF bands (400–600kHz). |
| Active-High TTL-Compatible SHDN | Simplifies interface with microcontroller GPIOs or system power sequencers without level-shifting or pull-up resistors. |
| Guaranteed ±2.5% Regulation | Ensures consistent FET bias point across battery voltage sag, temperature drift, and load variation in portable RF systems. |
| Four-External-Component Operation | Minimizes BOM count and PCB area: only input bypass, two flying caps, and output filter required for full functionality. |
Applications
| GaAs FET Transmitter Bias | Negative Rail Generation |
|---|---|
|
Use Scenario: Providing stable gate bias voltage for GaAs pHEMT power amplifiers in GSM/EDGE/WCDMA handsets. IC Role / Device Role / Timing Role: Fixed –4.1V negative bias generator with ultra-low ripple to maintain amplifier linearity and efficiency. Use Value: Enables consistent POUT and ACPR performance across battery discharge cycle without manual calibration. |
Use Scenario: Generating isolated negative supply for op-amp rails or sensor interfaces in single-supply industrial data acquisition systems. IC Role / Device Role / Timing Role: Compact, capacitor-based inverter replacing discrete charge pump + LDO solutions. Use Value: Reduces component count by 4+ parts versus discrete implementation while improving PSRR and noise floor. |
| Battery-Powered RF Modules | Portable Medical Instrumentation |
|
Use Scenario: Powering low-noise RF front-ends in Bluetooth LE or Zigbee modules where board space and EMI are constrained. IC Role / Device Role / Timing Role: Low-quiescent-current (0.2µA shutdown) negative voltage source synchronized to host MCU sleep/wake cycles. Use Value: Extends module battery life >30% versus non-shutdown alternatives while preserving RF spectral purity. |
Use Scenario: Biasing precision analog front-ends (e.g., ECG amplifiers) requiring clean negative rail in handheld diagnostic devices. IC Role / Device Role / Timing Role: Regulated –4.1V supply with <1mVP-P ripple to minimize baseline wander and improve SNR. Use Value: Eliminates need for external filtering stages, reducing design complexity and validation effort. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar negative voltage inverter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1550LCMS8-4.1#TRPBF | Identical architecture and specs, but features active-low SHDN pin instead of active-high. | Requires inverted control signal; unsuitable for direct replacement where MCU GPIO cannot drive active-low logic. | Select when existing firmware or hardware already implements active-low shutdown control. |
| LTC1261LCS8-4.1#PBF | Lower max output current (15mA), higher typical ripple (2mVP-P), no REG pin, 1MHz charge pump frequency. | Lacks power-good indication and has reduced load capability - insufficient for multi-FET PA biasing. | Consider only for cost-sensitive, lower-current applications where REG monitoring is unnecessary. |
Compared with LTC1550LCMS8-4.1#TRPBF and LTC1261LCS8-4.1#PBF, the LTC1551LCMS8-4.1#TRPBF uniquely combines active-high shutdown, 20mA drive, <1mVP-P ripple, and REG status signaling - making it optimal for modern RF power amplifier biasing where control simplicity and signal integrity are co-prioritized.
Availability
LTC1551LCMS8-4.1#TRPBF is available at Aetrix Electronics and suitable for GaAs FET biasing, portable RF transmitter modules, and battery-powered medical instrumentation requiring stable component supply, tight regulation, and low-noise negative voltage generation.
Supply support for LTC1551LCMS8-4.1#TRPBF 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, manufacturing, and documentation for the LTC portfolio.
The LTC1550L/LTC1551L family was designed specifically for low-noise, regulated negative voltage generation in portable RF systems - emphasizing minimal external components, sub-millivolt ripple, and robust operation across battery voltage ranges.
FAQ
What is the minimum input voltage required for LTC1551LCMS8-4.1#TRPBF to regulate –4.1V at 20mA?
The LTC1551LCMS8-4.1#TRPBF requires a minimum VCC of 4.75V to deliver –4.1V at 20mA load, as specified in the Electrical Characteristics table under "VOUT Output Regulation" for the –4.1V fixed version. Below 4.75V, regulation degrades or fails due to insufficient headroom for the linear post-regulator's dropout margin.
Can LTC1551LCMS8-4.1#TRPBF operate from a 3.3V supply?
No. The LTC1551LCMS8-4.1#TRPBF is not rated for 3.3V operation. Its absolute minimum VCC for –4.1V output is 4.5V, and guaranteed regulation at full load requires ≥4.75V. Attempting operation at 3.3V will result in unregulated output or device malfunction.
What is the purpose of the REG pin on LTC1551LCMS8-4.1#TRPBF?
The REG pin on LTC1551LCMS8-4.1#TRPBF is an open-drain power-good indicator that pulls low when the VOUT voltage is within ±5% of –4.1V. It sinks up to 4mA and requires an external pull-up resistor to monitor real-time regulation status - essential for system-level fault detection in RF power amplifiers.
Why does LTC1551LCMS8-4.1#TRPBF require a 10µF output capacitor with moderate ESR?
The LTC1551LCMS8-4.1#TRPBF's linear regulator feedback loop relies on the zero formed by the output capacitor's ESR and capacitance to provide phase lead. Very low-ESR capacitors (e.g., polymer or ultra-low-ESR ceramics) destabilize the loop, causing oscillation. A 10µF tantalum or aluminum electrolytic with ~1Ω ESR ensures stability and achieves <1mVP-P ripple when paralleled with 0.1µF ceramic.
Is LTC1551LCMS8-4.1#TRPBF pin-compatible with LTC1550LCMS8-4.1#TRPBF?
Yes - LTC1551LCMS8-4.1#TRPBF and LTC1550LCMS8-4.1#TRPBF share identical MSOP-8 pinout, package dimensions, and electrical connections. The sole functional difference is SHDN polarity: LTC1551L uses active-high, while LTC1550L uses active-low. No PCB changes are needed, but control logic must be verified.
LTC1551LCMS8-4.1#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Negative
- Topology:
- Charge Pump
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.5V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- -4.1V
- 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-MSOP
LTC1551LCMS8-4.1#TRPBF FAQ
1.How can I place an order for LTC1551LCMS8-4.1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1551LCMS8-4.1#TRPBF 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 LTC1551LCMS8-4.1#TRPBF reliable?
The price and inventory of LTC1551LCMS8-4.1#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1551LCMS8-4.1#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC1551LCMS8-4.1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1551LCMS8-4.1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1551LCMS8-4.1#TRPBF?
LTC1551LCMS8-4.1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1551LCMS8-4.1#TRPBF 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 LTC1551LCMS8-4.1#TRPBF?
For technical support, including LTC1551LCMS8-4.1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1551LCMS8-4.1#TRPBF requirements.
6.How does Aetrix verify that LTC1551LCMS8-4.1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC1551LCMS8-4.1#TRPBF 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 LTC1551LCMS8-4.1#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC1551LCMS8-4.1#TRPBF?
All LTC1551LCMS8-4.1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1551LCMS8-4.1#TRPBF, 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 LTC1551LCMS8-4.1#TRPBF part is unused and in its original packaging.
Return procedure for LTC1551LCMS8-4.1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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