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Analog Devices Inc. LTC1261LCMS8-4.5#TRPBF
- Part No.:
- LTC1261LCMS8-4.5#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LTC1261LCMS8-4.5#TRPBF.pdf
- Description:
- IC REG CHARGE PUMP -4.5V 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,475
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Product details
Overview
LTC1261LCMS8-4.5#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output switched-capacitor voltage inverter IC that generates a regulated –4.5V negative supply from a single 4.75V to 5.25V positive input. It delivers up to 20mA output current with ±4.5% regulation accuracy, features an open-drain REG flag indicating regulation status, and operates with only three external capacitors. It is used in GaAs FET bias generation and battery-powered systems requiring compact, low-quiescent-power negative rails.
For engineers reviewing the LTC1261LCMS8-4.5#TRPBF datasheet, LTC1261LCMS8-4.5#TRPBF pinout, LTC1261LCMS8-4.5#TRPBF application, or LTC1261LCMS8-4.5#TRPBF equivalent, key selection criteria include fixed –4.5V output tolerance, MSOP-8 package compatibility, shutdown current of 5µA, REG pin logic behavior, and guaranteed operation across 0°C to 70°C.
Technical Context
The LTC1261LCMS8-4.5#TRPBF implements a 650kHz internal oscillator-driven inverting charge pump topology with feedback regulation via an internal 1.23V reference. Output voltage is set by factory-trimmed resistor networks connected to the ADJ/COMP pin, eliminating external resistors for fixed-output variants.
Regulation is achieved by cycle-by-cycle pulse truncation: when the divided output at ADJ exceeds 1.23V, the RS latch resets, reducing effective duty cycle. A secondary comparator (1.17V threshold) drives the open-drain REG pin low when output magnitude is within 5% of –4.5V - i.e., VOUT ≥ –4.275V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed –4.5V, guaranteed over 4.75V–5.25V input and 0–10mA load per datasheet Table on page 3. |
| Output Regulation | ±4.5% - ensures VOUT stays between –4.343V and –4.657V under specified conditions. |
| Supply Current | 650µA typical operating current; drops to 5µA in shutdown - enables ultra-low-power standby modes. |
| Oscillator Frequency | 650kHz internal clock - determines charge transfer rate and sets minimum output ripple period (1.54µs). |
| Output Current | Up to 20mA continuous - sufficient for GaAs FET gate biasing and small-signal analog circuitry. |
| REG Pin Behavior | Open-drain output sinks ≥5mA at 5V VCC when VOUT ≥ –4.275V - provides system-level power-valid signaling. |
| Shutdown Threshold | SHDN pin pulled high disables charge pump; internal 5µA pull-down ensures default active state if floating. |
Pinout & Package
Package: 8-lead plastic MSOP (MS8), 3.00mm × 3.00mm body, 0.65mm pitch, exposed pad optional. Thermal resistance θJA = 200°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC (Pin 1) | Positive supply input | Accepts 4.75V–5.25V; requires ≥1µF ceramic bypass capacitor placed near pin for stable operation. |
| C1+ (Pin 2) | Flying capacitor positive terminal | Connects to one end of 0.1µF flying capacitor; forms charge-transfer path with C1–. |
| C1– (Pin 3) | Flying capacitor negative terminal | Connects to other end of 0.1µF flying capacitor; referenced to ground during charge phase. |
| GND (Pin 4) | Analog ground reference | Low-impedance return path for charge pump and regulation loop; critical for minimizing regulation error. |
| ADJ/COMP (Pin 5) | Internal feedback node | Internally connected to fixed resistor divider; optional 100pF compensation capacitor to ground reduces output ripple. |
| OUT (Pin 6) | Negative regulated output | Delivers –4.5V; requires ≥3.3µF output capacitor with low ESR to maintain regulation and limit ripple. |
| REG (Pin 7) | Regulation status indicator | Open-drain N-channel output; pulls low when |VOUT| ≥ 95% of setpoint - requires external pull-up for logic-high assertion. |
| SHDN (Pin 8) | Enable/disable control | Active-low logic: grounded = normal operation; >2V = shutdown mode (5µA quiescent current). |
Key Features
| Feature | Design Value |
|---|---|
| Fixed –4.5V output | Factory-trimmed internal resistor network eliminates external components and calibration effort. |
| Three-capacitor solution | Only 0.1µF flying + ≥1µF input + ≥3.3µF output capacitors required - minimizes BOM count and board area. |
| Power-valid REG signal | Open-drain REG pin provides system-level confirmation of output regulation without additional monitoring circuitry. |
| 650kHz charge pump | High-frequency switching enables use of small ceramic capacitors and reduces output filter size. |
| 5µA shutdown current | Enables long battery life in portable applications by disabling all internal circuitry except SHDN pull-down. |
Applications
| GaAs FET Bias Generator | Negative Supply Generator |
|---|---|
Use Scenario: Generating precise –4.5V gate bias for GaAs power amplifier stages in RF transmitters. IC Role / Device Role / Timing Role: Voltage inverter providing stable negative rail independent of main supply fluctuations. Use Value: Enables optimal FET pinch-off voltage setting; REG signal confirms bias stability before RF enable. | Use Scenario: Creating isolated –4.5V supply for op-amp dual-rail operation in single-supply instrumentation systems. IC Role / Device Role / Timing Role: Compact, capacitor-based negative rail generator replacing discrete inductor-based solutions. Use Value: Eliminates magnetic components and EMI concerns while maintaining ±4.5% output accuracy under 10mA load. |
| Battery-Powered Systems | Single-Supply Signal Conditioning |
Use Scenario: Powering low-noise analog front-ends in handheld test equipment running from 5V Li-ion or USB sources. IC Role / Device Role / Timing Role: Efficient negative rail source with 5µA shutdown current to extend battery runtime. Use Value: Reduces total system quiescent current by >99% vs linear inverter alternatives during sleep mode. | Use Scenario: Biasing precision ADC drivers and sensor interfaces requiring true bipolar input range from a 5V-only supply. IC Role / Device Role / Timing Role: Regulated auxiliary rail supporting rail-to-rail input stage operation. Use Value: Maintains 0.1% gain accuracy in instrumentation amplifiers by holding VOUT stable within ±207mV of –4.5V. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switched-capacitor voltage inverter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX680ESA+ | Fixed –5V output; 100kHz oscillator; requires four external capacitors; ±1.5% regulation. | Higher output voltage magnitude; lower switching frequency increases output capacitor size requirement. | Select when –5V (not –4.5V) is required and board space allows larger 4.7µF output capacitor. |
| LTC1983ES6-4.5#TRMPBF | Same –4.5V output; 1MHz oscillator; SOT-23-6 package; 1.2mA quiescent current; no REG pin. | Smaller footprint but higher IQ; lacks regulation status flag - requires external monitoring if power-valid needed. | Select for space-constrained designs where REG functionality is not required and 1.2mA IQ is acceptable. |
Compared with MAX680ESA+ and LTC1983ES6-4.5#TRMPBF, the LTC1261LCMS8-4.5#TRPBF offers tighter integration (three capacitors), built-in REG signaling, and lower quiescent current - making it optimal for GaAs bias and battery-sensitive applications demanding –4.5V specifically.
Availability
LTC1261LCMS8-4.5#TRPBF is available at Aetrix Electronics and suitable for GaAs FET bias generators, portable instrumentation power supplies, and single-supply analog signal conditioning circuits requiring stable component supply and lead-free compliance.
Supply support for LTC1261LCMS8-4.5#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, datasheet documentation, and manufacturing continuity for legacy Linear parts including the LTC1261L family.
The LTC1261L series was designed specifically for compact, low-component-count negative voltage generation in space- and power-constrained applications such as RF biasing and portable instrumentation - emphasizing regulation accuracy, shutdown efficiency, and ease of layout.
FAQ
What is the minimum input voltage required for reliable operation of the LTC1261LCMS8-4.5#TRPBF?
The LTC1261LCMS8-4.5#TRPBF requires a minimum supply voltage of 4.75V to guarantee ±4.5% output regulation across temperature and load. Operation below 4.75V is possible but not characterized - output may deviate beyond specification, especially at full 20mA load or elevated temperature. Always verify VCC ≥ 4.75V in final design.
Does the LTC1261LCMS8-4.5#TRPBF require an external resistor divider to set its output voltage?
No. The LTC1261LCMS8-4.5#TRPBF is a fixed-output variant with internal resistor trimming connected to the ADJ/COMP pin. No external resistors are needed - unlike the adjustable LTC1261L, this part delivers precisely –4.5V without configuration components.
Can the REG pin of the LTC1261LCMS8-4.5#TRPBF be left unconnected?
No. The REG pin is an open-drain output and must be pulled up externally (e.g., to 3.3V or 5V) with a resistor (typically 10kΩ) to provide a valid logic-high level when regulation is achieved. Leaving REG unconnected results in a floating node and no actionable power-valid signal.
What is the purpose of the 100pF capacitor recommended on the ADJ/COMP pin of the LTC1261LCMS8-4.5#TRPBF?
The 100pF capacitor from ADJ/COMP to GND compensates the regulation loop by counteracting parasitic capacitance, stabilizing feedback response, and reducing output voltage ripple - especially under dynamic load conditions. It does not affect DC output voltage but improves transient performance and prevents comparator "hunting".
Is the LTC1261LCMS8-4.5#TRPBF RoHS-compliant and lead-free?
Yes. The "#TRPBF" suffix indicates tape-and-reel packaging with 100% matte tin (Sn) lead finish, fully compliant with RoHS Directive 2011/65/EU and JEDEC J-STD-609. The device meets IPC/JEDEC standard J-STD-020 for moisture sensitivity level (MSL) 1.
LTC1261LCMS8-4.5#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):
- 5.25V
- Voltage - Output (Min/Fixed):
- -4.5V
- Voltage - Output (Max):
- -
- Current - Output:
- 20mA
- Frequency - Switching:
- 650kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP
LTC1261LCMS8-4.5#TRPBF FAQ
1.How can I place an order for LTC1261LCMS8-4.5#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1261LCMS8-4.5#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 LTC1261LCMS8-4.5#TRPBF reliable?
The price and inventory of LTC1261LCMS8-4.5#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1261LCMS8-4.5#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC1261LCMS8-4.5#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1261LCMS8-4.5#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1261LCMS8-4.5#TRPBF?
LTC1261LCMS8-4.5#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1261LCMS8-4.5#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 LTC1261LCMS8-4.5#TRPBF?
For technical support, including LTC1261LCMS8-4.5#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1261LCMS8-4.5#TRPBF requirements.
6.How does Aetrix verify that LTC1261LCMS8-4.5#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC1261LCMS8-4.5#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 LTC1261LCMS8-4.5#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC1261LCMS8-4.5#TRPBF?
All LTC1261LCMS8-4.5#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1261LCMS8-4.5#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 LTC1261LCMS8-4.5#TRPBF part is unused and in its original packaging.
Return procedure for LTC1261LCMS8-4.5#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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