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Analog Devices Inc. LTC1261LIS8-4#PBF
- Part No.:
- LTC1261LIS8-4#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1261LIS8-4#PBF.pdf
- Description:
- IC REG CHARGE PUMP -4V 20MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:2,838
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Product details
Overview
LTC1261LIS8-4#PBF from Analog Devices (formerly Linear Technology) is a fixed-output switched-capacitor voltage inverter IC that generates a regulated –4V output from a single 4.35V to 5.25V positive supply. It delivers up to 20mA output current with ±4.5% regulation accuracy, features an open-drain REG flag indicating regulation status, and operates across –40°C to +85°C industrial temperature range in SO-8 package.
For engineers reviewing the LTC1261LIS8-4#PBF datasheet, LTC1261LIS8-4#PBF pinout, LTC1261LIS8-4#PBF application, or LTC1261LIS8-4#PBF equivalent, key selection criteria include guaranteed –4V output regulation under load, shutdown quiescent current of 5µA, REG pin logic compatibility with 3.3V/5V systems, and SO-8 footprint suitability for battery-powered and space-constrained designs.
Technical Context
The LTC1261LIS8-4#PBF implements a 650kHz internal oscillator-driven charge pump topology with feedback regulation via an internal 1.23V reference and comparator network. Output voltage is fixed at –4V by on-die resistor divider connected to the ADJ (COMP) pin, eliminating external programming components.
Regulation is achieved by cycle-by-cycle duty-cycle truncation: when the divided output at ADJ exceeds 1.23V, the RS latch resets and disables charge transfer; the REG pin asserts low when the output reaches within 5% (–3.8V to –4.2V) of nominal –4V, using a separate 1.17V threshold comparator.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed –4.0V ±4.5% over 4.35V–5.25V input and 0–20mA load - ensures stable bias for GaAs FETs without trimming. |
| Supply Voltage Range | 4.35V to 5.25V - compatible with standard 5V rail and tolerant of 5% droop; operation below 4.35V not guaranteed. |
| Output Current | Up to 20mA continuous - sufficient for biasing multiple RF power switches or op-amp dual supplies. |
| Quiescent Current | 650µA typical operating / 5µA shutdown - enables low-power sleep modes in portable instrumentation. |
| Oscillator Frequency | 650kHz typical - enables compact 0.1µF flying capacitor and supports <3mV ripple with 3.3µF output cap + RC filter. |
| REG Pin Function | Open-drain output sinking ≥5mA at 5V - provides system-level power-valid signal for microcontroller monitoring or sequencer control. |
| Operating Temperature | –40°C to +85°C - qualified for industrial environments including automotive infotainment and base station subsystems. |
Pinout & Package
Package: 8-Lead Plastic Small Outline (SO-8), narrow body (0.150"), RoHS-compliant lead-free finish (PBF), θJA = 135°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC (Pin 1) | Positive supply input | Accepts 4.35V–5.25V; requires ≥1µF ceramic bypass close to pin to sustain charge pump peak currents. |
| C1+ (Pin 2) | Flying capacitor positive terminal | Connects to 0.1µF flying capacitor; forms half of charge-transfer path during clock phase 1. |
| C1– (Pin 3) | Flying capacitor negative terminal | Completes flying capacitor connection; referenced to GND during charging, to OUT during discharge. |
| GND (Pin 4) | Analog ground reference | Low-impedance return for all internal circuits; critical for regulation accuracy and noise immunity. |
| ADJ/COMP (Pin 5) | Internal feedback node | Internally tied to fixed resistor divider; optional 100pF compensation cap to ground reduces output ripple. |
| OUT (Pin 6) | Negative regulated output | Delivers –4V; requires ≥3.3µF output capacitor with low ESR to minimize droop and maintain regulation. |
| REG (Pin 7) | Regulation status indicator | Open-drain N-channel; pulls low when |VOUT| is within 5% of 4V; requires external pull-up to 3.3V/5V. |
| SHDN (Pin 8) | Shutdown enable | Active-low; floating defaults to operational mode via internal 5µA pull-down; drives high to enter 5µA shutdown. |
Key Features
| Feature | Design Value |
|---|---|
| Fixed –4V output | Eliminates external resistors and layout sensitivity - simplifies design and improves production yield. |
| Integrated 650kHz oscillator | Removes need for external timing components - reduces BOM count and board area vs discrete charge pumps. |
| REG pin with 5% tolerance window | Provides deterministic power-good signaling without additional comparators or voltage monitors. |
| Industrial temperature grade (–40°C to +85°C) | Enables deployment in extended-environment applications such as factory automation and outdoor telecom. |
| SO-8 package with 135°C/W thermal resistance | Supports 20mA continuous output without forced air - suitable for sealed enclosures and convection-cooled systems. |
Applications
| GaAs FET Bias Generator | Negative Supply for Op-Amp Circuits |
|---|---|
Use Scenario: Generating stable –4V gate bias for P-channel GaAs FETs in RF transmitter stages of portable radios or satellite modems. IC Role / Device Role / Timing Role: Regulated negative voltage source providing precise DC bias independent of input rail variation. Use Value: Maintains consistent FET transconductance and linearity across battery discharge (4.35V–5.25V), reducing distortion and improving EVM. | Use Scenario: Creating split-rail supplies for precision instrumentation amplifiers in data acquisition systems. IC Role / Device Role / Timing Role: Compact, low-noise negative rail generator enabling true bipolar signal swing without transformer or inductor. Use Value: Delivers 20mA at ±4.5% regulation - supports dual op-amps with headroom for 10Vpp output while minimizing PCB real estate. |
| Battery-Powered Portable Instrumentation | Industrial Sensor Signal Conditioning |
Use Scenario: Powering analog front-ends in handheld multimeters or portable oscilloscopes powered by single Li-ion cell (3.0–4.2V) with boost stage. IC Role / Device Role / Timing Role: Secondary regulated negative supply derived from boosted 5V rail, synchronized to internal 650kHz clock. Use Value: 5µA shutdown current extends battery life during standby; REG pin enables automatic wake-up on valid supply detection. | Use Scenario: Providing isolated negative bias for bridge sensor excitation and instrumentation amplifier references in PLC I/O modules. IC Role / Device Role / Timing Role: Fixed-output inverter delivering stable –4V for ratiometric ADC references and offset calibration circuits. Use Value: Industrial temp grade and ±4.5% regulation ensure accuracy over wide ambient ranges without recalibration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switched-capacitor inverter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX680ESA+ | Fixed –5V output; 800kHz oscillator; 10mA max output; SO-8 package; no REG pin. | Lacks regulation status flag; lower output current limits use in higher-load sensor biasing. | Select when –5V (not –4V) is required and REG monitoring is unnecessary. |
| LTC1044CS8#PBF | Unregulated charge pump; no internal reference or feedback; 20mA output; SO-8; requires external resistors for adjustable output. | No output regulation or REG indication; output varies with load and input - unsuitable for precision biasing. | Select only for non-critical applications where cost is primary and ±10% output tolerance is acceptable. |
Compared with MAX680ESA+ and LTC1044CS8#PBF, the LTC1261LIS8-4#PBF uniquely combines fixed –4V regulation, integrated REG flag, and industrial temperature rating - making it optimal for GaAs FET biasing and precision analog supply generation where output stability and system monitoring are essential.
Availability
LTC1261LIS8-4#PBF is available at Aetrix Electronics and suitable for GaAs FET bias generators, industrial sensor signal conditioning, and battery-powered portable instrumentation requiring stable component supply across extended temperature ranges.
Supply support for LTC1261LIS8-4#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, datasheet documentation, and long-term manufacturing commitment for legacy Linear parts.
The LTC1261LIS8-4#PBF belongs to Linear's precision switched-capacitor power conversion family, designed specifically for compact, low-noise negative voltage generation in space- and power-constrained analog systems.
FAQ
What is the minimum input voltage required for stable operation of the LTC1261LIS8-4#PBF?
The LTC1261LIS8-4#PBF is guaranteed to meet its ±4.5% output regulation specification only when supplied with 4.35V to 5.25V. Operation below 4.35V may function but is not characterized - VOUT regulation degrades and output current capability falls. Always verify performance across your actual input range using the "Minimum Required VCC vs VOUT and IOUT" curve in Figure G02 of the datasheet.
Can the LTC1261LIS8-4#PBF be used with a 3.3V input supply?
No - the LTC1261LIS8-4#PBF requires a minimum 4.35V supply to guarantee –4V output regulation. For 3.3V systems, consider the adjustable LTC1261LIS8#PBF (2.7V–5.25V input, –1.23V to –5V output) or alternative solutions like the LT3467. Using LTC1261LIS8-4#PBF below 4.35V risks output collapse, poor regulation, and failure to assert the REG pin correctly.
How does the REG pin on the LTC1261LIS8-4#PBF interface with a 3.3V microcontroller?
The REG pin is open-drain and rated for up to 6V absolute maximum. To interface with a 3.3V microcontroller GPIO, connect a pull-up resistor (e.g., 10kΩ) from REG to 3.3V. When LTC1261LIS8-4#PBF output is within –3.8V to –4.2V, REG pulls low (≤0.8V); otherwise it floats high (≈3.3V). This provides direct-compatible power-valid signaling without level-shifting circuitry.
What external capacitors are mandatory for the LTC1261LIS8-4#PBF, and what values are recommended?
Three mandatory capacitors: (1) 0.1µF ceramic flying capacitor between C1+ and C1–; (2) ≥1µF ceramic input bypass from VCC to GND; (3) ≥3.3µF ceramic output capacitor from OUT to GND. An optional 100pF compensation capacitor from ADJ/COMP to GND further reduces ripple. Avoid tantalum or aluminum electrolytics alone at OUT - use ceramic or parallel ceramic+tantalum to prevent regulation loop instability due to ESR.
Does the LTC1261LIS8-4#PBF require a heatsink in 20mA continuous operation?
No - the SO-8 package has θJA = 135°C/W. At 20mA output and 5V input, power dissipation is ~100mW. With 25°C ambient, junction temperature rise is ~13.5°C, well below the 150°C maximum. Standard FR-4 PCB with moderate copper pour is sufficient; no heatsink or thermal vias needed for typical industrial use cases.
LTC1261LIS8-4#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):
- 4.5V
- Voltage - Input (Max):
- 5.25V
- Voltage - Output (Min/Fixed):
- -4V
- Voltage - Output (Max):
- -
- Current - Output:
- 20mA
- Frequency - Switching:
- 650kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LTC1261LIS8-4#PBF FAQ
1.How can I place an order for LTC1261LIS8-4#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1261LIS8-4#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 LTC1261LIS8-4#PBF reliable?
The price and inventory of LTC1261LIS8-4#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1261LIS8-4#PBF is usually 5 days.
3.What payment methods are accepted for LTC1261LIS8-4#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1261LIS8-4#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1261LIS8-4#PBF?
LTC1261LIS8-4#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1261LIS8-4#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 LTC1261LIS8-4#PBF?
For technical support, including LTC1261LIS8-4#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1261LIS8-4#PBF requirements.
6.How does Aetrix verify that LTC1261LIS8-4#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1261LIS8-4#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 LTC1261LIS8-4#PBF meets industry standards.
7.What is the process for return or replacement of LTC1261LIS8-4#PBF?
All LTC1261LIS8-4#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1261LIS8-4#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 LTC1261LIS8-4#PBF part is unused and in its original packaging.
Return procedure for LTC1261LIS8-4#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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