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Analog Devices Inc. LTC1261LCS8#PBF
- Part No.:
- LTC1261LCS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1261LCS8#PBF.pdf
- Description:
- IC REG CHARGE PUMP ADJ 20MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:269
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Product details
Overview
LTC1261LCS8#PBF from Analog Devices (formerly Linear Technology) is a switched-capacitor regulated voltage inverter IC that generates a stable negative output from a single 2.7V–5.25V positive supply. It delivers up to 20mA output current with ±4.5% regulation accuracy, features an open-drain REG flag for power-valid indication, and operates with only three external capacitors. It is used in GaAs FET bias generation and battery-powered systems requiring compact, low-quiescent-current negative rails.
For engineers reviewing the LTC1261LCS8#PBF datasheet, LTC1261LCS8#PBF pinout, LTC1261LCS8#PBF application, or LTC1261LCS8#PBF equivalent, key selection criteria include output regulation tolerance (±4.5%), shutdown current (5µA), adjustable/fixed output variants, SO-8 package compatibility, and REG pin behavior under regulation.
Technical Context
The LTC1261LCS8#PBF implements a 650kHz internal oscillator-driven inverting charge pump topology with feedback-controlled duty-cycle modulation. Regulation is achieved by comparing a resistor-divided output voltage (at ADJ pin) against an internal 1.23V reference referenced to VOUT-not ground-enabling precise negative-voltage control.
It integrates dual comparators: COMP1 regulates output magnitude via cycle-by-cycle charge transfer truncation, while COMP2 (1.17V threshold) drives the open-drain REG output when output is within ±5% of setpoint. The device supports both adjustable (–1.23V to –5V) and fixed-output (–4V/–4.5V) configurations via internal or external resistor networks.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | Adjustable from –1.23V to –5V; this enables custom biasing for GaAs FETs or analog circuitry requiring non-standard negative rails. |
| Output Regulation Accuracy | ±4.5% over full load (0–20mA) and supply (2.7–5.25V); ensures stable operation across battery discharge and varying load conditions. |
| Supply Current (Active) | 650µA typical at 5.25V; minimizes power draw in portable instrumentation and always-on subsystems. |
| Shutdown Current | 5µA typical; allows deep-sleep mode in battery-powered devices without compromising wake-up responsiveness. |
| Oscillator Frequency | 650kHz fixed; enables compact external capacitor sizing (e.g., 0.1µF flying cap) and reduces EMI compared to lower-frequency charge pumps. |
| REG Output Function | Open-drain signal active-low when |VOUT| is within 5% of target; provides hardware-ready status for microcontroller monitoring or power sequencing logic. |
| Operating Temperature Range | 0°C to 70°C (Commercial grade); validated for use in consumer electronics, industrial HMI, and embedded control panels. |
Pinout & Package
Package: 8-Lead Plastic SO (SO-8, narrow 0.150-inch body). Pin pitch: 1.27mm. Thermal resistance θJA = 135°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC (Pin 1) | Positive supply input | Accepts 2.7V–5.25V; requires ≥1µF ceramic bypass capacitor placed adjacent to pin to stabilize charge pump switching currents. |
| C1+ (Pin 2) | Flying capacitor positive terminal | Connects to one end of 0.1µF flying capacitor; internal switch S1/S2 routes charge during pump phases. |
| C1– (Pin 3) | Flying capacitor negative terminal | Connects to other end of 0.1µF flying capacitor; forms charge-transfer path with C1+ during inversion cycle. |
| GND (Pin 4) | Analog ground reference | Low-impedance return for VCC bypass, output capacitor, and internal regulation circuitry; critical for minimizing regulation error. |
| ADJ (Pin 5) | Feedback adjust/compensation node | Receives resistor-divided VOUT to set regulation point; also accepts optional 100pF compensation cap to suppress ripple-induced hunting. |
| OUT (Pin 6) | Negative regulated output | Delivers –1.23V to –5V; must be bypassed with ≥1µF capacitor; ESR impacts regulation stability and ripple performance. |
| REG (Pin 7) | Regulation status indicator | Open-drain N-channel output; sinks ≥5mA at 5V VCC when |VOUT| is within 5% of target; requires external pull-up. |
| SHDN (Pin 8) | Shutdown control input | Active-low enable; internally pulled down with 5µA; floating defaults to operational mode; high disables charge pump and drops ICC to 5µA. |
Key Features
| Feature | Design Value |
|---|---|
| Three-capacitor operation | Requires only 0.1µF flying + input/output bypass caps-no inductors or transformers-reducing BOM count and PCB area in space-constrained designs. |
| Internal 1.23V reference referenced to VOUT | Enables accurate regulation of negative voltages without ground-referenced sensing errors; eliminates need for level-shifting circuitry. |
| REG pin with ±5% hysteresis window | Provides deterministic power-good signaling for system-level fault detection and safe startup sequencing in mixed-supply applications. |
| 650kHz fixed-frequency operation | Allows use of small, low-ESR ceramic capacitors and simplifies EMI filtering versus variable-frequency or lower-frequency alternatives. |
| Indefinite output short-circuit tolerance | Withstands sustained VOUT = 0V without damage or latch-up; protects downstream circuitry during fault conditions or hot-plug events. |
Applications
| GaAs FET Bias Generator | Negative Supply Generator |
|---|---|
Use Scenario: Generating –4V bias for GaAs power amplifier stages in RF transmitters operating from 5V battery supplies. IC Role / Device Role / Timing Role: Regulated negative voltage source providing stable gate bias independent of battery voltage sag or load transients. Use Value: Enables consistent RF output power and linearity by maintaining precise FET gate-source voltage despite input supply variation from 5.25V to 4.35V. | Use Scenario: Creating isolated –2.5V or –3.3V rails for op-amp inputs, ADC references, or sensor interfaces in single-supply data acquisition systems. IC Role / Device Role / Timing Role: Compact, capacitor-based inverter delivering low-noise negative rail without magnetic components or layout-sensitive inductors. Use Value: Eliminates need for discrete transformer-based solutions or larger DC/DC modules-reducing cost, height, and EMI in portable test equipment. |
| Battery-Powered Systems | Single-Supply Signal Conditioning |
Use Scenario: Powering analog front-ends in handheld medical sensors or IoT edge nodes using coin-cell or Li-ion batteries. IC Role / Device Role / Timing Role: Low-quiescent-current (650µA active / 5µA shutdown) negative rail generator enabling extended battery life and rapid wake-up capability. Use Value: Extends operational runtime by >30% versus higher-IQ alternatives while supporting instant-on functionality via SHDN-controlled sleep/wake cycles. | Use Scenario: Biasing precision instrumentation amplifiers or driving bipolar-input DACs in PLC I/O modules powered solely from +5V or +3.3V rails. IC Role / Device Role / Timing Role: Provides rail-to-rail signal swing capability by generating matched negative complement to the main supply. Use Value: Doubles effective dynamic range of analog signal paths without requiring dual-output power supplies or complex layout partitioning. |
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 only; no adjustable version; 800kHz oscillator; ±3% regulation; 1.2mA quiescent current. | Lacks ADJ pin and REG flag; unsuitable where programmable output or power-valid signaling is required. | Select when fixed –5V output suffices and lowest possible component count is prioritized over regulation flexibility. |
| LTC1983ES6#TRMPBF | Adjustable –1.2V to –5V; 1.2MHz switching; ±3.5% regulation; 120µA quiescent current; SOT-23-6 package. | Smaller footprint but lower max output current (15mA vs 20mA); no REG pin; different pinout and capacitor requirements. | Prefer for ultra-low-power, space-constrained applications where 15mA output and absence of REG monitoring are acceptable. |
Compared with MAX680ESA+ and LTC1983ES6#TRMPBF, the LTC1261LCS8#PBF uniquely combines adjustable output voltage, ±4.5% regulation, REG status flag, and SO-8 compatibility-making it optimal for industrial and RF biasing applications demanding configurability and system visibility.
Availability
LTC1261LCS8#PBF is available at Aetrix Electronics and suitable for GaAs FET bias generators, battery-powered instrumentation, and single-supply signal conditioning circuits requiring stable component supply, long-term lifecycle support, and commercial-grade temperature performance.
Supply support for LTC1261LCS8#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 legacy precision analog portfolio, including high-performance power management ICs for demanding industrial and communications applications.
The LTC1261LCS8#PBF belongs to Linear's switched-capacitor voltage converter family, designed specifically for compact, low-noise negative rail generation in battery-operated and space-constrained systems where inductor-free solutions are mandatory.
FAQ
What output voltage range does the LTC1261LCS8#PBF support?
The LTC1261LCS8#PBF supports an adjustable output voltage range from –1.23V to –5V when configured with external resistors on the ADJ pin. Fixed-output variants (e.g., LTC1261LCS8-4#PBF) deliver –4V or –4.5V. The regulation accuracy is ±4.5% across load (0–20mA) and supply (2.7–5.25V) variations, making LTC1261LCS8#PBF suitable for precision biasing applications such as GaAs FET gate control.
How does the REG pin on the LTC1261LCS8#PBF function?
The REG pin on the LTC1261LCS8#PBF is an open-drain output that pulls low when the magnitude of the output voltage is within ±5% of the set value (e.g., –3.8V to –4.2V for a –4V target). It sinks up to 5mA at 5V VCC and requires an external pull-up resistor. This feature enables hardware-level power-valid signaling in systems using LTC1261LCS8#PBF, allowing microcontrollers to confirm regulation before enabling downstream circuitry.
What external components are required for basic operation of the LTC1261LCS8#PBF?
The LTC1261LCS8#PBF requires three essential external capacitors: a 0.1µF ceramic flying capacitor between C1+ and C1–, a ≥1µF ceramic input bypass capacitor from VCC to GND, and a ≥1µF output bypass capacitor from OUT to GND. An optional 100pF compensation capacitor from ADJ to GND further reduces output ripple. No inductors or transformers are needed-making LTC1261LCS8#PBF ideal for compact, low-EMI designs.
Can the LTC1261LCS8#PBF operate from a 3.3V supply?
Yes, the LTC1261LCS8#PBF operates from a minimum supply voltage of 2.7V, so it functions reliably from a 3.3V rail. At 3.3V input, it can deliver regulated outputs down to –1.23V (minimum) with full 20mA capability. Output voltage range scales with input-for example, maximum achievable |VOUT| at 3.3V is approximately –3.0V. This makes LTC1261LCS8#PBF well-suited for modern low-voltage embedded systems powered by 3.3V LDOs or PMICs.
What is the thermal performance of the LTC1261LCS8#PBF in the SO-8 package?
The LTC1261LCS8#PBF in the 8-Lead Plastic SO package has a junction-to-ambient thermal resistance (θJA) of 135°C/W under standard JEDEC PCB conditions. With a maximum junction temperature of 150°C and ambient of 70°C, it can safely dissipate up to ~590mW continuously. At 20mA output into –4V (80mW load power) plus 3.3V × 0.65mA ≈ 2.15mW supply loss, total dissipation remains well below thermal limits-ensuring robust operation in commercial-temperature applications using LTC1261LCS8#PBF.
LTC1261LCS8#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):
- 5.25V
- Voltage - Output (Min/Fixed):
- -1.23V
- Voltage - Output (Max):
- -5V
- 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-SO
LTC1261LCS8#PBF FAQ
1.How can I place an order for LTC1261LCS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1261LCS8#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 LTC1261LCS8#PBF reliable?
The price and inventory of LTC1261LCS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1261LCS8#PBF is usually 5 days.
3.What payment methods are accepted for LTC1261LCS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1261LCS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1261LCS8#PBF?
LTC1261LCS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1261LCS8#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 LTC1261LCS8#PBF?
For technical support, including LTC1261LCS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1261LCS8#PBF requirements.
6.How does Aetrix verify that LTC1261LCS8#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1261LCS8#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 LTC1261LCS8#PBF meets industry standards.
7.What is the process for return or replacement of LTC1261LCS8#PBF?
All LTC1261LCS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1261LCS8#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 LTC1261LCS8#PBF part is unused and in its original packaging.
Return procedure for LTC1261LCS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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