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Analog Devices Inc. LTC1261CS8#PBF
- Part No.:
- LTC1261CS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1261CS8#PBF.pdf
- Description:
- IC REG CHARGE PUMP ADJ 12MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:6,743
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Product details
Overview
LTC1261CS8#PBF from Analog Devices (formerly Linear Technology) is a switched-capacitor regulated voltage inverter IC that generates a stable negative output from a single 3V–8V positive supply. It delivers up to 12mA output current with ±5% regulation, supports adjustable (–1.25V to –8V) or factory-fixed outputs (e.g., –4V, –4.5V), and operates in doubler mode only. It is used in battery-powered instrumentation requiring clean, low-noise negative bias for op-amps and ADCs.
For engineers reviewing the LTC1261CS8#PBF datasheet, LTC1261CS8#PBF pinout, LTC1261CS8#PBF application, or LTC1261CS8#PBF equivalent, this page provides verified technical context, SO-8 package mapping, real-world ripple and regulation behavior, shutdown control timing, and validated alternatives for negative rail generation in space-constrained designs.
Technical Context
The LTC1261CS8#PBF implements a fixed-doubler charge pump architecture-unlike the 14-lead LTC1261CS, it lacks C2+ and C2– pins and cannot operate in tripler mode. Its internal 550kHz oscillator drives MOSFET switches to invert and regulate VCC, using a single flying capacitor (C1) between C1+ and C1–.
Regulation is achieved via an internal 1.24V reference referenced to OUT, comparing a resistor-divided output at the ADJ/COMP pin. The open-drain REG pin asserts low when |VOUT| is within 5% of the set value, sinking up to 8mA at 5V VCC, and tolerates pull-up voltages up to 12V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | Adjustable –1.25V to –8V; fixed options include –4V and –4.5V (pin-strapped via internal resistor string) |
| Input Supply Range | 3V to 8V DC - supports common logic rails (3.3V, 5V); output magnitude limited to ≤ VCC in doubler mode |
| Max Output Current | 12mA with guaranteed ±5% regulation - sufficient for biasing dual op-amps or low-power ADC references |
| Output Ripple | 5mV typical at 5mA load with 3.3µF output capacitor - enables noise-sensitive analog signal chains |
| Quiescent Current | 600µA typical operating; 5µA in shutdown - extends battery life in portable medical or sensor nodes |
| Oscillator Frequency | 550kHz fixed - allows compact 0.1µF ceramic flying capacitors and minimizes EMI filtering burden |
| REG Pin Function | Open-drain status indicator - pulls low when |VOUT| is within 5% of target; requires external pull-up for logic-level signaling |
Pinout & Package
Package: 8-lead plastic SO (SO-8), 150°C/W junction-to-ambient thermal resistance, commercial temperature range (0°C to 70°C).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VCC) | Positive power input | Accepts 3V–8V; must be bypassed with ≥0.1µF ceramic capacitor placed adjacent to pin |
| 2 (C1+) | Flying capacitor positive terminal | Connects to one end of 0.1µF flying capacitor; forms charge transfer path in doubler mode |
| 3 (C1–) | Flying capacitor negative terminal | Connects to other end of same 0.1µF flying capacitor; no floating requirement (unlike 14-lead variant) |
| 4 (GND) | Analog ground reference | Low-impedance return for charge pump and regulation loop; tie directly to PCB ground plane |
| 5 (ADJ/COMP) | Feedback & compensation node | For adjustable versions: sets output via resistor divider; for fixed versions: internal tap + optional 100pF ripple reduction cap to GND |
| 6 (OUT) | Negative regulated output | Delivers –1.25V to –8V; requires ≥3.3µF low-ESR output capacitor for specified 5mV ripple |
| 7 (REG) | Regulation status flag | Open-drain N-channel output; sinks up to 8mA at 5V VCC; pull-up required for high-state indication |
| 8 (SHDN) | Shutdown enable | Active-low control; internally pulled down with 5µA; floating = normal operation; >2V = shutdown (5µA IQ) |
Key Features
| Feature | Design Value |
|---|---|
| Doubler-only SO-8 configuration | Eliminates tripler-mode complexity and extra pins - simplifies layout and reduces BOM count vs 14-lead version |
| Internal resistor string for fixed outputs | Enables –4V or –4.5V operation with zero external resistors - ideal for cost-sensitive, high-volume bias supplies |
| 550kHz charge pump frequency | Permits use of small, stable 0.1µF X7R ceramic flying capacitors - avoids electrolytic/tantalum reliability concerns |
| REG pin with 12V-tolerant pull-up | Allows direct interfacing with 3.3V/5V logic or higher-voltage monitoring circuits without level-shifting |
| 5µA shutdown quiescent current | Supports ultra-low-power sleep modes in portable devices - extends runtime between battery charges |
Applications
| Portable Instrumentation Power | Op-Amp Dual-Rail Bias |
|---|---|
Use Scenario: Handheld multimeter or portable oscilloscope requiring isolated negative rail for front-end amplifiers and ADC drivers. IC Role / Device Role / Timing Role: LTC1261CS8#PBF acts as the sole negative voltage generator, deriving –4V from a 5V Li-ion battery pack with integrated regulation and power-good signaling. Use Value: Eliminates need for discrete inductor-based DC/DC converters - reduces board area by >40% and avoids magnetic EMI in sensitive measurement paths. |
Use Scenario: Low-noise audio preamplifier stage using dual-supply op-amps (e.g., LT1028) powered from a single 3.3V system rail. IC Role / Device Role / Timing Role: LTC1261CS8#PBF provides tightly regulated –3.3V rail synchronized to the 550kHz internal clock - no external timing components required. Use Value: Achieves <5mV peak-to-peak ripple without LC filtering - preserves SNR in 24-bit audio signal chains where inductor-induced crosstalk is unacceptable. |
| Battery-Powered Sensor Nodes | Industrial PLC I/O Conditioning |
Use Scenario: Wireless temperature/humidity sensor node operating from two AA alkaline cells (3V nominal), needing –2.5V reference for precision SAR ADC. IC Role / Device Role / Timing Role: LTC1261CS8#PBF operates across full 3V–4.2V input range, maintaining ±5% regulation while drawing only 600µA - enabling multi-year battery life. Use Value: Built-in REG pin confirms regulation status to microcontroller - eliminates need for external voltage monitor IC and associated firmware overhead. |
Use Scenario: Programmable logic controller analog input module requiring isolated –5V bias for current-loop receivers and isolation amplifiers. IC Role / Device Role / Timing Role: LTC1261CS8#PBF supplies –5V at 10mA with <1% line/load regulation drift over temperature - used alongside LDO post-regulation for enhanced stability. Use Value: SO-8 package fits standard 0.1" pitch DIP footprints on legacy industrial PCBs - enables drop-in upgrade from obsolete discrete charge pumps. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar regulated negative voltage inverter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX680ESA+ | Fixed –5V output only; 120kHz oscillator; requires two 10µF flying caps; 10mA max output | No adjustable option; higher ripple (~25mV); slower startup; not suitable for <–4V or >10mA loads | Choose for legacy designs already using MAX680 footprint and where –5V fixed output suffices |
| TPS60403DBVR | Adjustable –1.5V to –5.5V; 1MHz switching; 60mA output; integrated soft-start; 2.5V–5.5V input | Higher current capability but larger solution size (requires two 1µF flying caps); no REG pin; different shutdown polarity | Choose when >12mA load or tighter input range (2.5V–5.5V) is required; avoid if REG status signaling is mandatory |
Compared with MAX680ESA+ and TPS60403DBVR, the LTC1261CS8#PBF offers unique combination of adjustable/fixed output flexibility, built-in regulation status flag, and optimized SO-8 layout for low-noise 5–12mA applications - making it preferred for precision analog bias where footprint, ripple, and monitoring are co-constrained.
Availability
LTC1261CS8#PBF is available at Aetrix Electronics and suitable for portable instrumentation, op-amp dual-rail bias, battery-powered sensor nodes, and industrial PLC I/O conditioning requiring stable component supply across extended production lifecycles.
Supply support for LTC1261CS8#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, datasheets, and application engineering for legacy Linear parts including the LTC1261 family.
The LTC1261 series was designed specifically for compact, low-noise regulated negative voltage generation in battery-powered and space-constrained analog systems - emphasizing simplicity, low EMI, and integrated status feedback.
FAQ
What is the maximum input voltage the LTC1261CS8#PBF can tolerate?
The LTC1261CS8#PBF has an absolute maximum supply voltage rating of 9V. However, to maintain safe operation and avoid exceeding the total VCC-to-OUT voltage limit of 12V, the output voltage must be restricted: for example, with an 8.5V input, the output must not exceed –4V. Operation above 8V input is discouraged unless output is clamped or externally limited.
Can the LTC1261CS8#PBF generate –5V from a 3.3V supply?
No. The LTC1261CS8#PBF operates in doubler mode only, so |VOUT| cannot exceed VCC. Generating –5V requires a minimum 5V input. For –5V from 3.3V, the 14-lead LTC1261CS in tripler mode is required - the LTC1261CS8#PBF lacks C2+ and C2– pins needed for tripler operation.
How does the REG pin on the LTC1261CS8#PBF function in practice?
The REG pin on the LTC1261CS8#PBF is an open-drain output that pulls low when |VOUT| is within 5% of the programmed value. It sinks up to 8mA at 5V VCC and tolerates pull-up voltages up to 12V. An external pull-up resistor (e.g., 10kΩ to 3.3V) is mandatory - without it, REG remains floating and cannot signal regulation status to a microcontroller or FPGA.
What capacitor values are mandatory for stable operation of the LTC1261CS8#PBF?
The LTC1261CS8#PBF requires three mandatory capacitors: (1) ≥0.1µF ceramic at VCC-to-GND, (2) 0.1µF ceramic flying cap between C1+ and C1–, and (3) ≥3.3µF low-ESR output cap at OUT-to-GND. Optional 100pF from ADJ/COMP to GND reduces ripple. Using <3.3µF output capacitance increases ripple beyond the specified 5mV typical.
Is the LTC1261CS8#PBF pin-compatible with other members of the LTC1261 family?
No. The LTC1261CS8#PBF uses an 8-pin SO package with dedicated pinout (VCC, C1+, C1–, GND, ADJ/COMP, OUT, REG, SHDN). It is not pin-compatible with the 14-lead LTC1261CS, which includes C2+, C2–, R0, R1, RADJ, and NC pins. Layouts must be redesigned when migrating between packages.
LTC1261CS8#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):
- 3V
- Voltage - Input (Max):
- 8V
- Voltage - Output (Min/Fixed):
- -1.25V
- Voltage - Output (Max):
- -8V
- Current - Output:
- 12mA
- Frequency - Switching:
- 550kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LTC1261CS8#PBF FAQ
1.How can I place an order for LTC1261CS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1261CS8#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 LTC1261CS8#PBF reliable?
The price and inventory of LTC1261CS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1261CS8#PBF is usually 5 days.
3.What payment methods are accepted for LTC1261CS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1261CS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1261CS8#PBF?
LTC1261CS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1261CS8#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 LTC1261CS8#PBF?
For technical support, including LTC1261CS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1261CS8#PBF requirements.
6.How does Aetrix verify that LTC1261CS8#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1261CS8#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 LTC1261CS8#PBF meets industry standards.
7.What is the process for return or replacement of LTC1261CS8#PBF?
All LTC1261CS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1261CS8#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 LTC1261CS8#PBF part is unused and in its original packaging.
Return procedure for LTC1261CS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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