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Analog Devices Inc. LTC1261IS8#PBF
- Part No.:
- LTC1261IS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1261IS8#PBF.pdf
- Description:
- IC REG CHARGE PUMP ADJ 12MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:591
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Product details
Overview
LTC1261IS8#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, 5mV typical output ripple, and features an open-drain REG pin indicating regulation status. Designed for industrial temperature range (–40°C to +85°C), it supports fixed or adjustable outputs (e.g., –4V, –4.5V, –5V) in an 8-lead SO package.
For engineers reviewing the LTC1261IS8#PBF datasheet, LTC1261IS8#PBF pinout, LTC1261IS8#PBF application, or LTC1261IS8#PBF equivalent, key selection considerations include its doubler-mode operation, shutdown current of 5µA, internal 1.24V reference, ADJ/COMP compensation capability, and compatibility with minimal external components (one 0.1µF flying capacitor plus input/output bypass caps).
Technical Context
The LTC1261IS8#PBF operates exclusively in doubler mode-unlike the 14-lead LTC1261CS-using a single flying capacitor between C1+ and C1– to invert VCC and generate VOUT = –(1× to 1×)VCC. Its charge pump is clocked at a fixed 550kHz internal oscillator frequency, and regulation is achieved via cycle-by-cycle duty-cycle control of the pump based on feedback at the ADJ/COMP pin referenced to the internal 1.24V bandgap.
It integrates a precision 1.24V reference, open-drain REG output (sinking up to 8mA at 5V VCC), and shutdown logic with internal 5µA pull-down on SHDN. The device requires no external resistors for fixed-output variants (e.g., LTC1261IS8-4#PBF), while adjustable versions use the ADJ/COMP pin with external or internal resistor dividers to set output voltage between –1.25V and –8V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | Adjustable from –1.25V to –8V; fixed options include –4V, –4.5V, –5V - enables direct biasing of GaAs FETs or dual-supply op-amps without negative rails. |
| Output Regulation Accuracy | ±5% over load (0–12mA) and temperature (–40°C to +85°C) - ensures stable bias under varying load and environmental conditions. |
| Output Ripple | 5mV typical at 5mA load and –4V output - meets low-noise analog supply requirements without additional filtering. |
| Supply Current | 600µA typical operating, 5µA in shutdown - extends battery life in portable instrumentation and sensor nodes. |
| Oscillator Frequency | 550kHz fixed internal clock - allows compact 0.1µF ceramic flying capacitors and minimizes EMI compared to lower-frequency charge pumps. |
| REG Pin Function | Open-drain output asserting low when |VOUT| is within 5% of set value - provides power-valid signal for system sequencing and fault monitoring. |
| Operating Temperature | –40°C to +85°C industrial grade - qualified for automotive body electronics, industrial PLC I/O, and outdoor embedded systems. |
Pinout & Package
Package: 8-lead plastic SO (SO-8), 150°C/W junction-to-ambient thermal resistance, narrow-body outline.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VCC) | Positive power supply input | Accepts 3V–8V; must be bypassed with ≥0.1µF ceramic capacitor close to pin to sustain charge pump peak currents. |
| 2 (C1+) | Flying capacitor positive terminal | Connects to one end of 0.1µF flying capacitor; forms doubler-stage charge transfer path with C1–. |
| 3 (C1–) | Flying capacitor negative terminal | Connects to other end of 0.1µF flying capacitor; floating in tripler mode (not applicable to LTC1261IS8#PBF). |
| 4 (GND) | Analog ground reference | Low-impedance return for charge pump, regulation circuitry, and bypass capacitors; critical for regulation accuracy. |
| 5 (ADJ/COMP) | Feedback and compensation node | Accepts divided VOUT for regulation; also serves as optional compensation point (e.g., 100pF to GND) to reduce ripple. |
| 6 (OUT) | Negative regulated output | Delivers –1.25V to –8V; requires ≥3.3µF low-ESR output capacitor for specified 5mV ripple performance. |
| 7 (REG) | Regulation status indicator | Open-drain output pulled low when |VOUT| is within 5% of target - used for power-good signaling or enable sequencing. |
| 8 (SHDN) | Shutdown control input | Logic-low enables operation; floating defaults to active via internal 5µA pull-down; high disables pump and reduces IQ to 5µA. |
Key Features
| Feature | Design Value |
|---|---|
| Doubler-mode only architecture | Eliminates need for C2+ and C2– pins, enabling compact SO-8 footprint and simplified layout versus 14-lead tripler variants. |
| Integrated 1.24V precision reference | Enables accurate output regulation without external references; referenced to OUT (not GND), supporting true negative rail generation. |
| REG pin with 8mA sink capability | Allows direct interfacing with TTL/CMOS logic or optocouplers for system-level power sequencing and fault reporting. |
| 5µA shutdown quiescent current | Supports ultra-low-power sleep modes in battery-backed data loggers, wearables, and remote sensors. |
| ADJ/COMP pin dual functionality | Permits both output voltage programming (via resistor divider) and loop compensation (via 100pF capacitor) using same terminal. |
Applications
| GaAs FET Bias Generator | Negative Supply for Op-Amp Circuits |
|---|---|
Use Scenario: Providing stable –4V gate bias to GaAs FETs in RF front-end modules operating from a 5V main rail. IC Role / Device Role / Timing Role: Regulated negative voltage inverter generating precise, low-ripple bias independent of load transients. Use Value: Enables consistent FET pinch-off voltage across temperature and process variation, improving RF gain stability and noise figure. |
Use Scenario: Generating –5V rail for dual-supply operational amplifiers in portable medical sensors powered by a single 3.3V Li-ion cell. IC Role / Device Role / Timing Role: Compact, low-quiescent-current negative supply generator supporting rail-to-rail input/output op-amp operation. Use Value: Eliminates need for discrete inductor-based DC/DC converters, reducing BOM cost and EMI while maintaining <5mV output noise. |
| Battery-Powered Instrumentation | Industrial PLC Analog I/O Module |
Use Scenario: Powering precision ADC reference buffers and DAC output stages in handheld multimeters with 3V coin-cell supply. IC Role / Device Role / Timing Role: Efficient switched-capacitor inverter delivering regulated –2.5V from 3V input with <600µA quiescent draw. Use Value: Extends battery life beyond 100 hours while maintaining reference accuracy better than ±0.1% over –20°C to +70°C. |
Use Scenario: Generating isolated –12V bias for current-loop transmitter circuits in DIN-rail mounted programmable logic controllers. IC Role / Device Role / Timing Role: Industrial-grade voltage inverter providing robust negative rail under wide ambient temperature swings and EMI-rich factory environments. Use Value: Guaranteed –40°C to +85°C operation and 5% regulation ensure reliable 4–20mA loop compliance across full industrial temperature range. |
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 |
|---|---|---|---|
| LTC1261CS8#PBF | Same SO-8 package and pinout, but rated for 0°C to 70°C commercial temperature range; identical electrical specs. | Suitable for consumer or lab equipment where extended temperature is not required. | Select LTC1261CS8#PBF for cost-sensitive commercial designs; LTC1261IS8#PBF is mandatory for industrial environments. |
| MAX680ESA+ | Fixed –5V output only; no ADJ/COMP pin; higher 10mV typical ripple; 125µA quiescent current; SO-8 package. | Lacks regulation monitoring (no REG pin) and adjustable output; simpler for fixed-rail-only use cases. | Choose MAX680ESA+ only when fixed –5V suffices and lowest IQ is critical; LTC1261IS8#PBF offers flexibility, regulation feedback, and tighter ripple. |
Compared with LTC1261CS8#PBF, the LTC1261IS8#PBF adds industrial temperature qualification without sacrificing performance; versus MAX680ESA+, it trades slightly higher quiescent current for adjustable output, regulation monitoring, and half the output ripple - making it superior for precision analog biasing.
Availability
LTC1261IS8#PBF is available at Aetrix Electronics and suitable for industrial automation, battery-powered instrumentation, RF biasing, and precision analog supply applications requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC1261IS8#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 space-constrained systems where inductors are undesirable - targeting portable test equipment, telecom line cards, and industrial sensor interfaces.
FAQ
What is the maximum output current capability of the LTC1261IS8#PBF?
The LTC1261IS8#PBF delivers up to 12mA output current while maintaining ±5% regulation across the full industrial temperature range (–40°C to +85°C). This rating assumes proper external capacitor selection: a 0.1µF ceramic flying capacitor, ≥3.3µF low-ESR output capacitor, and ≥0.1µF VCC bypass. At higher loads or elevated temperatures, output voltage may drift beyond regulation limits; derating is recommended for continuous 10mA+ operation above 70°C.
Does the LTC1261IS8#PBF support tripler-mode operation?
No, the LTC1261IS8#PBF does not support tripler-mode operation. It is a dedicated doubler-mode device with only C1+ and C1– pins - unlike the 14-lead LTC1261CS which includes C2+ and C2– for tripler configuration. The LTC1261IS8#PBF's internal architecture and pinout are optimized for simplicity and SO-8 compatibility, limiting its output magnitude to |VOUT| ≤ VCC. Tripler functionality (e.g., –5V from 3.3V) requires the LTC1261CS in 14-lead SO package.
How is the REG pin used in system design with the LTC1261IS8#PBF?
The REG pin on the LTC1261IS8#PBF is an open-drain output that pulls low when the absolute value of VOUT is within 5% of its programmed setpoint. To use it, an external pull-up resistor (e.g., 10kΩ to 3.3V or 5V) is required. The pin sinks up to 8mA at 5V VCC and tolerates voltages up to 12V above ground. In practice, REG serves as a "power-valid" signal to enable downstream circuitry (e.g., ADCs, DACs) only after stable negative rail establishment, preventing initialization errors in mixed-signal systems.
Can the LTC1261IS8#PBF generate –8V output, and what are the supply constraints?
Yes, the LTC1261IS8#PBF can be configured for –8V output using an external resistor divider on the ADJ/COMP pin, but only when VCC ≥ 8.5V. Per Absolute Maximum Ratings, the total VCC–VOUT differential must not exceed 12V; thus, –8V output requires VCC ≤ 4V to stay within safe margin - a contradiction. Therefore, –8V is achievable only with VCC = 8V (yielding VCC–VOUT = 16V), which violates the 12V limit. The practical maximum |VOUT| is –7V with VCC = 5V, or –4.5V with VCC = 3.3V. Always consult the "Output Voltage vs Supply Voltage" curves in the datasheet for valid combinations.
What capacitor values and types are mandatory for stable operation of the LTC1261IS8#PBF?
For stable operation, the LTC1261IS8#PBF requires three mandatory capacitors: (1) a 0.1µF X7R ceramic flying capacitor between C1+ and C1–; (2) a ≥0.1µF ceramic bypass capacitor between VCC and GND, placed adjacent to the IC; and (3) a ≥3.3µF low-ESR output capacitor (e.g., 4.7µF tantalum or polymer) between OUT and GND. A 100pF ceramic capacitor from ADJ/COMP to GND is strongly recommended to suppress output ripple. Avoid high-ESR output capacitors alone - pair them with a parallel 0.1µF ceramic to prevent regulation loop instability.
LTC1261IS8#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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LTC1261IS8#PBF FAQ
1.How can I place an order for LTC1261IS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1261IS8#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 LTC1261IS8#PBF reliable?
The price and inventory of LTC1261IS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1261IS8#PBF is usually 5 days.
3.What payment methods are accepted for LTC1261IS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1261IS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1261IS8#PBF?
LTC1261IS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1261IS8#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 LTC1261IS8#PBF?
For technical support, including LTC1261IS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1261IS8#PBF requirements.
6.How does Aetrix verify that LTC1261IS8#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1261IS8#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 LTC1261IS8#PBF meets industry standards.
7.What is the process for return or replacement of LTC1261IS8#PBF?
All LTC1261IS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1261IS8#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 LTC1261IS8#PBF part is unused and in its original packaging.
Return procedure for LTC1261IS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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