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Analog Devices Inc. LT1111CS8#PBF
- Part No.:
- LT1111CS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1111CS8#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:790
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Product details
Overview
LT1111CS8#PBF from Analog Devices (formerly Linear Technology) is a micropower step-up/step-down DC/DC converter IC with integrated 1A NPN power switch, 72kHz gated oscillator, and on-chip low-battery detector comparator. It operates from 2V to 30V input, delivers up to 100mA at 5V from 3V input (step-up), supports adjustable or fixed 5V/12V outputs, and uses only three external components in standard boost/buck configurations - widely deployed in portable instrumentation and battery-backed peripherals.
For engineers reviewing the LT1111CS8#PBF datasheet, LT1111CS8#PBF pinout, LT1111CS8#PBF application, or LT1111CS8#PBF equivalent, key selection criteria include its 72kHz oscillator frequency, 1.25V internal reference, programmable current limit via ILIM pin, ±0.5V SW2 voltage limit, and SO-8 package compatibility with surface-mount inductor designs requiring minimal board area.
Technical Context
The LT1111CS8#PBF implements a gated-oscillator architecture: the 72kHz oscillator activates only when the FB/SENSE pin voltage falls below the 1.25V internal reference, enabling ultra-low quiescent current (300µA). Its dual-mode operation-step-up (boost) with SW2 grounded and SW1 driving the inductor/diode, or step-down (buck) with SW1 tied to VIN and SW2 driving the inductor-relies on external component configuration rather than internal topology switching.
Control is achieved through direct feedback comparison (A1 comparator), auxiliary gain block (A2 op-amp with SET/A0 pins for low-battery detection or post-regulation), and user-programmable current limiting via resistor between ILIM and VIN. The device's 1.5A maximum switch current, 0.65V typical SW saturation voltage at 650mA (VIN = 3V), and built-in hysteresis (12.5mV comparator, 50mV output) ensure stable regulation across temperature and load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2V to 30V - supports wide battery input (e.g., single Li-ion down to 2V, or 24V industrial rails) without external regulators. |
| Oscillator Frequency | 72kHz (typical) - optimized for off-the-shelf surface-mount inductors with low core loss and minimal EMI. |
| Output Voltage Options | Adjustable (via FB/SENSE) or fixed 5V/12V - LT1111CS8#PBF is the adjustable version; -5/-12 variants integrate internal resistive dividers. |
| Quiescent Current | 300µA (switch OFF) - enables multi-year battery life in always-on remote sensors and backup supplies. |
| Switch Current Limit | Programmable up to 1.5A - resistor from ILIM to VIN sets precise peak current (e.g., 400mA with 220Ω), preventing inductor saturation and switch overstress. |
| Operating Temperature | 0°C to 70°C - commercial-grade rating suitable for consumer electronics, handhelds, and non-automotive embedded systems. |
| Package | 8-lead SOIC (SO-8) - RoHS-compliant, surface-mountable, with θJA = 150°C/W for thermal management in compact PCB layouts. |
Pinout & Package
LT1111CS8#PBF is housed in an 8-lead plastic SOIC (SO-8) package with standard JEDEC MS-012AC dimensions (4.9mm × 6.0mm × 1.75mm), gull-wing leads, and exposed pad not present. Pin 1 is marked by a beveled corner or dot.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ILIM (Pin 1) | Current Limit Programming Input | Connect to VIN via resistor to set peak switch current; open or tied directly to VIN for max 1.5A limit. |
| VIN (Pin 2) | Main Power Input | Supplies internal circuitry and power switch; absolute max 36V; must be decoupled near pin. |
| SW1 (Pin 3) | Power Switch Collector | In step-up: connects to inductor/diode node; in step-down: ties directly to VIN; rated to 50V. |
| SW2 (Pin 4) | Power Switch Emitter | In step-up: connects to GND; in step-down: drives inductor; must not go below –0.5V. |
| GND (Pin 5) | Analog & Power Ground | Common return for feedback, bias, and switch paths; requires low-impedance PCB connection. |
| A0 (Pin 6) | Auxiliary Gain Block Output | Open-collector output sinking up to 300µA; used for low-battery flag, error signal, or UVLO. |
| SET (Pin 7) | Auxiliary Gain Block Inverting Input | Connects to resistor divider for comparator trip point; referenced to internal 1.25V. |
| FB/SENSE (Pin 8) | Feedback Input / Voltage Sense | Compares against 1.25V reference; in adjustable version, connects to external resistor divider for VOUT setting. |
Key Features
| Feature | Design Value |
|---|---|
| Gated Oscillator Architecture | Enables 300µA quiescent current by disabling high-current circuitry when regulation is satisfied - critical for battery longevity. |
| Integrated 1A NPN Power Switch | Eliminates need for external transistor in ≤100mA step-up or ≤200mA step-down applications, reducing BOM count and layout complexity. |
| User-Programmable Current Limit | Resistor from ILIM to VIN sets precise switch current threshold (e.g., 400mA with 220Ω), protecting inductor and switch under varying input conditions. |
| On-Chip Low-Battery Detector | Auxiliary gain block (SET/A0 pins) provides configurable undervoltage warning with <12.5mV hysteresis - no external comparator required. |
| Multi-Topology Support | Single IC supports step-up, step-down, and inverting configurations via external component routing - reduces design reuse effort across power architectures. |
Applications
| Portable Instrumentation | Battery-Backed Peripherals |
|---|---|
Use Scenario: Handheld multimeter powered by two AA cells (2.0–3.2V) requiring stable 5V rail for ADC and display. IC Role / Device Role / Timing Role: Step-up DC/DC converter generating regulated 5V output from variable low-voltage battery source. Use Value: Delivers 100mA at 5V with 300µA quiescent current, extending battery life beyond 500 hours while maintaining ±2% output accuracy over temperature. |
Use Scenario: USB add-on card with EEPROM and real-time clock needing 5V backup during main power loss. IC Role / Device Role / Timing Role: Standby-mode DC/DC controller activated only when main supply drops below threshold. Use Value: On-chip low-battery comparator (SET/A0) triggers seamless switchover to coin-cell backup without external supervision logic. |
| Laptop Expansion Modules | Flash Memory VPP Generators |
Use Scenario: PC Card interface module requiring isolated 12V from 3.3V host bus for legacy peripheral signaling. IC Role / Device Role / Timing Role: Step-up converter configured for fixed 12V output using internal resistor network (LT1111CS8#PBF variant supports external feedback). Use Value: 72kHz switching frequency avoids audible noise and simplifies EMI filtering compared to higher-frequency alternatives. |
Use Scenario: Embedded microcontroller programming circuit needing +12V pulse for Flash memory VPP pin during write cycles. IC Role / Device Role / Timing Role: Burst-mode DC/DC generator activated only during programming windows to minimize average power draw. Use Value: Gated oscillator ensures zero static current between pulses - critical for low-duty-cycle, high-voltage generation in space-constrained designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar micropower DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1111CN8#PBF | Dual-inline package (N8) instead of SO-8; identical electrical specs and pinout; θJA = 130°C/W vs 150°C/W. | Suitable for through-hole prototyping or legacy DIP-based systems; less suited for high-density SMT production. | Select when manual assembly, breadboarding, or socket-based testing is required; same schematic and layout except for footprint. |
| LT1111CS8-5#PBF | Fixed 5V output version; internal feedback resistors replace external divider; FB/SENSE pin connected directly to output. | Reduces component count for dedicated 5V conversion; eliminates resistor tolerance errors and layout sensitivity of adjustable version. | Choose when output voltage is fixed at 5V and board space is constrained - no external R1/R2 needed, but no adjustability retained. |
Compared with LT1111CS8#PBF, the LT1111CN8#PBF offers identical performance in a through-hole package for prototyping, while the LT1111CS8-5#PBF removes external feedback components for simplified 5V-only designs - neither is pin-compatible without footprint or schematic revision.
Availability
LT1111CS8#PBF is available at Aetrix Electronics and suitable for portable instrumentation, battery-backed peripherals, and flash memory VPP generation requiring stable component supply, long-term lifecycle support, and guaranteed RoHS compliance.
Supply support for LT1111CS8#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, industrial, automotive, and communications markets.
The LT1111 product line was designed specifically for ultra-low-power, multi-topology DC/DC conversion in space- and battery-constrained applications - emphasizing micropower operation, minimal external parts, and robust thermal performance in SO-8 and DIP packages.
FAQ
What is the maximum input voltage rating for the LT1111CS8#PBF?
The LT1111CS8#PBF has an absolute maximum input voltage (VIN) rating of 36V. However, its specified operating range is 2V to 30V in step-down mode and 2V to 12V in step-up mode. Exceeding 30V in step-down or 12V in step-up may compromise regulation stability or reliability, even if within absolute max limits. Always observe the recommended operating conditions defined in the datasheet for LT1111CS8#PBF.
Can the LT1111CS8#PBF be used in inverting (positive-to-negative) configurations?
Yes, the LT1111CS8#PBF supports inverting configurations. In positive-to-negative mode, SW2 connects to the output capacitor ground, SW1 drives the inductor, and the feedback network references the negative output. The LT1111CS8#PBF's dual-switch topology and internal 1.25V reference enable this without external level-shifting circuitry - confirmed in Linear Technology Application Note AN45 and LT1111CS8#PBF typical application diagrams.
What is the purpose of the A0 and SET pins on the LT1111CS8#PBF?
The A0 (Pin 6) and SET (Pin 7) pins form an auxiliary gain block (op-amp) with the internal 1.25V reference. SET serves as the inverting input; A0 is an open-collector output sinking up to 300µA. This block can implement low-battery detection (via resistor divider to SET), linear post-regulation, or undervoltage lockout - all without external amplifiers. Its use is fully documented in the LT1111CS8#PBF datasheet functional description and BD01 block diagram.
How does the ILIM pin function in the LT1111CS8#PBF?
The ILIM pin (Pin 1) on the LT1111CS8#PBF allows user-programmable current limiting by connecting a resistor between ILIM and VIN. Internal circuitry senses ~0.5% of switch current; when voltage across the external resistor reaches ~0.6V, the switch cycle terminates early. For example, a 220Ω resistor limits peak current to ~400mA. This protects the LT1111CS8#PBF and external inductor under varying input conditions - detailed in the "Using the ILIM Pin" section of the LT1111CS8#PBF datasheet.
Is the LT1111CS8#PBF RoHS compliant and lead-free?
Yes, the LT1111CS8#PBF is RoHS compliant and lead-free. The "#PBF" suffix explicitly denotes lead-free (Pb-free) packaging per Analog Devices' product marking convention. It meets EU RoHS Directive 2011/65/EU and is qualified for commercial temperature range (0°C to 70°C) with JEDEC-standard SO-8 packaging - verified in the official Analog Devices LT1111CS8#PBF product page and packaging specification documents.
LT1111CS8#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:
- Positive or Negative
- Topology:
- Buck, Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2V
- Voltage - Input (Max):
- 30V
- Voltage - Output (Min/Fixed):
- 1.25V
- Voltage - Output (Max):
- 50V (Switch)
- Current - Output:
- 1.5A (Switch)
- Frequency - Switching:
- 72kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1111CS8#PBF FAQ
1.How can I place an order for LT1111CS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1111CS8#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 LT1111CS8#PBF reliable?
The price and inventory of LT1111CS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1111CS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1111CS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1111CS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1111CS8#PBF?
LT1111CS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1111CS8#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 LT1111CS8#PBF?
For technical support, including LT1111CS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1111CS8#PBF requirements.
6.How does Aetrix verify that LT1111CS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1111CS8#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 LT1111CS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1111CS8#PBF?
All LT1111CS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1111CS8#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 LT1111CS8#PBF part is unused and in its original packaging.
Return procedure for LT1111CS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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