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Analog Devices Inc. LT1111IS8#PBF
- Part No.:
- LT1111IS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1111IS8#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:273
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Product details
Overview
LT1111IS8#PBF from Analog Devices (formerly Linear Technology) is a micropower, 72kHz gated-oscillator DC/DC converter IC supporting step-up, step-down, and inverting topologies. It integrates a 1.5A internal NPN power switch, on-chip 1.25V reference, low-battery detector comparator, and auxiliary gain block. Delivers 5V at 100mA from 3V input (step-up) or 5V at 200mA from 12V input (step-down), used in portable instrumentation and battery-backed supplies.
For engineers reviewing the LT1111IS8#PBF datasheet, LT1111IS8#PBF pinout, LT1111IS8#PBF application, or LT1111IS8#PBF equivalent, key selection considerations include its –40°C to 105°C industrial temperature rating, user-programmable current limit via ILIM pin, fixed/adjustable output variants, and compatibility with surface-mount inductors and Schottky diodes in minimal-component designs.
Technical Context
The LT1111IS8#PBF implements a gated-oscillator architecture where the 72kHz oscillator activates only when feedback voltage falls below the 1.25V internal reference, enabling ultra-low quiescent current (300µA). Its dual-switch configuration (SW1 collector, SW2 emitter) supports reconfigurable topology: SW2 grounded for boost, SW1 tied to VIN for buck, and SW2 driving inductor for inverting operation.
It features two independent analog blocks: Comparator A1 for regulation loop control and Gain Block A2 (open-collector A0 output, SET input) configurable as low-battery detector, UVLO, or linear post-regulator. Current limiting is implemented via external resistor between ILIM and VIN, with trip threshold scaling inversely with resistance (e.g., 220Ω → ~400mA).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temp Range | –40°C to 105°C - qualified for industrial environments without derating. |
| Oscillator Frequency | 72kHz typical - optimized for standard surface-mount inductors (e.g., 22µH–56µH) with minimal EMI. |
| Internal Switch Rating | 1.5A max switch current - enables 100mA @ 5V out from 3V input (boost) or 200mA @ 5V out from 12V input (buck). |
| Quiescent Current | 300µA (switch OFF) - extends battery life in always-on portable systems. |
| Reference Voltage | 1.25V ±2.5% - sets output via external resistor divider (LT1111) or internal resistors (LT1111-5/-12). |
| Comparator Hysteresis | 8–12.5mV - ensures stable regulation without external compensation components. |
| Supply Voltage Range | 2V to 30V - supports wide-input applications including single-cell Li-ion (2.7–4.2V) and 9V/12V battery stacks. |
Pinout & Package
LT1111IS8#PBF is housed in an 8-lead plastic SOIC (S8) package, RoHS-compliant and rated for 150°C/W junction-to-ambient thermal resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ILIM (Pin 1) | Current Limit Programming Input | Resistor from ILIM to VIN sets switch current limit (e.g., 220Ω → ~400mA); tie directly to VIN for full 1.5A capability. |
| VIN (Pin 2) | Main Power Input | Accepts 2V–30V; powers internal circuitry and supplies SW1 in buck mode. |
| SW1 (Pin 3) | Power Switch Collector | In boost: drives inductor/diode; in buck: connects to VIN; max voltage = 50V. |
| SW2 (Pin 4) | Power Switch Emitter | In boost: connected to GND; in buck: drives inductor/diode; must not fall below –0.5V. |
| GND (Pin 5) | Analog & Power Ground | Common reference for feedback, comparator, and gain block; requires low-impedance PCB connection. |
| A0 (Pin 6) | Auxiliary Gain Block Output | Open-collector output sinking up to 300µA; used for low-battery detection or error amplification. |
| SET (Pin 7) | Gain Block Inverting Input | Connects to resistor divider for comparator trip point; referenced to internal 1.25V. |
| FB/SENSE (Pin 8) | Feedback Input / Fixed-Voltage Sense | In LT1111: connects to resistor divider; in LT1111-5/-12: internally connected to output-setting resistors. |
Key Features
| Feature | Design Value |
|---|---|
| Topology Flexibility | Single IC supports boost, buck, and inverting configurations via pin reconnection - eliminates need for multiple dedicated converters. |
| User-Programmable Current Limit | External resistor on ILIM pin sets precise switch current threshold - prevents inductor saturation and switch overstress across wide VIN ranges. |
| Integrated Low-Battery Detector | Gain block (A2) + 1.25V reference enables accurate undervoltage warning with <12.5mV hysteresis - no external comparator required. |
| Micropower Operation | 300µA quiescent current in idle state - extends runtime in battery-powered devices such as handheld test equipment. |
| Minimal External Components | Only three external parts needed for basic operation (inductor, diode, output capacitor) - reduces BOM cost and board space. |
Applications
| Battery-Powered Portable Instruments | Flash Memory VPP Generators |
|---|---|
|
Use Scenario: Handheld multimeters and oscilloscopes powered by two AA cells (2.0–3.2V) requiring stable 5V rail for microcontroller and analog front-end. IC Role / Device Role / Timing Role: Step-up DC/DC converter generating regulated 5V output; regulates via FB pin feedback and 72kHz gated oscillator. Use Value: Enables >100mA continuous output from low-voltage batteries while consuming only 300µA quiescent current during standby. |
Use Scenario: Embedded systems programming NAND/NOR flash memory requiring +12V VPP during write/erase cycles. IC Role / Device Role / Timing Role: Fixed-output step-up converter (LT1111IS8-12 variant) delivering 12V at 50mA from 3.3V system rail. Use Value: Eliminates need for separate high-voltage charge pump IC; uses same inductor footprint as 5V version for design reuse. |
| Uninterruptible Backup Supplies | Laptop/Palmtop Peripheral Cards |
|
Use Scenario: Real-time clock (RTC) backup circuit maintaining SRAM and timekeeping during main power loss using coin cell (3V). IC Role / Device Role / Timing Role: Micropower step-up converter sustaining 5V rail from depleting 2.5–3.0V battery; ILIM pin disables current limit to maximize efficiency at light load. Use Value: Maintains >72-hour hold-up time with <1µA total system leakage due to 300µA IQ and shutdown-capable architecture. |
Use Scenario: PC Card (PCMCIA) add-on modules drawing 100mA at 5V from 3.3V host bus, requiring isolated, compact power conversion. IC Role / Device Role / Timing Role: Buck-mode converter (SW1→VIN, SW2→inductor) stepping 3.3V down to 5V-compatible logic supply with minimal ripple. Use Value: Achieves >85% efficiency at 100mA with 22µH inductor and MBRS130T3 Schottky diode - fits within tight card thickness constraints. |
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 |
|---|---|---|---|
| LT1110CS8#PBF | Lower minimum input voltage (0.9V vs 2V); 120kHz oscillator; 0.8A switch; no A0 gain block. | Better suited for single-cell alkaline (0.9–1.8V) or NiMH (0.9–1.4V) inputs; lacks auxiliary comparator/gain functionality. | Select LT1110 if input drops below 2V; choose LT1111IS8#PBF when industrial temp range, programmable current limit, or low-battery detection are required. |
| MAX761CSA+ | Fixed 5V/12V outputs only; 100kHz oscillator; 1.2A switch; no ILIM pin; different pinout (8-pin SO). | Drop-in replacement only for fixed-output use cases; lacks adjustable topology and current limit flexibility. | Use MAX761CSA+ for cost-sensitive, fixed-output designs where topology reconfiguration is unnecessary. |
Compared with LT1110CS8#PBF and MAX761CSA+, the LT1111IS8#PBF uniquely combines industrial temperature rating, user-programmable current limiting, and dual-function analog blocks - making it optimal for ruggedized portable instruments requiring both power conversion and system monitoring.
Availability
LT1111IS8#PBF is available at Aetrix Electronics and suitable for battery-powered portable instruments, uninterruptible backup supplies, flash memory VPP generation, and laptop peripheral cards requiring stable component supply across extended temperature ranges.
Supply support for LT1111IS8#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; Linear's legacy precision analog and power management ICs remain industry benchmarks for performance and reliability.
The LT1111 product line was designed for ultra-low-power, multi-topology DC/DC conversion in space-constrained portable and battery-operated systems - emphasizing minimal external components, wide input range, and integrated system monitoring functions.
FAQ
What is the maximum input voltage rating for the LT1111IS8#PBF?
The LT1111IS8#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 12.6V in step-up mode. Exceeding 30V in buck operation risks violating internal transistor breakdown limits, so design margins should maintain VIN ≤ 30V for reliable long-term operation of the LT1111IS8#PBF.
Can the LT1111IS8#PBF be used in inverting (positive-to-negative) configurations?
Yes, the LT1111IS8#PBF supports inverting operation by connecting SW2 to the output inductor and grounding the feedback network's high side. In this mode, it generates negative outputs such as –5V from a +5V input. The LT1111IS8#PBF requires a Schottky catch diode (e.g., MBRS130T3) and limits |VOUT| to ≤6.2V unless modified with external components per Figure 7 in the datasheet.
How does the ILIM pin function in the LT1111IS8#PBF, and what resistor value sets 600mA current limit?
The ILIM pin on the LT1111IS8#PBF sinks current proportional to switch conduction; an external resistor between ILIM and VIN sets the current limit threshold. Based on the "Maximum Switch Current vs RLIM" curve, a 56Ω resistor programs a ~600mA limit. This prevents inductor saturation and switch overstress when input voltage varies - a critical feature for robust operation of the LT1111IS8#PBF in wide-range battery applications.
What is the purpose of the A0 and SET pins on the LT1111IS8#PBF?
The A0 (Pin 6) and SET (Pin 7) pins form an auxiliary gain block: SET is the inverting input referenced to the internal 1.25V reference, and A0 is an open-collector output capable of sinking 300µA. Together, they enable configurable functions like low-battery detection (using a resistor divider on SET), UVLO, or error amplification - extending the LT1111IS8#PBF's utility beyond basic regulation into system-level monitoring.
Is the LT1111IS8#PBF pin-compatible with the LT1111CS8#PBF?
Yes, the LT1111IS8#PBF and LT1111CS8#PBF share identical 8-pin SOIC (S8) packaging, pinout, and electrical functionality. The only difference is temperature grade: LT1111IS8#PBF is rated for –40°C to 105°C (industrial), while LT1111CS8#PBF is rated for 0°C to 70°C (commercial). Designs targeting extended temperature operation can directly substitute LT1111IS8#PBF without layout changes.
LT1111IS8#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:
- -40°C ~ 105°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1111IS8#PBF FAQ
1.How can I place an order for LT1111IS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1111IS8#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 LT1111IS8#PBF reliable?
The price and inventory of LT1111IS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1111IS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1111IS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1111IS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1111IS8#PBF?
LT1111IS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1111IS8#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 LT1111IS8#PBF?
For technical support, including LT1111IS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1111IS8#PBF requirements.
6.How does Aetrix verify that LT1111IS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1111IS8#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 LT1111IS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1111IS8#PBF?
All LT1111IS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1111IS8#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 LT1111IS8#PBF part is unused and in its original packaging.
Return procedure for LT1111IS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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