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Analog Devices Inc. LT1108CS8-12#TRPBF
- Part No.:
- LT1108CS8-12#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1108CS8-12#TRPBF.pdf
- Description:
- IC REG BUCK BOOST 12V 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,808
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Product details
Overview
LT1108CS8-12#TRPBF from Analog Devices (formerly Linear Technology) is a micropower, fixed-output 12V DC/DC converter IC operating in step-up, step-down, or inverting topologies. It delivers up to 150mA at 12V from a 2V–12V input in boost mode and supports 30V max input in buck mode. With 110µA quiescent current, 70% duty cycle, and internal 1A power switch, it targets battery-powered instrumentation requiring stable 12V bias rails.
For engineers reviewing the LT1108CS8-12#TRPBF datasheet, LT1108CS8-12#TRPBF pinout, LT1108CS8-12#TRPBF application, or LT1108CS8-12#TRPBF equivalent, key selection criteria include its fixed 12V output accuracy (±5% over temperature), programmable current limit via ILIM pin, on-chip low-battery comparator, and compatibility with standard 8-pin SOIC layout for space-constrained portable designs.
Technical Context
The LT1108CS8-12#TRPBF implements a gated-oscillator architecture with a 19kHz typical switching frequency and 36µs fixed ON-time, enabling discontinuous conduction mode operation across wide input ranges. Its internal 1.245V reference feeds a comparator that controls oscillator gating based on feedback voltage at the SENSE pin.
It integrates dual functionality: a main NPN power switch (1.5A max peak, 0.65V saturation at 650mA in boost) and an auxiliary gain block (A0/A2) configurable as low-battery detector or error amplifier. Pin 8 (SENSE) connects directly to output in fixed-12V versions, eliminating external resistors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 12V ±5% (guaranteed over 0°C–70°C, 11.4V–12.6V min/max) |
| Input Voltage Range | 2V–12V (step-up), up to 30V (step-down); enables single-cell AA to 9V battery inputs |
| Quiescent Current | 110µA (switch OFF), 250µA typical in boost mode - extends battery life in always-on systems |
| Switch Current Limit | Programmable via resistor from ILIM to VIN; 400mA with 220Ω - prevents inductor saturation and switch overstress |
| Oscillator Frequency | 14–25kHz (typical 19kHz); fixed 36µs ON-time ensures predictable timing without external components |
| Power Switch | Internal NPN transistor rated 1.5A peak, 0.65V VCE(SAT) at 650mA - reduces external component count and PCB area |
| Operating Temperature | 0°C to 70°C ambient - validated for commercial-grade portable electronics environments |
Pinout & Package
LT1108CS8-12#TRPBF uses an 8-lead plastic SOIC (S8) package, 3.9mm × 4.9mm body, 1.27mm pitch, RoHS-compliant and tape-and-reel packaged (#TRPBF).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - ILIM | Current limit programming input | Connect resistor to VIN to set precise switch current threshold; open or tied to VIN for full 1.5A capability |
| 2 - VIN | Main power supply input | Accepts 2V–30V; powers internal circuitry and switch driver; decoupling capacitor required |
| 3 - SW1 | Collector of internal NPN switch | In boost: connects to inductor/diode node; in buck: ties to VIN; handles full switch current |
| 4 - SW2 | Emiter of internal NPN switch | In boost: grounded; in buck: drives inductor; must not fall below –0.5V - mandates Schottky diode use |
| 5 - GND | Analog and power ground reference | Common return for feedback, gain block, and switch; requires low-impedance PCB connection |
| 6 - A0 | Open-collector output of auxiliary gain block | Sinks 100µA max; used for low-battery flag, post-regulator drive, or UVLO signaling |
| 7 - SET | Inverting input of auxiliary gain block | Connected to 1.245V reference internally; forms precision comparator with external resistor divider |
| 8 - SENSE | Feedback input (fixed 12V version) | Internally connected to output divider; must tie directly to 12V output - no external resistors needed |
Key Features
| Feature | Design Value |
|---|---|
| Fixed 12V output with internal resistor network | Eliminates external feedback resistors - reduces BOM count and layout complexity for dedicated 12V rails |
| Programmable switch current limit | Enables robust operation across wide input voltage ranges (e.g., 2V–9V batteries) without inductor saturation or thermal runaway |
| On-chip low-battery comparator | Uses internal 1.245V reference and SET/A0 pins to generate precise undervoltage warning at user-defined trip point |
| Gated-oscillator architecture | Reduces quiescent current to 110µA by disabling high-current circuitry when regulation is met - critical for multi-year battery life |
| Triple-mode topology support | Single IC supports boost (2V→12V), buck (9V→12V), and inverting (5V→–12V) configurations - simplifies design reuse across power domains |
Applications
| Portable Instrumentation Power | LCD Bias Generation |
|---|---|
|
Use Scenario: Handheld multimeters and portable oscilloscopes require isolated 12V rails for analog front-end op-amps and ADC references. IC Role / Device Role / Timing Role: LT1108CS8-12#TRPBF acts as primary 12V boost converter, sourcing 150mA from two AA cells while maintaining <1% output ripple under dynamic load. Use Value: Fixed 12V output eliminates trimming; 110µA quiescent current extends battery life beyond 500 hours in sleep mode. |
Use Scenario: Monochrome LCD modules in medical handhelds need negative bias (–12V) for contrast control alongside +5V logic. IC Role / Device Role / Timing Role: LT1108CS8-12#TRPBF configured in inverting topology generates –12V from 5V USB input, using SW2 as emitter-driven output node. Use Value: Internal 1.245V reference and SENSE pin enable accurate –12V regulation without external scaling resistors. |
| Cellular Telephone Peripherals | Battery Backup Supply |
|
Use Scenario: GSM modem add-on cards for ruggedized field tablets require 12V for RF power amplifiers during transmission bursts. IC Role / Device Role / Timing Role: LT1108CS8-12#TRPBF operates in step-down mode from 12V main rail to regulated 12V output, delivering 300mA with <50mV line regulation. Use Value: Programmable ILIM pin limits peak switch current to 650mA, preventing thermal shutdown during 200ms TX pulses. |
Use Scenario: Industrial PLCs use supercapacitor-backed 12V rails to maintain real-time clock and SRAM during AC mains failure. IC Role / Device Role / Timing Role: LT1108CS8-12#TRPBF serves as low-quiescent buck-boost controller, sustaining 12V output from decaying 3V–9V capacitor voltage. Use Value: 2V minimum input enables >95% energy extraction from backup capacitors before brownout. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1307CS8-12#TRPBF | Higher 1.3MHz switching frequency, lower 50µA IQ, but only 300mA max output current and no ILIM pin | Better for compact, high-efficiency 12V supplies >200mA; unsuitable where programmable current limiting or wide VIN range (2V–30V) is required | Select LT1307CS8-12#TRPBF only if board space and efficiency outweigh need for robust current limiting and ultra-low-VIN operation. |
| TPS61040DRVR | Adjustable output (1.8V–28V), 28V absolute max VIN, 400mA switch, but 250µA IQ and no integrated comparator/gain block | Preferred for flexible multi-rail systems; lacks built-in low-battery detection and requires external feedback resistors for 12V | Choose TPS61040DRVR when output voltage flexibility and higher current are prioritized over integrated monitoring features and minimal BOM count. |
Compared with LT1307CS8-12#TRPBF and TPS61040DRVR, the LT1108CS8-12#TRPBF uniquely combines fixed 12V accuracy, sub-120µA quiescent current, programmable current limiting, and on-chip comparator functionality - making it optimal for cost-sensitive, battery-critical 12V bias generation where external component count and long-term reliability are paramount.
Availability
LT1108CS8-12#TRPBF is available at Aetrix Electronics and suitable for portable instrumentation, LCD bias generation, and battery backup supplies requiring stable component supply, long-lifecycle assurance, and consistent parametric performance across production batches.
Supply support for LT1108CS8-12#TRPBF 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 industrial, automotive, communications, and healthcare markets.
The LT1108 product line was designed specifically for ultra-low-power, multi-topology DC/DC conversion in space-constrained portable electronics - emphasizing micropower operation, minimal external component count, and robustness across wide input voltage ranges.
FAQ
What is the guaranteed output voltage tolerance for LT1108CS8-12#TRPBF over temperature?
The LT1108CS8-12#TRPBF guarantees a 12V output within ±5% (11.4V to 12.6V) across the full 0°C to 70°C operating temperature range. This specification is verified per Electrical Characteristics table Note 2, which confirms fixed-output versions maintain regulation within this band regardless of input voltage or load current within rated limits.
Can LT1108CS8-12#TRPBF operate from a single 1.5V alkaline cell?
No - the LT1108CS8-12#TRPBF requires a minimum 2V input for step-up operation, as specified in Absolute Maximum Ratings and Electrical Characteristics. A single 1.5V cell falls below this threshold; two series AA cells (3V nominal) are the practical minimum for reliable 12V boost conversion using LT1108CS8-12#TRPBF.
How is current limiting implemented on LT1108CS8-12#TRPBF?
Current limiting on LT1108CS8-12#TRPBF is implemented via the ILIM pin: connecting a resistor between ILIM and VIN sets the peak switch current threshold. For example, a 220Ω resistor limits current to ~400mA. The internal sensing circuit compares voltage across an 80Ω internal resistor plus the external RLIM to trigger switch turn-off within ~2µs.
Does LT1108CS8-12#TRPBF require external feedback resistors to set the 12V output?
No - the LT1108CS8-12#TRPBF is a fixed-output variant with internal resistor dividers connected to the SENSE pin. Pin 8 (SENSE) must be connected directly to the 12V output node; no external resistors are required or recommended, ensuring factory-trimmed accuracy and eliminating drift-related errors.
What is the maximum allowable voltage on the SW2 pin of LT1108CS8-12#TRPBF?
The SW2 pin of LT1108CS8-12#TRPBF must never be allowed to fall below –0.5V, as stated in Absolute Maximum Ratings. In step-down or inverting operation, SW2 may swing slightly negative during switch turn-off; a Schottky diode (e.g., 1N5818) is mandatory to clamp excursion and prevent destructive internal power dissipation.
LT1108CS8-12#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Up, Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2V
- Voltage - Input (Max):
- 30V
- Voltage - Output (Min/Fixed):
- 12V
- Voltage - Output (Max):
- -
- Current - Output:
- 1.5A (Switch)
- Frequency - Switching:
- 19kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1108CS8-12#TRPBF FAQ
1.How can I place an order for LT1108CS8-12#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1108CS8-12#TRPBF 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 LT1108CS8-12#TRPBF reliable?
The price and inventory of LT1108CS8-12#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1108CS8-12#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1108CS8-12#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1108CS8-12#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1108CS8-12#TRPBF?
LT1108CS8-12#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1108CS8-12#TRPBF 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 LT1108CS8-12#TRPBF?
For technical support, including LT1108CS8-12#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1108CS8-12#TRPBF requirements.
6.How does Aetrix verify that LT1108CS8-12#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1108CS8-12#TRPBF 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 LT1108CS8-12#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1108CS8-12#TRPBF?
All LT1108CS8-12#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1108CS8-12#TRPBF, 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 LT1108CS8-12#TRPBF part is unused and in its original packaging.
Return procedure for LT1108CS8-12#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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