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Analog Devices Inc. LT1931IS5#TRM
- Part No.:
- LT1931IS5#TRM
- Manufacturer:
- Analog Devices Inc.
- Package:
- SOT-23-5 Thin, TSOT-23-5
- Datasheet:
-
LT1931IS5#TRM.pdf
- Description:
- IC REG CUK ADJ 1A TSOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:3,930
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Product details
Overview
LT1931IS5#TRM from Analog Devices (formerly Linear Technology) is a high-power, fixed-frequency inverting DC/DC converter IC with integrated 1A switch, operating at 1.2MHz to generate –5V at 350mA or –12V at 150mA from a 5V input. It employs dual-inductor current-mode control in a 5-lead ThinSOT package and delivers ultra-low 1mVP-P output ripple using ceramic capacitors-ideal for MR head bias and CCD supply in compact imaging systems.
For engineers reviewing the LT1931IS5#TRM datasheet, LT1931IS5#TRM pinout, LT1931IS5#TRM application, or LT1931IS5#TRM equivalent, this page provides verified specifications including switching frequency, feedback voltage (–1.255V), shutdown current (<1µA), VCE(SAT) (400mV @ 1A), and input range (2.6V–16V), all confirmed for the LT1931I grade in S5 package.
Technical Context
The LT1931IS5#TRM uses constant-frequency current-mode control with an internal 1.2MHz oscillator and a 1A NPN switch rated to 36V. Its dual-inductor inverting topology filters both input and output currents, enabling low-noise negative rail generation without charge-pump limitations.
It features a precision –1.255V feedback reference with ±20mV tolerance, 84% maximum duty cycle, and built-in current limiting (1.2A typ). The NFB pin sources bias current, requiring external resistive divider design per VOUT = –1.255 × (1 + R1/R2), and supports phase-lead compensation via capacitor across R1.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 1.2MHz - enables use of sub-3mm-height inductors and low-ESR ceramic capacitors for space-constrained designs |
| Output Ripple | 1mVP-P - achieved with X5R ceramic output caps; ensures clean bias for sensitive analog circuits like MR heads |
| Feedback Voltage | –1.255V ±20mV - precise reference for stable regulation of negative outputs; sets output via external resistor divider |
| Switch Current Limit | 1.2A typical - protects internal NPN switch and external components during overload or short-circuit conditions |
| VCE(SAT) | 400mV at 1A - low conduction loss improves efficiency in high-current inverting topologies |
| Input Voltage Range | 2.6V to 16V - supports wide-supply applications including USB-powered and industrial 12V systems |
| Shutdown Current | <1µA - enables ultra-low power-off state for battery-backed or always-on systems |
Pinout & Package
LT1931IS5#TRM is housed in a 5-lead ThinSOT (TSOT-23) package, 1mm profile, JEDEC MO-193 compliant, with exposed pad not connected internally.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pin 1) | Switch collector node | Connects to coupled/uncoupled inductor(s) and Schottky diode anode; high dI/dt node requiring minimal trace area |
| GND (Pin 2) | Power and signal ground reference | Must tie directly to local ground plane; serves as return for switch, feedback amplifier, and shutdown circuitry |
| NFB (Pin 3) | Inverting input of error amplifier | Sources 4–8µA bias current; connects to resistive divider tap; reference voltage is –1.255V |
| SHDN (Pin 4) | Enable/disable control input | Logic-high ≥2.4V enables operation; logic-low ≤0.5V disables with <1µA quiescent draw |
| VIN (Pin 5) | Main power input | Accepts 2.6V–16V; requires local 1µF ceramic bypass cap placed adjacent to pin |
Key Features
| Feature | Design Value |
|---|---|
| Dual-inductor inverting topology | Simultaneously filters input and output current ripple, reducing EMI and enabling <1mVP-P noise with ceramic caps |
| Integrated 1A NPN switch | Eliminates external transistor; rated for 36V VSW, supporting up to 34V VIN-to-VOUT differential |
| Fixed 1.2MHz switching | Ensures predictable EMI spectrum and avoids audio-band noise; enables small magnetics (e.g., Sumida CLS62-100) |
| Low VCE(SAT) (400mV @ 1A) | Minimizes conduction loss in high-current paths, sustaining >75% efficiency at 350mA –5V output |
| Pin-for-pin compatibility with LT1611 | Enables direct upgrade path from 150mA to 350mA output capability without PCB redesign |
Applications
| Disk Drive MR Head Bias | Digital Camera CCD Bias |
|---|---|
Use Scenario: Generating stable –5V bias for magnetoresistive read heads in HDD preamplifiers. IC Role / Device Role / Timing Role: Inverting DC/DC converter providing low-noise, regulated negative supply referenced to system ground. Use Value: 1mVP-P ripple and 1% load regulation ensure signal integrity during high-speed data reads. |
Use Scenario: Supplying –12V bias to CCD image sensors in portable digital cameras. IC Role / Device Role / Timing Role: High-efficiency inverting regulator delivering 150mA at –12V from single 5V rail. Use Value: Dual-inductor topology suppresses switching noise that could induce fixed-pattern noise in captured images. |
| LCD Panel Bias Supply | GaAs FET RF Bias |
Use Scenario: Creating localized –5V to –15V rails for LCD source/gate driver ICs in handheld displays. IC Role / Device Role / Timing Role: Compact, low-profile DC/DC converter mounted near display module for minimal trace inductance. Use Value: ThinSOT package (1mm height) fits tight mechanical envelopes; 84% max duty cycle supports wide VOUT/VIN ratios. |
Use Scenario: Providing low-impedance –5V bias to GaAs FET amplifiers in RF front-end modules. IC Role / Device Role / Timing Role: Negative supply generator with fast transient response and low output impedance. Use Value: Output remains within 1% of nominal during large load steps, preserving amplifier linearity and gain stability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar inverting DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1931AIS5#TRM | 2.2MHz switching (vs. 1.2MHz); 75% max duty cycle; 300mA –5V output (vs. 350mA) | Better suited for size-constrained designs using sub-2mm inductors; lower efficiency at high load | Select when board area and BOM cost outweigh peak current and efficiency requirements |
| LT1611ES5#TRM | 1.4MHz; 150mA –5V output; no dual-inductor filtering; higher output ripple | Legacy solution with lower power capability; lacks LT1931's low-noise topology and current rating | Use only for legacy replacement where 350mA capability and <1mVP-P ripple are not required |
Compared with LT1931AIS5#TRM and LT1611ES5#TRM, the LT1931IS5#TRM delivers highest output current and lowest noise in the same ThinSOT footprint-making it optimal for next-generation imaging and precision analog biasing where performance margins matter.
Availability
LT1931IS5#TRM is available at Aetrix Electronics and suitable for disk drive MR head bias, digital camera CCD bias, and LCD panel bias applications requiring stable component supply, extended temperature operation (–40°C to 85°C), and long-term industrial availability.
Supply support for LT1931IS5#TRM 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 technical and manufacturing continuity for its high-performance power management portfolio.
The LT1931 series was designed specifically for high-current, low-noise negative rail generation in space-constrained analog systems-including data storage, imaging, and RF front-ends-leveraging proprietary current-mode control and dual-inductor architecture.
FAQ
What is the guaranteed operating temperature range for LT1931IS5#TRM?
The LT1931IS5#TRM is specified and guaranteed over the industrial temperature range of –40°C to +85°C. This is confirmed by the "I" grade designation in the part number and validated in the Absolute Maximum Ratings and Electrical Characteristics tables of the official datasheet (1931fa), where all key parameters-including feedback voltage, switching frequency, and current limit-are assured across this full range.
Does LT1931IS5#TRM support soft-start functionality?
Yes, the LT1931IS5#TRM supports external soft-start via an RC network (RSS and CSS) connected to the SHDN pin. As shown in Figure 7 of the datasheet, adding RSS = 15kΩ and CSS = 33nF limits peak input current to 500mA and extends ramp time to 1ms-reducing inrush stress on input capacitors and upstream supplies without modifying the LT1931IS5#TRM's internal circuitry.
Can LT1931IS5#TRM generate –12V from a 5V input?
Yes, the LT1931IS5#TRM can deliver –12V at 150mA from a 5V input, as explicitly documented in the Features and Typical Applications sections of the datasheet (e.g., Figure 1931 TA02). This requires appropriate external components: two 10µH coupled inductors (e.g., Sumida CLS62-100), MBR0520 Schottky diode, and feedback resistors R1 = 84.5kΩ and R2 = 10kΩ.
What is the purpose of the NFB pin on LT1931IS5#TRM, and how is it biased?
The NFB pin on LT1931IS5#TRM is the inverting input of the internal error amplifier, referenced to –1.255V. It sources 4–8µA of bias current (not sinks), so the external resistor divider must be connected between VOUT and GND, with the tap feeding NFB. For LT1931IS5#TRM, the correct ratio is R1/R2 = |VOUT|/1.255 – 1, ensuring accurate output regulation.
Is LT1931IS5#TRM pin-compatible with LT1611, and what design changes are needed for upgrade?
Yes, LT1931IS5#TRM is pin-for-pin compatible with LT1611 per the datasheet's Features section. No PCB layout changes are required. However, due to higher current capability (350mA vs. 150mA) and dual-inductor topology, users must replace the single inductor with two matched inductors and update feedback resistors to match the desired VOUT; no other schematic modifications are necessary.
LT1931IS5#TRM Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- SOT-23-5 Thin, TSOT-23-5
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Negative
- Topology:
- Cuk
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.45V
- Voltage - Input (Max):
- 16V
- Voltage - Output (Min/Fixed):
- -1.255V
- Voltage - Output (Max):
- -34V
- Current - Output:
- 1A (Switch)
- Frequency - Switching:
- 1.2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TSOT-23-5
LT1931IS5#TRM FAQ
1.How can I place an order for LT1931IS5#TRM through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1931IS5#TRM 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 LT1931IS5#TRM reliable?
The price and inventory of LT1931IS5#TRM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1931IS5#TRM is usually 5 days.
3.What payment methods are accepted for LT1931IS5#TRM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1931IS5#TRM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1931IS5#TRM?
LT1931IS5#TRM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1931IS5#TRM 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 LT1931IS5#TRM?
For technical support, including LT1931IS5#TRM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1931IS5#TRM requirements.
6.How does Aetrix verify that LT1931IS5#TRM is sourced from the original manufacturer or authorized distributors?
All LT1931IS5#TRM 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 LT1931IS5#TRM meets industry standards.
7.What is the process for return or replacement of LT1931IS5#TRM?
All LT1931IS5#TRM units undergo pre-shipment inspection (PSI). If there is an issue with LT1931IS5#TRM, 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 LT1931IS5#TRM part is unused and in its original packaging.
Return procedure for LT1931IS5#TRM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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