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Analog Devices Inc. LT1931IS5#TR
- Part No.:
- LT1931IS5#TR
- Manufacturer:
- Analog Devices Inc.
- Package:
- SOT-23-5 Thin, TSOT-23-5
- Datasheet:
-
LT1931IS5#TR.pdf
- Description:
- IC REG CUK ADJ 1A TSOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:1,630
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Product details
Overview
LT1931IS5#TR 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 uses a dual-inductor inverting topology for ultra-low noise and delivers <1mVP-P output ripple with ceramic capacitors. Designed for compact negative bias supplies in imaging and RF systems.
For engineers reviewing the LT1931IS5#TR datasheet, LT1931IS5#TR pinout, LT1931IS5#TR application, or LT1931IS5#TR equivalent, this page provides verified specifications, validated pin functions, confirmed ThinSOT-23 package mapping, real-world application constraints (e.g., 84% max duty cycle, –1.255V feedback reference), and two rigorously cross-checked alternative parts.
Technical Context
The LT1931IS5#TR employs constant-frequency current-mode control with internal 1A NPN switch and 36V breakdown rating, enabling up to 34V VIN-to-VOUT differential. Its dual-inductor inverting architecture filters both input and output currents, achieving low-impedance regulation within ±1% during load transients.
It features a precision –1.255V feedback reference, 400mV typical VCESAT at 1A, <1µA shutdown current, and operates across –40°C to 85°C. The 1.2MHz switching frequency allows use of sub-3mm-height inductors and ceramic capacitors while maintaining >75% efficiency at 350mA into –5V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 1.2MHz - enables use of ≤2mm-height inductors and low-ESR ceramic caps without compromising stability |
| Output Voltage Ripple | <1mVP-P - achieved with X5R ceramic output capacitors; critical for MR head and CCD bias noise sensitivity |
| Max Output Current | 350mA at –5V from 5V input - supports high-current negative rail generation in compact footprints |
| Feedback Reference | –1.255V - sets precise output voltage via external resistor divider; tolerance ±20mV over temperature |
| Input Voltage Range | 2.6V to 16V - accommodates single-cell Li-ion, USB, and industrial 5V/12V rails |
| Shutdown Current | <1µA - preserves battery life in portable CCD or LCD bias applications during sleep mode |
| Switch VCESAT | 400mV at 1A - minimizes conduction loss and thermal rise in high-current inverting configurations |
Pinout & Package
LT1931IS5#TR is housed in a 5-lead ThinSOT™ (TSOT-23) package, 2.9mm × 1.6mm × 1.0mm profile, with exposed pad not connected internally. Pin 1 (SW) carries full switch current; Pin 2 (GND) requires direct connection to local ground plane; Pin 3 (NFB) sources bias current and references –1.255V; Pin 4 (SHDN) enables device above 2.4V; Pin 5 (VIN) must be locally bypassed.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pin 1) | Switch collector node | Connects to coupled/uncoupled inductor(s); trace area minimized to reduce EMI radiation |
| GND (Pin 2) | Power and signal ground reference | Tie directly to local ground plane; separates power and feedback return paths |
| NFB (Pin 3) | Inverting error amplifier input | Sources 4–8µA bias current; connects to resistive divider tap for output voltage setting |
| SHDN (Pin 4) | Enable/disable control input | Logic-high ≥2.4V enables operation; grounded disables with <1µA quiescent draw |
| VIN (Pin 5) | Main power supply input | Accepts 2.6–16V; requires local 1–4.7µF ceramic decoupling placed adjacent to pin |
Key Features
| Feature | Design Value |
|---|---|
| Dual-inductor inverting topology | Simultaneously filters input and output current ripple, reducing conducted EMI and enabling <1mVP-P output noise |
| 1.2MHz fixed-frequency operation | Permits use of small, low-cost 10µH coupled inductors (e.g., Sumida CLS62-100) under 2.5mm height |
| Integrated 1A NPN switch with 36V rating | Supports up to 34V VIN–VOUT differential; eliminates need for external high-voltage switch |
| –1.255V precision feedback reference | Enables accurate negative output regulation (e.g., –5.00V ±2%) using standard 1% resistors |
| Low 400mV VCESAT at 1A | Reduces switch conduction loss to ~400mW at full load, limiting junction temperature rise in SOT-23 |
Applications
| Disk Drive MR Head Bias | Digital Camera CCD Bias |
|---|---|
Use Scenario: Generating stable –5V bias for magnetoresistive read heads in 2.5″ HDDs with tight board space. IC Role / Device Role / Timing Role: Inverting DC/DC converter providing low-noise, regulated negative supply independent of main system rail. Use Value: <1mVP-P ripple ensures minimal head-positioning error; 350mA output supports multi-head actuator drivers. |
Use Scenario: Powering CCD image sensors requiring clean –12V bias in DSLR or industrial cameras. IC Role / Device Role / Timing Role: High-efficiency inverting regulator delivering –12V at 150mA from 5V USB or battery source. Use Value: Dual-inductor topology suppresses switching noise that would otherwise corrupt analog pixel signals. |
| LCD Panel Bias Supply | GaAs FET RF Amplifier Bias |
Use Scenario: Providing –5V gate bias for active-matrix LCD source drivers in portable displays. IC Role / Device Role / Timing Role: Compact negative rail generator with fast transient response (<500µs startup). Use Value: Low 1.2MHz switching frequency avoids interference with display pixel clock harmonics. |
Use Scenario: Delivering low-noise –5V supply to GaAs FETs in cellular front-end modules. IC Role / Device Role / Timing Role: Local negative bias IC with high PSRR and low output impedance. Use Value: 1% load regulation maintains consistent FET gate voltage across 0–300mA RF output power range. |
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#TR | 2.2MHz switching frequency, 75% max duty cycle, 300mA max –5V output | Requires smaller inductors (e.g., 4.7µH vs 10µH) but lower max current and efficiency | Select when board area and BOM cost are prioritized over peak output current |
| LT1611ES5#TR | 1.4MHz, 150mA max –5V output, no dual-inductor support, higher VCESAT (~600mV) | Limited to low-current bias; lacks LT1931IS5#TR's low-noise dual-inductor filtering | Use only for legacy designs where 150mA suffices and footprint compatibility is mandatory |
Compared with LT1931AIS5#TR, LT1931IS5#TR delivers 17% higher –5V output current and superior noise performance due to its 1.2MHz/dual-inductor architecture; versus LT1611ES5#TR, it doubles output capability and cuts output ripple by 5× through topology-level filtering.
Availability
LT1931IS5#TR is available at Aetrix Electronics and suitable for disk drive MR head bias, digital camera CCD bias, and GaAs FET RF amplifier bias applications requiring stable component supply across extended temperature ranges.
Supply support for LT1931IS5#TR 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, datasheet archives, and application engineering for legacy Linear parts including the LT1931 series.
The LT1931 family was designed specifically for high-current, low-noise negative voltage generation in space-constrained imaging, RF, and data storage systems - emphasizing thermal efficiency, EMI control, and robustness across –40°C to 85°C.
FAQ
What is the guaranteed operating temperature range for LT1931IS5#TR?
The LT1931IS5#TR is specified and tested over –40°C to +85°C ambient temperature. This industrial-grade rating is confirmed in the Absolute Maximum Ratings table and Electrical Characteristics section of the official 1931fa datasheet, with performance parameters assured across the full range via design correlation and statistical process controls.
Can LT1931IS5#TR generate –12V from a 5V input, and what is the maximum load current?
Yes, LT1931IS5#TR can generate –12V from a 5V input at up to 150mA continuous output current, as verified in the Typical Applications section (Figure 1931 TA02) and Electrical Characteristics table. This capability relies on the 84% maximum duty cycle and 36V switch rating, enabling a 17V total voltage swing across the switch node.
What is the exact feedback reference voltage of LT1931IS5#TR, and how is it used?
The LT1931IS5#TR has a nominal feedback reference voltage of –1.255V at Pin 3 (NFB), with a tolerance of ±20mV over temperature. This negative reference is used with an external resistor divider between VOUT and GND to set output voltage: VOUT = –1.255V × (1 + R1/R2). The NFB pin sources 4–8µA bias current, which must be accounted for in high-impedance dividers.
Does LT1931IS5#TR require external compensation components for stability?
No, LT1931IS5#TR is internally compensated and operates stably with standard ceramic output capacitors. However, a phase-lead capacitor (e.g., 220pF) across the upper feedback resistor improves transient response damping, as shown in Figure 1 and Figure 4 of the datasheet - reducing overshoot and ringing without altering loop compensation network.
Is LT1931IS5#TR pin-compatible with LT1611, and what are the key functional upgrades?
Yes, LT1931IS5#TR is pin-for-pin compatible with LT1611 per the datasheet's "Pin-for-Pin Compatible with the LT1611" feature line. Key upgrades include doubled output current (150mA → 350mA at –5V), 400mV vs 600mV VCESAT, dual-inductor topology for lower ripple, and extended input range (2.6V–16V vs 2.7V–10V).
LT1931IS5#TR 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#TR FAQ
1.How can I place an order for LT1931IS5#TR through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1931IS5#TR 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#TR reliable?
The price and inventory of LT1931IS5#TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1931IS5#TR is usually 5 days.
3.What payment methods are accepted for LT1931IS5#TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1931IS5#TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1931IS5#TR?
LT1931IS5#TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1931IS5#TR 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#TR?
For technical support, including LT1931IS5#TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1931IS5#TR requirements.
6.How does Aetrix verify that LT1931IS5#TR is sourced from the original manufacturer or authorized distributors?
All LT1931IS5#TR 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#TR meets industry standards.
7.What is the process for return or replacement of LT1931IS5#TR?
All LT1931IS5#TR units undergo pre-shipment inspection (PSI). If there is an issue with LT1931IS5#TR, 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#TR part is unused and in its original packaging.
Return procedure for LT1931IS5#TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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