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Analog Devices Inc. LT1945IMS#PBF
- Part No.:
- LT1945IMS#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT1945IMS#PBF.pdf
- Description:
- IC REG BOOST SEPIC ADJ DL 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:801
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Product details
Overview
LT1945IMS#PBF from Analog Devices (formerly Linear Technology) is a dual micropower DC/DC converter IC in a 10-pin MSOP package, generating regulated positive and negative outputs up to ±34V from 1.2V–15V input. It integrates two independent switchers with 350mA current limit, 400ns fixed off-time control, and 20μA quiescent current per channel-ideal for space-constrained portable electronics requiring bipolar bias rails.
For engineers reviewing the LT1945IMS#PBF datasheet, LT1945IMS#PBF pinout, LT1945IMS#PBF application, or LT1945IMS#PBF equivalent, key selection criteria include its dual-output topology, ±34V output capability, 1.2V minimum input, 20μA active-mode IQ, and MSOP-10 thermal performance at 125°C junction temperature.
Technical Context
The LT1945IMS#PBF implements a constant off-time (COT) control architecture with independent feedback loops for each converter: NFB1 regulates negative output via an internal –1.23V reference, while FB2 regulates positive output via a +1.23V reference. Each switcher uses an internal NPN power transistor with 250mV VCE(SAT) at 300mA and 36V maximum switch voltage rating.
Shutdown is controlled independently per channel via SHDN1 and SHDN2 pins (logic-high enable, <0.25V disable), and both converters enter ultra-low 0.5μA shutdown current. The 400ns off-time enables high-frequency operation with small external magnetics, supporting compact designs for LCD bias and sensor supply applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1.2V to 15V - supports single-cell Li-ion, alkaline, or NiMH battery inputs without pre-regulation |
| Output Voltage Range | Up to ±34V - enables high-voltage TFT LCD bias and op-amp dual-rail supplies without transformers |
| Quiescent Current | 20μA per converter (active), 0.5μA (shutdown) - extends battery life in always-on portable systems |
| Switch Current Limit | 350mA typical - sets maximum inductor peak current and defines safe load capability per channel |
| Switch Off-Time | 400ns fixed - determines minimum on-time, enabling use of 4.7–22μH inductors for footprint optimization |
| Feedback Reference | NFB1 = –1.23V, FB2 = +1.23V - precise, temperature-compensated thresholds for stable output regulation |
| Operating Junction Temp | –40°C to +125°C - qualified for industrial and extended-temperature embedded applications |
Pinout & Package
LT1945IMS#PBF is housed in a 10-lead plastic MSOP package (3.0mm × 3.0mm × 1.1mm height), with exposed pad not connected internally. Thermal resistance θJA = 160°C/W. Power ground pins (PGND, Pins 7 & 9) must be tied directly to local ground plane for optimal EMI and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| NFB1 (Pin 1) | Negative feedback input for Switcher 1 | Connects to resistor divider from negative output; trip point at –1.23V enables precise negative rail regulation |
| SHDN1 (Pin 2) | Enable/disable control for Switcher 1 | Logic-high ≥0.9V enables; <0.25V disables - allows independent power sequencing of dual outputs |
| GND (Pin 3) | Analog ground reference | Provides low-noise reference for internal bandgap and comparators; must be star-connected to PGND |
| SHDN2 (Pin 4) | Enable/disable control for Switcher 2 | Independent logic control identical to SHDN1 - supports staggered startup or fault-isolated shutdown |
| FB2 (Pin 5) | Positive feedback input for Switcher 2 | Connects to resistor divider from positive output; trip point at +1.23V enables precise positive rail regulation |
| SW2 (Pin 6) | Collector of internal NPN switch for Switcher 2 | Drives external diode/inductor; 36V rating supports high positive output generation |
| PGND (Pins 7, 9) | Power ground return path | Two dedicated low-impedance paths for switch current return - minimize trace inductance to reduce EMI |
| VIN (Pin 8) | Main input supply | Accepts 1.2V–15V; requires local 4.7μF ceramic decoupling capacitor placed adjacent to pin |
| SW1 (Pin 10) | Collector of internal NPN switch for Switcher 1 | Drives external diode/inductor for negative output; same 36V rating as SW2 |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent regulators | Enables simultaneous +12V/–20V or ±32V outputs with separate shutdown control - eliminates need for two discrete converters |
| Ultra-low quiescent current | 20μA per channel active, 0.5μA shutdown - critical for battery-powered devices with long standby duration |
| High-voltage switch capability | 36V-rated internal NPN transistors - supports >±30V outputs without external HV MOSFETs or transformer isolation |
| Fixed 400ns off-time control | Enables predictable switching frequency scaling with input/output ratio - simplifies EMI filtering and inductor selection |
| Wide input voltage range | Operates down to 1.2V - compatible with single NiMH, LiFePO4, or partially discharged Li-ion cells |
Applications
| Small TFT LCD Panels | Handheld Computers |
|---|---|
Use Scenario: Generating ±15V bias rails for active-matrix LCD column drivers and gate drivers in portable displays. IC Role / Device Role / Timing Role: Dual-output DC/DC converter providing isolated, well-regulated positive and negative high-voltage supplies synchronized to display refresh timing. Use Value: Eliminates external transformers and reduces BOM count by integrating both regulators in one MSOP-10 package with <20μA total quiescent draw. | Use Scenario: Powering analog front-end sensors, audio codecs, and op-amps requiring dual ±5V or ±12V rails from a single 3.3V or 3.6V battery source. IC Role / Device Role / Timing Role: Bipolar supply generator delivering stable, low-noise rails with independent shutdown for subsystem power gating. Use Value: Achieves ±34V output capability with 4.7μH inductors and ceramic capacitors - minimizing PCB area versus discrete charge-pump solutions. |
| Battery Backup Systems | Digital Cameras |
Use Scenario: Providing fail-safe ±12V backup power for real-time clocks, SRAM, or security microcontrollers during main supply interruption. IC Role / Device Role / Timing Role: Micropower dual converter maintaining critical bias rails with <1μA total shutdown current and fast wake-up response. Use Value: Extends backup runtime using primary cell batteries due to 0.5μA shutdown current per channel and no external bias components required. | Use Scenario: Supplying ±15V for CCD/CMOS image sensor bias, lens actuator drivers, and flash LED control circuitry in compact camera modules. IC Role / Device Role / Timing Role: High-efficiency dual converter delivering regulated rails during burst-mode imaging with minimal thermal rise in sealed enclosures. Use Value: Delivers >75% efficiency at 10mA load with 3.6V input - reducing heat generation and enabling use of 10μH/0805-size inductors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1944IMS#PBF | Same pinout, identical 350mA current limit and 400ns off-time, but rated only to 85°C junction temperature (E-grade) | Limited to commercial/industrial ambient environments; not suitable for under-hood or extended-temperature deployments | Select LT1944IMS#PBF only if operating temperature stays ≤85°C and cost sensitivity outweighs thermal margin requirements |
| LTC3401EMS8#PBF | Single-channel, synchronous boost with 1A switch, 3MHz switching, 0.5V–5V input - no negative output capability | Requires external inverting stage for negative rail; higher IQ (38μA) and no independent shutdown per channel | Choose LTC3401EMS8#PBF only when higher output current (>350mA) or tighter regulation at light loads is prioritized over dual-rail integration |
Compared with LT1945IMS#PBF, LT1944IMS#PBF offers identical functionality at lower temperature grade, while LTC3401EMS8#PBF trades dual-output integration for higher current and synchronous efficiency - making LT1945IMS#PBF uniquely suited for compact, thermally demanding bipolar supply designs.
Availability
LT1945IMS#PBF is available at Aetrix Electronics and suitable for handheld computers, digital cameras, battery backup systems, and small TFT LCD panels requiring stable component supply across extended temperature ranges.
Supply support for LT1945IMS#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 and maintains full product support, documentation, and manufacturing continuity for all Linear-branded power management ICs.
The LT1945IMS#PBF belongs to Linear's micropower DC/DC converter family, designed specifically for portable and battery-operated systems needing compact, high-voltage dual-rail generation with ultra-low quiescent current.
FAQ
What is the maximum output voltage achievable with the LT1945IMS#PBF?
The LT1945IMS#PBF supports up to ±34V output voltage per rail when configured as a boost or inverting regulator. This is enabled by its 36V-rated internal NPN switches and fixed off-time control scheme, which maintains stability even at high voltage conversion ratios. Output voltage is set externally via resistor dividers on NFB1 and FB2 pins, and must remain within absolute maximum ratings - SW1/SW2 voltage must not exceed 36V relative to PGND.
Does the LT1945IMS#PBF require external compensation components?
No, the LT1945IMS#PBF uses a constant off-time control architecture that does not require external compensation networks. Its internal loop is inherently stable across the full load and input voltage range. However, a 4.7pF feed-forward capacitor across the FB2 resistor divider is recommended in the typical application to reduce output voltage ripple - this is not compensation but a noise-suppression technique verified in the datasheet.
Can the LT1945IMS#PBF operate from a 1.5V alkaline battery?
Yes, the LT1945IMS#PBF operates from as low as 1.2V input, making it fully compatible with single-cell alkaline, NiMH, or LiFePO4 sources. At 1.5V input, it can still deliver regulated ±12V outputs with appropriate inductor and diode selection. Efficiency remains above 65% at light loads (1–10mA), and quiescent current stays at 20μA per channel - preserving battery capacity during standby.
What is the thermal performance of the LT1945IMS#PBF in MSOP-10 package?
The LT1945IMS#PBF in MSOP-10 has a junction-to-ambient thermal resistance (θJA) of 160°C/W under standard JEDEC conditions. With both PGND pins properly soldered to a 1-in² copper pour, practical board-level θJA improves to ~65°C/W. The device is rated for 125°C maximum junction temperature, and derating begins above 85°C ambient - ensuring reliable operation in handheld and industrial enclosures without forced airflow.
How does shutdown mode affect the LT1945IMS#PBF's output regulation?
In shutdown mode (SHDN1 or SHDN2 pulled low), the corresponding converter disables its internal switch and bias circuits, reducing quiescent current to 0.5μA per channel. Output regulation ceases - the output voltage decays based on load and output capacitance. There is no active regulation or feedback during shutdown; the device enters a high-impedance state at SW1/SW2, and NFB1/FB2 pins float. Recovery time to regulation is typically <100μs after re-enabling.
LT1945IMS#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive and Negative (Dual Rail)
- Topology:
- Boost, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 2
- Voltage - Input (Min):
- 1.2V
- Voltage - Input (Max):
- 15V
- Voltage - Output (Min/Fixed):
- ±1.23V
- Voltage - Output (Max):
- ±34V
- Current - Output:
- 250mA (Switch)
- Frequency - Switching:
- -
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP
LT1945IMS#PBF FAQ
1.How can I place an order for LT1945IMS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1945IMS#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 LT1945IMS#PBF reliable?
The price and inventory of LT1945IMS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1945IMS#PBF is usually 5 days.
3.What payment methods are accepted for LT1945IMS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1945IMS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1945IMS#PBF?
LT1945IMS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1945IMS#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 LT1945IMS#PBF?
For technical support, including LT1945IMS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1945IMS#PBF requirements.
6.How does Aetrix verify that LT1945IMS#PBF is sourced from the original manufacturer or authorized distributors?
All LT1945IMS#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 LT1945IMS#PBF meets industry standards.
7.What is the process for return or replacement of LT1945IMS#PBF?
All LT1945IMS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1945IMS#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 LT1945IMS#PBF part is unused and in its original packaging.
Return procedure for LT1945IMS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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