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Analog Devices Inc. LT1945EMS#TRPBF
- Part No.:
- LT1945EMS#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT1945EMS#TRPBF.pdf
- Description:
- IC REG BOOST SEPIC ADJ DL 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,332
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Product details
Overview
LT1945EMS#TRPBF 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 features two independent switchers with 350mA current limit, 20μA quiescent current per channel, and 400ns fixed off-time control for high efficiency in space-constrained portable systems.
For engineers reviewing the LT1945EMS#TRPBF datasheet, LT1945EMS#TRPBF pinout, LT1945EMS#TRPBF application, or LT1945EMS#TRPBF equivalent, key selection criteria include dual-output polarity support, ultra-low shutdown current (<1μA), 36V internal switch rating, MSOP-10 thermal performance (θJA = 160°C/W), and compatibility with ceramic output capacitors and low-profile inductors for TFT LCD bias and handheld power rails.
Technical Context
The LT1945EMS#TRPBF integrates two independent constant off-time switching regulators: Switcher 1 is an inverting topology generating negative output (NFB1 feedback), while Switcher 2 is a boost topology generating positive output (FB2 feedback). Each uses an internal 350mA NPN power switch with 250mV VCESAT at 300mA and supports input voltages as low as 1.2V.
Its control architecture employs hysteresis-based comparators (8mV NFB1/FB2 hysteresis), 400ns minimum off-time for both channels, and adaptive current limiting-reducing switcher 2's off-time to 1.5μs and current limit to 250mA during startup or short-circuit conditions to manage power dissipation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1.2V to 15V - enables direct operation from single-cell Li-ion, NiMH, or alkaline batteries without pre-regulation. |
| Output Voltage Range | Up to ±34V - supports high-voltage TFT LCD bias rails without transformers or external charge pumps. |
| Quiescent Current | 20μA per converter - extends battery life in always-on portable devices such as digital cameras and handheld computers. |
| Switch Current Limit | 350mA - sets maximum inductor peak current; overshoot up to ~700mA occurs due to 100ns turn-off delay but remains within safe SOA. |
| Switch Off-Time | 400ns (SW1/SW2) - permits use of small inductors (e.g., 10μH Murata LQH3C100) and minimizes footprint in compact layouts. |
| Feedback Reference | NFB1 = –1.23V, FB2 = +1.23V - enables precise output voltage setting via resistor dividers with <0.1%/V line regulation. |
| Shutdown Current | <1μA total - ensures negligible battery drain during system sleep modes across both channels. |
| Operating Temp Range | –40°C to +85°C - qualified for industrial and consumer portable equipment environments. |
Pinout & Package
LT1945EMS#TRPBF is housed in a 10-lead plastic MSOP package (3.0mm × 3.0mm × 0.86mm), with exposed thermal pad not connected internally. Pin 3 (GND) and pins 7/9 (PGND) require separate low-impedance connections to local ground plane for optimal noise immunity 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 accurate negative voltage regulation. |
| SHDN1 (Pin 2) | Enable control for Switcher 1 | Logic-high ≥0.9V enables; logic-low ≤0.25V disables with <1μA leakage - allows independent power sequencing. |
| GND (Pin 3) | Analog ground reference | Reference for internal bandgap and comparators; must be tied directly to clean analog ground plane. |
| SHDN2 (Pin 4) | Enable control for Switcher 2 | Independent enable/disable of positive-output channel; supports staggered startup or fault isolation. |
| FB2 (Pin 5) | Positive feedback input for Switcher 2 | Connects to resistor divider from positive output; 1.23V reference enables stable positive rail generation. |
| SW2 (Pin 6) | Collector of internal NPN switch for Switcher 2 | Drives external Schottky diode (e.g., ZHCS400); trace area must be minimized to reduce EMI radiation. |
| PGND (Pins 7, 9) | Power ground return path | Carries high-frequency switch currents; both pins must be connected to low-inductance power ground plane. |
| 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 inverting topology; same layout constraints as SW2 to maintain efficiency and EMI compliance. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent regulators | One inverting (negative output), one boost (positive output) - eliminates need for separate ICs in bipolar supply designs. |
| Ultra-low quiescent current | 20μA per channel active, <1μA total shutdown - critical for battery-powered applications with long standby periods. |
| 36V internal switch rating | Supports ±34V outputs from 2.7V–12V inputs - avoids external high-voltage components and reduces BOM count. |
| 400ns fixed off-time control | Enables use of 10μH inductors and 1μF ceramic capacitors - achieves compact 12mm² solution size for portable electronics. |
| Independent shutdown pins | SHDN1 and SHDN2 allow selective channel disablement - simplifies power management in multi-rail systems. |
| Low VCESAT switch | 250mV at 300mA - improves light-load efficiency and reduces thermal stress on internal transistor. |
Applications
| TFT LCD Panel Bias Supply | Handheld Computer Core Power |
|---|---|
Use Scenario: Generating ±12V to ±32V bias rails for active-matrix TFT displays in portable medical monitors and industrial HMIs. IC Role / Device Role / Timing Role: Dual-output DC/DC converter providing isolated, well-regulated positive and negative voltages from a single 3.6V Li-ion cell. Use Value: Eliminates need for external transformers or discrete charge pumps, reducing solution size by >40% versus dual-single-channel alternatives. | Use Scenario: Powering CPU I/O, memory, and interface ICs requiring tightly regulated +3.3V and –2.5V rails in ruggedized handheld terminals. IC Role / Device Role / Timing Role: Micropower dual regulator delivering stable outputs with fast transient response during processor wake/sleep cycles. Use Value: 20μA quiescent current per channel extends battery runtime beyond 72 hours in deep-sleep mode. |
| Digital Camera Sensor Bias | Battery Backup System |
Use Scenario: Supplying ±15V bias to CCD/CMOS image sensor analog front-ends in DSLR and mirrorless cameras. IC Role / Device Role / Timing Role: High-voltage dual converter operating from partially discharged 3.2V lithium polymer cells during burst capture sequences. Use Value: 1.2V minimum input enables full functionality down to 3.0V battery voltage, avoiding premature shutdown. | Use Scenario: Providing fail-safe ±5V backup rails for real-time clocks and SRAM in industrial controllers during main power loss. IC Role / Device Role / Timing Role: Always-on dual regulator drawing <1μA in shutdown, activated only when primary supply drops below threshold. Use Value: Sub-μA shutdown current preserves coin-cell energy for >10 years of RTC operation without maintenance. |
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 |
|---|---|---|---|
| LT1944EMS#TRPBF | Same 10-pin MSOP package, identical pinout, and dual 350mA switchers; differs in FB2 reference (1.25V vs 1.23V) and slightly higher quiescent current (22μA vs 20μA). | Optimized for lower-noise applications with improved PSRR; lacks NFB1 hysteresis spec but shares same core topology. | Select LT1944EMS#TRPBF if tighter output voltage tolerance (±0.5%) or enhanced ripple rejection is required over extended temperature range. |
| LTC3402EMS8#TRPBF | Single-channel 2A synchronous boost converter in MSOP-8; no negative output capability; requires external inverter stage for bipolar rails. | Higher output current (2A vs 350mA) and 3MHz switching frequency - suited for high-power single-rail needs, not dual-polarity systems. | Choose LTC3402EMS8#TRPBF only when redesigning for unipolar high-current rails; not a drop-in replacement for LT1945EMS#TRPBF's dual-output function. |
Compared with LT1944EMS#TRPBF, the LT1945EMS#TRPBF offers superior negative-output accuracy via dedicated NFB1 comparator and lower quiescent current, making it preferred for ultra-low-power bipolar biasing; versus LTC3402EMS8#TRPBF, it provides integrated dual-rail generation where board space and component count are constrained.
Availability
LT1945EMS#TRPBF is available at Aetrix Electronics and suitable for TFT LCD panels, handheld computers, digital cameras, battery backup systems, and portable medical devices requiring stable component supply with guaranteed long-term availability.
Supply support for LT1945EMS#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 acquired Linear Technology in 2017 and maintains full technical and manufacturing continuity for legacy Linear products including the LT1945 family.
The LT1945EMS#TRPBF belongs to Linear's micropower DC/DC converter product line, designed specifically for space- and power-constrained portable electronics needing dual-polarity high-voltage rails without transformers.
FAQ
What is the minimum input voltage supported by the LT1945EMS#TRPBF?
The LT1945EMS#TRPBF supports a minimum input voltage of 1.2V, enabling direct operation from single-cell alkaline, NiMH, or deeply discharged Li-ion batteries. This specification is confirmed across the full –40°C to +85°C operating temperature range and allows the LT1945EMS#TRPBF to remain functional even as battery voltage declines during discharge cycles in portable equipment.
Can the LT1945EMS#TRPBF generate both positive and negative outputs simultaneously?
Yes, the LT1945EMS#TRPBF integrates two independent switching regulators: Switcher 1 operates as an inverting converter to generate negative outputs (e.g., –20V), while Switcher 2 functions as a boost converter to produce positive outputs (e.g., +12V). Both channels operate concurrently from a shared VIN supply, and their feedback pins (NFB1 and FB2) allow independent voltage programming - a core capability of the LT1945EMS#TRPBF.
What is the purpose of the 4.7pF capacitor shown in the LT1945EMS#TRPBF typical application schematics?
The 4.7pF feed-forward capacitor placed across the upper feedback resistor (e.g., between FB2 and SW2 in boost configuration) reduces output voltage ripple by improving loop phase margin and suppressing high-frequency switching noise. This capacitor is a documented design technique specific to the LT1945EMS#TRPBF and appears in multiple official application circuits (TA01, TA02) to achieve sub-10mV ripple without increasing output capacitance.
Does the LT1945EMS#TRPBF require external diodes, and if so, what type is recommended?
Yes, the LT1945EMS#TRPBF requires two external Schottky diodes per channel (three total in dual-output configurations). The Zetex ZHCS400 (40V, 0.4A) is explicitly recommended in the datasheet for all typical applications due to its low forward voltage (0.4V), fast recovery, and surface-mount compatibility. Using non-Schottky diodes increases conduction losses and degrades LT1945EMS#TRPBF efficiency, especially at light loads.
How does the LT1945EMS#TRPBF handle short-circuit conditions on its outputs?
Under short-circuit or heavy overload, the LT1945EMS#TRPBF implements adaptive protection: when FB2 voltage drops below ~0.6V, Switcher 2 extends its off-time from 400ns to 1.5μs and reduces current limit from 350mA to ~250mA. This lowers average inductor current and power dissipation without latching off - a behavior verified in the "Operation" section and thermal performance graphs of the LT1945EMS#TRPBF datasheet.
LT1945EMS#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 0°C ~ 70°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP
LT1945EMS#TRPBF FAQ
1.How can I place an order for LT1945EMS#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1945EMS#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 LT1945EMS#TRPBF reliable?
The price and inventory of LT1945EMS#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1945EMS#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1945EMS#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1945EMS#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1945EMS#TRPBF?
LT1945EMS#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1945EMS#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 LT1945EMS#TRPBF?
For technical support, including LT1945EMS#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1945EMS#TRPBF requirements.
6.How does Aetrix verify that LT1945EMS#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1945EMS#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 LT1945EMS#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1945EMS#TRPBF?
All LT1945EMS#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1945EMS#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 LT1945EMS#TRPBF part is unused and in its original packaging.
Return procedure for LT1945EMS#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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