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Analog Devices Inc. LT1945EMS#PBF
- Part No.:
- LT1945EMS#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT1945EMS#PBF.pdf
- Description:
- IC REG BOOST SEPIC ADJ DL 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,700
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Product details
Overview
LT1945EMS#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 input voltages as low as 1.2V. Each channel features 350mA current limiting, 20μA quiescent current per converter, and a fixed 400ns off-time control scheme for high efficiency across wide load ranges. It serves as a compact, transformerless voltage source for portable display bias and low-power dual-rail systems.
For engineers reviewing the LT1945EMS#PBF datasheet, LT1945EMS#PBF pinout, LT1945EMS#PBF application, or LT1945EMS#PBF equivalent, key selection criteria include dual-output polarity support, ultra-low quiescent current in active/shutdown modes, 36V internal switch rating, 1.2V minimum input capability, and compatibility with small-footprint inductors and ceramic capacitors in space-constrained designs.
Technical Context
The LT1945EMS#PBF implements 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). Both use internal NPN power switches with 250mV VCE(SAT) at 300mA and share a common VIN and PGND structure.
Each regulator employs hysteresis-based feedback comparators (NFB1 trip: –1.23V typ; FB2 trip: 1.23V typ) and automatic current-limit reduction (to ~250mA) when FB2 < 0.6V-enabling safe startup and short-circuit protection. The 400ns off-time enables operation with 4.7–22μH inductors and supports output ripple suppression via optional 4.7pF feed-forward capacitors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1.2V to 15V - Enables direct operation from single-cell Li-ion (2.7–4.2V), alkaline, or NiMH batteries without pre-regulation. |
| Output Voltage Range | Up to ±34V - Supports high-voltage TFT LCD bias rails without external transformers or charge pumps. |
| Quiescent Current | 20μA per converter (active), 0.5μA total (shutdown) - Extends battery life in always-on portable instrumentation and backup systems. |
| Switch Current Limit | 350mA typical - Sets maximum inductor peak current; combined with 400ns off-time, defines minimum practical inductance for given VIN/VOUT. |
| Internal Switch Rating | 36V max SW pin voltage - Allows generation of ±32V outputs from 3.6V input without violating absolute maximum ratings. |
| Feedback Reference Voltage | NFB1 = –1.23V, FB2 = +1.23V - Enables precise resistor-divider programming of asymmetric positive/negative output voltages. |
| Shutdown Threshold | SHDNx < 0.25V (disable), > 0.9V (enable) - Compatible with standard logic-level GPIOs and open-drain supervisors. |
Pinout & Package
LT1945EMS#PBF is housed in a 10-lead plastic MSOP package (3.0mm × 3.0mm × 0.86mm height), RoHS-compliant and lead-free (PbF), rated for –40°C to +85°C operating junction temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| NFB1 (Pin 1) | Negative output feedback input | Connects to resistor divider from negative output; comparator trips at –1.23V to regulate VOUT1. |
| SHDN1 (Pin 2) | Switcher 1 enable control | Logic-level input: <0.25V disables Switcher 1; >0.9V enables it independently of Switcher 2. |
| GND (Pin 3) | Analog ground reference | Reference node for internal bandgap and comparators; must tie directly to local analog ground plane. |
| SHDN2 (Pin 4) | Switcher 2 enable control | Independent logic-level shutdown for positive-output channel; allows dynamic rail sequencing. |
| FB2 (Pin 5) | Positive output feedback input | Connects to resistor divider from positive output; comparator trips at +1.23V to regulate VOUT2. |
| SW2 (Pin 6) | Boost switch collector (Switcher 2) | High-side NPN collector node; requires minimal trace area to reduce EMI and parasitic inductance. |
| PGND (Pins 7 & 9) | Power ground return | Low-impedance return path for both switch currents; both pins must be connected to same solid ground plane. |
| VIN (Pin 8) | Main input supply | Accepts 1.2–15V; requires local 4.7μF ceramic decoupling capacitor placed adjacent to pin. |
| SW1 (Pin 10) | Inverting switch collector (Switcher 1) | Collector of internal NPN used in inverting topology; same layout constraints as SW2 for EMI control. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent regulators | One inverting (negative output), one boost (positive output); each with dedicated shutdown and feedback pins for flexible rail control. |
| Ultra-low quiescent current | 20μA per converter in active mode ensures >1-year battery life in low-duty-cycle handheld instruments. |
| Transformerless high-voltage generation | 36V-rated internal switches enable ±32V outputs from 3.6V input-eliminating bulky, costly isolation transformers. |
| Fixed 400ns off-time control | Enables stable operation with tiny 4.7–10μH inductors and reduces minimum component footprint by >40% vs. variable-frequency alternatives. |
| Startup and short-circuit protection | Automatic 1.5μs off-time extension and 250mA current limit when FB2 < 0.6V prevent thermal runaway during fault conditions. |
Applications
| Small TFT LCD Panels | Handheld Computers |
|---|---|
Use Scenario: Generating ±12V to ±32V bias rails for active-matrix LCD displays in medical handhelds and industrial PDAs. IC Role / Device Role / Timing Role: Dual-output DC/DC converter providing isolated positive and negative high-voltage rails from a single low-voltage battery source. Use Value: Eliminates need for external transformers or discrete charge-pump ICs, reducing BOM count by 3–5 components and PCB area by >25%. | Use Scenario: Powering dual-rail analog front-ends (e.g., op-amps, ADC drivers) and memory backup circuits in ruggedized field computers. IC Role / Device Role / Timing Role: Micropower dual converter supplying stable ±5V or ±15V rails during main system sleep, maintaining SRAM and real-time clock functionality. Use Value: 0.5μA shutdown current extends coin-cell or supercapacitor backup runtime to >3 months without recharge. |
| Battery Backup Systems | Digital Cameras |
Use Scenario: Maintaining real-time clock, configuration EEPROM, and security registers during main power loss in smart meters and IoT gateways. IC Role / Device Role / Timing Role: Low-quiescent dual converter generating regulated ±3.3V rails from backup lithium primary cell or supercapacitor. Use Value: 20μA per-channel active current enables >2-year backup operation on a single CR2032 cell under typical RTC load (1.5μA). | Use Scenario: Supplying programmable CCD/CMOS sensor bias voltages (e.g., +15V AVDD, –8V substrate) in compact digital still cameras. IC Role / Device Role / Timing Role: Dual micropower converter delivering precision-adjustable positive and negative sensor rails with independent shutdown control. Use Value: Resistor-divider programmability (via NFB1/FB2) allows fine-tuning of sensor bias without changing hardware-reducing NPI validation cycles. |
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 10-pin MSOP package, identical pinout, and dual 350mA boost architecture-but lacks inverting (negative-output) capability; only generates positive outputs. | Suitable only for dual-positive applications (e.g., +5V/+12V), not for ±V systems requiring negative bias. | Select LT1944IMS#PBF only when both outputs must be positive and board layout re-use of LT1945EMS#PBF footprint is required. |
| LTC3402EDD#TRPBF | 2A synchronous boost converter in 10-lead DFN; no native negative-output capability; higher IQ (38μA) but supports lower VIN (0.5V) and higher switching frequency (3MHz). | Requires external inverting stage for negative rail; better suited for high-current, single-rail applications where efficiency >85% at 100mA+ is critical. | Choose LTC3402EDD#TRPBF when output current demand exceeds 350mA per rail and synchronous rectification is needed to minimize diode losses. |
Compared with LT1944IMS#PBF, the LT1945EMS#PBF uniquely delivers true dual-polarity outputs in one IC, eliminating external inverter stages; versus LTC3402EDD#TRPBF, it trades higher peak current for micropower operation and integrated negative regulation-making it optimal for battery-critical, space-constrained ±V systems.
Availability
LT1945EMS#PBF is available at Aetrix Electronics and suitable for TFT LCD bias, handheld computer power management, battery backup systems, digital camera sensor supplies, and portable instrumentation requiring stable component supply with long-lifecycle assurance.
Supply support for LT1945EMS#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, 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 LT1945EMS#PBF belongs to Linear's micropower DC/DC converter product line, designed specifically for ultra-low-power, dual-rail portable electronics where transformerless high-voltage generation and minimal quiescent current are essential.
FAQ
What is the minimum input voltage supported by the LT1945EMS#PBF?
The LT1945EMS#PBF supports a minimum input voltage of 1.2V, enabling direct operation from partially discharged single-cell Li-ion, NiMH, or alkaline batteries. This specification is guaranteed over the full –40°C to +85°C temperature range and verified in electrical characteristics tables with test condition VIN = 1.2V.
Can the LT1945EMS#PBF generate both positive and negative outputs simultaneously?
Yes, the LT1945EMS#PBF is specifically designed to generate regulated positive and negative outputs simultaneously: Switcher 2 (FB2-controlled) operates as a boost regulator for positive VOUT, while Switcher 1 (NFB1-controlled) operates as an inverting regulator for negative VOUT. Typical configurations include ±12V, ±20V, and ±32V outputs from a single 2.7–5V input.
What is the purpose of the 4.7pF capacitor shown in the LT1945EMS#PBF typical application schematics?
The 4.7pF capacitor is a feed-forward compensation element placed across the upper feedback resistor (R1B) in the FB2 network of the LT1945EMS#PBF. It reduces output voltage ripple by improving transient response and phase margin-particularly effective for high-gain feedback loops driving high-impedance dividers, and confirmed in Figure 1945 TA01 and TA02 schematics.
Does the LT1945EMS#PBF require external Schottky diodes, and if so, what are the key selection criteria?
Yes, the LT1945EMS#PBF requires two external Schottky diodes per channel (three total in dual-output configs). Recommended parts include Zetex ZHCS400 (0.4A, 40V), with key criteria being: forward current rating ≥350mA, reverse voltage ≥40V, low VF (<0.4V at 300mA), and fast recovery (<10ns). Diode selection directly impacts efficiency and thermal performance, especially at high output voltages.
How does the LT1945EMS#PBF handle short-circuit or startup conditions on the positive output rail?
When the FB2 pin voltage falls below approximately 0.6V-indicating undervoltage, short-circuit, or soft-start-the LT1945EMS#PBF automatically extends the switch off-time from 400ns to 1.5μs and reduces the current limit from 350mA to ~250mA. This protects the internal switch and external components during fault conditions while maintaining regulation capability once the fault clears.
LT1945EMS#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:
- 0°C ~ 70°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP
LT1945EMS#PBF FAQ
1.How can I place an order for LT1945EMS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1945EMS#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 LT1945EMS#PBF reliable?
The price and inventory of LT1945EMS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1945EMS#PBF is usually 5 days.
3.What payment methods are accepted for LT1945EMS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1945EMS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1945EMS#PBF?
LT1945EMS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1945EMS#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 LT1945EMS#PBF?
For technical support, including LT1945EMS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1945EMS#PBF requirements.
6.How does Aetrix verify that LT1945EMS#PBF is sourced from the original manufacturer or authorized distributors?
All LT1945EMS#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 LT1945EMS#PBF meets industry standards.
7.What is the process for return or replacement of LT1945EMS#PBF?
All LT1945EMS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1945EMS#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 LT1945EMS#PBF part is unused and in its original packaging.
Return procedure for LT1945EMS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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