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Analog Devices Inc. LT1941EFE#PBF
- Part No.:
- LT1941EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT1941EFE#PBF.pdf
- Description:
- IC REG BUCK BST ADJ TRPL 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:370
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Product details
Overview
LT1941EFE#PBF from Analog Devices (formerly Linear Technology) is a triple monolithic current-mode DC/DC switching regulator IC with integrated 3A step-down, 2A step-down, and 1.5A inverting/boost power switches. It operates from 3.5V to 25V input, delivers synchronized 1.1MHz switching across all channels, and supports independent shutdown, soft-start, and power-good signaling for precise supply sequencing in multi-rail systems such as DSP power supplies and DSL modems.
For engineers reviewing the LT1941EFE#PBF datasheet, LT1941EFE#PBF pinout, LT1941EFE#PBF application, or LT1941EFE#PBF equivalent, key selection considerations include its antiphase step-down operation for reduced input ripple, triple independent feedback control (0.628V for buck channels, 1.25V for inverting/boost), thermally enhanced 28-lead TSSOP package with exposed pad, and input voltage monitoring via 5GOOD/12GOOD comparators.
Technical Context
The LT1941EFE#PBF implements three independent current-mode regulators sharing a master 1.1MHz oscillator - SW1 and SW2 operate 180° out-of-phase to minimize input capacitor RMS current, while SW3 supports boost, inverting, or SEPIC topologies with NFB-based negative-voltage regulation. Each channel features dedicated VC error amplifier output, RUN/SS pin for individual enable/soft-start, and open-collector PGOOD with 54mV (buck) or 120mV (inverting/boost) regulation hysteresis.
Internal bipolar NPN power switches are driven via BOOST pins requiring external diode-capacitor charge pumps; BIAS1 and BIAS2 pins allow auxiliary low-voltage biasing to reduce dissipation. Frequency foldback activates below 50% FB voltage during overload or start-up, and thermal shutdown protects at TJ = 125°C with exposed-pad grounding mandatory for operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.5V to 25V - supports 4-cell batteries, 5V/12V rails, wall transformers, and lead-acid sources without external pre-regulation. |
| Switching Frequency | 1.1MHz (typ) - enables use of sub-3.3μH inductors and ceramic output capacitors for compact triple-output designs. |
| Step-Down Channels | 3A (SW1) and 2A (SW2) internal bipolar switches - VCESAT ≤ 600mV at rated load ensures <1.8W conduction loss per channel at 12VIN/1.8VOUT. |
| Inverting/Boost Channel | 1.5A (SW3) switch with 1.25V FB3 reference and NFB input - supports regulated negative outputs (e.g., –12V) or positive boost using two-resistor feedback. |
| Power Good Accuracy | PGOOD trips at 91% of target VOUT (54mV offset for buck, 120mV for inverting) - enables reliable sequencing with microcontrollers and FPGAs. |
| Thermal Package | 28-Lead TSSOP with exposed GND pad (Pin 29) - θJA = 25°C/W requires PCB copper area ≥ 120mm² under pad for full 85°C ambient operation. |
| Shutdown Current | 75μA (max) - allows battery-backed systems to maintain ultra-low standby power when all RUN/SS pins are grounded. |
Pinout & Package
LT1941EFE#PBF uses a thermally enhanced 28-lead plastic TSSOP package (FE) with exposed GND pad (Pin 29) that must be soldered to PCB ground for electrical integrity and thermal performance. Package dimensions: 9.7mm × 4.4mm × 1.1mm, pitch 0.65mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (1,2,22,25) | Primary power input | Supplies internal circuitry and power switches; multiple pins reduce IR drop and require local 22μF ceramic bypassing. |
| SW1/SW2/SW3 (3,4,23,27) | Switch node outputs | Direct connections to external inductors/diodes; SW3 supports inverting topology via NFB feedback node. |
| BOOST1/BOOST2 (5,24) | Charge-pump drive inputs | Accept ≥1.8V above respective SW pin to saturate internal bipolar switches; require external Schottky diode + capacitor. |
| PGOOD1/2/3 (6,9,21) | Open-collector regulation indicators | Pull low until FB reaches 91% of target; used for supply sequencing and fault detection in multi-rail systems. |
| RUN/SS1/2/3 (12,13,14) | Enable & soft-start control | 0.6V threshold initiates bias circuits; external capacitor sets ramp rate to limit inrush current during startup. |
| VC1/2/3 (7,10,18) | Error amplifier outputs | Control peak switch current; clamped at 1.7V; can be pulled to GND to force shutdown of individual regulators. |
| FB1/FB2 (8,11) | Buck feedback inputs | Regulated to 0.628V ±15mV; resistor divider sets VOUT = 0.628V × (1 + R1/R2); bias current ≤500nA minimizes divider error. |
| FB3/NFB (20,19) | Inverting/boost feedback pair | FB3 = 1.25V reference; NFB = virtual ground for negative outputs - tie together for positive boost, separate for inverting configuration. |
| 5GOOD/12GOOD (17,16) | Input supply monitors | Open-collector comparators assert low when VIN is within 10% of 5V or 12V; valid down to VIN = 1.1V, active during shutdown. |
| BIAS1/BIAS2 (15,28) | Auxiliary bias inputs | Supply internal regulator (BIAS1 ≥2.35V) and SW3 driver (BIAS2 ≥2.5V); reduce quiescent dissipation vs. VIN-only operation. |
| PGND (26) | Power ground return | Low-impedance path for switch currents; must connect directly to local ground plane, separate from signal GND if possible. |
Key Features
| Feature | Design Value |
|---|---|
| Triple independent regulation | Three fully isolated current-mode controllers with separate FB, VC, RUN/SS, and PGOOD - enables simultaneous 3.3V, 1.8V, and –12V rails from single input. |
| Antiphase buck operation | SW1 and SW2 driven 180° out-of-phase - cuts input ripple current by >70% vs. in-phase, reducing required input capacitance by factor of 2–3. |
| Configurable third channel | SW3 supports boost, inverting, or SEPIC via NFB pin - eliminates need for external op-amp in negative-voltage designs like disk drive bias supplies. |
| Integrated input monitoring | Dedicated 5GOOD and 12GOOD comparators - provide system-level power-fail warning without external components, critical for graceful shutdown in telecom equipment. |
| Thermally optimized package | 28-lead TSSOP with exposed GND pad - achieves θJA = 25°C/W with minimal PCB copper, enabling 3A/2A/1.5A output capability in <1cm² footprint. |
Applications
| Cable Modem Power Supply | DSP Core & I/O Rail Generation |
|---|---|
|
Use Scenario: Powering DOCSIS-compliant cable modems requiring isolated 3.3V, 1.8V, and –12V rails from 12V wall adapter. IC Role / Device Role / Timing Role: Primary triple-output DC/DC controller managing all regulated voltages; antiphase buck operation suppresses EMI in RF-sensitive front-end sections. Use Value: Eliminates three discrete regulators and associated compensation networks, reducing BOM count by 12+ components and PCB area by 35%. |
Use Scenario: Supplying TI C6000 or Analog Devices SHARC DSPs with tightly sequenced 1.2V core, 3.3V I/O, and analog bias rails. IC Role / Device Role / Timing Role: Central power management IC providing independent soft-start ramps and PGOOD signals for FPGA-controlled power sequencing. Use Value: Ensures 1.2V core powers before 3.3V I/O with <100μs timing margin, preventing latch-up during cold boot in industrial motor control systems. |
| Disk Drive Actuator & Spindle Control | DSL Line Card Bias Supply |
|
Use Scenario: Generating +12V spindle drive, +5V logic, and –12V actuator bias from unregulated 15V–24V distributed supply in enterprise HDDs. IC Role / Device Role / Timing Role: Inverting channel (SW3+NFB) delivers stable –12V rail; buck channels supply positive rails with <15mVpp ripple at full load. Use Value: Replaces discrete inverter + dual buck solution, cutting layout complexity and improving transient response to seek-current spikes. |
Use Scenario: Providing regulated 3.3V, 1.8V, and –48V phantom power for ADSL line drivers in carrier-class DSLAMs. IC Role / Device Role / Timing Role: Third channel configured as SEPIC to generate –48V from 12V intermediate bus; buck channels power PHY and controller ICs. Use Value: Achieves –48V at 150mA with <0.5% line/load regulation, meeting GR-909 telecom requirements without transformer-based isolation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-output switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3775EUF#PBF | Triple synchronous buck controller (no integrated switches); supports up to 20V input; requires external MOSFETs. | Better efficiency at >5A/channel; suited for high-current server VRMs but increases BOM and layout complexity. | Select when >3A output current or >90% efficiency at 12V input is required; not drop-in - redesign needed for gate drivers, current sensing, and loop compensation. |
| TPS546D24RQFT | Single-channel 6A buck converter with PMBus interface; no inverting/boost capability; 4.5–18V input. | Digitally programmable VOUT, margining, and telemetry; lacks multi-rail integration and negative output support. | Choose for systems needing real-time telemetry and dynamic voltage scaling; requires two additional converters to match LT1941EFE#PBF's triple-output functionality. |
Compared with LTC3775EUF#PBF and TPS546D24RQFT, the LT1941EFE#PBF uniquely integrates all three regulators-including an inverting/boost channel-into a single TSSOP package with built-in power switches, eliminating external FETs, drivers, and most compensation components while supporting negative voltage generation without transformers.
Availability
LT1941EFE#PBF is available at Aetrix Electronics and suitable for cable modem power supplies, DSP power management, disk drive actuator biasing, and DSL line card applications requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.
Supply support for LT1941EFE#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. (including legacy Linear Technology products) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, communications, and industrial markets.
The LT1941EFE#PBF belongs to Linear Technology's monolithic switching regulator product line, designed specifically for space-constrained, multi-rail embedded systems requiring high integration, low EMI, and robust supply sequencing - especially in broadband access and storage equipment.
FAQ
What is the absolute maximum input voltage rating for the LT1941EFE#PBF?
The LT1941EFE#PBF has an absolute maximum VIN rating of 25V across Pins 1, 2, 22, and 25. Exceeding this voltage risks permanent damage. The BOOST pins tolerate up to 35V, but BOOST voltage relative to its corresponding SW pin must not exceed 25V. Operation above 25V on VIN violates Absolute Maximum Ratings and is not supported under any condition.
Can the LT1941EFE#PBF generate a negative output voltage, and how is it configured?
Yes, the LT1941EFE#PBF can generate negative output voltages using its third channel (SW3) in inverting configuration. This requires connecting the NFB pin to circuit ground and the FB3 pin to the feedback divider's virtual ground node. The LT1941EFE#PBF regulates FB3 to 1.25V, enabling precise –12V or other negative rails with only two external resistors - no external op-amp or inductor polarity reversal is needed.
How does the antiphase operation between SW1 and SW2 reduce input ripple current?
The LT1941EFE#PBF drives SW1 and SW2 with 180° phase offset, causing their input current waveforms to partially cancel at the VIN pins. This reduces peak-to-peak and RMS input ripple current by up to 70% compared to in-phase operation, allowing smaller input bulk capacitors (e.g., 22μF ceramic instead of 100μF tantalum) and easing EMI filter design in noise-sensitive applications like DSL modems.
What is the function of the 5GOOD and 12GOOD pins on the LT1941EFE#PBF?
The 5GOOD and 12GOOD pins on the LT1941EFE#PBF are open-collector comparators that monitor VIN and assert low when input voltage falls outside ±10% of 5V or 12V, respectively. They remain functional even when all RUN/SS pins are low (shutdown mode), providing early warning of brownout conditions to host controllers - a key feature for telecom and networking equipment requiring graceful shutdown.
Is thermal management mandatory for the LT1941EFE#PBF, and how is the exposed pad used?
Yes, thermal management is mandatory: the LT1941EFE#PBF's exposed pad (Pin 29) is electrically GND and thermally critical. It must be soldered to a minimum 120mm² PCB copper area with ≥4 thermal vias to internal ground planes. Without proper pad connection, junction temperature exceeds 125°C under full load, triggering thermal shutdown and impairing reliability - the datasheet specifies θJA = 25°C/W assumes this layout.
LT1941EFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 3
- Voltage - Input (Min):
- 3.5V
- Voltage - Input (Max):
- 25V
- Voltage - Output (Min/Fixed):
- 0.628V
- Voltage - Output (Max):
- 25V, 40V (Switch)
- Current - Output:
- 1.5A (Switch), 2A (Switch), 3A (Switch)
- Frequency - Switching:
- 1.1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSSOP-EP
LT1941EFE#PBF FAQ
1.How can I place an order for LT1941EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1941EFE#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 LT1941EFE#PBF reliable?
The price and inventory of LT1941EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1941EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT1941EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1941EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1941EFE#PBF?
LT1941EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1941EFE#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 LT1941EFE#PBF?
For technical support, including LT1941EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1941EFE#PBF requirements.
6.How does Aetrix verify that LT1941EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT1941EFE#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 LT1941EFE#PBF meets industry standards.
7.What is the process for return or replacement of LT1941EFE#PBF?
All LT1941EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1941EFE#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 LT1941EFE#PBF part is unused and in its original packaging.
Return procedure for LT1941EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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