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Analog Devices Inc. LT1940EFE#TRPBF
- Part No.:
- LT1940EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT1940EFE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.4A DL 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:6,332
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Product details
Overview
LT1940EFE#TRPBF from Analog Devices (formerly Linear Technology) is a dual monolithic 1.4A, 1.1MHz step-down DC/DC switching regulator with internal 2A bipolar NPN power switches, wide 3.6V–25V input range, anti-phase operation to reduce input ripple, and independent shutdown/soft-start and power-good signaling. It targets DSP power supplies, disk drives, and DSL/cable modems requiring compact, sequenced dual-rail regulation.
For engineers reviewing the LT1940EFE#TRPBF datasheet, LT1940EFE#TRPBF pinout, LT1940EFE#TRPBF application, or LT1940EFE#TRPBF equivalent, key selection criteria include confirmed dual 1.4A output capability, 1.1MHz constant-frequency current-mode control, thermal-enhanced 16-lead TSSOP package with exposed GND pad, and independent FB/PG/RUN-SS per channel for sequencing-critical embedded power systems.
Technical Context
The LT1940EFE#TRPBF implements two independent current-mode PWM buck regulators synchronized to a single 1.1MHz master oscillator with 180° phase offset-reducing input RMS ripple by canceling inductor currents. Each channel features a dedicated error amplifier (VC pin), 1.25V feedback reference with ±15mV tolerance over –40°C to 85°C, and cycle-by-cycle current limiting with 1.8A–2.4A switch current limit.
Operation relies on external BOOST capacitors and Schottky diodes to generate gate drive voltages > VIN for full saturation of internal bipolar switches. Power-good outputs (PG1/PG2) are open-collector comparators asserting high when FB voltage reaches 90% of regulation (±125mV offset), enabling precise supply sequencing with microcontrollers and DSPs without external logic.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 25V - supports 4-cell batteries, unregulated wall transformers, and distributed 12V/24V rails without pre-regulation. |
| Switching Frequency | 1.1MHz (TYP), 0.95–1.35MHz (full temp range) - enables use of sub-5mm ceramic inductors (e.g., 3.3µH) and low-ESR 10µF X5R/X7R output caps. |
| Output Current per Channel | 1.4A continuous - verified at VOUT = 3.3V/5V with proper inductor selection (e.g., Sumida CR43-3R3) and thermal layout. |
| Feedback Reference Voltage | 1.250V ±15mV (–40°C to 85°C) - sets output via resistor divider; enables accurate 1.8V–5V programmable rails with <±1% regulation error. |
| Power-Good Threshold | FB voltage ≥ 90% of target (±125mV offset) - provides clean, glitch-free sequencing signal compatible with FPGA/configurable logic reset inputs. |
| Thermal Resistance | θJA = 45°C/W, θJC = 10°C/W - requires soldered exposed pad (Pin 17) to PCB copper for sustained 1.4A operation at 85°C ambient. |
| Shutdown Current | 45µA max - ensures ultra-low system standby power when both RUN/SS pins are pulled low. |
Pinout & Package
LT1940EFE#TRPBF uses a 16-lead thermally enhanced TSSOP package with exposed GND pad (Pin 17), requiring soldering to PCB for thermal and electrical integrity. Pin numbering follows standard JEDEC TSSOP top-view convention.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BOOST1, BOOST2 (1, 8) | Bootstrap drive voltage input | Accepts externally generated voltage ≥2.5V above SW to fully saturate internal bipolar NPN switches; ties to VOUT or VIN via Schottky diode + 0.1µF capacitor. |
| SW1, SW2 (2, 7) | Internal switch node | Connects directly to inductor, catch diode cathode, and BOOST capacitor; carries high di/dt pulsed current requiring short, low-inductance routing. |
| VIN (3–6) | Main power input | Four parallel pins share input current; must be tied together and locally bypassed with ≥4.7µF X7R ceramic capacitor near Pins 3–6. |
| FB1, FB2 (9, 16) | Feedback sense input | Regulated to 1.25V; connects to resistor divider tap from output rail; bias current ≤1.2µA minimizes divider error. |
| VC1, VC2 (10, 15) | Error amplifier output | Controls peak switch current; used for loop compensation (type II/III) or external override; clamped at 0.75V threshold and 1.8V max. |
| PG1, PG2 (11, 14) | Open-collector power-good | Pulled high via external resistor when output is within 10% of target; valid only if VIN >2.4V and corresponding RUN/SS is high. |
| RUN/SS1, RUN/SS2 (12, 13) | Enable & soft-start control | Pulled high (>0.6V) to enable bias circuits; capacitor to GND sets soft-start ramp time; pulled low to shut down individual channel. |
| GND (17) | Ground reference & thermal path | Exposed pad must be soldered to ≥1cm² PCB copper pour for thermal dissipation and noise immunity; electrically connected to all internal grounds. |
Key Features
| Feature | Design Value |
|---|---|
| Anti-phase switching | Reduces input ripple current by up to 50% vs. in-phase dual converters-enabling smaller input bulk capacitance and lower EMI filter cost. |
| Independent power-good outputs | Eliminates need for external monitoring ICs or discrete comparators when sequencing 3.3V/5V rails for FPGAs or multi-core processors. |
| Current-mode PWM architecture | Provides inherent cycle-by-cycle overcurrent protection and stable loop response with minimal compensation components (2–3 passive parts). |
| Thermally enhanced TSSOP | Exposes die attach pad as Pin 17 GND-delivers 10°C/W junction-to-case resistance for reliable 1.4A/channel operation without heatsinks. |
| Wide VIN range support | Operates directly from unregulated 12V/24V industrial supplies or 4-cell Li-ion packs-removing need for upstream pre-regulators in portable equipment. |
Applications
| Disk Drive Power Supply | DSP Core & I/O Rail Generation |
|---|---|
Use Scenario: Dual-rail power for 2.5-inch HDD with separate 3.3V motor driver and 1.8V/2.5V logic interface. IC Role / Device Role / Timing Role: Primary DC/DC converter delivering regulated 3.3V (1.4A) and 1.8V (1.4A) from 12V input with anti-phase ripple cancellation. Use Value: Enables compact 2-layer PCB layout with <10mm² total converter footprint using 3.3µH and 2.2µH inductors and ceramic caps. | Use Scenario: Sequenced power for TI C6000 or Analog Devices SHARC DSPs requiring 1.2V core and 3.3V I/O before configuration. IC Role / Device Role / Timing Role: Dual buck regulator with independent RUN/SS and PG pins to enforce strict power-up order without external timers. Use Value: Guarantees 3.3V rail stabilizes first (via PG1 assertion), then enables 1.2V rail via PG1-controlled RUN/SS2, preventing latch-up during boot. |
| DSL/Cable Modem Power | Wall Transformer Regulation |
Use Scenario: Compact AC/DC adapter replacement powering ADSL line driver (5V), PHY (3.3V), and microcontroller (1.8V) from 9–15V unregulated DC. IC Role / Device Role / Timing Role: High-efficiency dual converter accepting wide-input unregulated supply; operates at 85°C ambient in sealed enclosure. Use Value: Achieves >85% efficiency at full load across 9–15V input range, eliminating need for forced air cooling in consumer broadband units. | Use Scenario: Regulating noisy 9V/12V wall transformer output into clean 3.3V/5V for IoT gateway MCU and sensors. IC Role / Device Role / Timing Role: Input ripple rejection via anti-phase operation and ceramic-capacitor-based filtering reduces conducted EMI below CISPR-22 Class B limits. Use Value: Meets EN55022 radiated emissions without ferrite beads or common-mode chokes-reducing BOM cost by $0.15/unit. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EFE#PBF | Single-channel 3A buck; no dual output or anti-phase; higher 3MHz freq; requires external MOSFETs | Suitable only for single-rail designs needing >1.4A; lacks integrated sequencing PG signals | Select only if redesigning for single-output + external sync or higher frequency operation. |
| TPS54290PWPR | Dual 2A channels; 300kHz–2MHz adjustable freq; no anti-phase; requires external compensation | Better light-load efficiency; wider freq tuning but higher input ripple due to in-phase switching | Prefer when input ripple is less critical and design flexibility for freq optimization is required. |
Compared with LTC3631EFE#PBF and TPS54290PWPR, LT1940EFE#TRPBF uniquely delivers guaranteed anti-phase operation, integrated PG sequencing, and bipolar-switch efficiency at 1.1MHz in a single 16-pin TSSOP-making it optimal for space-constrained dual-rail systems where input ripple and board area are primary constraints.
Availability
LT1940EFE#TRPBF is available at Aetrix Electronics and suitable for disk drive power supplies, DSP power management, and DSL/cable modem designs requiring stable component supply, long-term lifecycle support, and traceable sourcing for industrial and telecom applications.
Supply support for LT1940EFE#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT1940EFE#TRPBF belongs to ADI's legacy Linear Technology Power Management product line, designed specifically for compact, high-density dual-output DC/DC conversion in datacom, storage, and embedded computing applications where thermal performance and sequencing reliability are critical.
FAQ
What is the maximum input voltage rating for LT1940EFE#TRPBF?
The absolute maximum input voltage (VIN) for LT1940EFE#TRPBF is 25V, with recommended operating range from 3.6V to 25V. Exceeding 25V risks permanent damage. The LT1940EFE#TRPBF datasheet specifies that BOOST pin voltage must not exceed 35V, and BOOST-to-SW differential must stay below 25V-both critical when selecting external boost diodes and capacitors.
Does LT1940EFE#TRPBF support independent output voltage programming?
Yes, LT1940EFE#TRPBF supports fully independent output voltage programming via separate FB1 and FB2 pins, each regulated to 1.25V ±15mV. Designers set VOUT1 and VOUT2 using individual resistor dividers (e.g., R1/R2 for Channel 1, R3/R4 for Channel 2), enabling asymmetric rails like 1.8V/3.3V or 3.3V/5V without shared components.
How does LT1940EFE#TRPBF achieve anti-phase switching?
LT1940EFE#TRPBF achieves anti-phase switching using a master-slave oscillator architecture: a single 1.1MHz master oscillator generates CLK1 and CLK2 signals with precisely 180° phase offset. This forces SW1 and SW2 to switch alternately, reducing input capacitor RMS current and peak ripple amplitude-verified in Figure 1 and Typical Performance Characteristics.
What thermal design requirements apply to LT1940EFE#TRPBF?
LT1940EFE#TRPBF requires the exposed pad (Pin 17) to be soldered to a minimum 1cm² copper pour connected to system ground. With θJA = 45°C/W, failure to thermally anchor the pad results in junction temperatures exceeding 125°C at full 1.4A load and 85°C ambient-triggering thermal shutdown. Thermal vias (≥4×0.3mm) under the pad are strongly recommended.
Can LT1940EFE#TRPBF operate with ceramic output capacitors only?
Yes, LT1940EFE#TRPBF is explicitly optimized for ceramic output capacitors: its current-mode control loop is stable with zero-ESR ceramics, and typical designs use 10µF X5R/X7R caps per channel. The datasheet confirms low output ripple (e.g., <15mVpp at 1.4A) with 10µF ceramics and warns against Y5V/Z5U types due to voltage/temperature coefficient-induced capacitance loss.
LT1940EFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 2
- Voltage - Input (Min):
- 3.6V
- Voltage - Input (Max):
- 25V
- Voltage - Output (Min/Fixed):
- 1.25V
- Voltage - Output (Max):
- 22V
- Current - Output:
- 1.4A
- Frequency - Switching:
- 1.1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT1940EFE#TRPBF FAQ
1.How can I place an order for LT1940EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1940EFE#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 LT1940EFE#TRPBF reliable?
The price and inventory of LT1940EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1940EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1940EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1940EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1940EFE#TRPBF?
LT1940EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1940EFE#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 LT1940EFE#TRPBF?
For technical support, including LT1940EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1940EFE#TRPBF requirements.
6.How does Aetrix verify that LT1940EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1940EFE#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 LT1940EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1940EFE#TRPBF?
All LT1940EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1940EFE#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 LT1940EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT1940EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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