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Analog Devices Inc. LT1939EDD#TRPBF
- Part No.:
- LT1939EDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 12-WFDFN Exposed Pad
- Datasheet:
-
LT1939EDD#TRPBF.pdf
- Description:
- IC REG DL BUCK/LINEAR 12DFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,975
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Product details
Overview
LT1939EDD#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic dual-output DC/DC converter integrating a 2A current-mode step-down regulator and an adjustable linear regulator/controller. It operates from 3V to 25V input, delivers 0.8V–25V adjustable switching output and supports 13mA linear output with soft-start, power-good monitoring, and 250kHz–2.2MHz programmable frequency - used in automotive battery regulation and industrial distributed power systems.
For engineers reviewing the LT1939EDD#TRPBF datasheet, LT1939EDD#TRPBF pinout, LT1939EDD#TRPBF application, or LT1939EDD#TRPBF equivalent, key selection criteria include its dual-regulator architecture, 2.3A internal NPN switch saturation voltage (450mV at 2A), thermal shutdown protection, 12μA shutdown current, and 3mm × 3mm DFN-12 package with exposed ground pad for thermal management.
Technical Context
The LT1939EDD#TRPBF implements constant-frequency current-mode control with cycle-by-cycle peak current limiting, frequency foldback under overload, and internal slope compensation. Its dual-loop architecture uses separate FB and LFB inputs to regulate switching and linear outputs independently, both referenced to 0.8V with ±16mV tolerance over temperature.
It integrates a 2.3A NPN power switch with BST-driven base drive, a 13mA LDRV emitter output configurable as linear regulator or external transistor driver, and complementary open-collector PG/PG outputs with 30mV hysteresis triggered when FB or LFB deviates >10% from 0.8V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 25V - supports direct connection to automotive batteries and unregulated industrial supplies without pre-regulation. |
| Switching Output Current | 2A continuous - enabled by internal 2.3A NPN switch with 450mV saturation voltage at 2A, ensuring low conduction loss. |
| Linear Output Capability | 13mA at ≤1.6V dropout - LDRV pin provides regulated bias or drives external high-current pass transistor. |
| Feedback Reference Voltage | 0.8V ±16mV over –40°C to 125°C - enables precise output regulation down to 0.8V with resistor-divider programming. |
| Switching Frequency Range | 250kHz to 2.2MHz - set via RT/SYNC resistor or external sync signal; supports compact magnetics and EMI optimization. |
| Shutdown Quiescent Current | 12μA typical - enables ultra-low-power state in battery-powered systems without external disconnect. |
| Thermal Shutdown Threshold | Activated above 125°C junction - protects device during sustained overload; auto-recovery on cooldown. |
Pinout & Package
LT1939EDD#TRPBF is housed in a thermally enhanced 12-lead (3mm × 3mm) plastic DFN package with exposed ground pad (Pin 13), requiring PCB soldering for thermal and electrical integrity. Pin numbering follows top-view orientation per manufacturer marking LDJZ.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (1) | Main power input | Supplies internal bias circuits and collectors of both internal NPN switches; must be decoupled locally to ground. |
| SHDN (2) | Enable/disable control | 0.76V threshold with hysteresis; floating or >0.76V enables operation; <0.76V reduces supply current to 12μA. |
| SS (3) | Soft-start and tracking control | 2.75μA current source charges external capacitor; controls ramp rate of both switching and linear outputs. |
| PG (4) | Power-good active-low output | Open-collector NPN sinks current when FB or LFB falls below 90% of 0.8V reference. |
| VC (5) | Error amplifier output | Transconductance amplifier output (150–350μmho); used for loop compensation, current clamping, or override control. |
| RT/SYNC (6) | Frequency setting/synchronization | Resistor-to-ground sets 250kHz–2.2MHz; external clock syncs on rising edge with automatic slope compensation adjustment. |
| PG (7) | Power-good active-high output | Complementary open-collector NPN sinks current when FB or LFB rises above 90% of 0.8V reference. |
| FB (8) | Switching regulator feedback | Negative input to switcher error amp; regulated to 0.8V; bias current flows out (50–150nA). |
| LFB (9) | Linear regulator feedback | Negative input to linear error amp; regulated to 0.8V; bias current flows out (115–300nA). |
| LDRV (10) | Linear driver output | Emitting NPN output; 13mA max sink capability; configured as LDO output or external transistor driver. |
| BST (11) | Bootstrap supply | Drives internal NPN base above VIN; requires external diode + capacitor; minimum 2.2V boost voltage required. |
| SW (12) | Switch emitter node | Emitter of internal 2.3A NPN; connects to inductor; requires external Schottky catch diode to ground. |
| Exposed Pad (13) | Ground reference | Only GND connection; must be soldered to large copper area for thermal dissipation (θJC = 10°C/W). |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent regulation | Simultaneous 2A switching output and 13mA linear output, each with dedicated 0.8V reference and feedback path. |
| Programmable frequency with sync | 250kHz–2.2MHz resistor-set operation plus external clock synchronization with automatic slope compensation retention. |
| Robust protection suite | Cycle-by-cycle current limit, thermal shutdown, input undervoltage lockout, and short-circuit protection across full 3V–25V input range. |
| Tracking soft-start | Single SS capacitor controls ramp rate of both outputs; enables power sequencing and eliminates inrush current. |
| Low-power shutdown mode | 12μA quiescent current in shutdown - suitable for always-on battery-backed systems requiring long standby life. |
Applications
| Automotive Battery Regulation | Industrial Control Power |
|---|---|
Use Scenario: Regulating 12V automotive battery to stable 5V/3.3V rails for infotainment and ADAS modules under cold-crank (down to 3V) and load-dump (up to 25V) conditions. IC Role / Device Role / Timing Role: Primary dual-output power management IC providing isolated switching and linear regulation with integrated fault protection. Use Value: Eliminates need for external UVLO, thermal monitoring, and sequencing circuitry - reduces BOM count and board space in constrained automotive ECUs. | Use Scenario: Generating clean 3.3V and 5V supplies for PLC I/O modules and sensor interfaces operating from 24V industrial bus with wide ambient temperature range (–40°C to 125°C). IC Role / Device Role / Timing Role: Dual-rail DC/DC controller delivering regulated outputs with precise tracking and power-good signaling for system-level health monitoring. Use Value: Maintains regulation during brownouts and transients; PG/PG outputs enable safe power-up/down sequencing and watchdog reset coordination. |
| Wall Transformer Regulation | Distributed Power Regulation |
Use Scenario: Converting unregulated 9–24V AC/DC wall adapter output into tightly regulated 5V USB port and 3.3V microcontroller supply in consumer gateways and smart home hubs. IC Role / Device Role / Timing Role: Integrated buck + linear regulator replacing discrete solutions; supports variable input due to poor line regulation of low-cost adapters. Use Value: Achieves >87% efficiency at 1MHz (40.2kΩ RT/SYNC) while meeting CISPR-22 conducted EMI limits through programmable frequency and soft-switching control. | Use Scenario: Providing local point-of-load (POL) regulation in multi-board embedded systems where centralized 12V or 24V backplane feeds multiple subsystems. IC Role / Device Role / Timing Role: Compact dual-output POL regulator enabling independent voltage scaling and dynamic power management per subsystem. Use Value: 3mm × 3mm DFN package allows placement directly adjacent to FPGA or SoC; LDRV pin supports optional high-current linear post-regulation for noise-sensitive analog sections. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output DC/DC regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EMSE#PBF | Single 3A buck regulator only; no integrated linear regulator or LDRV output; 4mm × 3mm MSOP-10 package. | Suitable for higher-current single-rail applications but lacks dual-output tracking and linear assist capability. | Select when only high-current switching output is needed and board space permits larger MSOP package. |
| TPS65270RGET | Two 2A synchronous buck regulators; no linear regulator; integrated MOSFETs; 20-pin QFN; 2.95V–18V input. | Supports higher efficiency via synchronous rectification but excludes linear regulation and cannot operate above 18V input. | Select for 12V-input systems requiring dual synchronous bucks and lower quiescent current (25μA shutdown). |
Compared with LTC3631EMSE#PBF and TPS65270RGET, the LT1939EDD#TRPBF uniquely combines switching and linear regulation in one die, enabling precise output tracking, ultra-low-noise auxiliary rails, and seamless integration into 3V–25V wide-input systems - making it optimal for mixed-signal automotive and industrial designs requiring both efficiency and analog cleanliness.
Availability
LT1939EDD#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial control power, and wall transformer regulation requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT1939EDD#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, serving industrial, automotive, communications, and healthcare markets.
The LT1939EDD#TRPBF belongs to ADI's legacy Linear Technology power management portfolio, designed specifically for compact, wide-input dual-output DC/DC conversion in harsh environments where reliability, thermal performance, and design simplicity are critical.
FAQ
What is the maximum supported input voltage for the LT1939EDD#TRPBF?
The LT1939EDD#TRPBF has an absolute maximum VIN rating of 25V and operates continuously up to 25V input. Its internal NPN switch and BST circuitry are rated for 25V collector-emitter and 45V BST-to-SW differential voltage, enabling robust operation in automotive and industrial 24V systems with transient margin.
Does the LT1939EDD#TRPBF support synchronization to an external clock?
Yes, the LT1939EDD#TRPBF supports external clock synchronization via the RT/SYNC pin. When driven with a TTL/CMOS-compatible clock signal (250kHz–2500kHz), it locks switching to the rising edge and automatically adjusts internal slope compensation to prevent subharmonic oscillation - preserving stability without manual compensation changes.
How does the soft-start function work on the LT1939EDD#TRPBF?
The LT1939EDD#TRPBF uses a 2.75μA internal current source to charge an external capacitor on the SS pin, generating a controlled voltage ramp. This ramp directly modulates both the switching and linear regulator reference points, enabling simultaneous, tracked startup with no input surge current - critical for powering FPGAs and multi-rail processors.
Can the LT1939EDD#TRPBF drive an external pass transistor?
Yes, the LT1939EDD#TRPBF's LDRV pin functions as an emitter-follower output capable of sourcing up to 13mA. When configured with external components, it can drive the base of an external NPN transistor to deliver higher linear output current - extending its utility beyond the integrated 13mA capability while maintaining 0.8V reference accuracy.
What thermal management requirements apply to the LT1939EDD#TRPBF?
The LT1939EDD#TRPBF requires soldering of its exposed pad (Pin 13) to a minimum 100mm² copper area for effective heat dissipation. With θJC(PAD) = 10°C/W, this ensures junction temperature remains within –40°C to 125°C operating range under 2A load at 25°C ambient - essential for automotive and industrial reliability.
LT1939EDD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 12-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Topology:
- Step-Down (Buck) (1), Linear (LDO) (1)
- Number of Outputs:
- 2
- Frequency - Switching:
- 500kHz ~ 2.4MHz
- Voltage/Current - Output 1:
- 0.8V ~ 24.25V, 2A
- Voltage/Current - Output 2:
- 0.8V ~ 24.25V, 1A
- Voltage/Current - Output 3:
- -
- w/LED Driver:
- No
- w/Supervisor:
- No
- w/Sequencer:
- No
- Voltage - Supply:
- 3V ~ 25V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 12-DFN (3x3)
LT1939EDD#TRPBF FAQ
1.How can I place an order for LT1939EDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1939EDD#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 LT1939EDD#TRPBF reliable?
The price and inventory of LT1939EDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1939EDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1939EDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1939EDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1939EDD#TRPBF?
LT1939EDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1939EDD#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 LT1939EDD#TRPBF?
For technical support, including LT1939EDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1939EDD#TRPBF requirements.
6.How does Aetrix verify that LT1939EDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1939EDD#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 LT1939EDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1939EDD#TRPBF?
All LT1939EDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1939EDD#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 LT1939EDD#TRPBF part is unused and in its original packaging.
Return procedure for LT1939EDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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