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Analog Devices Inc. LT1939IDD#TRPBF
- Part No.:
- LT1939IDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 12-WFDFN Exposed Pad
- Datasheet:
-
LT1939IDD#TRPBF.pdf
- Description:
- IC REG DL BUCK/LINEAR 12DFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,690
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Product details
Overview
LT1939IDD#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic dual-output DC/DC regulator integrating a 2.3A current-mode step-down switcher and an adjustable linear regulator/controller. It operates from 3V to 25V input, delivers up to 2A total output current (1A per channel), regulates down to 0.8V, and features soft-start, power-good monitoring, and synchronization capability - used in automotive battery regulation and industrial distributed power systems.
For engineers reviewing the LT1939IDD#TRPBF datasheet, LT1939IDD#TRPBF pinout, LT1939IDD#TRPBF application, or LT1939IDD#TRPBF equivalent, key selection criteria include its dual-regulator architecture, 250kHz–2.2MHz programmable switching frequency, thermal shutdown protection, 12μA shutdown current, and 3mm × 3mm DFN-13 package with exposed ground pad.
Technical Context
The LT1939IDD#TRPBF implements current-mode PWM control for the buck converter, using cycle-by-cycle peak current limiting and slope compensation to ensure stability across duty cycles. Its internal 2.3A NPN switch supports wide VIN (3V–25V) operation and integrates BST boost drive for saturation.
It embeds a second independent control path: a transconductance error amplifier driving the LDRV pin (13mA max), configurable as either a linear regulator output or external NPN driver. Both regulators share soft-start via the SS pin and are monitored by complementary PG/PG outputs with 30mV hysteresis referenced to 0.8V FB/LFB thresholds.
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. |
| Switch Current Limit | 2.3A typical - guarantees robust short-circuit protection across full temperature range (–40°C to 125°C). |
| Switching Frequency | 250kHz to 2.2MHz - resistor-programmable or externally synchronized; enables trade-off between efficiency and component size. |
| Feedback Reference | 0.8V ±16mV over temperature - precise, stable reference for both switching and linear outputs, enabling accurate voltage programming. |
| Shutdown Current | 12μA typical - enables ultra-low-power management in battery-backed systems during standby. |
| Package Thermal Resistance | θJA = 45°C/W - thermally enhanced 3mm × 3mm DFN with exposed GND pad for high-power-density PCB layouts. |
| Power-Good Threshold | 90% of 0.8V (0.72V) with 30mV hysteresis - provides reliable system-level power sequencing and fault detection. |
Pinout & Package
LT1939IDD#TRPBF uses a 12-lead (3mm × 3mm) plastic DFN package with exposed thermal pad (Pin 13 = GND). The package is RoHS-compliant, lead-free, and supplied in tape-and-reel format (#TRPBF).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Main power input | Powers internal bias circuitry and connects to collectors of internal NPN switch and LDRV transistor; requires local high-frequency decoupling. |
| SHDN (Pin 2) | Enable/disable control | 0.76V threshold with hysteresis; pulls device into 12μA shutdown mode when below threshold - usable as undervoltage lockout. |
| SS (Pin 3) | Soft-start and tracking control | Sinks/supplies current to external capacitor; controls ramp rate of both switching and linear outputs; enables output voltage tracking. |
| PG / PG (Pins 4 & 7) | Complementary power-good indicators | Open-collector NPN outputs; PG sinks when FB/LFB < 0.72V, PG sinks when FB/LFB > 0.72V - supports logic-level sequencing and fault signaling. |
| VC (Pin 5) | Error amplifier output | Transconductance amplifier output; sets peak switch current; used for loop compensation and overload clamping. |
| RT/SYNC (Pin 6) | Frequency setting/synchronization | Accepts resistor-to-ground (250kHz–2.2MHz) or external clock (250kHz–2500kHz); auto-synchronizes on rising edge with slope compensation adjustment. |
| FB (Pin 8) | Switching regulator feedback | Negative input of buck error amplifier; regulated to 0.8V; bias current flows out - used with resistor divider to set VOUT1. |
| LFB (Pin 9) | Linear regulator feedback | Negative input of linear error amplifier; regulated to 0.8V; bias current flows out - used to set VOUT2 via external resistors or direct connection. |
| LDRV (Pin 10) | Linear regulator output/driver | Emitter of internal NPN; delivers up to 13mA; can source current as LDO output or drive external pass transistor for higher current. |
| BST (Pin 11) | Bootstrap supply | Provides >VIN gate drive to internal NPN switch; requires external diode + capacitor; minimum BST–SW voltage = 2.2V for full saturation. |
| SW (Pin 12) | Switch node | Emiter of internal power NPN; connects to inductor and catch diode; exhibits high dV/dt during turn-off - requires local Schottky diode and ground return. |
| Exposed Pad (Pin 13) | Ground reference & thermal path | Only GND connection; must be soldered to large PCB copper area for thermal performance and signal integrity - serves as both power and small-signal ground. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-output regulation | Integrates independent buck converter (2.3A switch) and linear regulator (13mA LDRV) - eliminates need for discrete secondary LDO in compact power trees. |
| Programmable switching frequency | 250kHz–2.2MHz via RT/SYNC resistor or external clock - allows optimization of inductor size, efficiency, and EMI profile for each application. |
| Soft-start and tracking | Single SS pin controls ramp rate of both outputs and enables precise voltage sequencing - prevents inrush current and ensures safe power-up of multi-rail systems. |
| Robust protection suite | Cycle-by-cycle current limit, thermal shutdown, input UVLO, and short-circuit protection across full 3V–25V input range - ensures reliability in harsh environments. |
| Low-quiescent-power shutdown | 12μA shutdown current - extends battery life in portable and always-on industrial sensors without sacrificing startup speed. |
Applications
| Automotive Battery Regulation | Industrial Control Systems |
|---|---|
Use Scenario: Regulating 12V or 24V vehicle battery to stable 5V and 3.3V rails for infotainment, ADAS camera modules, and CAN interface ICs. IC Role / Device Role / Timing Role: Primary dual-output DC/DC controller managing main system power with thermal resilience and load dump tolerance. Use Value: Wide 3V–25V input range accommodates cold-crank (≈6V) and load-dump (≈40V transient clamped) conditions; 125°C rated operation ensures under-hood reliability. | Use Scenario: Powering PLC I/O modules, sensor signal conditioners, and isolated communication interfaces in factory automation equipment. IC Role / Device Role / Timing Role: Compact, self-contained power solution delivering tightly regulated dual voltages from unregulated 24V industrial bus. Use Value: Integrated PG/PG outputs enable deterministic power sequencing; low shutdown current supports energy-efficient sleep modes in smart controllers. |
| Wall Transformer Regulation | Distributed Power Regulation |
Use Scenario: Converting noisy, unregulated AC/DC wall adapter output (e.g., 9–24V) into clean 5V/3.3V for embedded microcontrollers and peripherals. IC Role / Device Role / Timing Role: Input-stage regulator providing ripple rejection, overcurrent protection, and soft-start before downstream point-of-load converters. Use Value: Adjustable frequency avoids audible noise in consumer devices; 0.8V reference enables accurate low-voltage outputs critical for modern MCUs. | Use Scenario: Local regulation at board edges or remote subsystems where centralized 5V/12V rails require localized conversion to 3.3V/1.8V. IC Role / Device Role / Timing Role: Distributed buck-LDO pair minimizing IR drop and noise coupling in multi-board systems with long interconnects. Use Value: Synchronization capability allows multiple LT1939IDD#TRPBF units to operate at same frequency - reducing beat frequencies and simplifying EMI filtering. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EMSE#TRPBF | Monolithic 3A buck only (no integrated linear regulator); 4V–15V input; fixed 3.3V/5V options or adjustable via resistor. | Lacks LDRV linear output path - requires external LDO for second rail; better suited for single-output high-current apps. | Select when higher 3A switch current is required and linear regulation is handled separately. |
| TPS65270QPWPRQ1 | Automotive-grade dual 2A buck (no linear regulator); 4.5V–18V input; integrated power sequencing and fault reporting. | Designed for AEC-Q100 automotive use; includes watchdog timer and I²C interface - no analog LDRV functionality. | Select for automotive infotainment requiring ASIL-B compliance and digital supervision, not analog linear control. |
Compared with LTC3631EMSE#TRPBF and TPS65270QPWPRQ1, the LT1939IDD#TRPBF uniquely combines buck switching and linear regulation in one package, enabling compact dual-rail designs without external LDOs - ideal for space-constrained industrial and automotive subsystems where analog flexibility matters more than digital control.
Availability
LT1939IDD#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial control systems, and wall transformer regulation requiring stable component supply, extended temperature support (–40°C to 125°C), and long-term production continuity.
Supply support for LT1939IDD#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 power management semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT1939IDD#TRPBF belongs to ADI's legacy Linear Technology Power Management product line, designed specifically for compact, high-efficiency dual-output DC/DC conversion in demanding industrial and automotive environments.
FAQ
What is the maximum supported switching frequency for LT1939IDD#TRPBF?
The LT1939IDD#TRPBF supports a maximum switching frequency of 2.2MHz when configured with a 15kΩ resistor from RT/SYNC to ground. In synchronization mode, it accepts external clock inputs up to 2.5MHz. Operation above 2.2MHz may reduce efficiency and increase switching losses due to minimum on-time limitations (140ns typical) and internal propagation delays.
Can LT1939IDD#TRPBF regulate two independent output voltages simultaneously?
Yes, the LT1939IDD#TRPBF regulates two independent outputs: VOUT1 via the buck converter (programmed using FB and external resistors) and VOUT2 via the LDRV pin (configured as linear regulator output or external NPN driver). Both outputs track the SS pin during startup and are monitored by separate feedback paths (FB and LFB), enabling true dual-rail control.
What is the purpose of the exposed pad (Pin 13) on LT1939IDD#TRPBF?
The exposed pad (Pin 13) on LT1939IDD#TRPBF is the sole ground connection and primary thermal path. It must be soldered to a large PCB copper area to achieve θJA = 45°C/W. This pad serves as both power ground and small-signal reference - all ground traces should connect to it at a single point to avoid noise coupling and ensure stable regulation of both FB and LFB loops.
Does LT1939IDD#TRPBF support power sequencing between its two outputs?
Yes, LT1939IDD#TRPBF supports inherent power sequencing via the shared SS pin: both the buck and linear regulators ramp their outputs proportionally to the SS voltage. By adding external RC networks or diodes to the SS node, designers can implement staggered start-up - for example, delaying VOUT2 until VOUT1 reaches regulation - ensuring safe initialization of cascaded power domains.
How does the LT1939IDD#TRPBF handle overload or short-circuit conditions?
Under overload or short-circuit, the LT1939IDD#TRPBF employs cycle-by-cycle current limiting on the internal 2.3A switch, combined with frequency foldback and thermal shutdown. If current exceeds the limit, the SS pin is actively discharged, lowering the regulation point until current demand falls within safe limits - enabling automatic recovery once the fault clears without requiring reset.
LT1939IDD#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)
LT1939IDD#TRPBF FAQ
1.How can I place an order for LT1939IDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1939IDD#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 LT1939IDD#TRPBF reliable?
The price and inventory of LT1939IDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1939IDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1939IDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1939IDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1939IDD#TRPBF?
LT1939IDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1939IDD#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 LT1939IDD#TRPBF?
For technical support, including LT1939IDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1939IDD#TRPBF requirements.
6.How does Aetrix verify that LT1939IDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1939IDD#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 LT1939IDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1939IDD#TRPBF?
All LT1939IDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1939IDD#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 LT1939IDD#TRPBF part is unused and in its original packaging.
Return procedure for LT1939IDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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