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Analog Devices Inc. LT3999EDD#TRPBF
- Part No.:
- LT3999EDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3999EDD#TRPBF.pdf
- Description:
- IC REG PUSH-PULL ADJ 1A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:12,997
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Product details
Overview
LT3999EDD#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic high-voltage push-pull DC/DC transformer driver IC designed for isolated power generation in compact, low-noise applications. It integrates dual 1A current-limited switches operating out of phase, supports programmable switching frequency up to 1MHz, features duty cycle control for line regulation, and delivers stable isolated output in medical instrumentation, distributed power, and RS485/RS232 noise-immune interfaces.
For engineers reviewing the LT3999EDD#TRPBF datasheet, LT3999EDD#TRPBF pinout, LT3999EDD#TRPBF application, or LT3999EDD#TRPBF equivalent, key selection criteria include its 2.7V–36V input range, dual-switch current limit programmability, soft-start via ILIM/SS pin, UVLO/OVLO lockout thresholds, and compatibility with center-tapped transformer topologies requiring precise duty-cycle adjustment and harmonic synchronization.
Technical Context
The LT3999EDD#TRPBF implements a fixed-frequency, out-of-phase push-pull topology where SWA and SWB drive opposite ends of a center-tapped transformer primary. Its oscillator supports internal RT-programmed frequencies from 50kHz to 1MHz or external synchronization up to 1MHz, enabling precise harmonic placement in EMI-sensitive systems.
Duty cycle is controlled via the OVLO/DC and RDC pins, allowing VIN-dependent output voltage compensation; soft-start and cycle-by-cycle current limiting are both configured through the ILIM/SS pin using resistor-capacitor networks. Protection includes precision UVLO (1.25V ±100mV) and OVLO (1.25V ±100mV) with hysteresis, cross-conduction prevention, and <1µA shutdown current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 36V - supports wide industrial and automotive supply rails without pre-regulation |
| Switch Current Limit | 1.0A typical (internal), programmable down to 0.5A via ILIM/SS - enables safe operation with small transformers and tight current margins |
| Switching Frequency | 50kHz to 1MHz - selectable via RT resistor; higher frequencies reduce magnetic size but increase switching loss |
| Duty Cycle Range | 20% to 48% - adjustable via RDC and OVLO/DC voltage to compensate for input variation and stabilize VOUT |
| UVLO/OVLO Thresholds | 1.25V ±100mV - precision hysteresis enables accurate enable/disable points for input rail monitoring |
| Shutdown Current | <1µA - ensures minimal battery drain in always-on or standby-isolated systems |
| Package | 10-lead 3mm × 3mm DFN with exposed GND pad - provides low thermal resistance (θJC = 5.5°C/W) and compact footprint |
Pinout & Package
The LT3999EDD#TRPBF is housed in a 10-lead (3mm × 3mm) plastic DFN package with exposed GND pad (Pin 11), requiring soldering to PCB ground plane for thermal and electrical integrity. Pin pitch is 0.5mm; package conforms to JEDEC MO-229 variation WEED-2.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SWA (Pin 1) | Power switch A collector | Drives one end of center-tapped transformer primary; handles peak currents up to 1A; requires short/wide PCB trace |
| RBIAS (Pin 2) | Bias current reference | Sets internal switch bias via 49.9kΩ-to-GND resistor; determines optimal drive strength for transformer coupling |
| VIN (Pin 3) | Main supply input | Accepts 2.7V–36V; powers internal regulator and gate drivers; requires ≥4.7µF low-ESR ceramic bypass |
| UVLO (Pin 4) | Undervoltage lockout input | Disables switching when VIN drops below 1.25V threshold; enables low-quiescent shutdown mode |
| OVLO/DC (Pin 5) | Overvoltage lockout / duty cycle control | Configurable as OVLO disable input or duty cycle reference node; connects to resistor divider from VIN |
| RDC (Pin 6) | Duty cycle programming | Resistor-to-GND sets duty cycle percentage; floating or tied to OVLO/DC disables control and defaults to ~50% |
| RT (Pin 7) | Oscillator timing | Resistor-to-GND sets switching frequency (50kHz–1MHz); value inversely proportional to fSW |
| SYNC (Pin 8) | External clock input | Accepts 2V+ square wave; synchronizes internal oscillator to external source for harmonic alignment |
| ILIM/SS (Pin 9) | Current limit / soft-start | Resistor sets cycle-by-cycle current limit; capacitor adds soft-start ramp to limit inrush current at startup |
| SWB (Pin 10) | Power switch B collector | Drives opposite end of center-tapped transformer primary; complements SWA in out-of-phase operation |
| GND (Pin 11) | Ground / exposed pad | Thermal and electrical ground reference; must be soldered to PCB ground plane with multiple vias |
Key Features
| Feature | Design Value |
|---|---|
| Low-noise push-pull topology | Minimizes EMI in data acquisition and communication interfaces (e.g., RS485) by canceling common-mode transformer flux |
| Programmable duty cycle control | Enables pseudo-regulation of unregulated transformer outputs-reduces post-LDO power dissipation in medical and safety-critical supplies |
| Adjustable soft-start | Capacitor or RC network on ILIM/SS pin limits inrush current during startup, preventing input rail sag and transformer saturation |
| Frequency synchronization | SYNC pin allows harmonic alignment with system clocks-critical for meeting CISPR-22 conducted emission limits in industrial equipment |
| Cross-conduction prevention | Hardware-enforced non-overlap time (70ns) eliminates shoot-through risk between SWA and SWB during switching transitions |
| Wide temperature grade | E-grade rating (–40°C to +125°C junction) supports operation in harsh environments including industrial controls and automotive body electronics |
Applications
| Medical Instrument Isolation | Distributed Power Architecture |
|---|---|
Use Scenario: Providing isolated ±12V bias rails for analog front-end amplifiers and ADCs in portable ECG monitors. IC Role / Device Role / Timing Role: LT3999EDD#TRPBF acts as a low-noise, transformer-coupled DC/DC driver generating dual-polarity outputs from a single 5V or 12V battery input. Use Value: Achieves <100mVP-P output noise and galvanic isolation exceeding 2.5kVRMS, satisfying IEC 60601-1 patient safety requirements without additional filtering. |
Use Scenario: Generating isolated 12V/10W auxiliary supply for remote sensor nodes in factory automation PLC backplanes. IC Role / Device Role / Timing Role: LT3999EDD#TRPBF drives a center-tapped transformer to deliver regulated 12V output across long cables with minimal voltage drop. Use Value: Programmable UVLO/OVLO prevents brownout-induced resets; duty cycle control maintains stable output despite ±10% input rail variation across distributed bus. |
| Noise-Immune Communication Interfaces | Positive-to-Negative Voltage Conversion |
Use Scenario: Powering isolated RS485 transceivers in motor drive control cabinets subject to high dv/dt noise. IC Role / Device Role / Timing Role: LT3999EDD#TRPBF supplies clean, isolated 5V to RS485 ICs while rejecting common-mode noise from adjacent IGBT switching. Use Value: Push-pull topology inherently suppresses even-order harmonics; combined with optional LC filter, meets EN 55032 Class A conducted emissions. |
Use Scenario: Generating –12V rail from +12V main supply for op-amp biasing in precision test equipment. IC Role / Device Role / Timing Role: LT3999EDD#TRPBF operates in inverted push-pull mode with center-tapped secondary to produce symmetrical positive/negative outputs. Use Value: Dual 1A switches support high-current negative rails; programmable current limit protects against short-circuit faults on the negative output path. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar isolated push-pull DC/DC driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3439EMS#TRPBF | Lower max input (2.7V–17.5V); slew-rate controlled switches; SO-16 package | Better suited for ultra-low-noise (<100mVP-P) applications where EMI is critical, but lacks duty cycle control and has narrower VIN range | Select LT3439 if sub-100mVP-P noise is mandatory and input stays ≤17.5V; avoid if line regulation or >36V operation required |
| LT3748EMSE#TRPBF | Primary-side sensing flyback controller; no integrated switches; MSOP-10 package | Requires external MOSFETs and optocoupler feedback; supports higher power (>25W) but adds complexity and loop latency | Choose LT3748 for higher-power isolated supplies needing tight output regulation; use LT3999EDD#TRPBF for simplicity, lower component count, and inherent transformer symmetry |
Compared with LT3439EMS#TRPBF and LT3748EMSE#TRPBF, the LT3999EDD#TRPBF uniquely combines integrated dual 1A switches, programmable duty cycle for line regulation, and push-pull topology in a 3mm × 3mm DFN-making it optimal for compact, medium-power isolated supplies where transformer symmetry and input range flexibility are prioritized over absolute lowest noise or highest wattage.
Availability
LT3999EDD#TRPBF is available at Aetrix Electronics and suitable for medical instrumentation, distributed power architecture, and noise-immune communication interface designs requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for LT3999EDD#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. (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 LT3999 product line was designed specifically for compact, low-noise isolated DC/DC conversion using push-pull transformer topologies-targeting applications demanding galvanic isolation, EMI robustness, and design simplicity without external MOSFETs or optocouplers.
FAQ
What is the maximum switching frequency supported by the LT3999EDD#TRPBF?
The LT3999EDD#TRPBF supports an internal switching frequency up to 1MHz, set by the RT resistor or synchronized to an external clock up to 1MHz. At 1MHz, each switch (SWA/SWB) operates at 500kHz due to the push-pull out-of-phase configuration. This high frequency enables smaller magnetics and reduced solution footprint, though efficiency trade-offs require careful thermal design.
How does duty cycle control work on the LT3999EDD#TRPBF?
Duty cycle control on the LT3999EDD#TRPBF uses the OVLO/DC and RDC pins: OVLO/DC is biased from VIN via a resistor divider, and RDC connects to ground with a resistor. The resulting duty cycle (20–48%) adjusts dynamically with VIN, providing pseudo-regulation of the transformer output. This reduces post-regulator (e.g., LDO) power dissipation and improves overall efficiency in variable-input applications.
Can the LT3999EDD#TRPBF drive a center-tapped transformer for ±12V outputs?
Yes, the LT3999EDD#TRPBF is explicitly designed for center-tapped transformer topologies. In a typical ±12V application, SWA and SWB drive opposite ends of the primary winding, while the secondary uses full-wave rectification with two diodes to generate symmetrical positive and negative rails. Reference design TA04 in the datasheet demonstrates this configuration delivering ±12V at 200mA.
What is the purpose of the RBIAS pin on the LT3999EDD#TRPBF?
The RBIAS pin on the LT3999EDD#TRPBF sets the internal bias current for the power switches (SWA/SWB). A 49.9kΩ resistor to ground configures optimal drive strength for standard center-tapped transformers. Incorrect RBIAS values may cause insufficient gate drive, increased VCE(SAT), or thermal stress-so adherence to the recommended value is critical for reliable 1A switching performance.
Does the LT3999EDD#TRPBF require external MOSFETs?
No, the LT3999EDD#TRPBF integrates two 1A current-limited NPN power switches (SWA and SWB) on-die. It drives the transformer primary directly without external MOSFETs or discrete transistors. This integration reduces BOM count, layout complexity, and failure points-making it a true monolithic push-pull driver IC rather than a controller-only solution.
LT3999EDD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Push-Pull
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.7V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- 1A
- Frequency - Switching:
- 50kHz ~ 1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT3999EDD#TRPBF FAQ
1.How can I place an order for LT3999EDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3999EDD#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 LT3999EDD#TRPBF reliable?
The price and inventory of LT3999EDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3999EDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3999EDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3999EDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3999EDD#TRPBF?
LT3999EDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3999EDD#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 LT3999EDD#TRPBF?
For technical support, including LT3999EDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3999EDD#TRPBF requirements.
6.How does Aetrix verify that LT3999EDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3999EDD#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 LT3999EDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3999EDD#TRPBF?
All LT3999EDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3999EDD#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 LT3999EDD#TRPBF part is unused and in its original packaging.
Return procedure for LT3999EDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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