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Analog Devices Inc. LT3999EMSE#PBF
- Part No.:
- LT3999EMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3999EMSE#PBF.pdf
- Description:
- IC REG PUSH-PULL ADJ 1A 10MSOP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LT3999EMSE#PBF 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 systems. It integrates dual 1A current-limited switches, programmable 50kHz–1MHz switching frequency, duty cycle control for line regulation, and precision UVLO/OVLO thresholds. It delivers stable isolated supplies in medical instrumentation and data acquisition interfaces requiring <1µA shutdown current and cross-conduction prevention.
For engineers reviewing the LT3999EMSE#PBF datasheet, LT3999EMSE#PBF pinout, LT3999EMSE#PBF application, or LT3999EMSE#PBF equivalent, key selection criteria include its 2.7V–36V input range, dual-switch out-of-phase operation, exposed-pad MSOP-10 thermal performance, and programmable soft-start via ILIM/SS pin-critical for minimizing inrush in safety-critical isolated rails.
Technical Context
The LT3999EMSE#PBF implements a synchronous push-pull topology with two complementary 1A NPN power switches driven by an internal oscillator whose frequency is set by RT (50kHz–1MHz) and synchronizable to external clocks up to 1MHz. Its duty cycle is actively adjusted via OVLO/DC and RDC pins to compensate for input voltage variation, enabling pseudo-regulation before post-LDO stages.
Protection logic includes independent precision UVLO (1.25V ±100mV threshold) and OVLO (1.25V ±100mV) comparators with hysteresis, non-overlap timing (70ns), and cycle-by-cycle current limiting configurable via ILIM/SS resistor. The device operates from –40°C to +125°C junction temperature and achieves <1µA shutdown current when UVLO is pulled low.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 36V - supports wide industrial and automotive supply rails without external pre-regulation |
| Switch Current Limit | 1.0A typical (internal default) - limits peak primary current to protect transformer and switches under overload |
| Switching Frequency | 50kHz to 1MHz - adjustable via RT resistor; higher frequencies reduce magnetics size but increase switching loss |
| Duty Cycle Range | 20% to 48% - programmable via RDC and OVLO/DC voltage to maintain output stability across VIN variation |
| Shutdown Current | <1µA - enables ultra-low-power standby in battery-backed or safety-isolated systems |
| UVLO Threshold | 1.25V ±100mV - precise undervoltage lockout prevents erratic startup below minimum operating voltage |
| Package Thermal Resistance | θJA = 40°C/W - exposed pad (Pin 11) must be soldered to PCB ground plane for reliable 125°C operation |
Pinout & Package
LT3999EMSE#PBF is housed in a 10-lead MSOP package with exposed thermal pad (Pin 11 = GND). The package measures 3mm × 3mm × 1.1mm and requires soldering of the exposed pad to PCB ground for thermal integrity and EMI control.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SWA (Pin 1) | Switch A collector node | Drives one outer terminal of center-tapped transformer; carries full primary switching current (1A peak) |
| RBIAS (Pin 2) | Bias current reference | Sets internal switch bias via 49.9kΩ-to-GND resistor; determines drive strength and saturation voltage |
| VIN (Pin 3) | Main supply input | Powers internal regulator and gate drivers; requires ≥4.7µF low-ESR ceramic capacitor placed near pin |
| UVLO (Pin 4) | Undervoltage lockout input | Enables/disables operation at 1.25V threshold; direct connection to VIN or resistor divider sets turn-on point |
| OVLO/DC (Pin 5) | Overvoltage lockout / duty cycle control | Double-function pin: OVLO disables switching above threshold; used with RDC to adjust duty cycle vs. VIN |
| RDC (Pin 6) | Duty cycle programming | Resistor-to-GND sets duty cycle (20–48%); floating or tied to OVLO/DC disables control for ~50% fixed operation |
| RT (Pin 7) | Oscillator frequency setting | Resistor-to-GND programs switching frequency (50kHz–1MHz); value selected per datasheet table |
| SYNC (Pin 8) | External clock synchronization | Accepts >2V square wave; locks internal oscillator to external source for harmonic placement control |
| 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 |
| GND (Pin 11) | Power ground / thermal pad | Exposed pad is electrically GND; must be soldered to PCB ground plane for thermal dissipation and noise reduction |
Key Features
| Feature | Design Value |
|---|---|
| Low-noise push-pull topology | Eliminates transformer core saturation and reduces EMI vs. flyback; enables <100mVP-P output ripple with LC filter |
| Programmable duty cycle control | Compensates for input line variation (e.g., 12V±20%) to stabilize VOUT before LDO post-regulation |
| Cross-conduction prevention | 70ns non-overlap timing ensures SWA and SWB never conduct simultaneously-prevents shoot-through failure |
| Adjustable soft-start | Capacitor on ILIM/SS pin ramps peak switch current over user-defined time (e.g., 8ms/µF), limiting input inrush |
| Wide-temperature grade | –40°C to +125°C operating junction range (E-grade) supports industrial and medical environments without derating |
| Exposed-pad thermal management | θJC = 10°C/W enables 1W+ continuous power dissipation in MSOP-10 when pad is soldered to 2+ cm² copper area |
Applications
| Medical Isolated Power | Data Acquisition Front-End |
|---|---|
|
Use Scenario: Powering isolated ADC reference and signal conditioning circuitry in portable ECG monitors. IC Role / Device Role / Timing Role: LT3999EMSE#PBF serves as the primary isolated DC/DC driver for a 12V-to-±12V transformer stage, feeding low-noise LDOs. Use Value: Its <1µA shutdown current extends battery life during sleep mode; low EMI ensures sub-µV noise floor for 24-bit analog measurements. |
Use Scenario: Generating clean, isolated ±15V rails for RS485 transceivers and op-amp front-ends in industrial PLC I/O modules. IC Role / Device Role / Timing Role: LT3999EMSE#PBF drives a center-tapped transformer to produce dual outputs, synchronized to system clock via SYNC pin. Use Value: Frequency synchronization places switching harmonics away from critical 1Mbps RS485 bands, preventing data corruption. |
| Positive-to-Negative Conversion | Distributed Safety Power |
|
Use Scenario: Converting 24V bus to –12V rail for op-amp biasing in isolated sensor signal chains. IC Role / Device Role / Timing Role: LT3999EMSE#PBF operates in fixed 50% duty cycle mode (RDC floating) to generate symmetric bipolar outputs from single-ended input. Use Value: Dual 1A switches enable high-current negative rail generation without external P-channel devices or charge pumps. |
Use Scenario: Providing redundant, galvanically isolated 5V/3.3V supplies to safety-critical microcontrollers in automotive ADAS domain controllers. IC Role / Device Role / Timing Role: LT3999EMSE#PBF powers isolated auxiliary rails with UVLO/OVLO monitoring of main 12V battery input. Use Value: Precision lockout thresholds (±100mV) ensure fail-safe shutdown during battery transients, meeting ISO 16750-2 pulse requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar isolated push-pull driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3439EMS#PBF | Lower max input (17.5V), SO-16 package, slew-rate controlled switches for <100mVP-P noise | Better suited for ultra-low-noise medical imaging where EMI must be minimized below 10MHz | Select LT3439EMS#PBF only if input voltage ≤17.5V and sub-100mVP-P noise is mandatory; not drop-in due to different pinout and lower voltage rating |
| LT1533CS#PBF | SO-16, 2.7V–23V input, same 1A switches but no duty cycle control or SYNC pin | Lacks programmable line regulation and synchronization-requires external compensation for varying VIN | Choose LT1533CS#PBF for cost-sensitive designs where input is stable and harmonic control is unnecessary; verify thermal design due to higher θJA |
Compared with LT3439EMS#PBF and LT1533CS#PBF, the LT3999EMSE#PBF uniquely combines 36V input capability, duty cycle adjustment for line regulation, and SYNC functionality-making it optimal for wide-input, noise-sensitive, and spectrally constrained isolated power in medical and industrial systems.
Availability
LT3999EMSE#PBF is available at Aetrix Electronics and suitable for medical instrumentation, industrial data acquisition, and distributed safety power systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT3999EMSE#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, healthcare, and industrial markets.
The LT3999 product line was engineered specifically for low-noise, high-reliability isolated DC/DC conversion in safety-critical applications-emphasizing programmable protection, thermal robustness, and EMI-controlled push-pull operation.
FAQ
What is the maximum input voltage rating for LT3999EMSE#PBF?
The LT3999EMSE#PBF has an absolute maximum VIN rating of 60V, but its guaranteed operational input range is 2.7V to 36V. Exceeding 36V may trigger the internal OVLO (40–42V rising threshold) or cause reliability degradation. For sustained 36V operation, thermal design must account for increased power dissipation in the switches and internal regulator.
How does the LT3999EMSE#PBF achieve line regulation without a feedback loop?
The LT3999EMSE#PBF achieves pseudo-line regulation using duty cycle control: the OVLO/DC pin is biased from VIN via a resistor divider, and the RDC pin sets a reference that adjusts switch on-time proportionally to input voltage. This compensates for VIN variation before post-regulation, reducing LDO power dissipation-confirmed in Figure 3999 TA01b showing stable 12V output across 10–18V input at multiple loads.
Can LT3999EMSE#PBF drive a transformer with non-center-tapped secondary?
No-the LT3999EMSE#PBF is designed exclusively for center-tapped transformer topologies. Its dual out-of-phase switches (SWA/SWB) drive opposite ends of the primary winding, requiring symmetrical coupling to the center tap. Using a non-center-tapped transformer would prevent proper voltage reversal and likely cause saturation, excessive current, or switch failure.
What is the purpose of the RBIAS pin on LT3999EMSE#PBF, and what happens if left unconnected?
The RBIAS pin sets the internal bias current for the power switches, directly affecting VCE(SAT) and switching speed. A 49.9kΩ resistor to GND is required per datasheet; leaving RBIAS open causes undefined switch behavior, increased saturation voltage (>500mV), and potential thermal runaway. It must not be floated.
Is LT3999EMSE#PBF pin-compatible with other grades like LT3999HMSE#PBF?
Yes-LT3999EMSE#PBF, LT3999HMSE#PBF, and LT3999IMSE#PBF share identical MSOP-10 pinout, electrical characteristics, and thermal pad layout. The only difference is guaranteed operating junction temperature range (E: –40°C to +125°C; H: –40°C to +150°C). No PCB changes are needed when upgrading from E-grade to H-grade for extended thermal margin.
LT3999EMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tube
- 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-MSOP-EP
LT3999EMSE#PBF FAQ
1.How can I place an order for LT3999EMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3999EMSE#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 LT3999EMSE#PBF reliable?
The price and inventory of LT3999EMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3999EMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3999EMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3999EMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3999EMSE#PBF?
LT3999EMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3999EMSE#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 LT3999EMSE#PBF?
For technical support, including LT3999EMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3999EMSE#PBF requirements.
6.How does Aetrix verify that LT3999EMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3999EMSE#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 LT3999EMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3999EMSE#PBF?
All LT3999EMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3999EMSE#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 LT3999EMSE#PBF part is unused and in its original packaging.
Return procedure for LT3999EMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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