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Analog Devices Inc. LT3999EMSE#TRPBF
- Part No.:
- LT3999EMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3999EMSE#TRPBF.pdf
- Description:
- IC REG PUSH-PULL ADJ 1A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,450
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Product details
Overview
LT3999EMSE#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 LT3999EMSE#TRPBF datasheet, LT3999EMSE#TRPBF pinout, LT3999EMSE#TRPBF application, or LT3999EMSE#TRPBF equivalent, key selection criteria include its 2.7V–36V input range, dual-switch architecture with cross-conduction prevention, programmable soft-start via ILIM/SS, precision UVLO/OVLO thresholds, and MSOP-10 package with exposed GND pad for thermal management.
Technical Context
The LT3999EMSE#TRPBF 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 optionally synchronized to an external clock. Its duty cycle control loop uses OVLO/DC and RDC pins to adjust switch conduction time based on input voltage, enabling pseudo-regulation before post-LDO stages.
Protection circuitry includes independent precision undervoltage lockout (UVLO, 1.25V threshold ±125mV hysteresis) and overvoltage lockout (OVLO/DC, same threshold), both programmable via resistor dividers. Shutdown current is <1µA, and non-overlap timing prevents shoot-through during switching transitions.
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 |
| Switching Frequency | 50kHz to 1MHz - adjustable via RT resistor; higher frequencies reduce magnetics size but increase switching losses |
| Duty Cycle Range | 20% to 48% - programmable via RDC and OVLO/DC voltage to compensate VIN variation and stabilize VOUT |
| UVLO Threshold | 1.25V ±0.1V - precise enable/disable point with 125mV hysteresis prevents oscillation near trip point |
| Shutdown Current | <1µA - enables ultra-low-power standby in battery-backed or energy-sensitive systems |
| Package | 10-Lead MSOP with exposed GND pad - θJA = 40°C/W; requires PCB soldering of exposed pad for thermal integrity |
Pinout & Package
LT3999EMSE#TRPBF is housed in a 10-lead plastic MSOP package (MSE) with exposed GND pad (Pin 11), requiring soldering to PCB ground plane for thermal performance and EMI control. Pin pitch is 0.5mm; body dimensions are 3.00mm × 3.00mm × 1.10mm max.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SWA (Pin 1) | Switch A collector node | Drives outer terminal of center-tapped transformer primary; carries full 1A pulsed current - requires short, wide PCB trace |
| RBIAS (Pin 2) | Bias current reference | Sets internal bias for SWA/SWB drivers; 49.9kΩ to GND sets nominal operation per datasheet |
| VIN (Pin 3) | Main supply input | Powers internal regulator and gate drivers; requires ≥4.7µF low-ESR ceramic capacitor placed close to pin |
| UVLO (Pin 4) | Undervoltage lockout input | Enables/disables operation at 1.25V threshold; direct connection to VIN or divider sets startup voltage |
| OVLO/DC (Pin 5) | Overvoltage lockout / duty cycle control | Dual-function pin: resistor divider sets OVLO trip; voltage level modulates duty cycle for line regulation |
| RDC (Pin 6) | Duty cycle programming | Resistor to GND sets duty cycle range (20–48%); floating or tied to OVLO/DC disables control |
| RT (Pin 7) | Oscillator frequency setting | Resistor value determines switching frequency (e.g., 49.9kΩ = 300kHz); see Table 1 in datasheet |
| SYNC (Pin 8) | External clock synchronization | Accepts >2V square wave; forces oscillator to half-sync frequency for harmonic placement control |
| ILIM/SS (Pin 9) | Current limit / soft-start | Resistor sets cycle-by-cycle current limit; capacitor adds ramped start-up to limit inrush current |
| SWB (Pin 10) | Switch B collector node | Complementary to SWA; drives opposite outer terminal of transformer - must mirror SWA layout |
| GND (Pin 11) | Power ground / exposed pad | Thermal and electrical reference; exposed pad must be soldered to solid PCB ground plane with multiple vias |
Key Features
| Feature | Design Value |
|---|---|
| Low-noise push-pull topology | Minimizes common-mode EMI and transformer core saturation vs. flyback; enables sub-100mVP-P output ripple with LC filter |
| Programmable duty cycle control | Compensates for ±30% VIN variation to maintain stable VOUT before LDO post-regulation, reducing LDO thermal load |
| Cross-conduction prevention | 70ns non-overlap timing ensures SWA and SWB never conduct simultaneously, eliminating shoot-through current and loss |
| Adjustable soft-start | Capacitor on ILIM/SS pin ramps peak switch current over user-defined time (e.g., 0.01µF → ~0.8ms), limiting input inrush |
| Wide-input UVLO/OVLO protection | Independent 1.25V precision thresholds with 125mV hysteresis allow robust startup/shutdown across temperature and line variation |
Applications
| Medical Isolated Power Supplies | Distributed Industrial Power |
|---|---|
Use Scenario: Providing isolated ±12V rails for analog front-end amplifiers and ADCs in patient-connected diagnostic equipment. IC Role / Device Role / Timing Role: LT3999EMSE#TRPBF acts as primary-side push-pull driver controlling transformer primary; duty cycle adjusts dynamically with battery voltage decay. Use Value: Low EMI and <1µA shutdown current extend battery life while meeting IEC 60601 creepage/clearance requirements via transformer isolation. |
Use Scenario: Generating 12V isolated auxiliary power from 24V factory bus for PLC I/O modules with galvanic separation. IC Role / Device Role / Timing Role: LT3999EMSE#TRPBF drives center-tapped transformer at 500kHz; SYNC pin locks switching harmonics to avoid interference with CAN FD communication bands. Use Value: Programmable OVLO/DC prevents brownout-induced reset during bus transients; MSOP package fits dense industrial PCB layouts. |
| RS485/RS232 Noise-Immune Interfaces | Positive-to-Negative Converter |
Use Scenario: Powering isolated RS485 transceivers in noisy factory environments where ground loops induce data corruption. IC Role / Device Role / Timing Role: LT3999EMSE#TRPBF supplies clean 5V isolated rail; low-noise topology avoids coupling switching artifacts into differential data lines. Use Value: Sub-100mVP-P output ripple (with optional LC filter) eliminates false triggering in high-speed UART links. |
Use Scenario: Generating –12V rail from +12V input for op-amp biasing in precision instrumentation without split supplies. IC Role / Device Role / Timing Role: LT3999EMSE#TRPBF operates in push-pull mode with center-tapped secondary winding; duty cycle fixed at ~50% for symmetric bipolar output. Use Value: Eliminates need for separate negative charge pump IC; achieves <1% cross-regulation between +12V and –12V outputs using single transformer. |
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 |
|---|---|---|---|
| LT3439EFE#TRPBF | SO-16 package; slew-rate controlled switches; lower max VIN (17.5V); fixed 500kHz fSW | Better EMI control via adjustable slew rates; limited to lower input voltages; no duty cycle control | Choose LT3439EFE#TRPBF when ultra-low noise (<100mVP-P) is critical and input stays ≤17.5V; not suitable for 36V industrial rails. |
| LT1533CS#TRPBF | SO-16; 2.7V–23V VIN; no RDC/OVLO/DC duty cycle control; higher quiescent current (12mA) | Lacks line regulation capability; simpler configuration but less adaptable to varying input conditions | Choose LT1533CS#TRPBF for cost-sensitive designs where input voltage is tightly regulated and duty cycle adjustment is unnecessary. |
Compared with LT3439EFE#TRPBF and LT1533CS#TRPBF, the LT3999EMSE#TRPBF offers wider input range (2.7V–36V), active duty cycle control for line regulation, and smaller MSOP footprint - making it optimal for space-constrained, variable-input isolated supplies requiring post-LDO efficiency optimization.
Availability
LT3999EMSE#TRPBF is available at Aetrix Electronics and suitable for medical instrumentation, industrial distributed power, and RS485/RS232 interface design requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance across –40°C to +125°C.
Supply support for LT3999EMSE#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 developed specifically for compact, low-noise isolated DC/DC conversion in safety-critical and EMI-sensitive applications - emphasizing programmable protection, transformer-driven efficiency, and thermal robustness in small packages.
FAQ
What is the maximum input voltage rating for LT3999EMSE#TRPBF?
The absolute maximum rating for VIN on the LT3999EMSE#TRPBF is 60V, but the specified operational input voltage range is 2.7V to 36V. Exceeding 36V may trigger the internal overvoltage lockout (OVLO) function, disabling switching. The 60V absolute max is a stress limit - sustained operation above 36V is not guaranteed and risks reliability degradation. Always refer to the recommended operating conditions table in the official datasheet for LT3999EMSE#TRPBF.
Can LT3999EMSE#TRPBF drive a transformer with asymmetric windings?
Yes, the LT3999EMSE#TRPBF can drive transformers with asymmetric windings, but duty cycle control must be disabled (RDC pin floating or tied to OVLO/DC) to maintain balanced primary current. Asymmetric secondaries affect output voltage ratios but do not impact LT3999EMSE#TRPBF's switch timing or protection functions. Transformer magnetizing inductance and leakage inductance remain critical for stability - verify with bench testing under worst-case load and line conditions for LT3999EMSE#TRPBF.
How does the ILIM/SS pin function in soft-start versus current limiting modes?
The ILIM/SS pin on LT3999EMSE#TRPBF serves dual roles: a resistor to ground sets the cycle-by-cycle current limit (e.g., 43.2kΩ = 0.5A), while a capacitor to ground implements soft-start by ramping the current limit threshold over time (tSS ≈ CSS × 80ms). If only a capacitor is used, the internal 1.0A default limit applies during ramp-up. Both functions coexist - soft-start controls initial surge, and current limiting protects against overload throughout operation. This behavior is confirmed in the LT3999EMSE#TRPBF datasheet Section "Soft-Start and Current Limit".
Is LT3999EMSE#TRPBF pin-compatible with other LT3999 variants like LT3999EDD#TRPBF?
No, LT3999EMSE#TRPBF (MSOP-10) is not pin-compatible with LT3999EDD#TRPBF (3mm × 3mm DFN-10). Although both packages have 10 leads and identical pin functions, their physical pinouts differ: MSOP places GND at Pin 11 (exposed pad), while DFN assigns GND to Pin 11 *and* the exposed pad, with different lead numbering and spacing. PCB layout must be redesigned when switching between MSE and DD packages - no mechanical or electrical drop-in replacement exists for LT3999EMSE#TRPBF.
What thermal derating applies to LT3999EMSE#TRPBF at 125°C ambient?
LT3999EMSE#TRPBF is rated for operation from –40°C to +125°C junction temperature. At 125°C ambient, thermal derating depends on PCB copper area, via count under the exposed pad, and airflow. With standard 2oz copper, 4×0.3mm vias to inner ground plane, and no forced air, θJA ≈ 40°C/W implies ~1.25W max power dissipation before exceeding 125°C junction. Derate linearly above 25°C ambient; consult the "Thermal Considerations" section of the LT3999EMSE#TRPBF datasheet for layout-specific guidance.
LT3999EMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) 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-MSOP-EP
LT3999EMSE#TRPBF FAQ
1.How can I place an order for LT3999EMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3999EMSE#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 LT3999EMSE#TRPBF reliable?
The price and inventory of LT3999EMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3999EMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3999EMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3999EMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3999EMSE#TRPBF?
LT3999EMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3999EMSE#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 LT3999EMSE#TRPBF?
For technical support, including LT3999EMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3999EMSE#TRPBF requirements.
6.How does Aetrix verify that LT3999EMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3999EMSE#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 LT3999EMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3999EMSE#TRPBF?
All LT3999EMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3999EMSE#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 LT3999EMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3999EMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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