Calculation tool
LM25185-DESIGN-CALC — LM25185 PSR flyback controller quick start design calculator
LM25185 PSR flyback controller quick start design calculator
Data sheet
LM25185
- Functional Safety-Capable
- 4.5-V to 42-V wide input voltage range
- Extended power range from less than 1 W to more than 50 W
- Robust PSR flyback design for reliable and rugged applications
- Robust design with only a transformer crossing the isolation barrier
- ±1.5% total output regulation accuracy
- Optional VOUT temperature compensation
- Input UVLO and thermal shutdown protection
- Hiccup-mode overcurrent fault protection
- 0.9-mm HV-LV pin spacing in 14-pin HTSSOP package
- –40°C to +150°C junction temperature range
- Integration reduces design size and cost
- No optocoupler or transformer auxiliary winding required for V OUT regulation
- 2-A peak sink and 1-A peak source high-current power MOSFET gate driver
- High efficiency with best-in-class active I Q
- Quasi-resonant switching in boundary conduction mode (BCM) at heavy load
- External VCC option for improved efficiency
- High light-load efficiency with lowest I Q (25-µA typical with external VCC)
- Single and multiple output implementations
- Ultra-low conducted and radiated EMI signatures
- Soft switching avoids diode reverse recovery
- Designed for CISPR 32 EMI requirement
- Create a custom design using LM25185 with WEBENCH Power Designer
The LM25185 is a primary-side regulated (PSR) flyback controller with high efficiency over a wide input voltage range of 4.5 V to 42 V. The isolated output voltage is sampled from the primary-side flyback voltage, eliminating the need for an optocoupler, voltage reference, or third winding from the transformer for output voltage regulation.
The high level of integration results in a simple, reliable, and high-density design with only a transformer crossing the isolation barrier. Boundary conduction mode (BCM) switching enables a compact magnetic design and better than ±1.5% load and line regulation performance. BCM supports applications of up to 42-V input with enhanced headroom for line transients.
The LM25185 flyback controller simplifies implementation of isolated DC/DC supplies with optional features to optimize performance for the target end equipment. The output voltage is set by one resistor, while an optional resistor improves output voltage accuracy by negating the thermal coefficient of the flyback diode voltage drop. The LM25185 controller, with the integrated high-current MOSFET gate driver, extends the power range from less than 1 W to more than 50 W, making the device a scalable and easy-to-migrate design over a wide power range. The tunable compensation using the COMP pin and the adjustable peak current limit with the current-sensing resistor make the design flexible and an excellent choice towards different application requirements.
Additional features include an internally-fixed or externally-programmable soft start, optional external VCC for higher efficiency, precision enable input with hysteresis for adjustable line UVLO, peak current-mode control with shunt current sensing, hiccup-mode overload protection, a high-current MOSFET gate driver, and thermal shutdown protection with automatic recovery. A connection to the high-voltage MOSFET drain is not required, thus increasing safety and simplifying PCB clearance distance requirements.
The LM25185 flyback controller is available in a 14-pin, 5-mm × 4.4-mm, thermally-enhanced HTSSOP package with 0.65-mm pin pitch.
Technical documentation
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View all 2 | Type | Title | Date | ||
|---|---|---|---|---|
| * | Data sheet | LM2518542-VINPSR Flyback DC/DC Controller With Low IQand Low EMI datasheet | PDF | HTML | 10 Nov 2023 |
| Functional safety information | LMx5185 Functional Safety FIT Rate, FMD and Pin FMA | PDF | HTML | 24 May 2023 |
Design & development
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Evaluation board
LM5185EVM-SIO — LM5185-Q1 single isolated output evaluation module
The LM5185EVM-SIO evaluation module (EVM) demonstrates the features and performance of the LM5185-Q1, Primary-Side Regulated (PSR) flyback controller. It samples the voltage of the transformer's primary winding to achieve tight output regulation without using the opto-coupler or tertiary bias (...)
| Package | Pins | Download |
|---|---|---|
| HTSSOP (PWP) | 14 | View options |
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