75V Synchronous Buck Controller With Wide Input Voltage and Duty Cycle Ranges - LM5145


75V Synchronous Buck Controller With Wide Input Voltage and Duty Cycle Ranges



The LM5145 75-V synchronous buck controller is designed to regulate from a high input voltage source or from an input rail subject to high voltage transients, minimizing the need for external surge suppression components. A high-side switch minimum on-time of 40 ns facilitates large step-down ratios, enabling the direct step-down conversion from a 48 V nominal input to low-voltage rails for reduced system complexity and solution cost. The LM5145 continues to operate during input voltage dips as low as 6 V, at nearly 100% duty cycle if needed, making it well suited for high-performance industrial control, robotic, datacom, and RF power amplifier applications.

Forced-PWM (FPWM) operation eliminates frequency variation to minimize EMI, while a user-selectable diode emulation feature lowers current consumption at light-load conditions. Cycle-by-cycle overcurrent protection is accomplished by measuring the voltage drop across the low-side MOSFET or by using an optional current sense resistor. The adjustable switching frequency as high as 1 MHz can be synchronized to an external clock source to eliminate beat frequencies in noise-sensitive applications.

The LM5145 voltage-mode controller drives external high-side and low-side N-channel power switches with robust 7.5-V gate drivers suitable for standard-threshold MOSFETs. Adaptively-timed gate drivers with 2.3-A source and 3.5-A sink capability minimize body diode conduction during switching transitions, reducing switching losses and improving thermal performance when driving MOSFETs at high input voltage and high frequency. The LM5145 can be powered from the output of the switching regulator or another available source, further improving efficiency.

A 180° out-of-phase clock output relative to the internal oscillator at SYNCOUT is ideal for cascaded or multi-channel power supplies to reduce input capacitor ripple current and EMI filter size. Additional features of the LM5145 include a configurable soft-start, an open-drain Power Good monitor for fault reporting and output monitoring, monotonic start-up into prebiased loads, integrated VCC bias supply regulator and bootstrap diode, external power supply tracking, precision enable input with hysteresis for adjustable line undervoltage lockout (UVLO), hiccup-mode overload protection, and thermal shutdown protection with automatic recovery.

The LM5145 controller is offered in a 3.5-mm × 4.5-mm thermally-enhanced, 20-pin VQFN package with additional spacing for high-voltage pins and wettable flanks for optical inspection of solder joint fillets.


  • Versatile Synchronous Buck DC-DC Controller
    • Wide Input Voltage Range of 6 V to 75 V
    • Adjustable Output Voltage From 0.8 V to 60 V
  • Meets EN55022 / CISPR 22 EMI Standards
  • Lossless RDS(on) or Shunt Current Sensing
  • Switching Frequency From 100 kHz to 1 MHz
    • SYNC In and SYNC Out Capability
  • 40-ns Minimum On-Time for High VIN / VOUT Ratio
  • 140-ns Minimum Off-Time for Low Dropout
  • 0.8-V Reference With ±1% Feedback Accuracy
  • 7.5-V Gate Drivers for Standard VTH MOSFETs
    • 14-ns Adaptive Dead-Time Control
    • 2.3-A Source and 3.5-A Sink Capability
    • Low-Side Soft-Start for Prebiased Start-Up
  • Adjustable Soft-Start or Optional Voltage Tracking
  • Fast Line and Load Transient Response
    • Voltage-Mode Control With Line Feedforward
    • High Gain-Bandwidth Error Amplifier
  • Precision Enable Input and Open-Drain Power Good Indicator for Sequencing and Control
  • Inherent Protection Features for Robust Design
    • Hiccup Mode Overcurrent Protection
    • Input UVLO With Hysteresis
    • VCC and Gate Drive UVLO Protection
    • Thermal Shutdown Protection With Hysteresis
  • VQFN-20 Package With Wettable Flanks
  • Create a Custom Design Using the LM5145 With WEBENCH® Power Designer

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Parametrics Compare all products in Buck Controller (External Switch)

Vin (Min) (V)
Vin (Max) (V)
Vout (Min) (V)
Vout (Max) (V)
Iout (Max) (A)
Regulated Outputs (#)
Number of Phases
Switching Frequency (Min) (kHz)
Switching Frequency (Max) (kHz)
Iq (Typ) (mA)
Special Features
Duty Cycle (Max) (%)
Operating Temperature Range (C)
Package Group
LM5145 LM5116 LM5117 TPS40170
6    6    5.5    4.5   
75    100    65    60   
0.8    1.215    0.8    0.6   
60    80    62    57   
30    20    20    20   
1    1    1    1   
1    1    1    1   
100    50    50    100   
1000    1000    750    600   
1.5    4.6    4.8    4.5   
Adjustable Current Limit
Frequency Synchronization
Light Load Efficiency
Power Good
Pre-Bias Start-Up
Synchronous Rectification
UVLO Adjustable   
Adjustable Current Limit
Frequency Synchronization
Light Load Efficiency
Synchronous Rectification
UVLO Adjustable   
Adjustable Current Limit
Frequency Synchronization
Light Load Efficiency
Synchronous Rectification
UVLO Adjustable   
Frequency Synchronization
Power Good
Pre-Bias Start-Up
Synchronous Rectification
99    98    98    95   
-40 to 125    -40 to 150    -40 to 125    -40 to 125   
Catalog    Catalog    Catalog    Catalog   
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WEBENCH® Designer LM5145

  Min   Max Range
Vin  V 6.0 to 75.0V
Vout  V 0.8 to 60V
Iout  A ≤ 20A
Ambient Temp  °C -40 to 125°C

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