50V to 5V/7A Synchronous Buck (Step-down) Converter

Texas Instruments LM5116

Rajkumar Sharma

electronics-lab.com

This module is a non-isolated 7 A DC-DC converter. The module can convert any DC voltage between 7 V to 50 V to a 5 V DC with load current up to 7 A (Figure 1). The project has been designed around LM5116 Wide Range Synchronous Buck Controller IC. The design includes 6uH toroid inductor and two N channel MOSFETS (Figure 2). The operating frequency is 250 kHz.

50V to 5V/7A Synchronous Buck (Step-down) Converter.
Figure 1. 50 V to 5 V/7 A Synchronous Buck (Step-down) Converter.

Features:

  • Wide Operating Range 7 V – 50 V
  • Output 5 V DC
  • Load Current Up To 7 Amps
  • Thermal Shutdown
  • Operating Frequency 250 kHz
  • PCB Dimensions 45.04 mm x 22.82 mm

Synchronous Buck (Step-down) Converter Schematic Diagram shown in Figure 2. The list of used components is given in the Table 1.

50 V to 5 V/7 A Synchronous Buck (Step-down) Converter Schematic Diagram.
Figure 2. 50 V to 5 V/7 A Synchronous Buck (Step-down) Converter Schematic Diagram.

The LM5116 is a synchronous buck controller intended for step-down regulator applications from a high-voltage or widely varying input supply. The control method is based upon current mode control utilizing an emulated current ramp. Current mode control provides inherent line feed-forward, cycle-by-cycle current limiting, and ease-of-loop compensation. The use of an emulated control ramp reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable control of very small duty cycles necessary in high-input voltage applications.

The operating frequency is programmable from 50 kHz to 1 MHz and the LM5116 drives external high-side and low-side NMOS power switches with adaptive dead-time control. A user-selectable diode emulation mode enables discontinuous operation mode, for improved efficiency at light load conditions. A low quiescent current shutdown disables the controller and consumes less than 10 µA of total input current.

Additional features include a high-voltage bias regulator, automatic switch-over to external bias for improved efficiency, thermal shutdown, frequency synchronization, cycle-by-cycle current limit, and adjustable line under-voltage lockout. The device is available in a power enhanced HTSSOP-20 package featuring an exposed die attach PAD to aid thermal dissipation.

Table 1. Part List.
REF QNTY. Description
CN1 1 4 PIN HEADER CONNECTOR
CN2 1 4 PIN HEADER CONNECTOR
C1 1 1 µF 100 V, SMD 1210
R5, C7, C9 3 OMIT
C10, C11, C13, C14, C15 5 100 µF 10 V, SMD 1210
C12 1 270 pF, SMD 0805
C16 1 3300 pF, SMD 0805
C17 1 100 pF, SMD 0805
C18 1 0.01 µF, SMD 0805
D1 1 SS34, SMD
L1 1 6 µH 10 А, toroid
Q1 1 IRLR024N, SMD DPAK
Q2 1 IRLR024N, SMD DPAK
R1 1 102 K, 1%, SMD 0805
R2 1 1 M, SMD0805
R3 1 21 K, 1%, SMD0805
R4 1 12.4 K, 1%, SMD0805
R6 1 0.01 E, 1%, SMD 2512
R7, R12 2 0 E, SMD 0805
R8 1 3.74 K, 1%, SMD 0805
R9 1 10 K, 1%, SMD 0805
R10 1 1.21 K, 1%, SMD 0805
R11 1 18 K, SMD 0805
U1 1 LM5116, SMD
C5, C6, C8 3 1 µF 25 V, SMD 0805
C3, C4 2 10 µF 100 V, SMD 1210
C2 1 0.1 µF 100 V, SMD 0805

PCB photos shown in Figure 3. Converter Module Connections shown in Figure 4.

5V/7A Synchronous Buck (Step-down) Converter PCB photos.
5V/7A Synchronous Buck (Step-down) Converter PCB photos.
Figure 3. 5V/7A Synchronous Buck (Step-down) Converter PCB photos.
 
50 V to 5 V/7 A Synchronous Buck (Step-down) Converter Connections
Figure 4. 50 V to 5 V/7 A Synchronous Buck (Step-down) Converter Connections.

Downloads

  1. 5V/7A Synchronous Buck (Step-down) Converter Schematic Diagram (pdf)
  2. Gerber-files for PCB

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