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LM5145 Datasheet(PDF) 49 Page - Texas Instruments |
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LM5145 Datasheet(HTML) 49 Page - Texas Instruments |
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49 / 73 page  8.2.2 Design 2 – Two-Phase, Single-Output Synchronous Buck Regulator Figure 8-19 shows the schematic diagram of a single-output, two-phase synchronous buck regulator with an output voltage of 5V and rated load current of 20A. In this example, the target half-load and full-load efficiencies are 93% and 91%, respectively, based on a nominal input voltage of 12V that ranges from 6V to 36V. The switching frequency is set at 2.1MHz by resistor RRT. The 5V output supplies bias current to the controller to improve light-load efficiency. An output voltage of 3.3V is also possible simply by changing the voltage-set resistor (RFB tied from FB1 to VDDA) from 24.9kΩ to 7.5kΩ. RT RSS PFM/SYNC AGND COMP2 VOUT2 ISNS2+ LO2 SW2 HO2 CBOOT2 VIN COMP1 BIAS1/VOUT1 ISNS1+ LO1 SW1 HO1 CBOOT1 VCC FB1 FB2 VDDA SYNCOUT CFNG EN1 EN2 PG2 PG1 VIN = 6V...36V VOUT = 5V IOUT = 20A * VOUT tracks VIN if VIN < 5V LO1 COUT2 CIN1 CVDDA LO2 COUT1 RS2 RS1 Q2 Q1 RSS RRT RCNFG Q4 Q3 CVCC CBOOT1 CBOOT2 LM25137 2 10 F 4 10nF 4m 0.47 H 4.7 F 0.1 F 0.1 F 4 47 F 4 47 F 4m 0.47 H 1 F 10.5k 71.5k 20k CIN2 2 10 F 4 10nF VDDA RFB 68pF 3.3nF 10k CHF RCOMP CCOMP 24.9k Figure 8-19. Application Circuit 2 With an LM25137 Two-phase Buck Regulator at 2.1MHz 8.2.2.1 Design Requirements Table 8-4 shows the intended input, output, and performance parameters for this automotive circuit example. Table 8-4. Design Parameters DESIGN PARAMETER VALUE Input voltage range (steady state) 8V to 18V Minimum transient input voltage 6V Maximum transient input voltage 36V Output voltage 5V Output current 20A Switching frequency 2.1MHz Output voltage regulation ±1% No-load sleep current with phase 2 disabled < 20µA Shutdown current 4µA Resistor RRT of 10.5kΩ sets the switching frequency at 2.1MHz. In terms of control loop performance, the target loop crossover frequency is 80kHz with a phase margin greater than 50°. Leaving the RSS pin open sets the output voltage soft-start time to 6.5ms. www.ti.com LM25137 SNVSCU4 – OCTOBER 2025 Copyright © 2025 Texas Instruments Incorporated Submit Document Feedback 49 Product Folder Links: LM25137 |
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