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LM5145 Datasheet(PDF) 20 Page - Texas Instruments |
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LM5145 Datasheet(HTML) 20 Page - Texas Instruments |
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20 / 74 page  7.3 Feature Description 7.3.1 Input Voltage Range (VIN) The LM5137 input voltage operating range is from 4V to 80V. The device is intended for step-down conversions from 12V, 24V and 48V automotive supply rails. The circuit in Figure 7-1 shows the essential components to implement an LM5137 based wide-VIN dual-output buck regulator using a single input supply. The LM5137 uses an internal LDO subregulator to provide a 5V VCC bias rail for the gate drive and control circuits (assuming the input voltage is higher than 5V plus the necessary subregulator dropout specification). There is also an integrated 20µA charge pump always active in LM5137. As VIN approaches the VOUT setpoint, the 20µA charge pump charges the CBOOT and keeps the high-side MOSFET on, thus achieving true 100% duty cycle. This action allows for the lowest possible dropout voltage from input to output. RT RSS PFM/SYNC AGND COMP2 VOUT2 ISNS2+ LO2 SW2 HO2 CBOOT2 VIN COMP1 BIAS1/VOUT1 ISNS1+ LO1 SW1 HO1 CBOOT1 VCC FB1 VDDA FB2 SYNCOUT CFNG EN1 EN2 PG2 PG1 V IN L O1 C OUT2 C IN1 C VDDA L O2 C OUT1 R S2 R S1 Q 2 Q 1 R SS R RT R CNFG Q 4 Q 3 C VCC C BOOT1 C BOOT2 LM5137 V OUT2 VDDA C IN2 R FB3 R FB4 V OUT1 C HF2 R COMP2 C COMP2 C HF1 R COMP1 C COMP1 R FB1 R FB2 Figure 7-1. LM5137 Dual-Output Regulator Schematic In high input voltage applications, make sure that the VIN, SW1, and SW2 pin voltages do not exceed the absolute maximum voltage rating of 85V during line or load transient events. Voltage excursions that exceed the Absolute Maximum Ratings can damage the IC. Proceed carefully during PCB board layout and use high-quality input bypass capacitors to minimize switch-voltage overshoot and ringing. 7.3.2 Bias Supply Regulator (VCC, BIAS1/VOUT1, VDDA) The LM5137 contains an internal high-voltage VCC bias regulator that provides the bias supply for the PWM controller and the gate drivers of the external MOSFETs. Connect the input voltage pin (VIN) directly to an input voltage source up to 80V. When the input voltage is below the VCC setpoint of 5V, the VCC voltage tracks VIN minus a small voltage drop. The VCC regulator current limit is 175mA (minimum). At power up, the regulator sources current into the VCC capacitor. When the VCC voltage exceeds 3.8V (typical), both output channels are enabled (if EN1 and EN2 are above 1V) and the soft-start sequence begins. Both channels remain active unless the VCC voltage falls below the falling UVLO threshold of 3.5V (typical) or EN is switched to a low state. Connect a 2.2µF to 10µF ceramic capacitor from VCC to PGND. LM5137 SNVSCU3 – OCTOBER 2025 www.ti.com 20 Submit Document Feedback Copyright © 2025 Texas Instruments Incorporated Product Folder Links: LM5137 |
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