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LM5145 Datasheet(PDF) 49 Page - Texas Instruments

Part # LM5145
Description  LM25137 4V to 42V, 100% Duty Cycle Capable, Dual-Channel, Synchronous Buck DC/DC Controller
PDF  73 Pages
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Manufacturer  TI2 [Texas Instruments]
Direct Link  https://www.ti.com
Logo TI2 - Texas Instruments

LM5145 Datasheet(HTML) 49 Page - Texas Instruments

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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
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Product Folder Links: LM25137



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