SNVSCU4 October 2025 LM25137
PRODMIX
Table 8-6 shows the intended input, output, and performance parameters for this circuit example.
| DESIGN PARAMETER | VALUE |
|---|---|
| Input voltage range (steady state) | 18V to 34V |
| Minimum transient input voltage | 16V |
| Maximum transient input voltage | 36V |
| Output voltage | 12V |
| Output current | 30A |
| Switching frequency | 400kHz |
| Target efficiency at 25A | 97% |
| Input voltage UVLO on, off | 15V, 13V |
| No-load sleep current with phase 2 disabled | < 20μA |
| Shutdown current | 4μA |
Resistor RRT of 57.6kΩ sets the switching frequency at 400kHz. In terms of control loop performance, the target loop crossover frequency is 60kHz with a phase margin greater than 50°. An RSS resistance of 20kΩ sets the output voltage soft-start time to 4.5ms.
the following table cites the selected buck regulator powertrain components, with many of the components available from multiple vendors. This design uses 40V logic-level MOSFETs, shielded buck inductors, shunt resistors with wide aspect ratio for low ESL, 50V-rated ceramic input capacitors and 25V-rated ceramic output capacitors.
| REFERENCE DESIGNATOR | QTY | SPECIFICATION(1) | MANUFACTURER | PART NUMBER |
|---|---|---|---|---|
| CIN1, CIN2 | 8 | 10μF, 50V, X7R, 1210, ceramic | TDK | CNA6P1X7R1H106K |
| 10μF, 50V, X7S, 1210, ceramic | Murata | GCM32EC71H106K | ||
| COUT1, COUT2 | 8 | 22μF, 25V, X7R, 1210, ceramic | TDK | CGA6P3X7R1E226M250 |
| 22μF, 25V, X7S, 1210, ceramic | Murata | GCM32EC71E226KE36 | ||
| LO1, LO2 | 2 | 3.3μH, 6.2mΩ, 19A, 10.85 × 10 × 5.2mm | Cyntec | VCHA105D-3R3MS6 |
| 3.3μH, 6.2mΩ, 20A, 11 × 10 × 5.1mm | Bourns | SRP1050WA-3R3M | ||
| 3.3μH, 6mΩ, 28.6A, 10.5 × 10 × 6.5mm | TDK | SPM10065VT-3R3M-D | ||
| 3.3μH, 9.23mΩ, 16A, 10.8 × 10 × 5mm | Eaton | HCM1A1105V2-3R3-R | ||
| 3.3μH, 9.9mΩ, 22.1A, 10.85 × 10 × 3.8mm | Würth Electronik | 784373680033 | ||
| Q1, Q2,Q3, Q4 | 4 | 40V, 3.6mΩ, 9nC, SON 5 × 6 | Infineon | IAUCN04S7L028ATMA1 |
| RS1, RS2 | 2 | Shunt, 3mΩ ±1%, ±50ppm/°C, 0612 wide aspect ratio, 1.5W | Susumu | KRL3216E-C-R003-F |
| U1 | 1 | LM25137 42V two-phase synchronous buck controller | Texas Instruments | LM25137RHAR |