SNVSCU3 October 2025 LM5137
PRODMIX
Table 8-6 shows the intended input, output, and performance parameters for this circuit example.
| DESIGN PARAMETER | VALUE |
|---|---|
| Input voltage range (steady state) | 36V to 65V |
| Nominal input voltage | 48V |
| Minimum transient input voltage | 20V |
| Maximum transient input voltage | 72V |
| Output voltage setpoint | 12V |
| Rated output current | 20A |
| Switching frequency | 400kHz |
| Target efficiency at 10A, 20A | 96%, 95.5% |
| Input voltage UVLO on, off | 23V, 19V |
| 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.
Table 8-7 cites the selected buck regulator powertrain components, with many of the components available from multiple vendors. This design uses 80V logic-level MOSFETs, shielded buck inductors, shunt resistors with wide aspect ratio for low ESL, 100V-rated ceramic input capacitors and 25V-rated ceramic output capacitors.
| REFERENCE DESIGNATOR | QTY | SPECIFICATION(1) | MANUFACTURER | PART NUMBER |
|---|---|---|---|---|
| CIN1, CIN2 | 8 | 4.7μF, 100V, X7S, 1210, ceramic | TDK | CGA6M3X7S2A475K200 |
| Murata | GCM32DC72A475KE02L | |||
| COUT1, COUT2 | 8 | 22μF, 25V, X7R, 1210, ceramic | TDK | CGA6P3X7R1E226M250 |
| 22μF, 25V, X7S, 1210, ceramic | Murata | GCM32EC71E226KE36 | ||
| LO1, LO2 | 2 | 5.6μH, 10mΩ, 15A, 10.85 × 10 × 5.2mm | Cyntec | VCHW105D-5R6MS5 |
| 5.6μH, 14mΩ, 12A, 10.8 × 10 × 5mm | Eaton | HCM1A1105V2-5R6-R | ||
| 5.6μH, 10.2mΩ, 16.2A, 11 × 10 × 5.1mm | Bourns | SRP1050WA-5R6M | ||
| 4.7μH, 13.5mΩ, 16A, 10.85 × 10 × 3.8mm | Würth Electronik | 784373680047 | ||
| Q1, Q3 | 2 | 80V, 13.4mΩ, 8nC, SON 5 × 6 | onsemi | NVMFS6H852NLT1G |
| Q2, Q4 | 2 | 80V, 6.2mΩ, 16nC, SON 5 × 6 | onsemi | NVMFS6H836NLT1G |
| RS1, RS2 | 2 | Shunt, 4mΩ ±1%, ±50ppm/°C, 0612 wide aspect ratio, 1.5W | Susumu | KRL3216E-C-R004-F |
| U1 | 1 | LM5137 80V two-phase synchronous buck controller | Texas Instruments | LM5137RHAR |