ZHCSM29A September 2023 – June 2024 LM70840-Q1 , LM70860-Q1 , LM70880-Q1
PRODUCTION DATA
Table 8-3 shows the intended input, output, and performance parameters for this automotive design example.
| DESIGN PARAMETER | VALUE |
|---|---|
| Input voltage range (steady-state) | 8V to 60V |
| Min transient input voltage (cold crank) | 5.5V |
| Max transient input voltage (load dump) | 72V |
| Output voltage | 5V |
| Output current | 8A |
| Switching frequency | 400kHz |
| Output voltage regulation | ±1% |
| Active current, no load | 10μA |
| Shutdown current | 2.2μA |
| Soft-start time | 3ms |
The switching frequency is set at 400kHz by resistor RRT. In terms of control loop performance, the target loop crossover frequency is 30kHz with a phase margin greater than 50°.
The selected buck regulator powertrain components are cited in Table 8-4, and many of the components are available from multiple vendors. This design uses a low-DCR, metal-powder composite inductor, and ceramic output capacitor implementation.
| REFERENCE DESIGNATOR | QTY | SPECIFICATION | MANUFACTURER | PART NUMBER |
|---|---|---|---|---|
| CIN | 4 | 4.7μF, 100V, X7S, 1210, ceramic | Murata | GCM32DC72A475KE02L |
| TDK | CGA6M3X7S2A475K200 | |||
| CO | 4 | 47μF, 6.3V, X7R, 1210, ceramic, AEC-Q200 | Murata | GCM32ER70J476KE19L |
| Taiyo Yuden | JMK325B7476KMHTR | |||
| 47μF, 10V, X7S, 1210, ceramic, AEC-Q200 | TDK | CGA6P1X7S1A476M250AC | ||
| LO | 1 | 3.3μH, 5.9mΩ, 10.1A, 6.71 × 6.51 × 6.1mm, AEC-Q200 | Coilcraft | XGL6060-332MEC |
| 3.3μH, 10.8mΩ, 15A, 6.45 × 6.65 × 5.8mm, AEC-Q200 | Würth Electronik | 74439346033 | ||
| RS | 1 | Shunt, 5mΩ, 0508, 1W, AEC-Q200 | Susumu | KRL3216T4A-M-R005 |
| U1 | 1 | LM70880-Q1 80V buck converter, AEC-Q100 | Texas Instruments | LM70880QRRXRQ1 |