10.3.4.1 Example Efficiency Calculation
Table 3. Operating Conditions
| PARAMETER |
VALUE |
| VIN |
5 V |
| VOUT |
12 V |
| IOUT |
500 mA |
| VD |
0.4 V |
| FSW |
1.60 MHz |
| IQ |
4 mA |
| TRISE |
6 nS |
| TFALL |
5 nS |
| RDSon |
250 mΩ |
| RDCR |
50 mΩ |
| D |
0.64 |
| IIN |
1.4 A |
Equation 48. ΣPCOND + PSW + PDIODE + PIND + PQ = PLOSS
Quiescent Power Losses:
Equation 49. PQ = IQ × VIN = 20 mW
Switching Power Losses:
Equation 50. PSWR = 1/2(VOUT × IIN × FSW × TRISE) ? 6 ns ? 80 mW
Equation 51. PSWF = 1/2(VOUT × IIN × FSW × TFALL) ? 5 ns ? 70 mW
Equation 52. PSW = PSWR + PSWF = 150 mW
Internal NFET Power Losses:
Equation 53. RDSON = 250 mΩ
Equation 54. PCONDUCTION = IIN2 × D × RDSON × 305 mW
Diode Losses:
Equation 55. VD = 0.45 V
Equation 56. PDIODE = VD × IIN(1–D) = 236 mW
Inductor Power Losses:
Equation 57. RDCR = 75 mΩ
Equation 58. PIND = IIN2 × RDCR = 145 mW
Total Power Losses are:
Table 4. Power Loss Tabulation
| PARAMETER |
VALUE |
PARAMETER |
VALUE |
| VIN |
5 V |
|
|
| VOUT |
12 V |
|
|
| IOUT |
500 mA |
POUT |
6 W |
| VD |
0.4 V |
PDIODE |
236 mW |
| FSW |
1.6 MHz |
|
|
| TRISE |
6 nS |
PSWR |
80 mW |
| TFALL |
5 nS |
PSWF |
70 mW |
| IQ |
4 mA |
PQ |
20 mW |
| RDSon |
250 mΩ |
PCOND |
305 mW |
| RDCR |
75 mΩ |
PIND |
145 mW |
| D |
0.623 |
|
|
| η |
86% |
PLOSS |
856 mW |
Equation 59. PINTERNAL = PCOND + PSW = 475 mW