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SLVSGC3 May 2020 DRV8210P

PRODUCTION DATA

封裝選項

機械數據 (封裝 | 引腳)

DSG|8
- MPDS308C

散熱焊盤機械數據 (封裝 | 引腳)

DSG|8
- QFND141I

訂購信息

9.3.1 Power Dissipation and Output Current Capability

Total power dissipation for the device consists of three main components: quiescent supply current dissipation (P_VM and P_VCC), the power MOSFET switching losses (P_SW), and the power MOSFET R_DS(on) (conduction) losses (P_RDS). While other factors may contribute additional power losses, they are typically insignificant compared to the three main items.

Equation 2. P_TOT = P_VM + P_VCC + P_SW + P_RDS

P_VM can be calculated from the nominal motor supply voltage (V_VM) and the I_VM active mode current specification. P_VCC can be calculated from the nominal logic supply voltage (V_VCC) and the I_VCC active mode current specification. When V_VCC < V_VM, the DRV8210 draws active current from the VM pin rather than the VCC pin. During this operating condition, I_VCC is typically less than 500 nA.

Equation 3. P_VM = V_VM x I_VM

Equation 4. P_VM = 7 mW = 5 V x 1.4 mA

Equation 5. P_VCC = V_VCC x I_VCC

Equation 6. P_VCC = 0.594 mW = 3.3 V x 0.18 mA

P_SW can be calculated from the nominal motor supply voltage (V_VM), average output current (I_RMS), switching frequency (f_PWM) and the device output rise (t_RISE) and fall (t_FALL) time specifications.

Equation 7. P_SW = P_{SW_RISE} + P_{SW_FALL}

Equation 8. P_{SW_RISE} = 0.5 x V_M x I_RMS x t_RISE x f_PWM

Equation 9. P_{SW_FALL} = 0.5 x V_M x I_RMS x t_FALL x f_PWM

Equation 10. P_{SW_RISE} = 3.75 mW = 0.5 x 5 V x 0.5 A x 150 ns x 20 kHz

Equation 11. P_{SW_FALL} = 3.75 mW = 0.5 x 5 V x 0.5 A x 150 ns x 20 kHz

Equation 12. P_SW = 7.5 mW = 3.75 mW + 3.75 mW

P_RDS can be calculated from the device R_DS(on) and average output current (I_RMS).

Equation 13. P_RDS = I_RMS² x (R_{DS(ON)_HS} + R_{DS(ON)_LS})

R_DS(ON) has a strong correlation with the device temperature. Assuming a device junction temperature of 85 °C, R_DS(on) could increase ~1.5x based on the normalized temperature data. The calculation below shows this derating factor.

Equation 14. P_RDS = 394 mW = (0.5 A)² x (525 mΩ x 1.5 + 525 mΩ x 1.5)

Based on the example calculations above, the expressions below calculate the total expected power dissipation for the device.

Equation 15. P_TOT = P_VM + P_VCC + P_SW + P_RDS

Equation 16. P_TOT = 409 mW = 7 mW + 0.594 mW + 7.5 mW + 394 mW

The driver's junction temperature can be estimated using P_TOT, device ambient temperature (T_A), and package thermal resistance (R_θJA). The value for R_θJA depends heavily on the PCB design and copper heat sinking around the device. Section 9.3.2 describes this dependence in greater detail.

Equation 17. T_J = (P_TOT x R_θJA) + T_A

Equation 18. T_J = 126°C = (0.409 W x 99.6 °C/W) + 85°C

The device junction temperature should remain below its absolute maximum rating for all system operating conditions. The calculations in this section provide reasonable estimates for junction temperature. However, other methods based on temperature measurements taken during system operation are more realistic and reliable. Additional information on motor driver current ratings and power dissipation can be found in Section 9.3.2 and Section 12.1.1.