Relationship between cooling fan IC and current
Time:2023-08-14
Views:671
The maximum current that can be achieved with a 276/277 IC fan
The relationship curve between the power consumption Pd that SIP4 plastic packaging can withstand and temperature; calculation of the power consumption that can withstand at temperature t: Pd=660-4.4t (mW)
The actual power consumption of the 276/277 IC is calculated as follows: Pd=Vcc * Icc+Vsat * Isink=12 * 16+0.7 * Isink=192+0.7 * Isink. From this, the relationship between fan current and temperature can be determined in the table:
When the fan has no capacitance, the fan current Ifan is close to the current Isink of the IC driver that penetrates
The following temperatures are the ambient temperature plus the motor temperature rise:
T=85 ℃, Pd=192+0.7 * Isink ≤ 286, Isink ≤ 134mA;
T=80 ℃, Pd=192+0.7 * Isink ≤ 308, Isink ≤ 165mA;
T=75 ℃, Pd=192+0.7 * Isink ≤ 330, Isink ≤ 197mA;
T=70 ℃, Pd=192+0.7 * Isink ≤ 352, Isink ≤ 228mA;
T=65 ℃, Pd=192+0.7 * Isink ≤ 374, Isink ≤ 260mA;
T ＜ 65 ℃, Isink ≤ 260mA;
If safety regulations are considered, when the fan is blocked, the coil only has resistance but no inductance, while the 276/277 IC Ilock is ≤ 500mA, so the coil resistance is R ≥ 12/0.5=24 Ω; When the rotor is blocked, the coil is continuously energized, and the temperature rise continues to rise. Whether the fan is damaged is related to the locking current and duration. The 276/277 IC can achieve a fan current of around 260mA
When the fan is equipped with a capacitor, the current Isink of the IC driver is greater than the fan current Ifan. Considering this coefficient, the maximum current that the fan can achieve is smaller than the above
Conclusion: The Isink=400mA in the specification refers to the RMS value (effective value) of the current penetrating the IC driver at a surface temperature of 25 ℃, which cannot always reach 400mA. The current penetrating the IC driver is not equal to the fan current. The higher the ambient temperature used, the smaller the current that the IC driver can withstand
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