LB1975_08 SANYO [Sanyo Semicon Device], LB1975_08 Datasheet - Page 10

• Manufacturer Part Number: LB1975_08
• Description: For Fan Motor 3-phase Brushless Motor Driver
• Manufacturer: SANYO [Sanyo Semicon Device]

13. Sample calculation for internal power dissipation (approximate)
14. IC temperature Rise Measurement
15. NC Pins
14-1. Thermocouple measurement
14-2. Measurement using internal diode characteristics of IC
The calculation assumes the following parameters:
V CC = 5V
V M = 30V
Source-side output transistor ON duty cycle 80% (PWM control)
Output current I O = 1A (RF pin average current)
(1) I CC power dissipation P1
(2) Output drive current power dissipation P2
(3) Source-side output transistor power dissipation P3
(4) Sink-side output transistor power dissipation P4
(5) Total internal power dissipation P
Because the chip temperature of the IC cannot be measured directly, measurement according to one of the following
procedures should always be carried out.
Because NC pins are electrically open, they may be used for wiring purpose etc.
P1 = V CC × I CC = 5V × 14mA = 0.07W
P2 = V M × 11mA = 30V × 11mA = 0.33W
P3 = V O (source) × I O × Duty(on) = 0.9V × 1A × 0.8 = 0.72W
P4 = V O (sink) × I O = 1.1V × 1A = 1.10W
P = P1 + P2 + P3 + P4 = 2.22W
A thermocouple element is mounted to the IC heat dissipation fin. This measurement method is easy to implement,
but it will be subject to measurement errors if the temperature is not stable.
This is the recommended measurement method. It makes use of the parasitic diode incorporated in the IC between
FG1 and GND. Set FG1 to High and measure the voltage V F of the parasitic diode to calculate the temperature.
(Sanyo data: for I F = −1mA, V F temperature characteristics are about −2mV/°C)
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LB1975
PS No.6087-10/10