LB1975(2003) データシートの表示（PDF） - SANYO -> Panasonic

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LB1975
(Rev.:2003)

DC Fan Motor Driver

SANYO -> Panasonic 

LB1975

Power Supply Stabilizing Capacitors

If the VCC line fluctuates drastically, the low-voltage protection circuit may be activated by mistake, or other

malfunctions may occur. The VCC line must therefore be stabilized by connecting a capacitor of at least several µF

between VCC and GND. Because a large switching current flows in the VM line, wiring inductance and other factors can

lead to VM voltage fluctuations. As the GND line also fluctuates, the VM line must be stabilized by connecting a

capacitor of at least several µF between VM and GND, to prevent exceeding VMmax or other problems. Especially when

long wiring runs (VM, VCC, GND) are used, sufficient capacitance should be provided to ensure power supply stability.

VCREF Pin, VCOUT Pin

These pins are always used in the Open condition. If chattering occurs in the PWM switching output, connect a capacitor

(about 0.1 µF) between VCREF and ground or between VCOUT and GND.

IC Heat Dissipation Fins

A heat sink may be mounted to the heat dissipation fins of this IC, but it may not be connected to GND. The sink should

be electrically open.

Sample calculation for internal power dissipation (approximate)

The calculation assumes the following parameters:

VCC = 5 V

VM = 30 V

Source-side output transistor ON duty cycle 80% (PWM control)

Output current IO = 1 A (RF pin average current)

• ICC power dissipation P1

P1 = VCC × ICC = 5 V × 14 mA = 0.07 W

• Output drive current power dissipation P2

P2 = VM × 11 mA = 30 V × 11 mA = 0.33 W

• Source-side output transistor power dissipation P3

P3 = VO (source) × IO × Duty (on) = 0.9 V × 1 A × 0.8 = 0.72 W

• Sink-side output transistor power dissipation P4

P4 = VO (sink) × IO = 1.1 V × 1 A = 1.10 W

• Total internal power dissipation P

P = P1 + P2 + P3 + P4 = 2.22 W

IC temperature Rise Measurement

Because the chip temperature of the IC cannot be measured directly, measurement according to one of the following

procedures should always be carried out.

• Thermocouple measurement

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.

• Measurement using internal diode characteristics of IC

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 VF of the parasitic diode to calculate the temperature.

(Sanyo data: for IF = –1 mA, VF temperature characteristics are about –2 mV/°C)

NC Pins

Because NC pins are electrically open, they may be used for wiring purpose etc.

No. 6087-11/12

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