TA84006F/FG

2006-3-6

9

Equivalent Circuit

<Overcurrent detector (RF, VISD, ISD) >

• Input to the VISD1 pin the voltage generated at the overcurrent detection resistor RF connected to the

RF pin.

• At chopping ON, voltage spikes at the RF pin as a result of the Pch-MOS output capacitance. To cancel

the spike, externally connect a capacitor to the VISD2 pin. (10 k

Ω resistor built-in)

• If the VISD2 pin voltage exceeds the internal reference voltage (VRF = 0.5 V), the overcurrent detection

output ISD pin goes Low.

Inputting the inversion of the ISD pin output to the TB6537P/PG/F/FG or TB6548F/FG OC pin limits the

PWM ON time and the current at the ISD output rising edge.

<Pin voltage detector (COMP) >

• The pin voltage detector outputs the result of OR-ing the output pin voltages and the virtual mid-point N

voltage to determine the majority.

(If at least two phases of the three-phase output are greater than the mid-point potential, the detector

outputs “Low”. Conversely, if at least two phases are smaller than the mid-point potential, the circuit

outputs “High”.)

• With the virtual mid-point potential VN used as the reference for the pin voltage detection circuit

considered as half the voltage applied to the motor, then

VN

we have set the following: VN

<Overheating protector>

• Automatic restoration

TSD (ON)

= 165°C

TSD (OFF)

= 135°C

• Temperature hysteresis supported

TSD (HYS)

= 30°C

COMP

GND

Majority-determining

OR data

ISD

10 k

Ω

External

capacitor

VISD1

VISD2