SENSITRON

SEMICONDUCTOR

TECHNICAL DATA

Datasheet 4118, Rev. D.2

© 2004 Sensitron Semiconductor

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Page 14

SPM6M080-010D

f- Limitation With Trapezoidal Motor Drive

In trapezoidal motor drives, two phases are conducting while the third phase is off at any

time. In Fig. 9 shows the voltage waveform across one phase, during intervals t1 and t2,

the MOSFET is off while the active bias circuit is above 8V, and below 15V. This results in

activating the active pull up circuit and reducing the corresponding R1 or R2 down to about

110

Ω. A high current will flow from VCC or VBS through R2 or R1 and the motor winding

during intervals t1, and t2. This results in draining the bootstrap capacitor voltage quickly.

Contact the factory for adjustments to satisfy trapezoidal motor drive applications using

this module. The adjustment will disable the internal pull up circuit. The device part number

is SPM6M080-010D-B.

Figure 9.

Active Bias for DSH and DSL Internal Inputs

t1

V

t2

time

15

8