SCM1245MF datasheet(29/60 Pages) SANKEN

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SCM1200MF Series

SCM1200MF-DSJ Rev.1.1

SANKEN ELECTRIC CO.,LTD.

Feb. 19, 2016

http://www.sanken-ele.co.jp/en

operation waveforms at OCP. When the OCPx pin

voltage increases to an Overcurrent Protection Threshold

Voltage, VTRIP, of 0.50 V, and then keeps in that

condition for an Overcurrent Protection Blanking Time,

tBK, of 1.65 μs or longer, the OCP circuit starts operating.

The enabled OCP circuit then shuts off the output

transistors and puts the FOx pin into a logic low state.

Even if the OCPx pin voltage falls below VTRIP, the IC

keeps in a logic low state for a fixed OCP hold time (tP)

of 26 μs (typ.). Then, the output transistors operate

according to input signals. Then, the output transistors

operate according to input signals.

The OCP circuits in the SCM1200MF series are used

for detecting abnormal conditions, such as an output

transistor shorted. Therefore, motor operation must be

stopped by the external microcontroller, which can

receive and handle fault signals from the IC. Otherwise,

your application will be more likely to cause short

circuit conditions repeatedly, thus the breakdown of the

output transistors.

Care should also be taken when using a 3-shunt

resistor system in your application.

The IC running on

the 3-shunt resistor system only shuts off the output

transistor in the phase where an overcurrent condition

exists. And a fault signal is transmitted from the FOx pin

of the phase being under the overcurrent condition.

As already shown in Figure 12-12, if all of the FOx

pins being used makes a short circuit, a fault signal sent

from the corresponding phase can turn off the output

transistors of all phases (see Section 12.3.2).

To place a shunt resistor in an actual application,

users must set:

● the shunt resistor to have the resistance specified as

shunt resistor, RS (see the recommended operating

condition table, Section 2);

● input voltages of the OCPx pin to keep their levels

within the range defined as the OCPx pin voltage,

VOCP (see the absolute maximum rating table, Section

1); and

● currents through output transistors to keep their levels

under the rated output current (pulsed), IOP (see the

absolute maximum rating table, Section 1).

Because high-frequency switching currents flow

through the shunt resistors, RS, choose a resistor that has

low inductance and allows high power dissipation.

When adding a CR filter (a pair of a filter resistor, RO

and a filter capacitor, CO) to the OCPx pin, the following

should be taken into account. Time constants of RO and

CO should be set to the values listed in Table 12-3.

The larger the time constant, the longer the time that

the OCPx pin voltage rises to VTRIP. And this may cause

permanent damage to the transistors. Consequently, the

time

constants

given

here

are

determined

consideration of the total delay time the IC will have.

The filter capacitor, CO, should also be placed near the

IC, between the OCPx and COMx pins with a minimal

length of traces.

Note that overcurrents are undetectable when one or

more of the U, V, and W pins are shorted to ground

(ground fault). In case either of these pins falls into a

state of ground fault, the transistors may be destroyed.

VBB

LSx

COM

OCPx

COMx

A/D

DRS

VTRIP

200kΩ

Blanking

filter

Output SW turn-off

and QFO turn-on

1.65µs(typ.)

Figure 12-15.

Internal circuit diagram of OCPx pin

and OCPx pin peripheral circuitry

LINx

HINx

HOx

LOx

FOx

OCPx

VTRIP

tBK

tDELAY 0.3µs(typ.)

tBK

HO responds to input signal.

FO restarts

automatically after tP.

Figure 12-16.

OCP operational waveforms

Table 12-3.

Recommend time constants for CR filter

Products

Recommend time constants

SCM124×MF

SCM125×MF

0.22 µs or less

SCM126×MF

1 µs or less

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