L6208 查看數據表（PDF） - STMicroelectronics

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L6208

DMOS driver for bipolar stepper motor

STMicroelectronics 

L6208

7.5

9''

Decay modes

Non-dissipative overcurrent protection

The L6208 device integrates an “Overcurrent Detection” circuit (OCD). This circuit provides

protection against a short-circuit to ground or between two phases of the bridge. With this

internal overcurrent detection, the external current sense resistor normally used and its

associated power dissipation are eliminated. Figure 21 shows a simplified schematic of the

overcurrent detection circuit.

To implement the overcurrent detection, a sensing element that delivers a small but precise

fraction of the output current is implemented with each high-side power MOS. Since this

current is a small fraction of the output current there is very little additional power

dissipation. This current is compared with an internal reference current IREF. When the

output current reaches the detection threshold (typically 5.6 A), the OCD comparator signals

a fault condition. When a fault condition is detected, the EN pin is pulled below the turn off

threshold (1.3 V typical) by an internal open drain MOS with a pull down capability of 4 mA.

By using an external R-C on the EN pin, the off time before recovering normal operation can

be easily programmed by means of the accurate thresholds of the logic inputs.

Figure 21. Overcurrent protection simplified schematic

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Figure 22 shows the overcurrent detection operation. The disable time tDISABLE before

recovering normal operation can be easily programmed by means of the accurate

thresholds of the logic inputs. It is affected whether by CEN and REN values and its

magnitude is reported in Figure 23. The delay time tDELAY before turning off the bridge when

an overcurrent has been detected depends only by CEN value. Its magnitude is reported in

Figure 24.

CEN is also used for providing immunity to the pin EN against fast transient noises.

Therefore the value of CEN should be chosen as big as possible according to the maximum

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