STMicroelectronics L6227 DMOS Evaluation Board EVAL6227PD EVAL6227PD 데이터 시트
제품 코드
EVAL6227PD
Slow decay mode
L6227
18/32
DocID9453 Rev 2
7
Slow decay mode
shows the operation of the bridge in the slow decay mode. At the start of the off
time, the lower power MOS is switched off and the current recirculates around the upper half
of the bridge. Since the voltage across the coil is low, the current decays slowly. After the
deadtime the upper power MOS is operated in the synchronous rectification mode. When
the monostable times out, the lower power MOS is turned on again after some delay set by
the deadtime to prevent cross conduction.
of the bridge. Since the voltage across the coil is low, the current decays slowly. After the
deadtime the upper power MOS is operated in the synchronous rectification mode. When
the monostable times out, the lower power MOS is turned on again after some delay set by
the deadtime to prevent cross conduction.
Figure 13. Slow decay mode output stage configurations
7.1 Non-dissipative
overcurrent
protection
The L6227 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.
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.
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 I
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 I
REF
. When the
output current in one bridge reaches the detection threshold (typically 2.8 A) the relative
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.
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.
$217,0(
&6<1&+521286
5(&7,),&$7,21
5(&7,),&$7,21
',19