SA57 Datasheet, PDF (12/14 Pages) Cirrus Logic – Switching Amplifier

SA57
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The current limit feature may be disabled _{Figure 8. Current Limit Waveforms}
by tying the I_Lim/Dis1 pin to GND. The
current sense pins will continue to provide
top FET output current information.
It INPUT
Typically, the current sense pins source
current into grounded resistors which pro-
vide voltages to the current limit compara-
tors. If instead the current limit resistors are
connected to a voltage output DAC, the
current limit can be controlled dynamically
from the system controller. This technique
essentially reduces the current limit thresh-
old voltage to (Vth-VDAC). During expect-
ed conditions of high torque demand, such
as start-up or reversal, the DAC can adjust
the current limit dynamically to allow pe-
riods of high current. In normal operation
when low current is expected, the DAC
output voltage can increase, reducing the
current limit setting to provide more con-
servative fault protection.
V_th
I1
OUT 1
I_LIM/DIS1
2.6 EXTERNAL FLYBACK DIODES
Figure 9. Schottky Diodes
External fly-back diodes will offer superior reverse recovery characteristics
and lower forward voltage drop than the internal back-body diodes. In high
V_S V_S
current applications, external flyback diodes can reduce power dissipation
and heating during commutation of the motor current. Reverse recovery
time and capacitance are the most important parameters to consider when
SA57
OUT 1
OUT 2
selecting these diodes. Ultra-fast rectifiers offer better reverse recovery
time and Schottky diodes typically have low capacitance. Individual appli-
cation requirements will be the guide when determining the need for these
diodes and for selecting the component which is most suitable.
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SA57U