Datasheet

 
SLUS318B – APRIL 1999 – REVISED JANUARY 2002
15
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APPLICATION INFORMATION
power stage design considerations
The flexible architecture of the UCC3626 requires the user to pay close attention to the design of the power
output stage. Two- and four-quadrant applications not requiring the brake function are able to use the power
stage approach illustrated in Figure 13a. In many cases the body diode of the MOSFET can be used to reduce
parts count and cost. If efficiency is a key requirement, Schottky diodes can be used in parallel with the switches.
UDG–97190
(b)
(c)
TO
MOTOR
VMOT
CURRENT
SENSE
TO
MOTOR
VMOT
CURRENT
SENSE
T
O
MO
T
VMOT
CURRENT
SENSE
(a)
UDG–01122
TWO
FOUR
SAFE
POWER
CURRENT SENSE
TWO
QUADRANT
FOUR
QUADRANT
SAFE
BRAKING
POWER
REVERSAL
PULSE-BY-
PULSE
AVERAGE
(a) YES YES NO Four-Quad Only YES YES
(b) YES NO YES No YES NO
(c) YES YES YES Four-Quad Only YES YES
Figure 13. Power Stage Topologies
If the system requires a braking function, diodes must be added in series with the lower power devices and the
lower flyback diodes must be returned to ground, as pictured in Figure 13b, and 13c. This requirement prevents
brake currents from circulating in the lower half bridge and bypassing the sense resistor. In addition, the
combination of braking and four-quadrant control necessitates an additional resistor in the diode path to sense
current during the PWM off time as illustrated in Figure 13c.