Datasheet

OC(delay) HICC
0.6 V
T C
75 A
= ´
m
HICC HICC
2.4 V 0.3 V
T C
2.7 A
-
= ´
m
0.3V
0.6V
2.4V
HICC
t
t
4V
SS
OUTA
OUTB
Normal OC Normal OC Hiccup Soft Start
T
OCdealy
T
HICC
UCC28250
SLUSA29C –APRIL 2010– REVISED JULY 2011 www.ti.com
The cycle-by-cycle current limit operation time before all four outputs shut down is programmed by external
capacitor C
HICC
at HICC pin. The delay time can be calculated as:
(27)
The hiccup timer keeps all outputs being zero until the timer expires. The hiccup time T
HICC
is calculated as:
(28)
As soon as the outputs are shut-down, SS pin is pulled down internally until the hiccup restart timer is reset after
time duration T
HICC
. The detailed illustration of HICCUP mode is shown in Figure 45.
Figure 45. Cycle-by-Cycle Current Limit Delay Timer and Hiccup Restart Timer
Thermal Protection
Internal thermal shutdown circuitry protects the UCC28250 in the event the maximum rated junction temperature
is exceeded. When activated, typically at 160°C, with the maximum threshold at 170°C and minimum threshold at
150°C the controller is forced into a low power standby mode. The outputs (OUTA, OUTB, SRA, SRB) are
disabled. This helps to prevent accidental device overheating. A 20°C hysteresis is added to prevent comparator
oscillation. During thermal shutdown, the UCC28250 follows a normal start up sequence after the junction
temperature falls below 140°C (typical value, with 130°C minimum threshold and 150°C maximum threshold).
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