Datasheet

ST72334J/N, ST72314J/N, ST72124J
127/153
EMC CHARACTERISTICS (Cont’d)
True Open Drain Pin Protection
The centralized protection (4) is not involved in the
discharge of the ESD stresses applied to true
open drain pads due to the fact that a P-Buffer and
diode to V
DD
are not implemented. An additional
local protection between the pad and V
SS
(5a &
5b) is implemented to completely absorb the posi-
tive ESD discharge.
Multisupply Configuration
When several types of ground (V
SS
, V
SSA
, ...) and
power supply (V
DD
, V
DDA
, ...) are available for any
reason (better noise immunity...), the structure
shown in Figure 81 is implemented to protect the
device against ESD.
Figure 79. Positive Stress on a True Open Drain Pad vs. V
SS
Figure 80. Negative Stress on a True Open Drain Pad vs. V
DD
Figure 81. Multisupply Configuration
IN
V
DD
V
SS
(1)
(2b)
(4)
OUT
V
DD
V
SS
(3b)
Main path
Path to avoid
(5a) (5b)
IN
V
DD
V
SS
(1)
(2b)
(4)
OUT
V
DD
V
SS
(3b)
Main path
(3b) (3b)
V
DDA
V
SSA
V
DDA
V
DD
V
SS
BACK TO BACK DIODE
BETWEEN GROUNDS
V
SSA