STM1404 Pin descriptions
11/36
2 Pin descriptions
See Figure 1: Logic diagram and Table 2: Signal names for a brief overview of the signals
connected to this device.
2.1 SAL, security alarm output (open drain)
This signal can be generated when ANY of the following conditions occur:
● V
INT
> V
HV
, where V
HV
= upper voltage trip limit (4.2 V typ); and where V
INT
= V
CC
or
V
BAT
;
● V
INT
< V
LV
, where V
LV
= lower voltage trip limit (2.0 V typ); and where V
INT
= V
CC
or
V
BAT
; or
● When any of the physical tamper inputs, TP
1
to TP
4
, change from their normal states to
the opposite (i.e., intrusion of a physical enclosure).
● T
A
> T
H
, where T
H
is an upper temperature trip limit specified by the customer (+80°C,
+85°C, and +95°C), factory-programmed (STM1404 only);
● T
A
< T
L
, where T
L
is a lower temperature trip limit specified by the customer (–25°C or
–35°C), factory-programmed (STM1404 only);
Note: 1 The default state of the SAL
output during initial power-up is undetermined.
2 The alarm function will operate either with V
CC
on or when the part is internally switched
from V
CC
to V
BAT
.
2.2 TP
1
, TP
3
Physical tamper detect pin set normally to high (NH). They are connected externally through
a closed switch or a high-impedance resistor to V
OUT
(in the case of STM1404A) or V
TPU
(in
the case of STM1404B/C. A tamper condition will be detected when the input pin is pulled
low (see Figure 5 and Figure 6 on page 10). If not used, tie the pin to V
OUT
(for STM1404A)
or V
TPU
(for STM1404B/C).
2.3 TP
2
, TP
4
Physical tamper detect pin set normally to low (NL). They are connected externally through
a high-impedance resistor or a closed switch to V
SS
. A tamper condition will be detected
when the input pin is pulled high (see Figure 7 and Figure 8 on page 10). If not used, tie the
pin to V
SS
.
2.3.1 Vccsw, V
CC
switch output
This output is low when V
OUT
(see Section 2.10: V
OUT
on page 13) is internally switched to
V
CC
; in this mode it may be used to turn on an external p-channel MOSFET switch which
can source an external device directly from V
CC
for currents greater than 80 mA (bypassing
the STM1404).
This pin goes high when V
OUT
is internally switched to V
BAT
and may be used as a
“BATTERY ON” indicator.
