STM1404CTMDQ6 查看數據表（PDF） - STMicroelectronics

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STM1404CTMDQ6

3 V FIPS-140 security supervisor with battery switchover

STMicroelectronics 

STM1404

4

Tamper detection

Tamper detection

4.1

Physical

There are four (4) high-impedance physical tamper detect input pins, 2 normally set to high

(NH) and 2 normally set to low (NL). Each input is designed with a glitch immunity (see

Table 7 on page 29). These inputs can be connected externally to several types of actuator

devices (e.g., switches, wire mesh). A tamper on any one of the four inputs that causes its

state to change will trigger the security alarm (SAL) and drive it to active-low. Once the

tamper condition no longer exists, the SAL will return to its normal high state.

TP1 and TP3 are set normally to high (NH). They are connected externally through a closed

switch or a high-impedance resistor to VOUT (in the case of STM1404A or STM1404A) or

VTPU (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 VOUT or VTPU.

TP2 and TP4 are set normally to low (NL). They are connected externally through a high-

impedance resistor or a closed switch to VSS. 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

VSS.

4.2

Supply voltage

The internally switched supply voltage, VINT (either VCC input or VBAT input) is continuously

monitored. If VINT should exceed the over voltage trip point, VHV (set at 4.2V, typical), or

should go below the under voltage trip point, VLV (set at 2.0v, typical). SAL will be driven

active-low. Once the tamper condition no longer exists, the SAL pin will return to its normal

high state.

4.3

Note:

Temperature

The STM1404 has a built-in, bandgap-based sensor to monitor the temperature. If a preset

(customer-selectable, factory-programmed) over-temperature trip point (TH) or under-

temperature trip point (TL) is exceeded, the SAL is asserted low.

When no tamper condition exists, SAL is normally high (see Section 2: Pin descriptions on

page 11).

When a tamper is detected, the SAL is activated (driven low), independent of the part type.

VOUT can be driven to one of three states, depending on which variant of STM1404 is being

used (see Table 1 on page 1):

● ON

● High-Z or

● Ground (VSS)

The STM1404 must be initially powered above VRST to enable the tamper detection alarms.

For example, if the battery is on while VCC = 0 V, no alarm condition can be detected until

VCC rises above VRST (and trec expires). From this point on, alarms can be detected either

on battery or VCC. This is done to avoid false alarms when the device goes from no power to

its operational state.

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