ST7SCR
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EMC CHARACTERISTICS
(Cont’d)
14.7.2 Absolute Electrical Sensitivity
Based on three different tests (ESD, LU and DLU)
using specific measurement methods, the product
is stressed in order to determine its performance in
terms of electrical sensitivity. For more details, re-
fer to the AN1181 ST7 application note.
14.7.2.1 Electro-Static Discharge (ESD)
Electro-Static Discharges (1 positive then 1 nega-
tive pulse separated by 1 second) are applied to
the pins of each sample according to each pin
combination. The sample size depends of the
number of supply pins of the device (3 parts*(n+1)
supply pin). The Human Body Model is simulated.
This test conforms to the JESD22-A114A stand-
ard. See
Figure 40
and the following test sequenc-
es.
Human Body Model Test Sequence
– C
L
is loaded through S1 by the HV pulse gener-
ator.
– S1 switches position from generator to R.
– A discharge from C
L
through R (body resistance)
to the ST7 occurs.
– S2 must be closed 10 to 100ms after the pulse
delivery period to ensure the ST7 is not left in
charge state. S2 must be opened at least 10ms
prior to the delivery of the next pulse.
14.7.2.2 Designing hardened software to avoid
noise problems
EMC characterization and optimization are per-
formed at component level with a typical applica-
tion environment and simplified MCU software. It
should be noted that good EMC performance is
highly dependent on the user application and the
software in particular.
Therefore it is recommended that the user applies
EMC software optimization and prequalification
tests in relation with the EMC level requested for
his application.
Software recommendations:
The software flowchart must include the manage-
ment of runaway conditions such as:
– Corrupted program counter
– Unexpected reset
– Critical Data corruption (control registers...)
Prequalification trials:
Most of the common failures (unexpected reset
and program counter corruption) can be repro-
duced by manually forcing a low state on the RE-
SET pin or the Oscillator pins for 1 second.
To complete these trials, ESD stress can be ap-
plied directly on the device,over the range of spec-
ification values.When unexpected behaviour is de-
tected,the sofware can be hardened to prevent un-
recoverable errors occurring (see application note
AN1015).
Absolute Maximum Ratings
Figure 40. Typical Equivalent ESD Circuits
Notes:
1. Data based on characterization results, not tested in production.
Symbol
Ratings
Conditions
Maximum value
1)
Unit
V
ESD(HBM)
Electro-static discharge voltage
(Human Body Model)
T
A
=
+25°C
1500
V
ST7
S2
R=1500
S1
HIGH VOLTAGE
PULSE
GENERATOR
C
L
=
100pF
HUMAN BODY MODEL