ST72521 STMICROELECTRONICS [STMicroelectronics], ST72521 Datasheet - Page 180

• Manufacturer Part Number: ST72521
• Description: 8-BIT MCU WITH NESTED INTERRUPTS, FLASH, 10-BIT ADC, FIVE TIMERS, SPI, SCI, I2C, CAN INTERFACE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST72521
EMC CHARACTERISTICS (Cont’d)
12.7.3.2 Static and Dynamic Latch-Up
12.7.3.3 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
Electrical Sensitivities
Figure 94. Simplified Diagram of the ESD Generator for DLU
Notes:
1. Class description: A Class is an STMicroelectronics internal specification. All its limits are higher than the JEDEC spec-
ifications, that means when a device belongs to Class A it exceeds the JEDEC standard. B Class strictly covers all the
JEDEC criteria (international standard).
2. Schaffner NSG435 with a pointed test finger.
180/211
LU: 3 complementary static tests are required
on 10 parts to assess the latch-up performance.
A supply overvoltage (applied to each power
supply pin) and a current injection (applied to
each input, output and configurable I/O pin) are
performed on each sample. This test conforms
to the EIA/JESD 78 IC latch-up standard. For
more details, refer to the AN1181 ST7
application note.
DLU: Electro-Static Discharges (one positive
then one negative test) are applied to each pin
of 3 samples when the micro is running to
assess the latch-up performance in dynamic
mode. Power supplies are set to the typical
values, the oscillator is connected as near as
possible to the pins of the micro and the
component is put in reset mode. This test
conforms to the IEC1000-4-2 and SAEJ1752/3
standards and is described in
more details, refer to the AN1181 ST7
application note.
Symbol
DLU
LU
ESD
GENERATOR
Static latch-up class
Dynamic latch-up class
R
2)
CH
Parameter
C
=50M
S
150pF
Figure
R
D
=330
94. For
HV RELAY
DISCHARGE
RETURN CONNECTION
T
T
T
V
A
A
A
DD
+25°C
+85°C
+125°C
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
specification values. When unexpected behaviour
is detected, the software can be hardened to pre-
vent unrecoverable errors occurring (see applica-
tion note AN1015).
5.5V, f
DISCHARGE TIP
Conditions
OSC
4MHz, T
A
ST7
+25°C
V
V
DD
SS
Class
A
A
A
A
1)