
ST7L34, ST7L35, ST7L38, ST7L39
Electrical characteristics
Doc ID 11928 Rev 7
Designing hardened software to avoid noise problems
EMC characterization and optimization are performed at component level with a typical
application 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 management 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
reproduced by manually forcing a low state on the reset pin or the oscillator pins for 1
second.
To complete these trials, ESD stress can be applied directly on the device, over the range of
specification values. When unexpectedbehavior is detected, the software can be hardened
to prevent unrecoverable errors occurring (see application note AN1015).
13.7.2
Electromagnetic interference (EMI)
Based on a simple application running on the product (toggling 2 LEDs through the I/O
ports), the product is monitored in terms of emission. This emission test is in line with the
norm SAE J 1752/3 which specifies the board and the loading of each pin. See
Table 117:Table 116.
Electromagnetic test results
Symbol
Parameter
Conditions
Level/
class
VFESD
Voltage limits to be applied on any I/O pin
to induce a functional disturbance
VDD = 5 V, TA = 25 °C, fOSC = 8MHz,
conforms to IEC 1000-4-2
3B
VFFTB
Fast transient voltage burst limits to be
applied through 100 pF on VDD and VDD
pins to induce a functional disturbance
VDD = 5 V, TA = 25 °C, fOSC = 8MHz,
conforms to IEC 1000-4-4
Table 117.
EMI emissions
Sym. Parameter
Conditions
Monitored
frequency band
Max vs. [fOSC/fCPU]
Unit
8/4 MHz
16/8 MHz
SEMI
Peak
level(1)
1.
Data based on characterization results, not tested in production.
VDD = 5 V, TA = 25 °C,
SO20 package,
conforming to SAE J 1752/3
0.1MHz to 30 MHz
15
dBV
30 MHz to 130 MHz
13
19
130 MHz to 1 GHz
9
13
SAE EMI level
2.5
3
-