AN975 Datasheet, PDF (8/11 Pages) STMicroelectronics – As part of a process of continuous improvement

UPGRADING FROM ST625X/6XB TO ST625X/6XC
1.2.5 ADC
When an I/O pin is used as an analog input, A/D conversion accuracy will be impaired if neg-
ative current injections (V_INJ < V_SS) occur from adjacent I/O pins with analog input capability.
ST625X/6XC devices are more sensitive to this phenomenon than ST625X/6XB devices. In
the case of a loss of accuracy, we recommend to (refer to Figure 5.):
– Use another I/O port located further away from the analog pin, preferably not multiplexed on
the A/D converter
– Increase the input resistance R_{IN J} (to reduce the current injections) and reduce R_ADC (to
preserve conversion accuracy).
Figure 5. Leakage from Digital Inputs
Digital
Input
R_INJ ^PBy/AINy
I/O Port
(Digital I/O)
V_INJ
Analog
Input
R_ADC
Leakage Current
if V_INJ < V_SS
PBx/AINx
A/D
Converter
V_AIN
1.2.6 OSCR Register
On C revision devices, bit 3 of the OSCR register must be set to 0 in order to achieve low con-
sumption. On B revision devices, it was mandatory to set it to 1.
1.2.7 TROMIN input signal
The PB3/TROMIN input signal on ST625X/6XC devices for serial programming has been in-
verted.
This has to be taken into account if the user has implemented his own programming algorithm
and does not use STMicroelectronics or third party programming tools.
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