FAQ AN4488
46/50 AN4488 Rev 7
9.2.4 Where to find IBIS models?
IBIS models describe the electrical characteristics of the digital inputs and outputs of the
STM32F4xxxx through I=f (V) and V=f (T) data.
For further information on IBIS models refer to AN4803 (High-speed SI simulations using
IBIS and board-level simulations using HyperLynx SI on STM32 32-bit Arm
®
Cortex
®
MCUs)
IBIS models are available on ST’s website.
9.3 MCU does not work properly
The table below summarizes some possible root causes that prevents the MCU from
starting correctly. It presents also the most common suspects related to the possible root
cause that you may need to verify.
Table 11. MCU does not work properly
Possible root cause What you need to verify
VDD and GND feeding the
device
• Power delivered to the device must be stable.
• Monitor power supplies.
• Check if GND is properly supplied to device.
• Verify the GND coupling.
OSC_OUT
• Monitor OSC_OUT with oscillator to verify if it is working
properly.
• Refer to the AN2867: Oscillator design guide for ST
microcontrollers.
RESET pin
• Check if RESET pin is correctly driven.
• NRST connection includes a 100nF capacitor to ground.
BOOT PINs
• Monitor boot pins.
• MCU may not work properly if BOOT0 and BOOT1 are
floating.
VCAPs
• VCAP1 and VCAP2 should be connected to 2x2.2 µF
LowESR < 2 Ω Ceramic capacitor
(or one 4.7 µF LowESR < 1 Ω Ceramic capacitor if only
VCAP1 pin is provided on some packages).
PVD
• When programming the MCU, verify PLS [2:0] option bits.
(you can use ST Link utility for that)
• An interruption is generated depending of the programmed
PVD threshold.
Temperature range
• Respect worst conditions of temperature guaranteed by ST
in the Datasheet.
System RESET
• Care must be taken when PDR_ON pin =1, in such
configuration the PDR block is active, that means if VDD
drops down to 1.74 Volts (Refer to STM32F4xxxx
datasheets for actual value) a system reset will occur.
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