AnsweredAssumed Answered

HSE oscillator power consumption

Question asked by panasenko.eugene.002 on May 22, 2015
Latest reply on May 25, 2015 by waclawek.jan
Hello,


I estimate the total power consumption of a device operating from the HSE oscillator. 
The MCU part number is STM32L152RBT6.
I configured the MCU to operate from the MSI oscillator (2.1 MHz). All the GPIO are configured as push-pull in 'Low' state. Then I disabled PLL and HSE/HSI/LSE oscillators and measured current consumption in SLEEP mode (the MCU operating from MSI in SLEEP). In this case the current consumption is about 187 uA at 1.8V of VDD (Vcore = 1.8V). 
After that I configured the HSE oscillator operating with 16 MHz crystal with 10pF load capacitors. The MCU is still in SLEEP and operates from the MSI (2.1MHz), but the HSE is enabled. The current consumption was 1076uA.
The difference between those two values is 1076 - 187 = 889 uA and I expect this is the HSE current.


I checked out the HSE oscillator power consumption parameter in Table 28 of the datasheet http://www.st.com/web/en/resource/technical/document/datasheet/CD00277537.pdf
I do not know exactly what numbers should I compare with my measured value. 
In Table 28 there are 'HSE oscillator power consumption' Idd(HSE) 0.46mA and 'HSE driving current' I(HSE) 3mA.
I am confused what is'HSE driving current' parameter and why my measured value is higher than datasheet values?




BTW, when I switched the clock source from the 2.1MHz MSI oscillator to the 16MHz HSE oscillator at Vcore = 1.5V and VDD = 1.8V, the MCU failed, but the MCU this works fine at Vcore = 1.8V and VDD = 1.8V. Figure 6 in RM0038 says the MCU works at this frequency and this Vcore range.

Outcomes