STM32N657: absolute maximum ratings for VDDSMPS and VDDA18PMU (not in DS14791 Table 22)

[ArmandS]

Hello,

We are designing a PCB around the STM32N657B0 (VFBGA198) using the internal SMPS. VDDSMPS and VDDA18PMU are fed from a dedicated 1.8 V buck, with VDDA18PMU filtered from the same rail, as per Figure 2 in DS14791.

For our derating and fault analysis we need the absolute maximum ratings of these two pins, and we cannot find them in any current ST document:

• DS14791 Rev 11 (Sep 2026), Table 22 “Voltage characteristics”: no VDDSMPS or VDDA18PMU row. The “VDDA18 – VSS, 1.98 V” row lists only VDDA18PLL, VDDA18CSI, VDDA18USB and VDDA18ADC.
• DS14791 Rev 11, Table 25 “General operating conditions”: VDDSMPS and VDDA18PMU are 1.62 / 1.8 / 1.89 V.
• DS14791 Rev 11, Table 29 “Characteristics of SMPS step-down”: the input is called “VDDA18”, 1.62 to 1.89 V.
• AN5967 Rev 6, AN6000 Rev 1 and RM0486 Rev 4: no absolute maximum for either pin.

Questions

1. What are the absolute maximum ratings (min and max) for VDDSMPS and VDDA18PMU?
2. Does the “VDDA18 – VSS, 1.98 V” row in Table 22 also cover VDDSMPS and VDDA18PMU? Table 29 uses the same symbol “VDDA18” for the SMPS input.
3. Between 1.89 V and the absolute maximum, is the internal SMPS still functional, or only guaranteed not to be damaged? Is there a lifetime or reliability penalty for continuous operation in that band?
4. Transient tolerance. Is a single event above the maximum rating for roughly 200 µs survivable on VDDSMPS and VDDA18PMU? If not, what peak voltage and duration are survivable?
5. Is there any internal protection on VDDSMPS or VDDA18PMU (clamp, over-voltage detector, SMPS shutdown) that we should take into account?
6. Will the values be added to DS14791 in a future revision?

Thank you,

Armand

[mƎALLEm]

Hello ​@ArmandS and welcome to the ST community,

For the questions 3 and 4: in the range values of Max normal condition and Max Absolute ratings, there is indeed a lifetime penalty for continuous operation in that range and the product life time will decrease. Above absolute max rating you’ll damage the device and I’m not sure if the information about the transient tolerance time above the absolute maximum rating is available.

For the rest of the questions I’ll ask internally and I’ll get back to you as soon if I have any feedback.