SLAA689B December 2015 – August 2021 CC430F6125 , CC430F6126 , CC430F6127 , CC430F6135 , CC430F6137 , CC430F6147 , MSP430AFE221 , MSP430AFE222 , MSP430AFE223 , MSP430AFE231 , MSP430AFE232 , MSP430AFE233 , MSP430AFE251 , MSP430AFE252 , MSP430AFE253 , MSP430BT5190 , MSP430F1101 , MSP430F1101A , MSP430F1111A , MSP430F112 , MSP430F1121 , MSP430F1121A , MSP430F1122 , MSP430F1132 , MSP430F122 , MSP430F1222 , MSP430F123 , MSP430F1232 , MSP430F133 , MSP430F135 , MSP430F147 , MSP430F1471 , MSP430F148 , MSP430F1481 , MSP430F149 , MSP430F1491 , MSP430F155 , MSP430F156 , MSP430F157 , MSP430F1610 , MSP430F1611 , MSP430F1612 , MSP430F167 , MSP430F168 , MSP430F169 , MSP430F2001 , MSP430F2002 , MSP430F2003 , MSP430F2011 , MSP430F2012 , MSP430F2013 , MSP430F2013-EP , MSP430F2101 , MSP430F2111 , MSP430F2112 , MSP430F2121 , MSP430F2122 , MSP430F2131 , MSP430F2132 , MSP430F2232 , MSP430F2234 , MSP430F2252 , MSP430F2254 , MSP430F2272 , MSP430F2274 , MSP430F233 , MSP430F2330 , MSP430F235 , MSP430F2350 , MSP430F2370 , MSP430F2410 , MSP430F2416 , MSP430F2417 , MSP430F2418 , MSP430F2419 , MSP430F247 , MSP430F2471 , MSP430F248 , MSP430F2481 , MSP430F249 , MSP430F2491 , MSP430F2616 , MSP430F2617 , MSP430F2618 , MSP430F2619 , MSP430F412 , MSP430F413 , MSP430F4132 , MSP430F415 , MSP430F4152 , MSP430F417 , MSP430F423 , MSP430F423A , MSP430F425 , MSP430F4250 , MSP430F425A , MSP430F4260 , MSP430F427 , MSP430F4270 , MSP430F427A , MSP430F435 , MSP430F4351 , MSP430F436 , MSP430F4361 , MSP430F437 , MSP430F4371 , MSP430F438 , MSP430F439 , MSP430F447 , MSP430F448 , MSP430F4481 , MSP430F449 , MSP430F4491 , MSP430F4616 , MSP430F46161 , MSP430F4617 , MSP430F46171 , MSP430F4618 , MSP430F46181 , MSP430F4619 , MSP430F46191 , MSP430F47126 , MSP430F47127 , MSP430F47163 , MSP430F47166 , MSP430F47167 , MSP430F47173 , MSP430F47176 , MSP430F47177 , MSP430F47183 , MSP430F47186 , MSP430F47187 , MSP430F47193 , MSP430F47196 , MSP430F47197 , MSP430F477 , MSP430F478 , MSP430F4783 , MSP430F4784 , MSP430F479 , MSP430F4793 , MSP430F4794 , MSP430F5212 , MSP430F5214 , MSP430F5217 , MSP430F5219 , MSP430F5222 , MSP430F5224 , MSP430F5229 , MSP430F5232 , MSP430F5234 , MSP430F5237 , MSP430F5239 , MSP430F5242 , MSP430F5244 , MSP430F5247 , MSP430F5249 , MSP430F5252 , MSP430F5253 , MSP430F5254 , MSP430F5255 , MSP430F5256 , MSP430F5257 , MSP430F5258 , MSP430F5259 , MSP430F5304 , MSP430F5308 , MSP430F5309 , MSP430F5310 , MSP430F5324 , MSP430F5325 , MSP430F5326 , MSP430F5327 , MSP430F5328 , MSP430F5329 , MSP430F5333 , MSP430F5335 , MSP430F5336 , MSP430F5338 , MSP430F5340 , MSP430F5341 , MSP430F5342 , MSP430F5358 , MSP430F5359 , MSP430F5418 , MSP430F5418A , MSP430F5419 , MSP430F5419A , MSP430F5435 , MSP430F5435A , MSP430F5436 , MSP430F5436A , MSP430F5437 , MSP430F5437A , MSP430F5438 , MSP430F5438A , MSP430F5500 , MSP430F5501 , MSP430F5502 , MSP430F5503 , MSP430F5504 , MSP430F5505 , MSP430F5506 , MSP430F5507 , MSP430F5508 , MSP430F5509 , MSP430F5510 , MSP430F5513 , MSP430F5514 , MSP430F5515 , MSP430F5517 , MSP430F5519 , MSP430F5521 , MSP430F5522 , MSP430F5524 , MSP430F5525 , MSP430F5526 , MSP430F5527 , MSP430F5528 , MSP430F5529 , MSP430F5630 , MSP430F5631 , MSP430F5632 , MSP430F5633 , MSP430F5634 , MSP430F5635 , MSP430F5636 , MSP430F5637 , MSP430F5638 , MSP430F5658 , MSP430F5659 , MSP430F6433 , MSP430F6435 , MSP430F6436 , MSP430F6438 , MSP430F6458 , MSP430F6459 , MSP430F6630 , MSP430F6631 , MSP430F6632 , MSP430F6633 , MSP430F6634 , MSP430F6635 , MSP430F6636 , MSP430F6637 , MSP430F6638 , MSP430F6658 , MSP430F6659 , MSP430F6720 , MSP430F6720A , MSP430F6721 , MSP430F6721A , MSP430F6723 , MSP430F6723A , MSP430F6724 , MSP430F6724A , MSP430F6725 , MSP430F6725A , MSP430F6726 , MSP430F6726A , MSP430F6730 , MSP430F6730A , MSP430F6731 , MSP430F6731A , MSP430F6733 , MSP430F6733A , MSP430F6734 , MSP430F6734A , MSP430F6735 , MSP430F6735A , MSP430F6736 , MSP430F6736A , MSP430F6745 , MSP430F67451 , MSP430F67451A , MSP430F6746 , MSP430F67461 , MSP430F67461A , MSP430F6747 , MSP430F67471 , MSP430F67471A , MSP430F6748 , MSP430F67481 , MSP430F67481A , MSP430F6749 , MSP430F67491 , MSP430F67491A , MSP430F67621 , MSP430F67621A , MSP430F67641 , MSP430F67641A , MSP430F6765 , MSP430F67651 , MSP430F67651A , MSP430F6766 , MSP430F67661 , MSP430F67661A , MSP430F6767 , MSP430F67671 , MSP430F67671A , MSP430F6768 , MSP430F67681 , MSP430F67681A , MSP430F6768A , MSP430F6769 , MSP430F67691 , MSP430F67691A , MSP430F6769A , MSP430F6775 , MSP430F67751 , MSP430F67751A , MSP430F6776 , MSP430F67761 , MSP430F67761A , MSP430F6776A , MSP430F6777 , MSP430F67771 , MSP430F67771A , MSP430F6777A , MSP430F6778 , MSP430F67781 , MSP430F67781A , MSP430F6778A , MSP430F6779 , MSP430F67791 , MSP430F67791A , MSP430FE423 , MSP430FE4232 , MSP430FE423A , MSP430FE4242 , MSP430FE425 , MSP430FE4252 , MSP430FE425A , MSP430FE427 , MSP430FE4272 , MSP430FE427A , MSP430FG4250 , MSP430FG4260 , MSP430FG4270 , MSP430FG437 , MSP430FG438 , MSP430FG439 , MSP430FG4616 , MSP430FG4617 , MSP430FG4618 , MSP430FG4619 , MSP430FG477 , MSP430FG478 , MSP430FG479 , MSP430FG6425 , MSP430FG6426 , MSP430FG6625 , MSP430FG6626 , MSP430FR2032 , MSP430FR2033 , MSP430FR2110 , MSP430FR2111 , MSP430FR2311 , MSP430FR2433 , MSP430FR2532 , MSP430FR2533 , MSP430FR2632 , MSP430FR2633 , MSP430FR4131 , MSP430FR4132 , MSP430FR4133 , MSP430FR5720 , MSP430FR5721 , MSP430FR5722 , MSP430FR5723 , MSP430FR5724 , MSP430FR5725 , MSP430FR5726 , MSP430FR5727 , MSP430FR5728 , MSP430FR5729 , MSP430FR5730 , MSP430FR5731 , MSP430FR5732 , MSP430FR5733 , MSP430FR5734 , MSP430FR5735 , MSP430FR5736 , MSP430FR5737 , MSP430FR5738 , MSP430FR5739 , MSP430FR5847 , MSP430FR58471 , MSP430FR5848 , MSP430FR5849 , MSP430FR5857 , MSP430FR5858 , MSP430FR5859 , MSP430FR5867 , MSP430FR58671 , MSP430FR5868 , MSP430FR5869 , MSP430FR5870 , MSP430FR5872 , MSP430FR58721 , MSP430FR5887 , MSP430FR5888 , MSP430FR5889 , MSP430FR58891 , MSP430FR5922 , MSP430FR59221 , MSP430FR5947 , MSP430FR59471 , MSP430FR5948 , MSP430FR5949 , MSP430FR5957 , MSP430FR5958 , MSP430FR5959 , MSP430FR5967 , MSP430FR5968 , MSP430FR5969 , MSP430FR5969-SP , MSP430FR59691 , MSP430FR5970 , MSP430FR5972 , MSP430FR59721 , MSP430FR5986 , MSP430FR5987 , MSP430FR5988 , MSP430FR5989 , MSP430FR5989-EP , MSP430FR59891 , MSP430FR5994 , MSP430FR6820 , MSP430FR6822 , MSP430FR68221 , MSP430FR6870 , MSP430FR6872 , MSP430FR68721 , MSP430FR6877 , MSP430FR6879 , MSP430FR68791 , MSP430FR6887 , MSP430FR6888 , MSP430FR6889 , MSP430FR68891 , MSP430FR6920 , MSP430FR6922 , MSP430FR69221 , MSP430FR6927 , MSP430FR69271 , MSP430FR6928 , MSP430FR6970 , MSP430FR6972 , MSP430FR69721 , MSP430FR6977 , MSP430FR6979 , MSP430FR69791 , MSP430FR6987 , MSP430FR6988 , MSP430FR6989 , MSP430FR69891 , MSP430FW423 , MSP430FW425 , MSP430FW427 , MSP430FW428 , MSP430FW429 , MSP430G2001 , MSP430G2101 , MSP430G2102 , MSP430G2111 , MSP430G2112 , MSP430G2121 , MSP430G2131 , MSP430G2132 , MSP430G2152 , MSP430G2153 , MSP430G2201 , MSP430G2202 , MSP430G2203 , MSP430G2210 , MSP430G2211 , MSP430G2212 , MSP430G2213 , MSP430G2221 , MSP430G2230 , MSP430G2231 , MSP430G2232 , MSP430G2233 , MSP430G2252 , MSP430G2253 , MSP430G2302 , MSP430G2303 , MSP430G2312 , MSP430G2313 , MSP430G2332 , MSP430G2333 , MSP430G2352 , MSP430G2353 , MSP430G2402 , MSP430G2403 , MSP430G2412 , MSP430G2413 , MSP430G2432 , MSP430G2433 , MSP430G2444 , MSP430G2452 , MSP430G2453 , MSP430G2513 , MSP430G2533 , MSP430G2544 , MSP430G2553 , MSP430G2744 , MSP430G2755 , MSP430G2855 , MSP430G2955 , MSP430L092 , MSP430TCH5E
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The methods described in this application report do not apply when the main supply (typically DVCC) is unpowered and a voltage is applied on a GPIO pin. This condition can cause unintended power sourcing to the MCU through the ESD structures on the GPIOs. This is a concern in both the power up and power down scenarios. If the main supply and a GPIO are powered at the same time, ensure that delays in the main supply (due, for example, to inline capacitance or LDO delays) are accounted for and that a GPIO is not powered before the main supply.
Due to the physical architecture of the ESD diodes, which is explained in the following sections, other secondary side effects can appear if the MSP microcontroller is not properly powered. Improper power scenarios include sensors that are sourced by a different supply or communication lines that are driven by other ICs in the application, if these signals are connected to the MCU while the main supply of the MCU is off. During the power-down scenario, a side effect is that the device can be back powered through the ESD diodes. However, this is not the intended powering scheme for the MSP microcontroller and can lead to erroneous and unpredictable behavior, due to the current limitations of the ESD diodes and the bypassing of the intended power path. In worst case scenarios, this can lead to physical damage to the device, unexpected execution, or memory corruption causing a malfunction in the application.
Most MSP microcontrollers specify the maximum ESD diode current in the Absolute Maximum Ratings section (see Figure 2-1). The diode current specified as ±2 mA is a constant current that flows through the ESD structure to the supply rails to protect the device. These ESD structures are triggered if a signal is applied that exceeds the maximum or minimum supply voltage specifications of the device. To follow the specification, the application must protect the device pin externally so that a signal does not exceed the ±2-mA specification.
In other words, voltages greater than the actual device supply (DVCC and AVCC) or lower than VSS can be applied, but the current that flows through the ESD diodes must be controlled.
While the current is specified as ±2 mA, the ESD structure can withstand much higher current levels, such as those that appear during typical ESD events according HBM or CDM. The cells are made to pass standard ESD tests like HBM or CDM as shown in Figure 2-2. During this high-voltage stress, current peaks in the range of several amperes flow through the ESD structures.
However, the duration of the high-current pulse is quite short (in the range of several nanoseconds), which leads to less thermal stress and much less heating compared to a long-term high-current event. This is the main reason why the constant current through the ESD diodes is limited to ±2 mA for longer or constant operation.
When considering the ESD diode current specification of the device data sheet during the development of an application, first analyze if signals connected to the GPIO pins can exceed the actual supply. One example would be the output of analog sensors, which might go above the MSP MCU supply for a longer period of time (several milliseconds). In such a case, the maximum voltage levels that can be seen by the MSP MCU must be defined or evaluated, and a current-protection mechanism must be developed. This protection mechanism is important to prevent permanent damage on the ESD structure of the MSP microcontroller caused by high current beyond the allowed level. This protection also prevents the secondary effect of increasing the supply voltage due to energy introduced through the ESD diodes.
In most cases, the current limitation can be implemented as a simple series resistance that is sized based on the maximum expected current. However, in some cases, this might not be enough to fulfill all aspects of a reliable working application. Even if the current limitation specification of the ESD diodes is met, the supply of the MSP microcontroller might be disturbed. This is because the ESD structures draw the current to the supply rail of the MSP MCU, which boosts the supply as long as current is flowing. If the supply connected to the MSP MCU cannot sink current, the maximum DVCC specification of the MSP MCU might be violated over time. This high supply voltage can cause permanent damage that can lead to malfunction of the device or high current consumption. The high supply voltage can also cause wear-out effects that lead to functional and parametric failures over time.
The principle of supply voltage increase can be explained using a principle I/O schematic (see Figure 3-1). The external serial resistors R1 and R2 limit the current that flows through the ESD diodes D1 and D2 when an overvoltage is applied. Protecting the CMOS devices against this kind of overvoltage is the essential function of the internal ESD diode. Assuming that the rating for the continuous current through the diode of ±2 mA is considered, no physical damage occurs. At the same time, the current of ±2 mA maximum flows to the supply potential through the ESD diodes and raises the potential by providing "extra" current. If this "extra" current is larger than the current that is consumed by a load connected to the supply, the voltage increases. If more than one GPIO adds current to the supply, the sum of "extra" currents added to the VCC potential flowing through all protection diodes must be considered. Figure 3-1 shows this case, when two GPIOs experience overvoltage at the same time. If the sum of currents exceeds the maximum current consumption of the whole system connected to VCC, additional protection mechanisms must be considered. The whole system is defined by the supply architecture itself which can have current sink capability but also by the microcontroller and connected loads to the microcontroller. If the microcontroller is running in active mode and driving some LEDs, it is probable that the energy provided by the ESD diodes during overvoltage condition will be consumed. However, if the microcontroller is in low-power mode and consuming only a few nanoamperes, the supply voltage will increase due to the extra current from the ESD diodes.
A similar principle applies if a voltage lower than VSS is applied to a GPIO; however, current would flow through D2 and D4. This condition can cause an adverse effect on the device ground, depending on the capabilities of the supply.
To remove this adverse effect on the supply's voltage and ground, TI recommends consideration of the best choice of the regulator to fit the application requirements. In addition to form factor, performance parameters, cost, and power consumption, the impact on the whole system must also be considered. Section 3.1 describes the advantages and disadvantages of regulator circuits with good current sinking capabilities, and also lists alternative solutions to prevent the supply increase effect.
A similar effect to the overvoltage condition appears if the device is powered down and no voltage is applied to VCC. In this case, a voltage greater than 0.3 V can result in backward supply through the ESD diodes. Section 1 provides more details on this scenario.
In battery-supplied applications, the supply voltage boosting effect due to overvoltage on I/O pins can cause the battery to explode or burn.