Shulou(Shulou.com)06/01 Report--

Today, I will talk to you about why internal power in library is negative. Many people may not understand it very well. In order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.

Statement

The following figure shows the internal_power table of Q pin, a register in library, and the internal power of this pin is mostly negative in the table. In fact, the internal_power in library is not power, but heat, in joules, not watts.

Reason

The negative value of Internal power is determined by the modeling mode of Liberate K library. when Liberate K library is used, there are three modes for modeling internal power, which are controlled by the value of variable pin_based_power.

Pin_based_power=1, default value, monitor Vdd and Gnd, this modeling method, the rise of "heat" and the decrease of "heat" are respectively the measured "heat" of rise / fall minus 1 * Vdd ^ 2. In this mode, the rise of "heat" is always positive, because when the capacitor is charged during the rising process, the Vout seen by the load cannot exceed CVO. However, the reduced power consumption may be negative, because sometimes some currents flow back to the power supply due to the coupling capacitor, resulting in voltage overshoot at the output node, and the Vout exceeds the Vdd before the output voltage begins to drop, thus reducing the "heat" to negative.

Pin_based_power=0, monitor Vdd only, this modeling method, the rising "heat" is the measured rising "heat" minus the "heat" consumed by the load, and the decreasing "heat" is the measured heat. So in this mode, the rising "heat" may be negative, but the decreasing "heat" is always positive.

Pin_based_power=2, also monitor current on side inputs, this modeling method is consistent with the first modeling method, except that the state of the input pin is taken into account in the K library.

Regardless of the modeling method, although the increase in "heat" or the decrease in "heat" may be negative, the total "heat" (Edyn,fall + Edyn,rise) is definitely positive.

Supplement

In K library, internal power is divided into two categories: Switching power and Hidden power.

Switching power: input flipping will lead to output flipping. Usually, the internal power corresponding to pin in library has "related_pin", the table is a two-dimensional table, and the index is input transition and output load respectively. There are also internal power that outputs pin without "related_pin". In this case, the table is an one-dimensional table, and index is the output load.

Hidden power: input flipping does not cause output flipping. Use the internal power of input pin in library to calculate, and the internal power of input pin is only related to the transition of this pin, so use transition as index to look up the table.

After reading the above, do you have any further understanding of why the internal power in library is negative? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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