Datasheet

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PMM Legacy
TPS23841
SLUS745A – NOVEMBER 2006 – REVISED MAY 2007
POWER MANAGEMENT MODE FUNCTIONAL DESCRIPTION (continued)
PMM Legacy function is used to detect PDs that are non compliant. Legacy detection uses a current source
(typically 3.5 mA) as a test current while the A/D measures the average voltage for approximately 18 ms. The
waveform shown in Figure 12 is the Legacy function charging a 10- µ F capacitor. The capacitance charges to a
value that is no greater than 20V below the P port voltage. As the capacitor is charging the A/D is accumulating
counts in the voltage A/D register. Figure 13 shows the relationship between port capacitance and the number of
counts. A user can characterize non-compliant PD's signatures and use the Legacy function to recognize these
devices.
Figure 12.
Figure 13.
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