Datasheet

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PMM Classification
PMM Legacy
0 60 110
5000
4500
3000
2500
2000
500
0
10 30 40 80 100
4000
1000
90705020
1500
3500
Count
Capacitor - mF
y = 478x
- 1.0133
TPS2384
SLUS634D – NOVEMBER 2004 – REVISED MARCH 2007
POWER MANAGEMENT MODE FUNCTIONAL DESCRIPTION (continued)
PMM Classification function looks similar to Discovery 1 and 2 except that the voltage between the P and N pins
regulates to approximately 17.5 V. At the end of the A/D cycle the classification current is stored in the Port
Current Register and the done bit is set. The applied classification level remains until a new function is called.
The data for this measurement remains stored in the Port Current Register until either the Classify or ISample
function is called.
As indicated in the flow diagram of Figure 1 , the TPS2384 in AM only performs classification at one port at a
time. Similarly, PMM applications should take care to ensure that only one port per device is put into the
classification mode at any one time to limit power dissipation in the package.
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 20 V 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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