Other Parts Discussed in Thread: TUSB4020BI
While using the automated USB testing (USB-PET) for DCP mode, I get 2 test failures:
[30.566,146] Checking leakage from D+ or D-
[30.566,146] 7. Connect D+ via 100k to 0V
[30.566,153] 8. Wait 2 seconds to eliminate capacitive effects.
[32.566,153] 9. Check that voltage at D+ is below 1.44V (Two RDAT_LKG (300k)
in parallel, VDAT_LKG = 3.6V).
[32.566,158] - Leakage sourced by D+/D- in spec (V = 0.014V).
[32.566,166] 10. 10. Connect D+ via 100K to 3.6V. Connect D- via 100K to 3.6V.
[32.566,190] 11. Wait 2 seconds to eliminate capacitive effects.
[34.566,190] 12. Check that D+ is not less than 2.65V (Two RDAT_LKG (300k) in
parallel, VDAT_LKG = 0V).
[34.566,197] FAIL: Excessive leakage source by D+/D- (V = 0.636V)
and also
[34.566,216] Checking Capacitance of D+ or D-
[34.566,216] 13. Discharge Standard 1nF capacitor and Capacitance under Test
[34.566,216] Connect 0V to D+ via 1nF test capacitor. Connect 0V to D- via
200R resistor. There is a tested, <200R, resistor between DM
and DP. This will discharge the standard 1nF capacitor and
the capacitance under test to 0V. Wait 10ms.
[34.576,240] 14. Isolate Capacitances
[34.576,240] Disconnect 0V from test capacitor to isolate it. Disconnect
0V from 200R resistor.
[34.576,252] Note: We will now use the D+ voltage watch-block to determine
whether, during the charge-sharing process, D+ rises
above 1.65V. The watch-block amplifier has a limited
band-width by design, so that the watch-block voltage set
is lower than 1.65V. The actual value can be found in the
test script.
[34.576,252] 15. Share Charge Between Capacitances
[34.576,253] Set DP watch-block to be testing for voltage less than the
value required. Connect 3.3V to D+ via 1nF test capacitor.
Wait 1ms. This allows for charge sharing between standard 1nF
capacitor and capacitance under test.
[34.577,276] 16. Read watch-block to see if voltage on DP went above 1.65V. If
it did, then the capacitance under test is less than 1nF and
therefore in specification.
[34.577,283] FAIL: Capacitance exceeds 1nF.
[34.577,295] End of Test
[34.577,309] FAILED TEST - (Does not prevent further tests).