Date:2011-12-22 05:28:19 (8 years 10 months ago)
Author:Werner Almesberger
Commit:8f983300279fb93ffdedf779ff4bb7731d3e930c
Message:m1rc3/usbpwr/: M1pre-rc4 USB short-circuit tests

Files: m1rc3/usbpwr/README (1 diff)
m1rc3/usbpwr/tap-j21j3.jpg (0 diffs)
m1rc3/usbpwr/tap-usb.jpg (0 diffs)
m1rc3/usbpwr/usb-2R-200us.png (0 diffs)
m1rc3/usbpwr/usb-short-100us.png (0 diffs)
m1rc3/usbpwr/usb-short-10us.png (0 diffs)
m1rc3/usbpwr/usb-short-5V4.png (0 diffs)

Change Details

m1rc3/usbpwr/README
1M1pre-rc4 vs. shorted USB
2=========================
3
4These are the results of supplying an M1 equipped with a
5current-limiting power switch from a lab supply and shorting or
6(over)loading one USB port. Note that this test involved only
7resistive loads.
8
9Source Input J21/J3 Boot Short USB Load USB (2 Ohm)
10------- --------------- --------------- ------- --------------- ---------------
114.50 - - No - -
124.60 4.41/4.46/4.50 4.03/4.20/4.33 Unstbl. Reset 4.04/4.09/4.33
134.70 4.51/4.57/4.60 4.15/4.31/4.43 Unstbl. Reset 4.16/4.22/4.43
144.80 4.61/4.66/4.70 4.22/4.40/4.52 Yes Reset 4.25/4.32/4.53
154.90 4.71/4.76/4.80 4.29/4.47/4.60 Yes Reset 4.39/4.46/4.62
165.00 * 4.71/4.86/4.90 4.47/4.62/4.72 Yes Reset [1,2] 4.48/4.55/4.72
175.10 - - Yes Reset - [3]
185.20 - - Yes Reset -
195.30 5.10/5.16/5.19 4.61/4.86/4.99 Yes Unstbl. -
205.40 - 4.85/5.01/5.10 Yes 4.89/5.01/5.11 [4] -
21
22* Voltage at source: 4.99/5.01/5.01 V
23
24- not measure either because measurement was not applicable or
25  because the result would have been of limited interest.
26
27All voltage measurements min/avg/max, over 3000 samples. Flickernose
28was rendering "The Tunnel" at the time. The M1pre-rc4 was running
29the vanilla 2011-07-13 installation.
30
31"Source" is the nominal supply voltage, from a Leaptronix mPP-3040D,
32with current limit set to 3.0 A.
33
34"Input" is the voltage measured on the supply cables near the M1's
35DC input.
36
37"J21/J3" is the voltage on the internal 5 V rail measured across
38J21.1 and J3.14, with a Fluke 8845A with averaging set to 10 PLC.
39[5] shows the measurement configuration.
40
41"Boot" indicates whether the M1 can boot out of standby with the
42respective voltage and current limit. If only unstable operation
43was achieved, M1 only sometimes booted or reset after running for
44some minutes.
45
46"Short USB" indicates what happens if one USB port is shorted
47through labsw. In all most, the voltage drop on the 5 V rail was
48sufficiently large to cause a reset. [1] and [2] show the internal
495 V rail in channel 1, and the external VBUS on channel 2. Note
50that the resistive probes used have a few percent of linear error.
51[6] shows the external setup on the USB port.
52
53If setting a supply voltage well above the nominal 5.0 V, even
54shorts on USB can be survived. At 5.30 V and 5.40 V, resets still
55occurred frequently. [4] shows the 5 V rail (barely) escaping a
56reset.
57
58"Load USB (2 Ohm)" repeats the same experiment with a 2 Ohm series
59resistor added. [3] shows the response. Occasional resets occurred
60at nominal voltages of 4.80 V or below.
61
62[1] usb-short-100us.png
63[2] usb-short-10us.png
64[3] usb-2R-200us.png
65[4] usb-short-5V4.png
66[5] tap-j21j3.jpg
67[6] tap-usb.jpg
m1rc3/usbpwr/tap-j21j3.jpg
m1rc3/usbpwr/tap-usb.jpg
m1rc3/usbpwr/usb-2R-200us.png
m1rc3/usbpwr/usb-short-100us.png
m1rc3/usbpwr/usb-short-10us.png
m1rc3/usbpwr/usb-short-5V4.png

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