Werner's Miscellanea
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Source at commit 8361bfac8bac9e8fa9776abc3355dd3298934dee created 12 years 3 months ago. By Werner Almesberger, m1rc3/usbpwr/README: corrected averaging: 1 PLC instead of 10 PLC | |
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1 | M1pre-rc4 vs. shorted USB |
2 | ========================= |
3 | |
4 | These are the results of supplying an M1 equipped with a |
5 | current-limiting power switch from a lab supply and shorting or |
6 | (over)loading one USB port. Note that this test involved only |
7 | resistive loads. |
8 | |
9 | Source Input J21/J3 Boot Short USB Load USB (2 Ohm) |
10 | ------- --------------- --------------- ------- --------------- --------------- |
11 | 4.50 - - No - - |
12 | 4.60 4.41/4.46/4.50 4.03/4.20/4.33 Unstbl. Reset 4.04/4.09/4.33 |
13 | 4.70 4.51/4.57/4.60 4.15/4.31/4.43 Unstbl. Reset 4.16/4.22/4.43 |
14 | 4.80 4.61/4.66/4.70 4.22/4.40/4.52 Yes Reset 4.25/4.32/4.53 |
15 | 4.90 4.71/4.76/4.80 4.29/4.47/4.60 Yes Reset 4.39/4.46/4.62 |
16 | 5.00 * 4.81/4.86/4.90 4.47/4.62/4.72 Yes Reset [1,2] 4.48/4.55/4.72 |
17 | 5.10 - - Yes Reset - [3] |
18 | 5.20 - - Yes Reset - |
19 | 5.30 5.10/5.16/5.19 4.61/4.86/4.99 Yes Unstbl. - |
20 | 5.40 - 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 | |
27 | All voltage measurements min/avg/max, over 3000 samples. Flickernose |
28 | was rendering "The Tunnel" at the time. The M1pre-rc4 was running |
29 | the vanilla 2011-07-13 installation. |
30 | |
31 | "Source" is the nominal supply voltage, from a Leaptronix mPP-3040D, |
32 | with current limit set to 3.0 A. |
33 | |
34 | "Input" is the voltage measured on the supply cables near the M1's |
35 | DC input. |
36 | |
37 | "J21/J3" is the voltage on the internal 5 V rail measured across |
38 | J21.1 and J3.14, with a Fluke 8845A with averaging set to 1 PLC. |
39 | [5] shows the measurement configuration. |
40 | |
41 | "Boot" indicates whether the M1 can boot out of standby with the |
42 | respective voltage and current limit. If only unstable operation |
43 | was achieved, M1 only sometimes booted or reset after running for |
44 | some minutes. |
45 | |
46 | "Short USB" indicates what happens if one USB port is shorted |
47 | through labsw. In all most, the voltage drop on the 5 V rail was |
48 | sufficiently large to cause a reset. [1] and [2] show the internal |
49 | 5 V rail in channel 1, and the external VBUS on channel 2. Note |
50 | that the resistive probes used have a few percent of linear error. |
51 | [6] shows the external setup on the USB port. |
52 | |
53 | If setting a supply voltage well above the nominal 5.0 V, even |
54 | shorts on USB can be survived. At 5.30 V and 5.40 V, resets still |
55 | occurred frequently. [4] shows the 5 V rail (barely) escaping a |
56 | reset. |
57 | |
58 | "Load USB (2 Ohm)" repeats the same experiment with a 2 Ohm series |
59 | resistor added. [3] shows the response. Occasional resets occurred |
60 | at 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 |
68 |
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