2011-12-22 06:28:19 +02:00
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M1pre-rc4 vs. shorted USB
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=========================
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These are the results of supplying an M1 equipped with a
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current-limiting power switch from a lab supply and shorting or
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(over)loading one USB port. Note that this test involved only
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resistive loads.
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Source Input J21/J3 Boot Short USB Load USB (2 Ohm)
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------- --------------- --------------- ------- --------------- ---------------
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4.50 - - No - -
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4.60 4.41/4.46/4.50 4.03/4.20/4.33 Unstbl. Reset 4.04/4.09/4.33
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4.70 4.51/4.57/4.60 4.15/4.31/4.43 Unstbl. Reset 4.16/4.22/4.43
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4.80 4.61/4.66/4.70 4.22/4.40/4.52 Yes Reset 4.25/4.32/4.53
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4.90 4.71/4.76/4.80 4.29/4.47/4.60 Yes Reset 4.39/4.46/4.62
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2011-12-22 13:03:58 +02:00
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5.00 * 4.81/4.86/4.90 4.47/4.62/4.72 Yes Reset [1,2] 4.48/4.55/4.72
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2011-12-22 06:28:19 +02:00
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5.10 - - Yes Reset - [3]
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5.20 - - Yes Reset -
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5.30 5.10/5.16/5.19 4.61/4.86/4.99 Yes Unstbl. -
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5.40 - 4.85/5.01/5.10 Yes 4.89/5.01/5.11 [4] -
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* Voltage at source: 4.99/5.01/5.01 V
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- not measure either because measurement was not applicable or
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because the result would have been of limited interest.
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All voltage measurements min/avg/max, over 3000 samples. Flickernose
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was rendering "The Tunnel" at the time. The M1pre-rc4 was running
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the vanilla 2011-07-13 installation.
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"Source" is the nominal supply voltage, from a Leaptronix mPP-3040D,
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with current limit set to 3.0 A.
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"Input" is the voltage measured on the supply cables near the M1's
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DC input.
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"J21/J3" is the voltage on the internal 5 V rail measured across
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2011-12-22 13:54:25 +02:00
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J21.1 and J3.14, with a Fluke 8845A with averaging set to 1 PLC.
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2011-12-22 06:28:19 +02:00
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[5] shows the measurement configuration.
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"Boot" indicates whether the M1 can boot out of standby with the
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respective voltage and current limit. If only unstable operation
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was achieved, M1 only sometimes booted or reset after running for
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some minutes.
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"Short USB" indicates what happens if one USB port is shorted
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through labsw. In all most, the voltage drop on the 5 V rail was
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sufficiently large to cause a reset. [1] and [2] show the internal
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5 V rail in channel 1, and the external VBUS on channel 2. Note
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that the resistive probes used have a few percent of linear error.
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[6] shows the external setup on the USB port.
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If setting a supply voltage well above the nominal 5.0 V, even
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shorts on USB can be survived. At 5.30 V and 5.40 V, resets still
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occurred frequently. [4] shows the 5 V rail (barely) escaping a
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reset.
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"Load USB (2 Ohm)" repeats the same experiment with a 2 Ohm series
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resistor added. [3] shows the response. Occasional resets occurred
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at nominal voltages of 4.80 V or below.
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[1] usb-short-100us.png
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[2] usb-short-10us.png
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[3] usb-2R-200us.png
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[4] usb-short-5V4.png
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[5] tap-j21j3.jpg
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[6] tap-usb.jpg
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