BeagleBone Power Management

Revision as of 16:16, 25 May 2015 by Matthijs (talk | contribs) (Initial work on powerdown pictures)
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Work in progress: plan is to first collect the raw info, then organize and add prose.

Power supplies

Main voltage regulators (supplied by SYS)
BBone White (TPS65217B) BBone Black (TPS65217C)
LDO1 1.8 V 100 mA vrtc LDO1 1.8 V 100 mA vrtc
DCDC1 1.8 V 1200 mA ddr2 DCDC1 1.35 V 1200 mA ddr3l
1v8 LDO3 1.8 V 400 mA 1v8
LDO2 3.3 V 100 mA power led LDO2 3.3 V 100 mA power led
LDO3 3.3 V 200 mA 3v3a LDO3 3.3 V 400 mA 3v3a
LDO4 3.3 V 200 mA 3v3b U4 3.3 V 500 mA 3v3b
U8 3.3 V 1000 mA 3v3exp 3v3exp
DCDC2 1.285 V 1200 mA vdd_mpu DCDC2 1.325 V 1200 mA vdd_mpu
DCDC3 1.125 V 1200 mA vdd_core DCDC3 1.125 V 1200 mA vdd_core

Power down

Hardware is a BBB rev C to have a unified 3v3 rail, no external connections other than power, probes, and console cable.

Two kernels are compared: the one on the left is a standard kernel + device tree which enables the (reset-insensitive) HDMI framer, while the one on the right leaves the HDMI framer in standby (its default state, negligible power consumption). There are other differences, but those should be irrelevant during shutdown, certainly once power-on reset is asserted (PGOOD low).

Clean shutdown while powered via BAT:
Bbb-c-3v3u-shutdown-bat5v.png Bbb-c-3v3u-shutdown-bat5v-hdmi.png

Most current consumption is eliminated at the start of the powerdown sequence when PGOOD goes low, although there's a brief burst shortly afterwards (no idea why). Current ramps down more 2 ms later when the core and mpu supplies are disabled, and drops to negligible once the 3v3 supply is cut. Current temporarily increases again due to VDDS leakage until it too is cut.

When the HDMI framer is enabled, its continued current consumption (until 1v8 is cut) is clearly visible.