Talk:HP Smart Pin
smart pin notes and comments
HP PN# 482133-001
outer layer go to GND, mid layer go to VOUT, inner layer to ID.
TRIVIAL NOTE: Seems like the ID pin is used for some kind of communication between adapter and notebook.. It transmit a signal at lower tension so that notebook recognize the adapter as an original HP product!
This pin is used to identify that a HP adapter is being used and not a 3rd party one.It is wired to some sort of DC signal input on the motherboard.
Ground is on the outside as normal, +19 volts on the inner ring and the center is where the "smart-pin" goes. If you only apply power to the inner & outer rings the laptop will not power up. You need to apply +19 to the center pin as well. According to HP "The Smart technology signals the power rating and if maximum rating of the adapter is reached, the notebook will reduce its power consumption". I do not know how the signaling works as I do not have a "smart-pin" adapter.
If you want to bypass it you can simply add a resistor between voltage and the smart pin. 430k will be good. The original resistor on HP power supplies is 390K.
If the voltage of the center pin differs from 5V, the processor will run on 10% of its nominal performance. Check the connection of the center pin. If it shorted to the main supply line, it will behaves the same. Under load, you should measure 5V on the center, and 20V on the main supply (center ring) pin.
This is your way if you wish to use replacement charger: Make voltage divider like mentioned before and aim getting 5,75V out to middle pin. You can get it work by using 10K and 4,7K resistors. This results 6,2V, which is close enough to fool your HP.
L2-cache got disabled when the middle-pin doesn’t supply at least 4V. the result is, that the system behaves just normal in bios, grub or memtest, but gets slow after leaving real-mode.
that the 65W charger output something around 2.5 to 3v on the centre pin, and the 90W mains charger some 5-7v, but the relationship between control voltage and current drawn was not obvious. However, one thing was clear: less than 5v on the control pin causes the laptop to be in "don't charge" mode: the word "charging" disappears, and the batter icon loses the "lightning bolt".
The 65W charger (in charge mode) starts with about 5.2v on the centre pin, then at some point it jumps to about 6.8v and seems to stay there. It draws about 3.3A.