dock connector

https://web.archive.org/web/20150108184014/http://rootzwiki.com:80/topic/8523-reverse-engineering-the-dock-charger/

Posted 31 October 2011 - 03:09 AM #1
I got my desktop charger today and unpacked it only to rip it aparts to check whats inside.
By first view theese are the highlights:

The dock connector is 40 pins
Dock connector is on a separate small pcb with a 40 pin board to board connector to a larger board.
On this small pcb is a 12 pin MLF package marked:
AAU
NAD

Probably has a ground pad underneath.

The main pcb has a few more circuits and connectors on it.
There is a micro usb, a full size master usb, audio out and microphone jacks. A bit more exiting there is room for a HDMI connector as well there with unpopulated spaces for line filters and a hdmi circuit. By first look it seems to be a displayport or MHL to HDMI bridge chip of some kind. I is TQFP-48 package.
edit:
It seems to be a PI3VDP411LS from pericom
http://www.pericom.c...PI3VDP411LS.pdf

It is a displayport levelshifter / bridge to HDMI. It is the only 48 pin package I have found to match the input with the differential pairs.

The power supply is 20 VDC 65 Watts. It does not seem like the center connector is connected. The connector is the standard "IBM" charger, outer case ground, inner case + 20 vdc, center pin power diag.

There is a fet transistor between the dock connector and the psu marked FA1K18 and it is controlled by some regulator marked 920A4 in a SOT-223 package. The 20 VDC goes in on pin 2 and the tab on it.

the HDMI chip has differential pair inputs on pin 47,48 - 44,45 - 41,41 - 38,39

I will do my best reversing the whole schematic for this unit and split it into parts so we can make other chargers and hopefully add HDMI to the dock.

Pinout Docking Connector Thinkpad Tablet

1 charge 2 gnd
3 charge 4 hdmi pin 44 In D3-
5 Charger control (to pq2) 6 hdmi pin 45 In D3+
7 hdmi VDD 3.3V 8 gnd
9 gnd 10 hdmi pin 47 In D4-
11 USB Micro D- 12 hdmi pin 48 In D4 +
13 USB micro D+ 14 gnd
15 USB Master D- 16 nc
17 USB MAster D+ 18 nc
19 gnd 20 hdmi pin 29 SDA
21 gnd 22 hdmi pin 28 SCL
23 hdmi pin 41 IN D2- 24 hdmi pin 7 HPD_Source
25 hdmi pin 42 In D2+ 26 gnd
27 gnd 28 audio out L
29 hdmi pin 38 IN D1- 30 audio out R
31 hdmi pin 39 IN D1+ 32 headset inserted switch
33 gnd 34 mic inserted switch feed
35 USB micro + 36 mic inserted switch
37 gnd 38 mic tip
39 + 5V to usb master 40 mic ring

Pinout AAU chipAAU chip is audio amp.
audio out
pin 10 ring
pin 11 tip
pin 2, 7 gnd

Charger stuff :
The supplied DC apater is 20Volt 3.25Amps
In the dock there is a voltage regulator PV1. It is a 3.3 V LDO Tab has 20 volts in and pin 3 gives 3.30 Volts out.
There is also a FET in SSO8 (?) package. It is controlled by 2 transistors and works only as a switch.
On the base of PQ2 (pin 1, I guess it is the base) there is a float of 3.30 volts when there is nothing in the dock. The FET is OPEN and no voltage to the charger pins.
When grounding PQ2 pin1 (dock pin 5) the FET CLOSES and the charger outputs 20,5volts which basically is the same as dc power into the dock.

Now I am just waiting for the TPT to get fully charged so I can measure if there is any difference when fully charged.

Note:
By charging at 20 volts instead of 5 volts I understand why the charger only uses 2 pins into the TPT.
At 20 volts you can transfer 4 times the energy instead of just charging at 5 volts from USB powers. There is no need for step ups to charge the LI-Po battery as it would need more than 5 volts.

This is the schematics of the charger part:

www.r-888.com/tpt/schema.pdf

I am not sure of the 2 transitors if they are pnp or npn yet but the rest is how it is.
The original mosfet is a P-channel AON7403.
The regulator is just any 3,3 volt LDO.

The TPT charger control pin 5 gets a 3,3 volt float via the resistor to the left in the schematic. When it is connected the TPT grounds the pin and the FET lets current through.

Edited by ZebCrs, 05 November 2011 - 12:56 PM.

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dock connector