Motorola Cell Phone Unauthorized Charger Message

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You connect your Motorola Razor to a phone charger with the miniUSB connector. Instead of charging, your phone displays an error message on the screen "Unauthorized Charger."

  • Using a non-motorola brand AC/DC charger
  • Using PC to cell phone connection cable

Many cellphones once made use of the mini-USB connection, one of the standardized USB Connector Types.

Motorola goes to some trouble to protect your USB devices from the overcurrent their cellphones would cause by charging off your USB ports. USB ports are rated for only 500ma of current drain and may damage your computer if you exceed that value. So, to prevent this possibility, Motorola has encorporated protective circuitry to measure exactly which power supply it has been plugged into as there are several types of USB power cables available. The pinouts and special circuitry in the proper power cables look like this:

Motorola RAZR V3 mini-USB Charger pinout http://pinouts.ru/connectors/mini-usb_male.gif

RAZR V3 will not charge by simply supplying 5V through USB (it's possible to use common USB cable for charging if you are using Motorola special PC driver software). Motorola uses the pin between Pin #3 and #4 (Pin X) to sense what device is attached to the mini-USB port. Shorting Pin #3 to #2 and #X causes the phone to go into handsfree/carkit mode and the LCD backlight will ignore timeout settings and stay on. Shorting pin X to pin 2 and to pin 4 via R=200KOhm causes the phone to go into charge mode.

AC adapter Pin Name Direction Description 1 +5 VDC -?- PC USB Pin 1 (+5 VDC). 2 USB Data -?- shorted to pin x in charger cable. 3 USB Data -?- not connected X -?- Shorted to pin 2 + shorted to pin 4 via R=200KOhm in charge cable. (R=165KOhm?) 4 GND -?- PC USB pin 4 (GND). Connected to pin X via R=200KOhm in charge cable. (R=165KOhm?)

Comment by Darrin A standard Motorola USB charger puts ~1.4vdc onto the x pin of the mini USB plug. A 200k resistor between pin 2 and 4 produces ~1.9vdc on the x pin. This works for Motorola Q (which works from ~1.2vdc to ~1.9vdc), but not for Razr V3m. I had to lower the resistor to 165k. This produces ~1.5vdc and allows the charger to become authorized.

End of quoted text.....

By overriding this safety feature, you load the USB device the phone is plugged into upwards of 2 amps of operating (transmitting) and very quick charging current as consumers demand the battery recharge so rapidly. To recharge quickly, requires lots of current your USB ports are not designed to supply.

Obviously, the nice high current switching charger Motorola has provided you that is SO TINY, not some heavy old 2A transformer, is the correct device to charge and operate your phone.

There's a variety of USB Connector Types, each having specific places on the evolution of the technology as well as specific device types a connector is best suited for.

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