True Blue Power
9
Revision 1, June 15, 2018
SECTION 4 OPERATION
4.1
ELECTRICAL PERFORMANCE
The USBT102 Series Dual USB Charging Port converts a
system’s (DC) input voltage within the range
specified to a 5V (DC) output. This output power is applied to a dual USB-A connector in accordance with
the
USB Implementers Forum.
The USB D+ and D- data lines communicate with the USB portable device to tell the device it is a
dedicated charging port (DCP), capable of a higher current than a standard USB port. This allows the
USB portable device to draw up to 2.1 Amps.
The unit is designed as a DC-to-DC converter with a series switch on each output to regulate current
applied to that output. Each series switch independently reduces the output current to a safe level if the
USB portable device draws excess current, is shorted or has a fault.
If the temperature of the USBT102 becomes elevated due to a fault or excessive load, the device will
seamlessly communicate with the USB portable device to lower the charge current. This allows the device
to continue charging while the unit returns to a temperature within designed limits. When the temperature
returns to a safe level the USBT102 will automatically reestablish the higher charge current level with the
device and continue charging.
4.2
PROTECTIVE FEATURES
4.2.1 Short Circuit Protection
The USBT102 is capable of surviving a short circuit event without permanent damage. The
unit goes into an over-current condition so that the average current is significantly reduced
and the device is protected.
4.2.2 Over-Current Protection
The USBT102 monitors the current draw individually on each port. During an over-current
condition the voltage is reduced. If the voltage falls below 3.8 VDC the output is turned off for
a period of 12 seconds. The output is then checked for continued over-current conditions
every 16 milliseconds. This condition is referred to as a hiccup mode. The device stays in this
mode until the over-current condition is removed, then returns to normal operation.
4.2.3 Low Input Voltage Shutdown
If the input voltage applied to the USBT102 drops below 10 VDC the unit will shut down until
the applied voltage returns to a level within range.
4.2.4 Over-Temperature
When the temperature of the USBT102 becomes elevated, the unit communicates with the
USB portable device to reduce the charge current output (1 amp limit). When the temperature
returns to an acceptable level the unit automatically returns to a higher charge current as
required (up to 2.1 amps).
