DocID023275 Rev 1
3/17
UM1551
Description
17
Description
Quick guide and default configuration
By default, the board is powered from a USB host (notebook, PC, docking station, etc.)
through the J2 USB connector. No external power supply is necessary.
In this mode, evaluation of all STCC50x1 device features is possible with the following
limitation:
Maximum charging current is limited by the USB host capabilities (typically 500 mA
to 2000 mA).
Jumper and selector settings for default configuration
J5: ON (closed)
SW6: V
EXT
(1 - 2)
Settings and connections
Variable resistors
Resistor R18
This resistor adjusts the V
LDO
voltage to verify proper functionality of the attach detector for
the whole V
DD
operating range. The equation is as follows:
Equation 1
Minimum adjustable voltage is approx. 1.7 V, maximum voltage is close to V
EXT
. The V
LDO
increases in a counter-clockwise direction.
For externally set V
DD
voltage, the jumper selector SW6 can be placed in the V
EXT
position,
connecting V
EXT
directly to V
DD
.
Resistor R26
This resistor adjusts the current limiter threshold according to
Equation 2
Minimum current is approx. 400 mA, maximum current is approx. 2700 mA. The current limit
increases in a clockwise direction.
For minimum current, the accuracy is not defined. The host/power supply capability may be
at least equal to the current limiter threshold set by R26.
V
LDO
1,2 R18 6,2 15
+
+
15
-----------------------------------------------------
V k
=
ISC
48000
R26 18
+
------------------------
mA k
=
