Jumper Options - Microchip Developer Explorer 16/32 User Manual

Explorer 16/32 Development Board User's Guide - Developer Help
exceeds 10 µF, the USB specification expects the device to implement some form of
soft start/inrush limiting circuit. When the device's capacitance exceeds 10 µF
(effective across VBUS), with no in-rush limiting circuit a large transient will occur at
the moment of device attachment. This in-rush transient can potentially cause a
significant voltage droop within the local host/hub's power net, leading to
malfunction in the host or hub, or in an adjacent USB device that may also be
already attached and powered by that host/hub. This can potentially cause
problems with enumeration or otherwise lead to a poor end user experience.
During a USB attachment event, the Explorer 16/32 Development Board MOSFET
Q5 is driven in the linear region (due to the effect of C61 and R132), allowing for
slower output voltage rising waveform (and correspondingly reduced inrush current
profile).
The components Q5, R99, and Q4 are used to implement a USB current limiting and
short circuit protection feature. This will begin to activate when the total load on the
5 V and 3.3 V Explorer 16/32 supply rails exceeds approximately 400 mA (when
powered only by USB, without additional power from the DC barrel jack). Under hard
short circuit conditions, resistors R131 and R134 implement a current foldback
scheme. This dynamically reduces the current limit to ~260 mA, thereby reducing
thermal power dissipation in Q5, allowing for a continuous short circuit to be
sustained when the ambient conditions are near 25° Celsius.
On-Off toggle power switching of the 5 V and 3.3 V rails on the Explorer 16/32 board
is implemented with U3 + S7 + the surrounding resistor/capacitor components. The
dual inverter U3 is connected in a circular chain, providing positive feedback and an
effective 1-bit latching memory cell. Pushbutton S7, C28, R130, and R135
implement a de-bounced means of toggling the state of the 1-bit memory cell.
Components R129, R136, and C62 help establish an initial "default to on" state
during the initial power up ramp of U3.

Jumper Options

The Explorer 16/32 Development Board has several jumpers, summarized as
follows:
Jumper
JP2
J19
J22
J23
7 z 18
Description
LED D3-D10 group enable/disable
LCD Read/Write Connection
USB Type-C Host VBUS enable control signal
Potentiometer R6 disconnect
http://microchipdeveloper.com/boards:explorer1632
7.6.2017 8:59