PIC24FJ256DA210 Datasheet, PDF (241/408 Pages) Microchip Technology – 64/100-Pin, 16-Bit Flash Microcontrollers with Graphics Controller and USB On-The-Go (OTG)

PIC24FJ256DA210 FAMILY
18.1 Hardware Configuration
18.1.1 DEVICE MODE
18.1.1.1 D+ Pull-up Resistor
PIC24FJ256DA210 family devices have a built-in
1.5 k resistor on the D+ line that is available when the
microcontroller is operating in Device mode. This is
used to signal an external Host that the device is
operating in Full-Speed Device mode. It is engaged by
setting the USBEN bit (U1CON<0>). If the OTGEN bit
(U1OTGCON<2>) is set, then the D+ pull-up is enabled
through the DPPULUP bit (U1OTGCON<7>).
Alternatively, an external resistor may be used on D+,
as shown in Figure 18-2.
FIGURE 18-2:
PIC^® MCU
EXTERNAL PULL-UP FOR
FULL-SPEED DEVICE
MODE
Host
Controller/HUB
VUSB
To meet compliance specifications, the USB module
(and the D+ or D- pull-up resistor) should not be enabled
until the host actively drives VBUS high. One of the 5.5V
tolerant I/O pins may be used for this purpose.
The application should never source any current onto
the 5V VBUS pin of the USB cable.
The Dual Power mode with Self-Power Dominance
(Figure 18-5) allows the application to use internal
power primarily, but switch to power from the USB
when no internal power is available. Dual power
devices must also meet all of the special requirements
for inrush current and Suspend mode current previ-
ously described, and must not enable the USB module
until VBUS is driven high.
FIGURE 18-3:
BUS POWER ONLY
100
Attach Sense
VBUS
VBUS
~5V
3.3V
VDD
Low IQ Regulator
VUSB
VSS
1.5 k
D+
D-
18.1.1.2 Power Modes
Many USB applications will likely have several different
sets of power requirements and configuration. The
most common power modes encountered are:
• Bus Power Only mode
• Self-Power Only mode
• Dual Power with Self-Power Dominance
Bus Power Only mode (Figure 18-3) is effectively the
simplest method. All power for the application is drawn
from the USB.
To meet the inrush current requirements of the USB 2.0
Specification, the total effective capacitance appearing
across VBUS and ground must be no more than 10 F.
In the USB Suspend mode, devices must consume no
more than 2.5 mA from the 5V VBUS line of the USB
cable. During the USB Suspend mode, the D+ or D-
pull-up resistor must remain active, which will consume
some of the allowed suspend current.
In Self-Power Only mode (Figure 18-4), the USB
application provides its own power, with very little
power being pulled from the USB. Note that an attach
indication is added to indicate when the USB has been
connected and the host is actively powering VBUS.
FIGURE 18-4:
SELF-POWER ONLY
VBUS
~5V
VSELF
~3.3V
100
Attach Sense
VBUS
VDD
100 k
VUSB
VSS
FIGURE 18-5:
DUAL POWER EXAMPLE
100
VBUS
~5V
3.3V
Low IQ
Regulator
VSELF
~3.3V
100 k
Attach Sense
VBUS
VDD
VUSB
VSS
 2010 Microchip Technology Inc.
DS39969B-page 241