PIC24FJ256GB210 Datasheet, PDF (236/386 Pages) Microchip Technology – 64/100-Pin, 16-Bit Flash Microcontrollers with USB On-The-Go (OTG)

PIC24FJ256GB210 FAMILY
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
18.1.2 HOST AND OTG MODES
18.1.2.1 D+ and D- Pull-Down Resistors
PIC24FJ256GB210 family devices have a built-in
15 k pull-down resistor on the D+ and D- lines. These
are used in tandem to signal to the bus that the micro-
controller is operating in Host mode. They are engaged
by setting the HOSTEN bit (U1CON<3>). If the OTGEN
bit (U1OTGCON<2>) is set, then these pull-downs are
enabled by setting the DPPULDWN and DMPULDWN
bits (U1OTGCON<5:4>).
18.1.2.2 Power Configurations
In Host mode, as well as Host mode in On-The-Go
operation, the “USB 2.0 OTG Specification” requires
that the host application should supply power on VBUS.
Since the microcontroller is running below VBUS, and is
not able to source sufficient current, a separate power
supply must be provided.
When the application is always operating in Host mode,
a simple circuit can be used to supply VBUS and
regulate current on the bus (Figure 18-6). For OTG
operation, it is necessary to be able to turn VBUS on or
off as needed, as the microcontroller switches between
Device and Host modes. A typical example using an
external charge pump is shown in Figure 18-7.
FIGURE 18-6:
HOST INTERFACE EXAMPLE
150 µF
Micro A/B
Connector
VBUS
D+
D-
ID
GND
+5V
Thermal Fuse
Polymer PTC
+3.3V +3.3V _{PIC® MCU}
VDD
VUSB
2 k
0.1 µF,
3.3V
A/D Pin
2 k
VBUS
D+
D-
ID
VSS
DS39975A-page 236
 2010 Microchip Technology Inc.