PIC24FJ256GB108-I Datasheet, PDF (210/352 Pages) Microchip Technology – 64/80/100-Pin, 16-Bit Flash Microcontrollers with USB On-The-Go (OTG)

PIC24FJ256GB110 FAMILY
18.1.2 HOST AND OTG MODES
18.1.2.1 D+ and D- Pull-down Resistors
PIC24FJ256GB110 family devices have 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 microcon-
troller is operating in Host mode. They are engaged 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 specification requires that the
Host application 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® Microcontroller}
VDD
VUSB
2 k
0.1 µF,
3.3V
A/D pin
2 k
VBUS
D+
D-
ID
VSS
FIGURE 18-7:
OTG INTERFACE EXAMPLE
Micro A/B
Connector
4.7 µF
VBUS
D+
D-
ID
GND
1 µF
MCP1253
GND
C+
VIN
SELECT
C-
VOUT
SHND
PGOOD
40 k
VDD
PIC^® Microcontroller
10 µF
I/O
I/O
VBUS
D+
D-
ID
VSS
DS39897C-page 210
 2009 Microchip Technology Inc.