Datasheet

PIC24FJ256GB110 FAMILY
DS39897C-page 210  2009 Microchip Technology Inc.
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 V
BUS 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 V
BUS 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
FIGURE 18-7: OTG INTERFACE EXAMPLE
A/D pin
VUSB
VDD
VSS
D+
D-
V
BUS
ID
D+
D-
V
BUS
ID
GND
+3.3V
+3.3V
Polymer PTC
Thermal Fuse
Micro A/B
Connector
150 µF
2 k
2 k
0.1 µF,
3.3V
+5V
PIC
®
Microcontroller
I/O
I/O
V
SS
D+
D-
V
BUS
ID
D+
D-
V
BUS
ID
GND
Micro A/B
Connector
40 k
4.7 µF
VDD
PIC
®
Microcontroller
10 µF
VIN
SELECT
SHND
PGOOD
MCP1253
VOUT
C+
C-
GND
1 µF