Datasheet

PIC24FJ256DA210 FAMILY
DS39969B-page 242  2010 Microchip Technology Inc.
18.1.2 HOST AND OTG MODES
18.1.2.1 D+ and D- Pull-Down Resistors
PIC24FJ256DA210 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 Specification requires that the
host application should 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 regu-
late current on the bus (Figure 18-6). For OTG opera-
tion, 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
®
MCU
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
®
MCU
10 µF
VIN
SELECT
SHND
PGOOD
MCP1253
VOUT
C+
C-
GND
1 µF