MAX3420EEVKIT-2+ Maxim Integrated Products, MAX3420EEVKIT-2+ Datasheet - Page 19

• Manufacturer Part Number: MAX3420EEVKIT-2+
• Description: EVAL KIT FOR MAX3420E
• Manufacturer: Maxim Integrated Products

Specifications of MAX3420EEVKIT-2+

• Main Purpose: Interface, USB 2.0 Slave
• Embedded: No
• Utilized Ic / Part: MAX3420E
• Primary Attributes: Full Speed (12Mbps), SPI Interface, No Custom USB Drivers
• Secondary Attributes: 4 GPI Pushbuttons, 4 GPO LEDs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 16. MAX3420E in a Bus-Powered Application
Figure 16 depicts the MAX3420E in a peripheral device
that is powered by V
geous because it requires no external power supply.
V
lator is required to power the MAX3420E. This diagram
assumes that the microprocessor is powered by 3.3V
as well, so the V
connected to V
pose inputs/outputs) are referenced to 3.3V.
USB is a hot-plug system (V
is plugged in), so it is good design practice to use a
power-on reset circuit to provide a clean reset to the
system when the device is plugged in. The MAX6349TL
serves as an excellent USB regulator, since it has very
low quiescent current and a POR circuit built in.
Because this design is bus powered, it is not necessary
to test for the presence of V
voltage-detection input, VBCOMP, makes an excellent
general-purpose input when pulled up to V
VBCOMP input has two interrupts associated with it,
VBUSIRQ and NOVBUSIRQ. These interrupts can detect
both edges of any transitions on the VBCOMP input.
BUS
MAX3420E in a Bus-Powered Application
is specified from 4.75V to 5.25V, so a 3.3V regu-
"B" CONNECTOR
CC
USB
L
______________________________________________________________________________________
. Therefore, the GPIO (general-pur-
pin (logic-level reference voltage) is
BUS
V
GND
BUS
. This configuration is advanta-
4.7μF
D+
D-
BUS
BUS
REGULATOR
MAX6349TL
is hot when the device
. In this case, the bus
3.3V
GPI
33Ω
33Ω
10kΩ
CERAMIC
1.0μF
RES
D+
D-
VBCOMP
L
. The
V
CC
USB Peripheral Controller
V
GND
L
0.1μF
The configuration in Figure 16 shows the SPI interface
using the maximum number of SPI interface pins. The
data pins, MOSI and MISO, are separate, and the
MAX3420E supplies an interrupt signal through the INT
output pin to the µP to notify the µP when its attention
is required.
Figure 17 shows a self-powered design in which the µP
has its own power source. This is a common configura-
tion in battery-powered handheld devices. Figure 17
also illustrates the SPI interfacing with the minimum
number of pins. This is achieved by using a single bidi-
rectional data line and no interrupt pin connection. The
MAX3420E register bit, FDUPSPI, configures the SPI
interface for bidirectional operation.
Although Figure 17 shows V
troller uses a different interface voltage (1.71V to 3.6V)
this reference voltage can be connected to V
shows a connection from the MAX3420E GPX output to
the microcontroller. GPX can be programmed (see Table
3) to connect the output of the internal V
to the GPX output. This enables the microprocessor to
detect a USB plug-in event even if the MAX3420E is put
into its power-down state.
MAX3420E
MAX3420E in a Self-Powered Application
GPIN GPOUT
4
with SPI Interface
C
XI
XI
12MHz
4
XO
MOSI
MISO
SCLK
C
INT
SS
XO
L
= V
CC
, if the microcon-
μP
BUS
L
comparator
. Figure 17
19