MAX3420E データシートの表示（PDF） - Maxim Integrated
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MAX3420E Datasheet PDF : 23 Pages
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MAX3420E
USB Peripheral Controller with SPI Interface
The MAX3420E connects to any microprocessor using 3
or 4 interface pins (Figure 1). On a simple microprocessor
without SPI hardware, these can be bit-banged general-
purpose I/O pins. Four GPIN and four GPOUT pins on
the MAX3420E more than replace the µP pins necessary
to implement the interface. Although the MAX3420E SPI
hardware includes separate data-in (MOSI, (master-out,
slave-in)) and data-out (MISO, (master-in, slave-out))
pins, the SPI interface can also be configured for the
MOSI pin to carry bidirectional data, saving an interface
pin. This is referred to as half-duplex mode.
Two MAX3420E features make it easy to connect to large,
fast chips such as ASICs and DSPs (see Figure 2). First,
Typical Application Circuits
the SPI interface can be clocked up to 26MHz. Second,
a VL pin and internal level translators allow running the
system interface at a lower voltage than the 3.3V required
for VCC.
The MAX3420E provides an ideal method for electrically
isolating a USB interface (Figure 3). USB employs flow
control in which the device automatically answers host
requests with a NAK handshake, until the microprocessor
completes its data-transfer operations over the SPI port.
This means that the SPI interface can run at any frequen-
cy up to 26MHz. Therefore, the designer is free to choose
the interface operating frequency and to make opto-
isolator choices optimized for cost or performance.
3.3V
REGULATOR
SPI
3, 4
USB
MAX3420E
µP
INT
Figure 1. The MAX3420E Connects to Any Microprocessor Using 3 or 4 Interface Pins
3.3V
REGULATOR
SPI
3, 4
USB
MAX3420E
INT
POWER RAIL
ASIC,
DSP,
ETC.
Figure 2. The MAX3420E Connected to a Large Chip
3.3V
REGULATOR
USB
MAX3420E
Figure 3. Optical Isolation of USB Using the MAX3420E
www.maximintegrated.com
LOCAL
POWER
I
S
O
MISO
L
INT
A
MICRO
T
ASIC
O
DSP
R
SCLK
S
MOSI
SS
LOCAL
GND
Maxim Integrated │ 6
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