EVALUATION KIT AVAILABLE
MAX3421E
USB Peripheral/Host Controller
with SPI Interface
General Description
The MAX3421E USB peripheral/host controller contains
the digital logic and analog circuitry necessary to
implement a full-speed USB peripheral or a full-/low-
speed host compliant to USB specification rev 2.0. A
built-in transceiver features ±15kV ESD protection and
programmable USB connect and disconnect. An inter-
nal serial interface engine (SIE) handles low-level USB
protocol details such as error checking and bus retries.
The MAX3421E operates using a register set accessed
by an SPI interface that operates up to 26MHz. Any SPI
master (microprocessor, ASIC, DSP, etc.) can add USB
peripheral or host functionality using the simple 3- or 4-
wire SPI interface.
The MAX3421E makes the vast collection of USB
peripherals available to any microprocessor, ASIC, or
DSP when it operates as a USB host. For point-to-point
solutions, for example, a USB keyboard or mouse inter-
faced to an embedded system, the firmware that oper-
ates the MAX3421E can be simple since only a
targeted device is supported.
Internal level translators allow the SPI interface to run at
a system voltage between 1.4V and 3.6V. USB-timed
operations are done inside the MAX3421E with inter-
rupts provided at completion so an SPI master does not
need timers to meet USB timing requirements. The
MAX3421E includes eight general-purpose inputs and
outputs so any microprocessor that uses I/O pins to
implement the SPI interface can reclaim the I/O pins
and gain additional ones.
The MAX3421E operates over the extended -40°C to
+85°C temperature range and is available in a 32-pin
TQFP package (5mm x 5mm) and a 32-pin TQFN pack-
age (5mm x 5mm).
Features
o
Microprocessor-Independent USB Solution
o
Software Compatible with the MAX3420E USB
Peripheral Controller with SPI Interface
o
Complies with USB Specification Revision 2.0
(Full-Speed 12Mbps Peripheral, Full-/Low-Speed
12Mbps/1.5Mbps Host)
o
Integrated USB Transceiver
o
Firmware/Hardware Control of an Internal D+
Pullup Resistor (Peripheral Mode) and D+/D-
Pulldown Resistors (Host Mode)
o
Programmable 3- or 4-Wire, 26MHz SPI Interface
o
Level Translators and V
L
Input Allow Independent
System Interface Voltage
o
Internal Comparator Detects V
BUS
for Self-
Powered Peripheral Applications
o
ESD Protection on D+, D-, and VBCOMP
o
Interrupt Output Pin (Level- or Programmable-
Edge) Allows Polled or Interrupt-Driven SPI
Interface
o
Eight General-Purpose Inputs and Eight General-
Purpose Outputs
o
Interrupt Signal for General-Purpose Input Pins,
Programmable Edge Polarity
o
Intelligent USB SIE
o
Automatically Handles USB Flow Control and
Double Buffering
o
Handles Low-Level USB Signaling Details
o
Contains Timers for USB Time-Sensitive
Operations so SPI Master Does Not Need to Time
Events
o
Space-Saving Lead-Free TQFP and TQFN
Packages (5mm x 5mm)
Applications
Embedded Systems
Medical Devices
Microprocessors and
DSPs
Custom USB Devices
Cameras
Desktop Routers
PLCs
Set-Top Boxes
PDAs
MP3 Players
Instrumentation
Ordering Information
PART
MAX3421EEHJ+
MAX3421EETJ+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
32 TQFP
32 TQFN-EP*
TOP
MARK
—
BTBG
*EP
= Exposed pad.
+Denotes
a lead(Pb)-free/RoHS-compliant package.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-3953; Rev 4; 7/13
MAX3421E
USB Peripheral/Host Controller
with SPI Interface
Features in Host Operation
o
Eleven Registers (R21–R31) are Added to the
MAX3420E Register Set to Control Host Operation
o
Host Controller Operates at Full Speed or Low
Speed
o
FIFOS
SNDFIFO: Send FIFO, Double-Buffered 64-Byte
RCVFIFO: Receive FIFO, Double-Buffered 64-Byte
o
Handles DATA0/DATA1 Toggle Generation and
Checking
o
Performs Error Checking for All Transfers
o
Automatically Generates SOF (Full-Speed)/EOP
(Low-Speed) at 1ms Intervals
o
Automatically Synchronizes Host Transfers with
Beginning of Frame (SOF/EOP)
o
Reports Results of Host Requests
o
Supports USB Hubs
o
Supports ISOCHRONOUS Transfers
o
Simple Programming
SIE Automatically Generates Periodic SOF
(Full-Speed) or EOP (Low-Speed) Frame
Markers
SPI Master Loads Data, Sets Function Address,
Endpoint, and Transfer Type, and Initiates the
Transfer
MAX3421E Responds with an Interrupt and
Result Code Indicating Peripheral Response
Transfer Request Can be Loaded Any Time
SIE Synchronizes with Frame Markers
For Multipacket Transfers, the SIE
Automatically Maintains and Checks the
Data Toggles
USB
Features in Peripheral Operation
o
Built-In Endpoint FIFOS
EP0: CONTROL (64 bytes)
EP1: OUT, BULK or INTERRUPT, 2 x 64 Bytes
(Double-Buffered)
EP2: IN, BULK or INTERRUPT, 2 x 64 Bytes
(Double-Buffered)
EP3: IN, BULK or INTERRUPT (64 Bytes)
o
Double-Buffered Data Endpoints Increase
Throughput by Allowing the SPI Master to
Transfer Data Concurrent with USB Transfers
o
SETUP Data Has its Own 8-Byte FIFO, Simplifying
Firmware
Typical Application Circuits
3.3V
REGULATOR
SPI
3, 4
INT
μP
MAX3421E
Figure 1. The MAX3421E Connects to Any Microprocessor
Using 3 or 4 Interface Pins
The MAX3421E connects to any microprocessor (µP)
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. Eight GPIN and
eight GPOUT pins on the MAX3421E more than
replace the µP pins necessary to implement the inter-
face. Although the MAX3421E 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 bidi-
rectional data, saving an interface pin. This is referred
to as half-duplex mode.
2
Maxim Integrated
MAX3421E
USB Peripheral/Host Controller
with SPI Interface
Typical Application Circuits (continued)
3.3V
REGULATOR
SPI
3, 4
INT
ASIC,
DSP,
ETC.
POWER RAIL
USB
MAX3421E
Two MAX3421E features make it easy to connect to
large, fast chips such as ASICs and DSPs (Figure 2).
First, the SPI interface can be clocked up to 26MHz.
Second, the V
L
pin and internal level translators allow
running the system interface at a lower voltage than
the 3.3V required for V
CC
.
Figure 2. The MAX3421E Connected to a Large Chip
3.3V
REGULATOR
LOCAL
POWER
USB
MAX3421E
I
S
O
L
A
T
O
R
S
MISO
INT
MICRO
ASIC
DSP
SCLK
MOSI
SS
LOCAL
GND
The MAX3421E provides an ideal method for electrically
isolating a USB interface (Figure 3). USB employs flow
control in which the MAX3421E automatically answers
host requests with a NAK handshake, until the micro-
processor completes its data-transfer operations over
the SPI port. This means that the SPI interface can run
at any frequency up to 26MHz. Therefore, the designer
is free to choose the interface operating frequency and
to make opto-isolator choices optimized for cost or per-
formance.
Figure 3. Optical Isolation of USB Using the MAX3421E
5V
V
BUS
SWITCH
V
BUS
POWER
ON/OFF
FAULT
3.3V
REGULATOR
MICRO,
ASIC,
DSP
SPI
3, 4
INT
V
BUS
MAX3421E
USB
"A"
D+
D-
GND
USB
USB
"B" PERIPHERAL
Figure 4 shows a block diagram for a system in which
the MAX3421E operates as a USB host. A USB host
supplies 5V power to the V
BUS
pin of the USB “A” con-
nector to power USB peripherals. A system that pro-
vides power to an external peripheral should use
protection circuitry on the power pin to prevent an
external overcurrent situation from damaging the sys-
tem. A V
BUS
switch, such as the MAX4789, provides
power control plus two additional features: it limits the
current delivered to the peripheral (for example to
200mA), and it indicates a fault (overcurrent) condition
to the SPI controller. Maxim offers a variety of V
BUS
switches with various current limits and features.
Consult the Maxim website for details.
A 3.3V regulator (for example, the MAX6349TL) powers
the MAX3421E, and optionally the system controller. If
the system controller operates with a lower voltage, the
MAX3421E SPI and I/O interface can run at the lower
voltage by connecting the system voltage (for exam-
ple, 2.5V or 1.8V) to the MAX3421E V
L
pin.
Figure 4. The MAX3421E in an Embedded Host Application
Maxim Integrated
3
MAX3421E
USB Peripheral/Host Controller
with SPI Interface
Functional Diagram
RES
XI
XO
V
CC
INTERNAL
POR
RESET
LOGIC
1.5kΩ
OSC
AND
4x PLL
POWER
DOWN
D+
D-
ESD
PROTECTION
FULL-SPEED/
LOW-SPEED
USB
TRANSCEIVER
15kΩ
USB SIE
(SERIAL-
INTERFACE
ENGINE)
48MHz
15kΩ
SCLK
MOSI
MISO
SS
INT
ENDPOINT
BUFFERS
ESD
PROTECTION
1V TO 3V
R
IN
SPI SLAVE
INTERFACE
V
BUS
COMP
VBUS_DET
R
GPIN
GPIN0
GPIN1
GPIN2
GPIN3
GPIN4
GPIN5
GPIN6
GPIN7
GPOUT0
GPOUT1
GPOUT2
GPOUT3
GPOUT4
GPOUT5
GPOUT6
GPOUT7
V
L
VBCOMP
OPERATE
BUSACT/
INIRQ
SOF
1
MUX
2
3
MAX3421E
0
GND
GPX
4
Maxim Integrated
MAX3421E
USB Peripheral/Host Controller
with SPI Interface
Pin Description
PIN
1
2
3, 19
4
5
6
7
8
9
10
11
NAME
GPIN7
V
L
GND
GPOUT0
GPOUT1
GPOUT2
GPOUT3
GPOUT4
GPOUT5
GPOUT6
GPOUT7
Device Reset. Drive
RES
low to clear all of the internal registers except for PINCTL (R17),
USBCTL (R15), and SPI logic. The logic level is referenced to the voltage on V
L
. (See the
Device Reset
section for a description of resets available on the MAX3421E.)
Note:
The
MAX3421E is internally reset if either V
CC
or V
L
is not present. The register file is not accessible
under these conditions.
SPI Serial-Clock Input. An external SPI master supplies SCLK with frequencies up to 26MHz. The
logic level is referenced to the voltage on V
L
. Data is clocked into the SPI slave interface on the
rising edge of SCLK. Data is clocked out of the SPI slave interface on the falling edge of SCLK.
SPI Slave Select Input. The
SS
logic level is referenced to the voltage on V
L
. When
SS
is driven
high, the SPI slave interface is not selected, the MISO pin is high impedance, and SCLK
transitions are ignored. An SPI transfer begins with a high-to-low
SS
transition and ends with a
low-to-high
SS
transition.
SPI Serial-Data Output (Master-In Slave-Out). MISO is a push-pull output. MISO is tri-stated in
half-duplex mode or when
SS
= 1. The MISO logic level is referenced to the voltage on V
L
.
SPI Serial-Data Input (Master-Out Slave-In). The logic level on MOSI is referenced to the
voltage on V
L
. MOSI can also be configured as a bidirectional MOSI/MISO input and output.
(See Figure 15.)
General-Purpose Multiplexed Push-Pull Output. The internal MAX3421E signal that appears on
GPX is programmable by writing to the GPXB and GPXA bits of the PINCTL (R17) register and the
SEPIRQ bit of the MODE (R27) register. GPX indicates one of five signals (see the
GPX
section).
Interrupt Output. In edge mode, the logic level on INT is referenced to the voltage on V
L
and is
a push-pull output with programmable polarity. In level mode, INT is open-drain and active low.
Set the IE bit in the CPUCTL (R16) register to enable INT.
USB D- Signal. Connect D- to a USB connector through a 33Ω ±1% series resistor. A
switchable 15kΩ D- pulldown resistor is internal to the device.
Output
General-Purpose Push-Pull Outputs. GPOUT7–GPOUT0 logic levels are referenced to the
voltage on V
L
.
INPUT/
OUTPUT
Input
Input
Input
FUNCTION
General-Purpose Input. GPIN7–GPIN0 are connected to V
L
with internal pullup resistors.
GPIN7–GPIN0 logic levels are referenced to the voltage on V
L
.
Level-Translator Voltage Input. Connect V
L
to the system’s 1.4V to 3.6V logic-level power
supply. Bypass V
L
to ground with a 0.1µF capacitor as close to V
L
as possible.
Ground
12
RES
Input
13
SCLK
Input
14
SS
Input
15
MISO
Output
Input or
Input/
Output
Output
16
MOSI
17
GPX
18
INT
Output
Input/
Output
20
D-
Maxim Integrated
5
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