MAX3421E

USB Peripheral/Host Controller

with SPI Interface

6

Maxim Integrated

Pin Description (continued)

PIN

NAME

INPUT/

OUTPUT

FUNCTION

21

D+

Input/

Output

USB D+ Signal. Connect D+ to a USB connector through a 33

Ω ±1% series resistor. A

switchable 1.5k

Ω D+ pullup resistor and 15kΩ D+ pulldown resistor is internal to the device.

22

VBCOMP

Input

SPI master to detect (through an interrupt or checking a register bit) the presence or loss of

23

Input

24

XI

Input

Crystal Oscillator Input. Connect XI to one side of a parallel resonant 12MHz ±0.25% crystal

25

XO

Output

Crystal Oscillator Output. Connect XO to the other side of a parallel resonant 12MHz ±0.25% crystal

and a load capacitor to GND. Leave XO unconnected if XI is driven with an external source.

26

GPIN0

27

GPIN1

28

GPIN2

29

GPIN3

30

GPIN4

31

GPIN5

32

GPIN6

Input

—

EP

Input

Exposed Pad, Connected to Ground. Connect EP to GND or leave unconnected. EP is located on

the bottom of the TQFN package. The TQFP package does not have an exposed pad.