MAX3420E
USB Peripheral Controller
with SPI Interface
4 _______________________________________________________________________________________
Pin Description
OUTPUT
GPOUT0
GPOUT1
Output
G ener al - P ur p ose P ush- P ul l O utp uts. G P OU T3–G P OU T0 l og i c l evel s ar e r efer enced
to the vol tag e on V
L
. The S P I m aster contr ol s the G P OU T3–GP OU T0 states b y
w r i ti ng to b i t 3 thr oug h b i t 0 of the IOP IN S ( R20) r eg i ster .
3 3, 4 V
L
Input
Level-Translator Reference Voltage. Connect V
L
to the system’s 1.71V to 3.6V
logic-level power supply. Bypass V
L
to ground with a 0.1µF capacitor as close to
the V
L
pin as possible.
4, 14
5, 6, 18, 19
GPOUT2
GPOUT3
Output
Gener al - P ur p ose P ush- P ul l O utp uts. GP OU T3–GP O U T0 l og i c l evel s ar e r efer enced to
the vol tag e on V
L
. The S P I m aster contr ol s the GP O U T3–GP OU T0 states b y w r i ti ng to
b i t 3 thr oug h b i t 0 of the IOP IN S ( R20) r eg i ster .
710RES Input
Device Reset. Drive RES low to clear all of the internal registers except for
PINCTL (R17), USBCTL (R15), and SPI logic. See the Device Reset section for a
description of resets available on the MAX3420E.
811SCLK Input
SPI Serial-Clock Input. An external SPI master supplies this clock 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 positive edge of SCLK. Data is clocked out of
the SPI slave interface on the falling edge of SCLK.
912SS Input
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 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. The MAX3420E SS pin is sensitive to
undershoot. A 33pF capacitor should be connected from SS to ground to prevent
any noise spikes.*
10 13 MISO
Output
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
.
11 14 MOSI
Input or
Input/
Output
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.
12 15 GPX
Output
General-Purpose Multiplexed Output. The internal MAX3420E signal that appears
on GPX is programmable by writing to the GPXB and GPXA bits of the PINCTL
(R17) register. GPX indicates one of four signals: OPERATE (00, Default),
VBUS_DET (01), BUSACT (10), and SOF (11).
13 17 INT
Output
Inter r up t Outp ut. In ed g e m od e, the l og i c l evel on IN T i s r efer enced to the vol tag e
on V L. In ed g e m od e , IN T i s a p ush- p ul l outp ut w i th p r og r am m ab l e p ol ar i ty. In l evel
m od e, IN T i s op en d r ai n and acti ve l ow . S et the IE b i t i n the C P U C TL ( R16) r eg i ster to
enab l e IN T.
15 20 D-
Input/
Output
U S B D - S i g nal . C onnect D - to a U S B “B” connector thr ough a 33Ω ( ±1%) ser ies resi stor .
*33pF capacitor will not be required after redesign.
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