The VBUS detect input, VBCOMP, is an important MAX3420E feature. Because the P i" />
參數(shù)資料
型號: MAX3420EETG+T
廠商: Maxim Integrated Products
文件頁數(shù): 13/22頁
文件大?。?/td> 0K
描述: IC USB PERIPH CONTROLLER 24TQFN
產(chǎn)品培訓(xùn)模塊: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標(biāo)準(zhǔn)包裝: 2,500
控制器類型: USB 外設(shè)控制器
接口: USB/串行
電源電壓: 3 V ~ 3.6 V
電流 - 電源: 15mA
工作溫度: -40°C ~ 85°C
安裝類型: 表面貼裝
封裝/外殼: 24-WFQFN 裸露焊盤
供應(yīng)商設(shè)備封裝: 24-TQFN-EP(4x4)
包裝: 帶卷 (TR)
配用: MAX3420EEVKIT-2+-ND - EVAL KIT FOR MAX3420E
The VBUS detect input, VBCOMP, is an important
MAX3420E feature. Because the P is powered
whether the USB device is plugged in or not, it needs
some way to detect a plug-in event. A comparator
inside the MAX3420E checks for a valid VBUS connec-
tion on VBCOMP and provides a connect status bit to
the P. Once connected, the P can delay the logical
connection to the USB bus to perform any required ini-
tialization, and then connect by setting the CONNECT
bit to 1 in the MAX3420E register USBCTL (R15). This
connects the internal 1.5k
Ω resistor from D+ to VCC, to
signal the host that a device has been plugged in.
If a host turns off VBUS while the device is connected,
the USB rev. 2.0 specification requires that the device
must not power its 1.5k
Ω pullup resistor connected to
D+. The MAX3420E has two features to help service
this event. First, the NOVBUSIRQ bit indicates the loss
of VBUS. Second, the P can set a bit called VBGATE
(VBUS gate) to instruct the MAX3420E to disconnect the
pullup resistor anytime VBUS goes away, regardless of
the CONNECT bit setting.
Crystal Selection
The MAX3420E requires a crystal with the following
specifications:
Frequency: 12MHz
±0.25%
CLOAD: 18pF
CO: 7pF max
Drive level: 200W
Series resonance resistance: 60
Ω max
Note: Series resonance resistance is the resistance
observed when the resonator is in the series resonant
condition. This is a parameter often stated by quartz crys-
tal vendors and is called R1. When a resonator is used in
the parallel resonant mode with an external load capaci-
tance, as is the case with the MAX3420E oscillator circuit,
the effective resistance is sometimes stated. This effec-
tive resistance at the loaded frequency of oscillation is:
R1 x ( 1 + (CO / CLOAD))2
For typical CO and CLOAD values, the effective resis-
tance can be greater than R1 by a factor of 2.
USB Peripheral Controller
with SPI Interface
MAX3420E
VCC
VL
XI
XO
N.C.
INT
MOSI
GPX
MISO
SCLK
RES
D+
D-
D+
D-
VBCOMP
SS
0.1
μF
GND
GPIN
GPIO
GPOUT
VBUS
33
Ω
33
Ω
1.0
μF
CERAMIC
1.0
μF
CERAMIC
CXI
CXO
12MHz
μP
4
USB
"B" CONNECTOR
+3.3V
Figure 17. MAX3420E in a Self-Powered Application
MAX3420E
20
Maxim Integrated
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