參數(shù)資料
型號(hào)： MAX14502AETL+T
廠商： Maxim Integrated Products
文件頁(yè)數(shù)： 26/41頁(yè)
文件大小： 0K
描述： IC CARD READER USB-SD 40-TQFN
產(chǎn)品培訓(xùn)模塊： Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標(biāo)準(zhǔn)包裝： 2,500
應(yīng)用： USB
接口： I²C，2 線串口
電源電壓： 1.8 V ~ 3.3 V
封裝/外殼： 40-WFQFN 裸露焊盤
供應(yīng)商設(shè)備封裝： 40-TQFN-EP（5x5）
包裝： 帶卷 (TR)
安裝類型： 表面貼裝
MAX14500–MAX14503
Hi-Speed USB-to-SD Card
Readers with Bypass
32
______________________________________________________________________________________
Power-Supply Modes
The MAX14500–MAX14503 have four power-supply
inputs (Table 6). Bypass VCC, VIO, VSD, and VTM with
high-frequency, surface-mount ceramic capacitors as
close as possible to the supply pins.
Power-supply inputs:
1) VTM USB Transceiver Power. This supply powers the
USB analog switches, PLL subsystem, and the USB
2.0 transceiver. This regulator can be internal to a
power-management IC, or it can be discrete and is
recommended to be powered from USB VBUS. This
supply must be present when the MAX14500–
MAX14503 are used in Card Reader mode to pass
USB signals in Pass Thru mode.
2) VCC Digital Logic Power. This supply powers the
digital logic/internal microcontroller/flash memory.
There is an internal +1.8V LDO (CLDO) with shut-
down controlled by the state of the MODE input and
internal logic.
3) VSD SD Card Power. This supply powers the SD
card level translator and SD card switches. VSD
needs to be present to pass SD signals in Pass Thru
mode.
4) VIO Host Interface Power. This supply powers the
digital I/O and I2C interface.
Power modes:
1) Idle. Only VIO is required to be present. I2C registers
can be updated, but no operation is possible.
2) Pass Thru Mode. VIO needs to be present so the
voltage level at MODE can be detected. To allow
USB pass thru, the VTM supply needs to be present.
To allow SD pass thru, VSD supply needs to be pre-
sent. Each supply is independent from the others
and no power-supply sequencing is required.
3) Card Reader Mode. All supplies are needed. When
the card reader is actively transferring data, this mode
draws the most current, mainly from VCC and VTM.
Layout Considerations
The MAX14500–MAX14503 support Hi-Speed USB and
requires careful PCB layout. Use controlled-impedance
matched traces of equal lengths to the USB connector
with no discontinuities and a minimum number of
feedthroughs. All SD traces (CLK, CMD, DAT_) should
be of equal lengths and as short as possible.
Choosing Pullup Resistors
I2C requires pullup resistors to provide a logic-high level
to data and clock lines. There are tradeoffs between
power dissipation and speed, and a compromise must
be made in choosing pullup resistor values. Every
device connected to the bus introduces some capaci-
tance, even when the device is not in operation. I2C
specifies 300ns rise time to go from low to high (30% to
70%) for fast mode, which is defined for data rates up to
400kbps. To meet the rise time requirement, choose
pullup resistors so the rise time (tR) is less than 300ns
where tR
≈ 0.85 x RPULLUP x CBUS. If the transition time
becomes too slow, the setup and hold times may not be
met and waveforms may not be recognized.
SUPPLY
FUNCTION
RANGE (V)
VTM
USB transceiver and USB
switch power
+2.91 to +3.4
VCC
Digital core 1.8V LDO
+2.1 to +3.6
VSD
SD card level translator and SD
switches
+2.0 to +3.6
VIO
Host microprocessor level
translator
+1.5 to +3.6
Table 6. Power-Supply Inputs
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參數(shù)描述
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