XR21V1412IL32-F 查看數據表（PDF） - Exar Corporation

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XR21V1412IL32-F

2-CH FULL-SPEED USB UART

Exar Corporation 

XR21V1412

2-CH FULL-SPEED USB UART

REV. 1.3.0

NAME

32-QFN

PIN #

TYPE

DESCRIPTION

Miscellaneous Signals

LOWPOWER

2

O Low power status output. The LOWPOWER pin will be asserted whenever it is not

safe to draw the amount of current from VBUS power requested in the Device Max

Power field of the Configuration Descriptor. The LOWPOWER pin will behave differ-

ently for a low power device and a high power device.

• Low-power device (<= 1 unit load or 100 mA i.e. bMaxPower <= 0x32):

LOWPOWER pin is asserted when the USB UART is in suspend mode.

VCC

GND

GND

• High-power deivce (bMaxPower > 0x32): LOWPOWER pin is

asserted when the USB UART is in suspend mode or when it is not yet

configured.

The LOWPOWER pin will be de-asserted whenever it is safe to draw the

amount of current requested in the Device Maximum Power field.

This pin is sampled momentarily at power-up or at any USB bus reset to configure the

polarity of the LOWPOWER output during suspend mode. An external (10K) pull-up

resistor will cause the LOWPOWER pin to be asserted HIGH during suspend mode.

An external (3.3K) pull-down resistor will cause the LOWPOWER pin to be asserted

LOW during suspend mode.

4, 13, 24, Pwr +3.3V power supply.

31, 32

1, 3, 14, Pwr Power supply common, ground.

23, 27,

28

Center

Pad

Pwr The center pad on the back side of the QFN package is metallic and should be con-

nected to GND on the PCB. The thermal pad size on the PCB should be the approx-

imate size of this center pad and should be solder mask defined. The solder mask

opening should be at least 0.0025" inwards from the edge of the PCB thermal pad.

NOTE: Pin type: I=Input, O=Output, I/O= Input/output, OD=Output Open Drain.

6

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