XR21V1412IL-0A Datasheet, PDF (6/32 Pages) Exar Corporation – 2-CH FULL-SPEED USB UART

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