XR21V1414IM-0B-EB Datasheet, PDF (8/34 Pages) Exar Corporation – 4-CH FULL-SPEED USB UART

XR21V1414
4-CH FULL-SPEED USB UART
Pin Description
REV. 1.3.0
NAME
48-QFN
PIN #
Miscellaneous Signals
LOWPOWER
2
Power / Ground Signals
VCC
GND
5, 18, 33,
44, 45
1, 4, 19,
32, 40, 41
TYPE
DESCRIPTION
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 LOW-
POWER pin will behave differently 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.
• 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.
Pwr _{+3.3V power supply.}
Pwr _{Power supply common, ground.}
NOTE: Pin type: I=Input, O=Output, I/O= Input/output, OD=Output Open Drain.
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