XR19L400 Datasheet, PDF (4/45 Pages) Exar Corporation – SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER

XR19L400
PRELIMINARY
SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER
Pin Descriptions
REV. P1.0.0
NAME
40-QFN
PIN#
TYPE
DESCRIPTION
XTAL2
13
O _{Crystal or buffered clock output.}
PwrSave 11
I _{Power-Save (active high). This feature isolates the L400’s data bus interface from the host}
preventing other bus activities that cause higher power drain during sleep mode.
ACP
19
I _{Autosleep for Charge Pump (active HIGH). When this pin is HIGH, the charge pump is shut}
off if the UART is already in sleep mode, i.e. the XTAL2 output is LOW.
I/M#
17
I _{Intel or Motorola Bus Select.}
When I/M# pin is HIGH, 16 or Intel Mode, the device will operate in the Intel bus type of
interface.
When I/M# pin is LOW, 68 or Motorola mode, the device will operate in the Motorola bus
type of interface.
RESET
18
(RESET#)
I _{When I/M# pin is HIGH for Intel bus interface, this input becomes RESET (active high).}
When I/M# pin is LOW for Motorola bus interface, this input becomes RESET# (active low).
A 40 ns minimum active pulse on this pin will reset the internal registers and all outputs of
the UART. The UART transmitter output will be held HIGH, the receiver input will be ignored
and outputs are reset during reset period.
C1+
25
- _{Charge pump capacitors. As shown in Figure 1, a 0.22 uF capacitor should be placed}
C1-
26
between these 2 pins.
R_EN
20
I _{When the supply voltage is < 3.6V, connect R_EN to GND.}
When the supply voltage is > 3.6V, connect R_EN to VCC.
VCC33
21
Pwr _{3.3V power supply. When VCC33 is used, R_EN pin should be connected to GND and}
VCC50 should be left unconnected. A 0.1 uF capacitor to GND is recommended on this
power supply pin. All CMOS/TTL input pins, except XTAL1, are 5V tolerant.
VCC50
33
Pwr _{5.0V power supply. When VCC50 is used, R_EN pin should be connected to VCC and}
VCC33 should be left unconnected. A 1 uF capacitor to GND is recommended on this
power supply pin. All CMOS/TTL input pins, except XTAL1, are 5V tolerant.
GND
31, 35 Pwr _{Power supply common, ground.}
-
PAD Pwr _{The center pad on the backside of the 64-QFN package is metallic and is not electrically}
connected to anything inside the device. It must be soldered on to the PCB and may be
optionally connected to GND on the PCB. The thermal pad size on the PCB should be the
approximate 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.
NC 16, 22, 23, - _{No Connect. Note that in Motorola mode, the IOR# pin also becomes an NC pin.}
24, 29, 36,
37
NOTE: Pin type: I=Input, O=Output, I/O= Input/output, OD=Output Open Drain. For CMOS/TTL Voltage levels, ’LOW’
indicates a voltage in the range 0V to VIL and ’HIGH" indicates a voltage in the range VIH to VCC.
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