XR19L400_09 Datasheet, PDF (4/46 Pages) Exar Corporation – SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER

XR19L400
SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER
Pin Descriptions
REV. 1.0.3
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 the power supply is 3.3V, this pin shuts off}
the charge pump if the UART is already in sleep mode, i.e. the XTAL2 output is LOW. When
the power supply is 5V, this pin should be connected to GND.
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 _{Regulator Enable. This pin regulates the 5V VCC down to 3.3V internally for the UART.}
When the supply voltage is 3.3V, connect R_EN to GND.
When the supply voltage is 5V, connect R_EN to VCC.
TEST0
TEST1
TEST2
VCC33
35
I _{Factory Test Modes. For normal operation, these pins must be connected to GND.}
36
I
10
I
21
Pwr _{3.3V power supply. When VCC33 is used, R_EN pin should be connected to GND.}
A 0.1 uF capacitor to GND is recommended on this power supply pin. If VCC33 is not used
as the power supply pin, VCC33 should be left unconnected. See Figure 3. 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.}
A 1uF capacitor to GND is recommended on the VCC50 power supply pin. The 1uF capac-
itor is recommended whether VCC33 or VCC50 is used as the power supply pin. See
Figure 3. All CMOS/TTL input pins, except XTAL1, are 5V tolerant.
GND
31
Pwr _{Power supply common, ground.}
-
PAD Pwr _{The center pad on the backside of the QFN package is metallic and is not electrically con-}
nected to anything inside the device. It must be soldered on to the PCB and may be option-
ally 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
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.
4