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PDF XR19L402 Data sheet ( Hoja de datos )
| Número de pieza | XR19L402 | |
| Descripción | TWO CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER | |
| Fabricantes | Exar Corporation | |
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XR19L402
TWO CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER
JUNE 2007
REV. 1.0.0
GENERAL DESCRIPTION
The XR19L402 (L402) is a highly integrated device that
combines a full-featured two channel Universal
Asynchronous Receiver and Transmitter (UART) and RS-
485 transceivers. The L402 is designed to operate with a
single 3.3V or 5V power supply. The L402 is fully compliant
with RS-485 Standards.
The L402 operates in four different modes: Active, Partial
Sleep, Full Sleep and Power-Save. Each mode can be
invoked via hardware or software. Upon power-up, the
L402 is in the Active mode where the UART and RS-485
transceiver function normally. In the Partial Sleep mode, the
internal crystal oscillator of the UART or charge pump of the
RS-485 transceiver is turned off. In Full Sleep mode, both
the crystal oscillator and the charge pump are turned off.
While the UART is in the Sleep mode, the Power-Save
mode isolates the core logic from the control signals (chip
select, read/write strobes, address and data bus lines) to
minimize the power consumption. The RS-485 receivers
remain active in any of these four modes.
APPLICATIONS
• Battery-Powered Equipment
• Handheld and Mobile Devices
• Handheld Terminals
• Industrial Peripheral Interfaces
• Point-of-Sale (POS) Systems
FEATURES
• Meets true RS-485 Standards at 3.3V or 5V operation
• Up to 8 Mbps data transmission rate
• 45us sleep mode exit (charge pump to full power)
• ESD protection for RS-485 I/O pins at
■ +/-15kV - Human Body Model
■ +/- 8kV - IEC 1000-4-2, Contact Discharge
■ +/- 15kV - IEC 61000-4-2, Air-Gap Discharge
• Software compatible with industry standard 16550 UART
• Intel/Motorola bus select
• Complete modem interface
• Sleep and Power-save modes to conserve battery power
• Wake-up interrupt upon exiting low power modes
FIGURE 1. BLOCK DIAGRAM
PwrSave
A2:A0
D7:D0
IOR#
IOW# (R/W#)
CSA# (CS#)
CSB#
INTA (IRQ#)
INTB
RESET (RESET#)
I/M#
TEST_EN
HALF/FULLA#
HALF/FULLB#
RXBSEL
*5 V Tolerant
Inputs
Crystal
Osc/Buffer
BRG
64 Byte
TX FIFO
TXA
Charge Pump
64 Byte
RX FIFO
Modem
I/Os
Channel A
Channel B
( Similar to
ChannelA )
RXA
VCC33
CTSA#
DSRA#
RIA#
CDA#
RS-485 Transceiver
TXB
RXB
UART
TXA+
TXA-
RXA+
RXA-
TXB+
TXB-
RXB+
RXB-
TXB
RXB
XR19L402
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com
1 page  
REV. 1.0.0
Pin Descriptions
XR19L402
TWO CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER
NAME
48-QFN
PIN#
TYPE
DESCRIPTION
RXBSEL
44
I When RXBSEL is HIGH, RXB is the receive data input.
When RXBSEL is LOW, RXB+ and RXB- are the receive data inputs.
VCC33
22 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
39 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
24, 37 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 26, 29, 32, - No Connect. Note that in Motorola mode, the IOR# pin also becomes an NC pin.
35
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.
5
5 Page 
XR19L402
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER
The closest divisor that is obtainable in the L402 can be calculated using the following formula:
ROUND( (Required Divisor - TRUNC(Required Divisor) )*16)/16 + TRUNC(Required Divisor), where
DLM = TRUNC(Required Divisor) >> 8
DLL = TRUNC(Required Divisor) & 0xFF
DLD = ROUND( (Required Divisor-TRUNC(Required Divisor) )*16)
In the formulas above, please note that:
TRUNC (N) = Integer Part of N. For example, TRUNC (5.6) = 5.
ROUND (N) = N rounded towards the closest integer. For example, ROUND (7.3) = 7 and ROUND (9.9) = 10.
A >> B indicates right shifting the value ’A’ by ’B’ number of bits. For example, 0x78A3 >> 8 = 0x0078.
FIGURE 5. BAUD RATE GENERATOR
To Other
Channel
XTAL1
XTAL2
Crystal
Osc/
Buffer
Prescaler
Divide by 1
Prescaler
Divide by 4
DLL, DLM and DLD
Registers
MCR Bit-7=0
(default)
Fractional Baud
Rate Generator
Logic
MCR Bit-7=1
16X or 8X
Sampling
Rate Clock
to Transmitter
and Receiver
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet XR19L402.PDF ] | |
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