XR16L2551 Datasheet, PDF (12/48 Pages) Exar Corporation – LOW VOLTAGE DUART WITH POWERSAVE

XR16L2551
LOW VOLTAGE DUART WITH POWERSAVE
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REV. 1.0.0
To obtain maximum data rate, it is necessary to use full rail swing on the clock input. See external clock
operating frequency over power supply voltage chart in Figure 6.
FIGURE 6. OPERATING FREQUENCY CHART. REQUIRES A 2K OHMS PULL-UP RESISTOR
ON XTAL2 PIN TO INCREASE OPERATING SPEED
Operating frequency for XR16L2551
with external clock and a 2K ohms
pull-up resistor on XTAL2 pin.
80
-40^oC
70
25^oC
85^oC
60
50
40
30
3.0 3.5 4.0 4.5 5.0 5.5
Suppy Voltage
The L2551 divides the basic external clock by 16. The basic 16X clock provides table rates to support standard
and custom applications using the same system design. The Baud Rate Generator divides the input 16X clock
by any divisor from 1 to 2¹⁶ -1. The rate table is configured via the DLL and DLM internal register functions.
Customized Baud Rates can be achieved by selecting the proper divisor values for the MSB and LSB sections
of baud rate generator.
Table 6 shows the standard data rates available with a 14.7456 MHz crystal or external clock at 16X sampling
rate. When using a non-standard frequency crystal or external clock, the divisor value can be calculated for
DLL/DLM with the following equation.
divisor (decimal) = (XTAL1 clock frequency) / (serial data rate x 16)
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