XR17D158_05 Datasheet, PDF (9/73 Pages) Exar Corporation – UNIVERSAL (3.3V AND 5V) PCI BUS OCTAL UART

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REV. 1.2.2
XR17D158
UNIVERSAL (3.3V AND 5V) PCI BUS OCTAL UART
1.0 APPLICATION EXAMPLES
The XR17D158 is designed to operate with VCC (voltage to the UART Core Logic) at 5V only, irrespective of
whether the PCI bus is at 3.3V or 5V. Table 1 below shows the valid combinations of VCC and the PCI Bus
Voltage, VIO that can be used for the device..
TABLE 1: VALID COMBINATIONS OF VCC AND VIO SUPPLY VOLTAGES
VCC
VIO
5.0V
5.0V
Valid
5.0V
3.3V
Valid
3.3V
5.0V
Invalid
3.3V
3.3V
Invalid
A typical application for a universal add-in card (VCC must be 5V) is shown in Figure 3. In an embedded
system, the designer must still choose 5V power supply for the VCC regardless of VIO (3.3 or 5V). In
Figure 4, examples 1 and 2 show valid applications of the XR17D158 in an embedded system.
FIGURE 3. TYPICAL APPLICATION FOR A UNIVERSAL ADD-IN CARD
VIO
(3.3V or 5V)
CLK
(up to 33.34 MHz)
PCI
Local
Bus
Interface
UART Core Logic
UART Channel 0
UART Channel 1
UART Channel 2
UART Channel 3
UART Channel 4
UART Channel 5
UART Channel 6
UART Channel 7
VCC = 5V
Max Crystal Frequency = 24MHz
Max External Clock = 50MHz
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