APEX 20K Programmable Logic Device Family Data Sheet
The APEX device architecture supports the MultiVolt I/ O interface
MultiVolt I/O
Interface
feature, which allows APEX devices in all packages to interface with
systems of different supply voltages. The devices have one set of VCCpins
for internal operation and input buffers (VCCINT), and another set for I/ O
output drivers (VCCIO).
The APEX 20K VCCINTpins must always be connected to a 2.5 V power
supply. With a 2.5-V VCCINT level, input pins are 2.5-V and 3.3-V tolerant.
Certain devices, identified by a “V” suffix following the speed grade in the
ordering code (e.g., EP20K400BC652-1V), are 5.0-V tolerant. The VCCIO
pins can be connected to either a 2.5-V or 3.3-V power supply, depending
on the output requirements. When VCCIOpins are connected to a 2.5-V
power supply, the output levels are compatible with 2.5-V systems. When
the VCCIOpins are connected to a 3.3-V power supply, the output high is
3.3 V and is compatible with 3.3-V or 5.0-V systems.
Table 12 summarizes 5.0-V tolerant APEX 20K MultiVolt I/ O support.
Table 12. 5.0-V Tolerant APEX 20K MultiVolt I/O Support
VCCIO (V)
Input Signals (V)
3.3
Output Signals (V)
2.5
5.0
2.5
3.3
5.0
2.5
3.3
v
v
v(1)
v(1), (2)
v(1), (2)
v
v
v(3)
v
v
Notes:
(1) The PCI clamping diode must be disabled to drive an input with voltages higher
than V
.
CCIO
(2) APEX 20K devices with a “V” suffix are 5.0-V tolerant.
(3) When V = 3.3 V, an APEX 20K device can drive a 2.5-V device with 3.3-V
CCIO
tolerant inputs.
Open-drain output pins on 5.0-V tolerant APEX 20K devices (with a pull-
up resistor to the 5.0-V supply) can drive 5.0-V CMOS input pins that
require a VIH of 3.5 V. When the pin is inactive, the trace will be pulled up
to 5.0 V by the resistor. The open-drain pin will only drive low or tri-state;
it will never drive high. The rise time is dependent on the value of the pull-
up resistor and load impedance. The IOL current specification should be
considered when selecting a pull-up resistor.
46
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