40MX and 42MX FPGA Families
MX devices are designed to operate in both 5.0V and 3.3V environments. In particular, 42MX devices
can operate in mixed 5.0V/3.3V systems. Table 1-1 describes the voltage support of MX devices.
Table 1-1 • Voltage Support of MX Devices
VCC VCCA VCCI Maximum Input Tolerance Nominal Output Voltage
Power-Up/Down in Mixed-Voltage Mode
When powering up 42MX in mixed voltage mode (VCCA = 5.0 V and VCCI = 3.3 V), VCCA must be
greater than or equal to VCCI throughout the power-up sequence. If VCCI exceeds VCCA during power-
up, one of two things will happen:
• The input protection diode on the I/Os will be forward biased
• The I/Os will be at logical High
In either case, ICC rises to high levels.
For power-down, any sequence with VCCA and VCCI can be implemented.
Due to the simultaneous random logic switching activity during power-up, a transient current may appear
on the core supply (VCC). Customers must use a regulator for the VCC supply that can source a
minimum of 100 mA for transient current during power-up. Failure to provide enough power can prevent
the system from powering up properly and result in functional failure. However, there are no reliability
concerns, since transient current is distributed across the die instead of confined to a localized spot.
Since the transient current is not due to I/O switching, its value and duration are independent of the
Low Power Mode
42MX devices have been designed with a Low Power Mode. This feature, activated with setting the
special LP pin to HIGH for a period longer than 800 ns, is particularly useful for battery-operated systems
where battery life is a primary concern. In this mode, the core of the device is turned off and the device
consumes minimal power with low standby current. In addition, all input buffers are turned off, and all
outputs and bidirectional buffers are tristated. Since the core of the device is turned off, the states of the
registers are lost. The device must be re-initialized when exiting Low Power Mode. I/Os can be driven
during LP mode, and clock pins should be driven HIGH or LOW and should not float to avoid drawing
current. To exit LP mode, the LP pin must be pulled LOW for over 200 µs to allow for charge pumps to
power up, and device initialization will begin.