Chapter 5: Using MAX V Devices in Multi-Voltage Systems
5–3
MultiVolt I/O Operation
MultiVolt I/O Operation
MAX V devices allow the device core and I/O blocks to be powered-up with separate
supply voltages. The VCCINTpins supply power to the device core and the VCCIOpins
supply power to the device I/O buffers. The VCCINTpins are powered-up with 1.8 V
for MAX V devices. All the VCCIOpins for a given I/O bank that have MultiVolt
capability must be supplied from the same voltage level (for example, 5.0, 3.3, 2.5, 1.8,
1.5, or 1.2 V). Figure 5–2 shows how to implement a multiple-voltage system for
MAX V devices.
Figure 5–2. Implementing a Multi-Voltage System with a MAX V Device (Note 1), (2)
1.8-V
Power Supply
V
CCINT
3.3-, 2.5-, 1.8-,
1.5-, 1.2-V
Device
V
CCIO
V
CCIO
5.0-V
Device
MAX V
Device
Notes to Figure 5–2:
(1) MAX V devices can drive a 5.0-V transistor-to-transistor logic (TTL) input when VCCIO = 3.3 V. To drive a 5.0-V
CMOS, you must have an open-drain setting with an internal I/O clamp diode and external resistor.
(2) MAX V devices can be 5.0-V tolerant with the use of an external resistor and the internal I/O clamp diode on
5M1270Z and 5M2210Z devices.
5.0-V Device Compatibility
A MAX V device can drive a 5.0-V TTL device by connecting the VCCIOpins of the
MAX V device to 3.3 V. This is possible because the output high voltage (VOH) of a
3.3-V interface meets the minimum high-level voltage of 2.4 V of a 5.0-V TTL device.
A MAX V device may not correctly interoperate with a 5.0-V CMOS device if the
output of the MAX V device is connected directly to the input of the 5.0-V CMOS
device. If the MAX V device‘s VOUT is greater than VCCIO, the PMOS pull-up transistor
still conducts if the pin is driving high, preventing an external pull-up resistor from
pulling the signal to 5.0 V. To make MAX V device outputs compatible with 5.0-V
CMOS devices, configure the output pins as open-drain pins with the I/O clamp
diode enabled and use an external pull-up resistor.
December 2010 Altera Corporation
MAX V Device Handbook
ALTERA [ ALTERA CORPORATION ]
