afs600 Actel Corporation, afs600 Datasheet - Page 146

• Manufacturer Part Number: afs600
• Description: Actel Fusion Programmable System Chips Mixed-signal Family With Optional Arm Support
• Manufacturer: Actel Corporation

Solution 4
Figure 2-98 • Solution 4
Table 2-74 • Comparison Table for 5 V–Compliant Receiver Scheme
5 V Output Tolerance
Fusion I/Os must be set to 3.3 V LVTTL or 3.3 V LVCMOS
mode to reliably drive 5 V TTL receivers. It is also critical
that there be NO external I/O pull-up resistor to 5 V, since
this resistor would pull the I/O pad voltage beyond the
3.6 V absolute maximum value and consequently cause
damage to the I/O.
2 -1 3 2
Scheme
1
2
3
4
Notes:
1. Speed and current consumption increase as the board resistance values decrease.
2. Resistor values ensure I/O diode long-term reliability.
Actel Fusion Programmable System Chips
Two resistors
Resistor and Zener 3.3 V
Bus switch
Minimum resistor value
•
•
•
R = 47 Ω at T
R = 150 Ω at T
R = 420 Ω at T
Board Components
J
= 70°C
J
J
= 85°C
= 100°C
2
5.5 V
Off-Chip
Rext1
Available for LVCMOS 2.5 V / 5.0 V.
Low to high
Requires one board resistor.
Medium
Medium
Speed
High
A d v a n c e d v 1 . 4
Solution 4
On-Chip
1
Fusion I/O Input
Limited by transmitter's drive strength
Limited by transmitter's drive strength
N/A
Maximum diode current at 100% duty cycle, signal constantly at '1'
•
•
•
For duty cycles other than 100%, the currents can be increased by
a factor = 1 / (duty cycle).
Example: 20% duty cycle at 70°C
Maximum current = (1 / 0.2) * 52.7 mA = 5 * 52.7 mA = 263.5 mA
When set to 3.3 V LVTTL or 3.3 V LVCMOS mode, Fusion I/Os
can directly drive signals into 5 V TTL receivers. In fact,
V
3.3 V LVCMOS modes exceed the V
level requirements of 5 V TTL receivers. Therefore, level
'1' and level '0' will be recognized correctly by 5 V TTL
receivers.
2.5 V On-Chip
52.7 mA at T
16.5 mA at T
5.9 mA at T
OL
= 0.4 V and V
Clamp
Diode
J
= 100°C / 10-year lifetime
J
J
=70°C / 10-year lifetime
= 85°C / 10-year lifetime
Current Limitations
2.5 V
OH
= 2.4 V in both 3.3 V LVTTL and
IL
= 0.8 V and V
IH
= 2 V