ATF1504BE ATMEL Corporation, ATF1504BE Datasheet - Page 8

• Manufacturer Part Number: ATF1504BE
• Description: High Speed CPLD
• Manufacturer: ATMEL Corporation

2. Input and I/O Pins
2.1
8
Programmable Pin-keeper Option for Inputs and I/Os
ATF1504BE
The ATF1504BE offers the option of programming each of its input or I/O pin so that pin-keeper
circuit can be utilized. When any pin is driven high or low and then subsequently left floating, it
will stay at that previous high or low level. This circuitry prevents unused input and I/O lines from
floating to intermediate voltage levels, which causes unnecessary power consumption and sys-
tem noise. The keeper circuits eliminate the need for external pull-up resistors and eliminate
their DC power consumption.
Figure 2-1
I/O pin. The pin-keeper circuit is a weak feedback latch and has an effective resistance that is
approximately 50 kΩ.
Figure 2-1.
Figure 2-2.
shows the pin-keeper circuit for an Input Pin and
Input with Programmable Pin-keeper
I/O with Programmable Pin-keeper
V
CCIO
V
CCINT
50K
50K
Figure 2-2
V
CCINT
shows the same for an
3637A–PLD–11/06