
1.4 Product Family
Introduction
STDM110
1-14
Samsung ASIC
1.4.4 INPUT/OUTPUT CELLS
There are about seven hundreds different I/O buffers. Each I/O cell is
implemented solely on the basic I/O cell architecture which forms the periphery
of a chip.
A test logic is provided to enable the efficient parametric (threshold voltage)
testing on input buffers including LVCMOS and TTL level converters, Schmitt
trigger input buffers, clock drivers and oscillator buffers. Pull-up and pull-down
resistors are optional features.
Three basic types of output buffers (non-inverting, tri-state and open drain) are
available in a range of driving capabilities from 1mA to 12mA for 2.5V, 3.3V drive
and from 1mA to 3mA for 5.0V tolerant drive. One or two levels of slew rate
controls are provided for each buffer type (except 1mA, 2mA and 3mA buffers) to
reduce output power/ground noise and signal ringing, especially in simultaneous
switching outputs.
Bi-directional buffers are combinations of input buffers and output buffers (tri-
state and open drain) in a single unit. The I/O structure has been fully
characterized for ESD protection and latch-up resistance.
For user's convenience, STDM110 library provides 100K
pull-down and pull-up
resistance respectively.
1.4.4.1
I/O Applications
To support mixed voltage environments, LVTTL, LVCMOS and Schmitt trigger I/
O cells are available at 2.5V, 3.3V interface and 5V tolerant interface. The I/O
application diagram is as follows.
Figure 1-6.
I/O Applications
1.4.4.2
I/O Cell Drives Options
To provide designers with the greater flexibility, each I/O buffer can be selected
among various current levels (e.g., 1mA, 2mA,..., 12mA). The choice of current-
level for I/O buffers affects their propagation delay and current noise.
The slew rate control helps decrease the system noise and output signal
overshoot/undershoot caused by the switching of output buffers. The output edge
rate can be slowed down by selecting the high slew rate control cells.
2.5V
B
T
D
3.3V
B
T
D
2.5
3.3
2.5V
C
S
3.3V
C
S
T
Internal Circuit
operating
voltage: 1.8V
2.5
3.3/
5V
tolerant
Input Buffer
Output Buffer