S1K50000 Epson Electronics America, Inc., S1K50000 Datasheet - Page 48

• Manufacturer Part Number: S1K50000
• Description: Design Guide S1k50000 Series
• Manufacturer: Epson Electronics America, Inc.

STANDARD CELL S1K50000 SERIES
DESIGN GUIDE
(4) List of Fail-Safe cells
• Fail-Safe input buffers
• Fail-Safe output buffers
Note: The indicated resistance values apply to the case where V
LVTTL
LVTTL
Schmitt
This is an input cell with the protective diode on the V
is used in cases in which, in a single power-supply system, high-voltage signals above
V
2.0 V). The input level of this buffer when V
1) N-channel open-drain type
2) Tri-state type
Input Level
DD
This output buffer is used in cases in which, in a 3-V single-power-supply system, 5.0-
V signals are output. With the P-channel removed, this type of buffer can only output
a low-level signal but, by tying the pull-up resistors external to the standard cell to 5 V,
it can send 5-V signals to external 5-V devices.
In ordinary tri-state output buffers, if a 5-V system voltage propagates while their
outputs are disabled (Hi-Z state), DC current flows into the internal part of the ASIC
chip. The Fail-Safe cell, however, is constructed so as to prevent such a current from
flowing in. Furthermore, it can output a 3-V-system full-swing signal. Unlike the N-
channel open-drain type, however, this type of Fail-Safe cell cannot have its output
pulled high to 5 V through the addition of a pull-up resistor external to the standard
cell.
are entered (for example, 5-V signals when V
XIDC
XIDH
Resistor
Without
Table 3-4-1 Fail-Safe Input Buffers
Chapter 3: Types of Input/Output Buffers and Usage Precautions
XIDCD1
XIDHD1
50 k
EPSON
Pull-down*
DD
= 2.0 V is the CMOS level.
XIDCD2
XIDHD2
100 k
DD
DD
= 3.3 V, or 3.3-V signals when V
DD
= 3.3 V.
side eliminated. This input buffer
XIBBP1
50 k
—
Pull-up*
XIBBP2
100 k
(V
DD
—
= 3.3 V)
DD
43
=