N74F85N
Philips Semiconductors
74F85
4-bit magnitude comparator
Product specification 1994 Sep 27
INTEGRATED CIRCUITS
IC15 Data Handbook
Philips Semiconductors Product specification
74F854-bit magnitude comparator
2
September 27, 1994 853–0055 13903
FEA TURES
•High-impedance NPN base inputs for reduced loading
(20µA in High and Low states)
•Magnitude comparison of any binary words
•Serial or parallel expansion without extra gating
DESCRIPTION
The 74F85 is a 4-bit magnitude comparator that can be expanded to
almost any length. It compares two 4-bit binary, BCD, or other
monotonic codes and presents the three possible magnitude results
at the outputs. The 4-bit inputs are weighted (A0–A3) and (B0–B3)
where A3 and B3 are the most significant bits. The operation of the
74F85 is described in the Function Table, showing all possible logic
conditions. The upper part of the table describes the normal
operation under all conditions that will occur in a single device or in
a series expansion scheme. In the upper part of the table the three
outputs are mutually exclusive. In the lower part of the table, the
outputs reflect the feed-forward conditions that exist in the parallel
expansion scheme. The expansion inputs I
A>B
, and I
A=B
and I
A<B
are the least significant bit positions. When used for series
expansion, the A>B, A=B and A<B outputs of the lease significant
word are connected to the corresponding I
A>B
, I
A=B
and I
A<B
inputs
of the next higher stage. Stages can be added in this manner to any
length, but a propagation delay penalty of about 15ns is added with
each additional stage. For proper operation, the expansion inputs of
the least significant word should be tied as follows: I
A>B
= Low,
I
A=B
= High, and I
A<B
= Low.
PIN CONFIGURATION
16
15
14
13
12
11
107
6
5
4
3
2
1
A<B
V
CC
A1
B1
A0
A2
A3
B2
B3
I
A<B
A=B
I
A=B
I
A>B
A>B
98GND B0
SF00075
TYPE TYPICAL
PROPAGATION
DELAY
TYPICAL
SUPPLY CURRENT
(TOTAL)
74F85 7.0ns 40mA
ORDERING INFORMATION
DESCRIPTION
COMMERCIAL RANGE
V
CC
= 5V ±10%,
T
amb
= 0°C to +70°C
PKG DWG #
16-pin plastic DIP N74F85N SOT38-4
16-pin plastic SO N74F85D SOT162-1
INPUT AND OUTPUT LOADING AND FAN OUT TABLE
PINS DESCRIPTION 74F (U.L.) HIGH/LOW LOAD VALUE HIGH/LOW
A0–A3 Comparing inputs 1.0/0.033 20µA/20µA
B0–B3 Comparing inputs 1.0/0.033 20µA/20µA
I
A<B
, I
A=B
, I
A>B
Expansion inputs (active High) 1.0/0.033 20µA/20µA
A<B, A=B, A>B Data outputs (active High) 50/33 1.0mA/20mA
NOTE: One (1.0) FAST unit load is defined as: 20µA in the High state and 0.6mA in the Low state.
LOGIC SYMBOL
567
10 12 13 15 9 11 14
V
CC
= Pin 16
GND = Pin 8
SF00076
1
A0 A1 A2 A3 B0 B1 B2 B3
A>B A=B A<B
I
A>B
I
A=B
I
A<B
2
3
4
IEC/IEEE SYMBOL
SF00077
COMP
7
6
5
10
12
13
15
9
11
14
1
2
3
4
0
3
0
3
<
=
>
P<Q
P=Q
P>Q
P
Q
Philips Semiconductors Product specification
74F854-bit magnitude comparator
September 27, 1994
3
LOGIC DIAGRAM
5
6
7
A>B
A=B
A<B
V
CC
= Pin 16
GND = Pin 8
15
1
13
14
2
3
4
12
11
10
9
A3
B3
A2
B2
I
A<B
I
A=B
I
A>B
A1
B1
A0
B0
SF00078
FUNCTION TABLE
COMPARING INPUTS EXPANSION INPUTS OUTPUTS
A3,B3 A2,B2 A1,B1 A0,B0 I
A>B
I
A<B
I
A=B
A>B A<B A=B
A3>B3 X X X X X X H L L
A3<B3 XXXXXXLHL
A3=B3 A2>B2 X X X XXHLL
A3=B3 A2<B2 X X X XXLHL
A3=B3 A2=B2 A1>B1 X X X X H L L
A3=B3 A2=B2 A1<B1 X X XXLHL
A3=B3 A2=B2 A1=B1 A0>B0 X XXHLL
A3=B3 A2=B2 A1=B1 A0<B0 X XXLHL
A3=B3 A2=B2 A1=B1 A0=B0 H L L H L L
A3=B3 A2=B2 A1=B1 A0=B0 L HLLHL
A3=B3 A2=B2 A1=B1 A0=B0 L LHLLH
A3=B3 A2=B2 A1=B1 A0=B0 X X H L L H
A3=B3 A2=B2 A1=B1 A0=B0 H HLLLL
A3=B3 A2=B2 A1=B1 A0=B0 L L L H H L
H = High voltage level
L = Low voltage level
X = Don’t care
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