Slew Rate Programming
The slew rate for the ADM5170 is controlled by a single resistor
connected between the SRA pin and GND. The slew rate is
approximately.
Slew Rate (V/µs) = 20/R
SRA
(kΩ)
Resistors between 2 kΩ and 10 kΩ may be used providing a slew
rate which may be varied from 10 V/µs to 2.2 V/µs. Figure 5 in the
Typical Performance Characteristics section shows how the slew
rate varies with R
SRA
while Figure 8 shows how the transition time
(10% to 90%) varies with R
SRA
. Waveshaping of the output allows
the user to control the level of interference (near-end crosstalk)
which may be coupled to adjacent circuits in an interconnection.
The recommended output characteristics for cable length and data
rate are given in the EIA RS-423A specifications.
Maximum Data Rate (kB/s) = 300/t (for rates from 1 kB/s to
100 kB/s).
Cable Length (feet) = 100 X t (Max Length = 4000 ft.)
where t is the transition time (in µs) for the output to swing from
10% to 90% of its steady state values. The absolute maximum data
rate is 100 kB/s and the maximum cable length is limited to 4000 ft.
Output Mode Programming
The ADM5170 has two programmable output modes which
provide different output voltage levels. The low output mode meets
the specifications of EIA standards RS-423A while the high output
mode meets the RS-232 specifications. The high output mode
provides greater output swings and is suitable for driving lines
where higher attenuation levels must be tolerated. This mode is
selected by connecting the mode select pins to the supplies, MS+ to
V
DD
and MS– to V
SS
. The low output mode is selected by connect-
ing both mode select pins MS+ and MS– to GND. This mode
provides a controlled output swing with lower output levels.
Inputs Outputs
MS+ MS– EN Data Output
GND GND 0 0 5 V to 6 V (RS-423)
GND GND 0 1 –5 V to –6 V (RS-423)
V
DD
V
SS
00 (V
DD
– 3 V) (RS-232)
1
V
DD
V
SS
01 (V
SS
+ 3 V) (RS-232)
1
X X 1 X High Z
1
Minimum Output Level.
Typical Application Circuit
A typical application circuit using a single driver in the ADM5170
is shown in Figure 4. This circuit is suitable for either RS-232 or
RS-423 communication. An ADM5180 octal receiver is used to
translate the signal back to CMOS logic level at the receiving end.
V
L
V
H
1/8
ADM5170
EN
V
SS
V
DD
TIE TO GND
FOR RS-232
INPUT
RS-232/RS-422A
TRANSMISSION
+V
–V
R
SL
1/8
ADM5180
V
L
V
H
PIN FUNCTION DESCRIPTION
Mnemonic Function
V
DD
Power Supply Input, +10 V ± 10%.
V
SS
Power Supply Input, –10 V ± 10%.
GND Ground Pin. Must be connected to 0 V.
A
I
...H
I
Digital Input to Drivers A to H.
A
O
...H
O
RS-232/RS-423 Output from Drivers A to H.
EN Enable Pin. When high, all outputs are 3-stated.
MS+, MS– Mode Select Inputs. Used to control the output
level swing. With MS+ & MS– connected to GND,
RS-423A output levels are selected. With MS+
connected to V
DD
and MS– connected to V
SS
,
RS-232 output levels are developed.
SRA Slew Rate Adjust Input. An external resistor (2 kΩ
to 10 kΩ) connected between this pin and GND is
used to control the Output Slew Rate (10 V/µs to
2.2 V/µs).
REV. 0
–4–
ADM5170
PIN CONFIGURATIONS
DIP
GND
NC = NO CONNECT
NC
A
O
H
O
H
I
B
O
C
O
C
I
F
O
F
I
E
I
A
I
B
I
G
I
G
O
D
I
E
O
D
O
V
DD
EN MS+
V
SS
SRA MS–
NC NC
NC NC
13
18
1
2
28
27
5
6
7
24
23
22
3
4
26
25
8
21
9
20
10
19
11
12
17
16
14
15
TOP VIEW
(Not to Scale)
ADM5170
PLCC
NC = NO CONNECT
G
O
F
O
E
O
V
DD
MS+
F
I
E
I
B
O
C
O
D
O
EN
V
SS
C
I
D
I
B
I
A
I
H
O
H
I
G
I
A
O
SRA
NC
NC
MS–
GND
NC
NC
NC
26
27
28 4
2
3
15 18
17
16 12
14
13
25
24
21
20
19
23
22
TOP VIEW
(Not to Scale)
1
5
6
9
10
11
7
8
ADM5170
Figure 4. RS-232/RS-423A Typical Application Circuit
