TI1 DS1487N Low power rs-485 unit load multipoint transceiver Datasheet

DS1487
DS1487 Low Power RS-485 ¼ Unit Load Multipoint Transceiver
Literature Number: SNLS132
DS1487
Low Power RS-485 1⁄4 Unit Load Multipoint Transceiver
General Description
Features
The DS1487 is a low-power transceiver for RS-485 and
RS-422 communication. The device contains one driver and
one receiver. The drivers slew rate allows for operation up to
2.0 Mbps (see Applications Information section). The transceiver presents 1⁄4 unit loading to the RS-485 bus allowing up
to 128 nodes to be connected together without the use of repeaters.
The transceiver draws 200 µA of supply current when unloaded or fully loaded with the driver disabled and operates
from a single +5V supply.
The driver is short-circuit current limited and is protected
against excessive power dissipation by thermal shutdown
circuitry that places the driver outputs into TRI-STATE ®
(High Impedance state) under fault conditions. The driver
guarantees a minimum of 1.5V differential output voltage
with maximum loading across the common mode range
(VOD3).
The receiver has a failsafe feature that guarantees a
logic-high output if the input is open circuit.
The DS1487 is available in surface mount and DIP packages.
n
n
n
n
n
n
n
Connection and Logic Diagram
Truth Table
n
n
n
n
Meets TIA/EIA RS-485 multipoint standard
Allows up to 128 transceivers on the bus (1⁄4 U.L.)
Guaranteed full load output voltage (VOD3)
Low quiescent current: 200 µA typ
−7V to +12V common-mode input voltage range
TRI-STATE outputs on driver and receiver
AC performance:
— Driver transition time: 25 ns typ
— Driver propagation delay: 40 ns typ
— Driver skew: 1 ns typ
— Receiver propagation delay: 200 ns typ
— Receiver skew: 20 ns typ
Half-duplex flow through pinout
Operates from a single 5V supply
Current-limiting and thermal shutdown for driver
overload protection
Pin and functional compatible with MAX1487
DRIVER SECTION
DIP and SOIC
RE
(Note 1)
DE
DI
A
B
X
H
H
H
L
X
H
L
L
H
X
L
X
Z
Z
RECEIVER SECTION
DS012920-1
*Note: Non Terminated, Open Input only
Order Number
Temp. Range
Package/###
DS1487N
0˚C to +70˚C
DIP/N08E
DS1487M
0˚C to +70˚C
SOP/M08A
RE
(Note 1)
DE
A-B
RO
L
L
≥+0.2V
H
L
L
≤−0.2V
L
H
X
X
Z
L
L
OPEN (Note 1)
H
X = indeterminate
Z = TRI-STATE
Note 1: Non Terminated, Open Input only
TRI-STATE ® is a registered trademark of National Semiconductor Corporation.
© 2000 National Semiconductor Corporation
DS012920
www.national.com
DS1487 Low Power RS-485 1⁄4 Unit Load Multipoint Transceiver
July 1998
DS1487
Absolute Maximum Ratings (Note 2)
M Package
N Package
Storage Temperature Range
Lead Temperature Range
(Soldering, 4 sec.)
ESD (HBM)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (VCC)
+12V
Enable Input Voltage
(RE (Note 1), DE)
−0.5V to (VCC + 0.5V)
Driver Input Voltage (DI)
−0.5V to (VCC + 0.5V)
Driver Output Voltage (A, B)
−14V to +14V
Receiver Input Voltage (A, B)
−14V to +14V
Receiver Output Voltage (RO)
−0.5V to (VCC + 0.5V)
Maximum Package Power Dissipation @ +25˚C
M Package
1.19W
N Package
0.74W
Derate M Package 9.5 mW/˚C above +25˚C
Derate N Package 6.0 mW/˚C above +25˚C
Maximum Package Power Dissipation @ +70˚C
0.76W
0.47W
−65˚C to +150˚C
+260˚C
≥2 kV
Recommended Operating
Conditions
Supply Voltage (VCC)
Operating Free Air
Temperature (TA)
DS1487
Bus Common Mode Voltage
Min
+4.75
Typ
+5.0
0
−7
+25
Max Units
+5.25
V
+70
+12
˚C
V
Electrical Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 3, 4)
Symbol
Parameter
Conditions
Pin
Min
Typ Max Units
A, B
1.5
5
VOD1
Differential Driver Output Voltage
(No Load)
VOD2
Differential Driver Output Voltage
RL = 50Ω, (RS422), Figure 1
2
2.8
with Load
RL = 27Ω, (RS485), Figure 1
1.5
2.3
Change in Magnitude of Output
RL = 27Ω or 50Ω (Note 5)
∆VOD
V
V
5
V
0.2
|V|
5
V
3
V
0.2
|V|
Differential Voltage
VOD3
Differential Driver Output Voltage —
R1 = 54Ω, R2 = 375Ω
Full Load with Max VCM
VTEST = −7V to +12V, Figure 2
VOC
Driver Common-Mode Output Voltage
RL = 27Ω or 50Ω, Figure 1
∆VOC
Change in Magnitude of
Common-Mode Output Voltage
RL = 27Ω or 50Ω, Figure 1 (Note 5)
1.5
2.0
0
VIH
Input High Voltage
DI, DE,
VIL
Input Low Voltage
RE (Note 1)
IIN1
Input Current
IIN2
Input Current (Note 6)
VIN = +12V
DE = 0V, VCC = 0V or 5.25V
VIN = −7V
VTH
Receiver Differential Threshold
Voltage
−7V ≤ VCM ≤ +12V
∆VTH
Receiver Input Hysteresis
VCM = 0V
VOH
Receiver Output High Voltage
IO = −4 mA, VID = 0.2V
VOL
Receiver Output Low Voltage
IO = 4 mA, VID = −0.2V
0.5
V
IOZR
TRI-STATE Output Current at
Receiver
0.4V ≤ VO ≤ 2.4V
±1
µA
2.0
V
±2
µA
250
µA
0 −100 −200
µA
VIN = 0V or VCC
A, B
0
190
−0.2
0.2
70
RO
RIN
Receiver Input Resistance
−7V ≤ VIN ≤ +12V
A, B
ICC
No-Load Supply Current (Note 7)
DE = VCC, RE (Note 1) = 0V or VCC
VCC
IOSD1
Driver Short Circuit Current, VO =
HIGH
−7V ≤ VO ≤ +12V
IOSD2
Driver Short Circuit Current, VO =
LOW
−7V ≤ VO ≤ +12V
IOSR
Receiver Short Circuit Current
VO = GND
48
68
200
RO
2
V
200
A, B
7
V
mV
3.5
DE = 0V, RE (Note 1) = 0V or VCC
www.national.com
V
0.8
kΩ
500
µA
500
µA
250
mA
−250
mA
85
mA
DS1487
Switching Characteristics
Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 4, 8, 9)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
RL = 54Ω, CL = 100 pF
10
40
80
ns
10
39
80
ns
tPLHD
Driver Differential Propagation Delay — Low to High
tPHLD
Driver Differential Propagation Delay — High to Low
tSKEW
Differential Skew |tPHLD − tPLHD|
0
1
10
ns
tr
Driver Rise Time
3
25
50
ns
tf
Driver Fall Time
3
25
50
ns
tZH
Driver Enable to Output High
CL = 100 pF
50
200
ns
tZL
Driver Enable to Output Low
CL = 100 pF
65
200
ns
tLZ
Driver Disable from Output Low
CL = 15 pF
80
200
ns
tHZ
Driver Disable from Output High
CL = 15 pF
80
200
ns
tPLHD
Receiver Differential Propagation Delay — Low to High
CL = 15 pF (RO)
30
190
400
ns
tPHLD
Receiver Differential Propagation Delay — High to Low
30
210
400
ns
tSKEW
Differential Skew |tPHLD − tPLHD|
0
20
50
ns
tZH
Receiver Enable to Output High
45
150
ns
CL = 15 pF
tZL
Receiver Enable to Output Low
40
150
ns
tLZ
Receiver Disable from Output Low
50
150
ns
tHZ
Receiver Disable from Output High
55
150
ns
fmax
Maximum Data Rate
(Note 10)
2.0
Mbps
Note 2: “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the devices
should be operated at these limits. The table of “Electrical Characteristics” specifies conditions of device operation.
Note 3: Current into device pins is defined as positive. Current out of device pins is defined as negative. All voltages are referenced to ground except VOD1/2/3and
VID.
Note 4: All typicals are given for: VCC = +5.0V, TA = +25˚C.
Note 5: ∆|VOD| and ∆|VOC| are changes in magnitude of VOD and VOC respectively, that occur when the input changes state.
Note 6: IIN2 includes the receiver input current and driver TRI-STATE leakage current.
Note 7: Supply current specification is valid for loaded transmitters when DE = 0V or enabled (DE = H) with no load.
Note 8: f = 1 MHz, tr and tf ≤ 6 ns, ZO = 50Ω.
Note 9: CL includes jig and probe capacitance.
Note 10: fmax is the guaranteed data rate for 50 ft of twisted pair cable. fmax may be conservatively determined from the ratio of driver transition time (tr) to the data
rate unit interval (1/fmax). Using a 10% ratio yields fmax = (0.1)/50 ns = 2.0 Mb/s. Higher data rates may be supported by allowing larger ratios.
Parameter Measurement Information
DS012920-2
FIGURE 1. VOD
DS012920-4
FIGURE 3.
DS012920-3
FIGURE 2. VOD3
3
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DS1487
Parameter Measurement
Information (Continued)
DS012920-8
FIGURE 7.
DS012920-5
DS012920-9
FIGURE 4.
FIGURE 8.
DS012920-10
*Note: Non Terminated, Open Input only
FIGURE 9.
DS012920-6
FIGURE 5.
DS012920-7
DS012920-11
FIGURE 6.
FIGURE 10.
DS012920-12
*Note: Non Terminated, Open Input only
FIGURE 11.
www.national.com
4
DS1487
Parameter Measurement Information
(Continued)
DS012920-13
*Note: Non Terminated, Open Input only
FIGURE 12.
DS012920-14
*Note: Non Terminated, Open Input only
FIGURE 13.
Pin Descriptions
Pin
#
I/O
Name
Function
1
O
RO
2
I
RE (Note 1)
3
I
DE
Driver Output Enable: The driver outputs (A and B) are enabled when DE is high; they are in
TRI-STATE when DE is low. Pins A and B also function as the receiver input pins (see below).
4
I
DI
Driver Input: A low on DI forces A low and B high while a high on DI forces A high and B low when
the driver is enabled.
5
NA
GND
6
I/O
A
Non-inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling
levels.
7
I/O
B
Inverting Driver Output and Receiver Input pin. Driver output levels conform to RS-485 signaling
levels.
8
NA
VCC
Receiver Output: If A > B by 200 mV, RO will be high; If A < B by 200 mV, RO will be low. RO will
be high also if the inputs (A and B) are open (non-terminated).
Receiver Output Enable: RO is enabled when RE (Note 1) is low; RO is in TRI-STATE when RE
(Note 1) is high.
Ground
Power Supply: 4.75V ≤ VCC ≤ 5.25V
Applications Information
The DS1487 is a low power transceiver designed for use in
RS-485 multipoint applications. The DS1487 can transmit
data up to 2.0 Mbps based on a ratio of driver transition time
to the unit interval (bit time) of 10%. This maximum data rate
may be further limited by the interconnecting media. The
DS1487 provides a 1⁄4 unit load to the RS-485 bus across the
common mode range of −7V to +12V. This allows up to 128
transceivers (1⁄4 unit load) to be connected to the bus. The
DS1487 also guarantees the driver’s output differential voltage into a worst case load that models standard termination
loads and 32 unit loads (=128 DS1487’s) referenced to the
maximum common mode voltage extremes. With a minimum
of 1.5V swing into this load, a 1.3V differential noise margin
is supported along with the standard common mode rejection range of the receivers.
5
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DS1487
Applications Information
A typical multipoint application is shown in the following figure. Note that termination is typically required but is only located at the two ends of the cable (not on every node). Commonly pull up and pull down resistors may be required at one
end of the bus to provide a failsafe bias. These resistors provide a bias to the line when all drivers are in TRI-STATE. See
National Application Note 847 for a complete discussion of
failsafe biasing of differention buses.
(Continued)
Due to the multipoint nature of the bus, contention between
drivers may occur. This will not cause damage to the drivers
since they feature short-circuit protection and also thermal
shutdown protection. Thermal shutdown senses die temperature and puts the driver outputs into TRI-STATE if a fault
condition occurs that causes excessive power dissipation
which can elevate the junction temperature to +150˚C.
DS012920-16
www.national.com
6
DS1487
Physical Dimensions
inches (millimeters) unless otherwise noted
Order Number DS1487N
NS Package Number N08E
7
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DS1487 Low Power RS-485 1⁄4 Unit Load Multipoint Transceiver
Notes
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