National Semiconductor DS485 Technical data

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DS485
Low Power RS-485/RS-422 Multipoint Transceiver

DS485 Low Power RS-485/RS-422 Multipoint Transceiver

July 1998

General Description

The DS485 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

2.5 Mbps (see Applications Information section).
The transceiver draws 200 µA of supply current when un-

loaded 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
(V

).

OD3

The receiver has a failsafe feature that guarantees a
logic-high output if the input is open circuit.

The DS485 is available in surface mount and DIP packages
and is characterized for Industrial and Commercial tempera­ture range operation.

Connection and Logic Diagram

DIP and SOIC

DS012880-1

Order Number Temp. Range Package/

DS485N 0˚C to +70˚C DIP/N08E
DS485M 0˚C to +70˚C SOP/M08A
DS485TN −40˚C to +85˚C DIP/N08E
DS485TM −40˚C to +85˚C SOP/M08A

###

Features

n Meets TIA/EIA RS-485 multipoint standard
n Guaranteed full load output voltage (V
n Low quiescent current: 200 µA typ
n −7V to +12V common-mode input voltage range
n TRI-STATE outputs on driver and receiver
n 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

n Half-duplex flow through pinout
n Operates from a single 5V supply
n Allows up to 32 transceivers on the bus
n Current-limiting and thermal shutdown for driver

overload protection

n Industrial temperature range operation
n Pin and functional compatible with MAX485 and LTC485

OD3

)

Truth Table

DRIVER SECTION

*

RE

XHHHL
XHLLH
XLXZZ

RECEIVER SECTION

RE

LL ≥+0.2V H
LL ≤−0.2V L
HX X Z
L L OPEN

*

Note: Non Terminated, Open Input only
X=indeterminate
Z=TRI-STATE

DE DI A B

*

DE A-B RO

*

H

TRI-STATE®is a registered trademark of National Semiconductor Corporation.

© 1999 National Semiconductor Corporation DS012880 www.national.com

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Supply Voltage (V
Enable Input Voltage (RE
Driver Input Voltage (DI) −0.5V to (V
Driver Output Voltage (A, B) −14V to +14V
Receiver Input Voltage (A, B) −14V to +14V
Receiver Output Voltage (RO) −0.5V to (V

Maximum Package Power Dissipation

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

) +12V

CC

*

, DE) −0.5V to (VCC+ 0.5V)

CC

@

@

CC

+25˚C

+70˚C

+ 0.5V)

+ 0.5V)

N Package 0.47W
Storage Temperature Range −65˚C to +150˚C
Lead Temperature Range

(Soldering, 4 sec.) +260˚C
ESD (HBM) ≥2kV

Recommended Operating
Conditions

Supply Voltage (V

) +4.75 +5.0 +5.25 V

CC

Operating Free Air
Temperature (T

)

A

DS485 0 +25 +70 ˚C

DS485T −40 +25 +85 ˚C
Bus Common Mode Voltage −7 +12 V

Min Typ Max Units

M Package 0.76W

Electrical Characteristics

Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 2, 3)

Symbol Parameter Conditions Pin Min Typ Max Units

V
V

∆V

V

V
∆V

V
V
I

IN1

I

IN2

V
∆V
V
V
I

OZR

R
I

CC

I

OSD1

I

OSD2

I

OSR

Differential Driver Output Voltage (No Load) A, B 5 V

OD1

Differential Driver Output Voltage R

OD2

with Load R
Change in Magnitude of Output R

OD

=

50Ω, (RS422),

L

=

27Ω, (RS485),

L

=

27Ω or 50Ω (Note 4) 0.2 |V|

L

Figure 1
Figure 1

2 2.8 V

1.5 2.3 5 V

Differential Voltage
Differential Driver Output Voltage— R1=54Ω,R2=375Ω 1.5 2.0 5 V

OD3

Full Load with Max V
Driver Common-Mode Output Voltage R

OC

Change in Magnitude of Common-Mode R

OC

CM

V

TEST

=

L

=

L

=

−7V to +12V,
27Ω or 50Ω,
27Ω or 50Ω,

Figure 5
Figure 1
Figure 1

(Note 4) 0.2 |V|
Output Voltage
Input High Voltage DI,

IH

Input Low Voltage 0.8 V

IL

Input Current V
Input Current (Note 5) V
DE=0V, V
Receiver Differential Threshold Voltage −7V ≤ VCM≤ +12V −0.2 0.2 V

TH

Receiver Input Hysteresis V

TH

Receiver Output High Voltage I

OH

Receiver Output Low Voltage I

OL

=

0V or 5.25V V

CC

=

0V or V

IN

=

IN

=

IN

CM

=

O

=

O

CC

+12V A, B 1.0 mA

−7V −0.8 mA

=

0V 70 mV

−4 mA, V
4 mA, V

=

0.2V RO 3.5 V

ID

=

−0.2V 0.4 V

ID

2.0 V

DE,

*

RE

TRI-STATE Output Current at Receiver 0.4V ≤ VO≤ 2.4V
Receiver Input Resistance −7V ≤ VIN≤ +12V A, B 12 kΩ

IN

No-Load Supply Current (Note 6) DE=VCC,RE

Driver Short Circuit Current, V
Driver Short Circuit Current, V

=

HIGH −7V ≤ V

O

=

LOW −7V ≤ V

O

Receiver Short Circuit Current 0V ≤ VO≤ V

DE=0V, RE

=

*

0V or V

0V or V

CC

CC

=

*

≤ +12V A, B 35 250 mA

O

≤ +12V 35 250 mA

O

CC

V

CC

RO 7 85 mA

3V

±

2µA

±

1µA

200 900 µA
200 500 µA

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Switching Characteristics

Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 3, 7, 8)

Symbol Parameter Conditions Min Typ Max Units

t

PLHD

t

PHLD

t

SKEW

t

r

t

f

t

ZH

t

ZL

t

LZ

t

HZ

t

PLHD

t

PHLD

t

SKEW

t

ZH

t

ZL

t

LZ

t

HZ

f

max

Note 1: “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 2: Current into device pins is defined as positive. Current out of device pins is defined as negative. All voltages are referenced to ground except V
V

Note 3: All typicals are given for: V
Note 4: ∆|V
Note 5: I
Note 6: Supply current specification is valid for loaded transmitters when DE=0V or enabled (DE=H) with no load.
Note 7: f=1 MHz, t
Note 8: C
Note 9: f

rate unit interval (1/f

Driver Differential Propagation Delay— Low to High R
Driver Differential Propagation Delay— High to Low 10 39 65 ns
Differential Skew |t

PHLD−tPLHD

| 1 10 ns
Driver Rise Time 32540 ns
Driver Fall Time 32540 ns
Driver Enable to Output High C
Driver Enable to Output Low C
Driver Disable from Output Low C
Driver Disable from Output High C
Receiver Differential Propagation Delay— Low to High C
Receiver Differential Propagation Delay— High to Low 70 210 320 ns
Differential Skew |t

PHLD−tPLHD

|2050ns
Receiver Enable to Output High C
Receiver Enable to Output Low 110 ns
Receiver Disable from Output Low 110 ns
Receiver Disable from Output High 110 ns
Maximum Data Rate (Note 9) 2.5 Mbps

.

ID

| and ∆|VOC| are changes in magnitude of VODand VOCrespectively, that occur when the input changes state.

OD

includes the receiver input current and driver TRI-STATE leakage current.

IN2

and tf≤ 6 ns, Z

r

includes jig and probe capacitance.

L

is the guaranteed data rate for 50 ft of twisted pair cable. f

max

). Using a 10%ratio yields f

max

=

CC

O

+5.0V, T

=

50Ω.

=

+25˚C.

A

may be conservatively determined from the ratio of driver transition time (tr) to the data

=

(0.1)/40 ns=2.5 Mb/s. Higher data rates may be supported by allowing larger ratios.

max

max

=

L

=

L

=

L

=

L

=

L

=

L

=

L

=

54Ω,C

100 pF 10 40 65 ns

L

100 pF 170 ns
100 pF 170 ns
15 pF 170 ns
15 pF 170 ns
15 pF (RO) 70 190 320 ns

15 pF 110 ns

OD1/2/3

and

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