NSC DS485TN, DS485TMX, DS485TM, DS485N, DS485MX Datasheet

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

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.

Features

n Meets TIA/EIA RS-485 multipoint standard
n Guaranteed full load output voltage (V

OD3

)

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

Connection and Logic Diagram

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

Truth Table

DRIVER SECTION

RE

*

DE DI A B

XHHHL
XHLLH
XLXZZ

RECEIVER SECTION

RE

*

DE A-B RO

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

*

H

*

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

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

DIP and SOIC

DS012880-1

July 1998

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

© 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

CC

) +12V

Enable Input Voltage (RE

*

, DE) −0.5V to (VCC+ 0.5V)

Driver Input Voltage (DI) −0.5V to (V

CC

+ 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 (V

CC

+ 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
M Package 0.76W

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

Min Typ Max Units

Supply Voltage (V

CC

) +4.75 +5.0 +5.25 V
Operating Free Air
Temperature (T

A

)
DS485 0 +25 +70 ˚C
DS485T −40 +25 +85 ˚C

Bus Common Mode Voltage −7 +12 V

Electrical Characteristics

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

Symbol Parameter Conditions Pin Min Typ Max Units

V

OD1

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

V

OD2

Differential Driver Output Voltage R

L

=

50Ω, (RS422),

Figure 1

2 2.8 V

with Load R

L

=

27Ω, (RS485),

Figure 1

1.5 2.3 5 V

∆V

OD

Change in Magnitude of Output R

L

=

27Ω or 50Ω (Note 4) 0.2 |V|

Differential Voltage

V

OD3

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

CM

V

TEST

=

−7V to +12V,

Figure 5

V

OC

Driver Common-Mode Output Voltage R

L

=

27Ω or 50Ω,

Figure 1

3V

∆V

OC

Change in Magnitude of Common-Mode R

L

=

27Ω or 50Ω,

Figure 1

(Note 4) 0.2 |V|

Output Voltage

V

IH

Input High Voltage DI,

DE,

RE

*

2.0 V

V

IL

Input Low Voltage 0.8 V

I

IN1

Input Current V

IN

=

0V or V

CC

±

2µA

I

IN2

Input Current (Note 5) V

IN

=

+12V A, B 1.0 mA

DE=0V, V

CC

=

0V or 5.25V V

IN

=

−7V −0.8 mA

V

TH

Receiver Differential Threshold Voltage −7V ≤ VCM≤ +12V −0.2 0.2 V

∆V

TH

Receiver Input Hysteresis V

CM

=

0V 70 mV

V

OH

Receiver Output High Voltage I

O

=

−4 mA, V

ID

=

0.2V RO 3.5 V

V

OL

Receiver Output Low Voltage I

O

=

4 mA, V

ID

=

−0.2V 0.4 V

I

OZR

TRI-STATE Output Current at Receiver 0.4V ≤ VO≤ 2.4V

±

1µA

R

IN

Receiver Input Resistance −7V ≤ VIN≤ +12V A, B 12 kΩ

I

CC

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

*

=

0V or V

CC

V

CC

200 900 µA

DE=0V, RE

*

=

0V or V

CC

200 500 µA

I

OSD1

Driver Short Circuit Current, V

O

=

HIGH −7V ≤ V

O

≤ +12V A, B 35 250 mA

I

OSD2

Driver Short Circuit Current, V

O

=

LOW −7V ≤ V

O

≤ +12V 35 250 mA

I

OSR

Receiver Short Circuit Current 0V ≤ VO≤ V

CC

RO 7 85 mA

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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

Driver Differential Propagation Delay— Low to High R

L

=

54Ω,C

L

=

100 pF 10 40 65 ns

t

PHLD

Driver Differential Propagation Delay— High to Low 10 39 65 ns

t

SKEW

Differential Skew |t

PHLD−tPLHD

| 1 10 ns

t

r

Driver Rise Time 32540 ns

t

f

Driver Fall Time 32540 ns

t

ZH

Driver Enable to Output High C

L

=

100 pF 170 ns

t

ZL

Driver Enable to Output Low C

L

=

100 pF 170 ns

t

LZ

Driver Disable from Output Low C

L

=

15 pF 170 ns

t

HZ

Driver Disable from Output High C

L

=

15 pF 170 ns

t

PLHD

Receiver Differential Propagation Delay— Low to High C

L

=

15 pF (RO) 70 190 320 ns

t

PHLD

Receiver Differential Propagation Delay— High to Low 70 210 320 ns

t

SKEW

Differential Skew |t

PHLD−tPLHD

|2050ns

t

ZH

Receiver Enable to Output High C

L

=

15 pF 110 ns

t

ZL

Receiver Enable to Output Low 110 ns

t

LZ

Receiver Disable from Output Low 110 ns

t

HZ

Receiver Disable from Output High 110 ns

f

max

Maximum Data Rate (Note 9) 2.5 Mbps

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

OD1/2/3

and

V

ID

.

Note 3: All typicals are given for: V

CC

=

+5.0V, T

A

=

+25˚C.

Note 4: ∆|V

OD

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

Note 5: I

IN2

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

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

r

and tf≤ 6 ns, Z

O

=

50Ω.

Note 8: C

L

includes jig and probe capacitance.

Note 9: f

max

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

max

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

rate unit interval (1/f

max

). Using a 10%ratio yields f

max

=

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

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