SGS Thomson Microelectronics ST491ACN, ST491ACDR, ST491ACD, ST491ABN, ST491ABD Datasheet

ST491A

LOW POWER HIGH SPEED RS-485/RS-422 TRANSCEIVER

■ LOW SUPPLY CURRENT: 5mA MAX

■ DESIGNED FOR RS485 INTERFACE

APPLICATIONS

■ -7 TO 12 COMMON MODE INPUT VOLTAGE

RANGE

■ 70mV TYPICAL INPUT HYSTERESIS

■ DESIGNED FOR 25Mbps OPERATION

■ OPERATE FROM SINGLE 5 SUPPLY

■ ±4kV ESD PROTECTION

■ CURRENT LIMITING AND T HER MAL

SHUTDOWN FOR DRIVER OVERLOAD
PROTECTION

DESCRIPTION

The ST491A is a low power transceiver for
RS-485 and RS-422 communications. The device
contains one driver and one receiver in full duplex
configuration. The ST491A draws 5mA (typ.) of
supply current when unloaded a nd operates from
a single 5V supply.

Driver is short-circuit current limited and is
protected against ex cessive power dissipation by
thermal shutdown circuitry that place the driver
outputs into a high-impedance state. The receiver
input has a fail-safe feature that guarantees a
logic high out put if both inputs are open circuit.

DIP SOP

ORDERING CODES

Type

ST491ACN 0 to 70 °C DIP-14 25parts per tube /40tube per box
ST491ABN -40 to 85 °C DIP-14 25parts per tube / 40tube per box
ST491ACD 0 to 70 °C SO-14 (Tube) 50parts per tube / 20tube per box

ST491ABD -40 to 85 °C SO-14 (Tube) 50parts per tube / 20tube per box
ST491ACDR 0 to 70 °C SO-14 (Tape & Reel) 2500 parts per reel
ST491ABDR -40 to 85 °C SO-14 (Tape & Reel) 2500 parts per reel

Temperature

Range

Package Comments

1/12July 2003

ST491A

PIN CONFIGURA TION

PIN DESCRIPTION

PlN N° SYMBOL NAME AND FUNCTION

1 NC Not Connected
2 RO Receiver Output.
3 RE Receiver Output Enable
4 DE Driver Output Enable
5 DI Inverting Driver Input.
6 GND Ground
7 GND Ground
8 NC Not Connected

9 Y Non-inverting Driver Output
10 Z Inverting Driver Output
11 B Inverting Receiver Input
12 A Non-inverting Receiver Input
13 NC Not Connected
14

V

CC

Supply Voltage

TRUTH TABLE (DRIVER)

INPUT OUTPUTS

DI DE Y Z

LHLH
HHHL
XLZZ

X= Don’t Care; Z=High Impedance

2/12

TRUTH TABLE (RECEIVER)

INPUT OUTPUT

A-B RE RO

≥ -0.2V L H

between -0.2V to 0.2V L ?

≤ -0.2V L L

OPEN L H

XHZ

?= Irrelevant; X= Don’t Care; Z=High Impedance

ST491A

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

V

V

Y,VZ

V

A,VB

V

RO

ESD Human Body Model 3.5 KV

Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.

ELECTRICAL CHARACTERISTICS

V

=4.5Vto5.5V,TA=-40to85°C, unless otherwise specified.TypicalvaluesarereferredtoTA=25°C)

CC

Symbol Parameter Test Conditions Min. Typ. Max. Unit

I

SUPPLY

C

IN

C

YZ

C

OUT

Supply Voltage

CC

Driver Input Voltage

DI

Driver Output Voltage
Receiver Input Voltage

7V

-0.5 to 7 V

-7.5 to 12.5 V

-7.5 to 12.5 V

Receiver Output Voltage -0.3 to (VCC+ 0.3)

No Load Supply Current 2 5 mA
Input Capacitance 1.8 pF
Driver Output Capacitance 1.2 pF
Output Capacitance 2.3 pF

V

TRANSMITTER ELECTRICAL CHARACTERISTICS

V

=4.5Vto5.5V,TA= -40 to 85°C,unless oth erwise specified. Typical v alues arereferred to Ta= 25°C)

CC

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

V

V

∆V

V

∆V

I

I

OSD

V

Differential Drive Output

OD1

(No load)
Differential Drive Output

OD2

(With Load)
Differential Drive Output

OD3

(With Load)
Change in magnitude of

OD

Driver Differential Output

RL=54Ω(RS-422) (Figure 1) 1.5 2.6 5 V

RL= 100Ω (RS-422) (Figure 1) 2 3 V

=54Ωor 100Ω (Figure 1) 0 0.2 V

R

L

Voltage for Complementary
Output States (Note1)

Driver Common Mode

OC

Output Voltage
Change in magnitude of

OC

Driver Common Mode

RL=54Ω(Figure 1) 1 3 V

=54Ω(Figure 1) 0 0.2 V

R

L

Output Voltage (Note1)
Power Off Output Current VCC=0V VO=-7V to 12V ± 100 µA

OFF

Driver Short Circuit Output

VO=-7V to 12V ± 35 ± 250 mA

Current

V

Input Logic Threshold Low 0.8 V

IL

Input Logic Threshold High 2 V

IH

V

CC

V

3/12

ST491A

RECEIVER ELECTRICAL CHARACTERISTICS

V

=4.5Vto5.5V,TA= -40 to 85°C,unless oth erwise specified. Typical v alues arereferred to Ta= 25°C)

CC

Symbol Parameter Test Conditions Min. Typ. Max. Unit

I

Input Current (A, B) other input=0V

V

∆V

V

V

R

IN

Receiver Differential

TH

Threshold Voltage
Receiver Input Hysteresis VCM=0V 70 mV

TH

Receiver Output High

OH

Voltage
Receiver Output Low

OL

Voltage
Receiver Input Resistance VCM= -7V to 12V 12 24 KΩ

RIN

= 0 or 5.25V

V

CC

VCM= -7V to 12V -0.2 0.2 V

I

= -8mA, VID= 200mV 3.5 4.7 V

OUT

I

= 8mA, VID= -200mV 0.3 0.5 V

OUT

DRIVER SWITCHING CHARACTERISTICS

=4.5Vto5.5V,TA=-40to 85°C, unlessotherwise specified. Typicalvalues are referred toTa=25°C)

V

CC

Symbol Parameter Test Conditions Min. Typ. Max. Unit

Maximum Data Rate Jitter <5% 25 50 Mbps

D

R

t

PLH

t

PHL

t

SKEW

t

TLH

t

THL

t

PZL

t

PZH

t

PHZ

t

PLZ

Propagation Delay Input to
Output

Differential Output Delay
Skew

Rise or Fall Differential
Time

Output Enable Time CL= 50pF S1 Closed 14 25 ns
Output Enable Time CL= 50pF S2 Closed 14 25 ns
Output Disable Time CL= 15pF S2 Closed 10 25 ns
Output Disable Time CL= 15pF S1 Closed 16 25 ns

RL=54Ω CL1=CL2=50pF, (Figure 1) 10 16 ns

RL=54Ω CL1=CL2=50pF, (Figure 1) 1 3 ns

RL=54Ω CL1=CL2=50pF, (Figure 1) 8 12 ns

V

=12V 0.5 1 mA

IN

=-7V -0.35 -0.8 mA

V

IN

RECEIVER SWITCHING CHARACTERISTICS

=4.5Vto5.5V,TA=-40to85°C, unless otherwisespecified.Typicalvalues are ref erred toTa=25°C)

V

CC

Symbol Parameter Test Conditions Min. Typ. Max. Unit

Propagation Delay Input to

t

PLH

Output

t

PHL

t

SKD|tPLH -tPHL

Skew

t
t

t
t

Rise or Fall Time CL= 15pF (Figures 2,4) 6 ns

TLH
THL

Output Enable Time CRL= 15pF S1 Closed 6 12 ns

t

PZL

Output Enable Time CRL= 15pF S2 Closed 7 12 ns

PZH

Output Disable Time CRL= 15pF S2 Closed 6 12 ns

PHZ

Output Disable Time CRL= 15pF S1 Closed 6 12 ns

t

PLZ

4/12

| Receiver Output

CL= 15pF (Figures 2,4) 19 30 ns

CL= 15pF (Figures 2,4) 1 3 ns