ST ST485EB, ST485EC, ST485EX User Manual

ST485EB ST485EC - ST485EX

±15 kV ESD protected, low power RS-485/RS-422 transceiver

Features

■Low quiescent current: 300 µA

■Designed for RS-485 interface application

■- 7 V to 12 V common mode input voltage range

■Driver maintains high impedance in 3-state or with the power OFF

■70 mV typical input hysteresis

■30 ns propagation delay, 5 ns skew

■Operates from a single 5 V supply

■Current limiting and thermal shutdown for driver overload protection

■ESD protection:

–± 15 kV (HBM)

–± 8 kV (IEC-1000-4-2 contact discharge)

■Allows up to 256 transceivers on the bus

SO-8

Driver is short-circuit current limited and is protected against excessive power dissipation by thermal shutdown circuitry that place the driver outputs into a high-impedance state.

The ST485E is designed for bi-directional data communications on multipoint bus transmission lines (half-duplex applications).

Description

The ST485E is a low power transceiver for RS485 and RS-422 communication. Each driver output and receiver input is protected against

± 15 kV electrostatic discharge (HBM) (ESD) shocks, without latch-up. These parts contain one driver and one receiver in half duplex configuration.

This transceiver draws 300 µA (typ.) of supply current when unloaded or fully loaded with disabled drivers.

It operates from a single 5 V supply.

	Table 1.	Device summary
	Order codes		Temperature	Package	Packaging
			range
	ST485EBD		- 40 to 85 °C	SO-8 (tube)	100 parts per tube / 20 tube per box
	ST485ECDR		0 to 70 °C	SO-8 (tape and reel)	2500 parts per reel
	ST485EBDR		- 40 to 85 °C	SO-8 (tape and reel)	2500 parts per reel
	ST485EXDR		- 55 to 125 °C	SO-8 (tape and reel)	2500 parts per reel
	February 2009			Rev 14	1/18

www.st.com

Contents	ST485EB - ST485EC - ST485EX

Contents

1	Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 3
2	Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	4
3	Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
4	Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
5	Test circuit and typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . .	9
6	Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	14
7	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17

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ST485EB - ST485EC - ST485EX	Pin configuration

1 Pin configuration

Figure 1. Pin connections (top view)

Table 2.	Pin description
Pin n°		Symbol			Name and function
	1	RO			Receiver output
	2				Receiver output enable
			RE
	3		DE		Driver output enable
	4		DI		Driver input
	5	GND			Ground
	6		A		Non-inverting receiver input and non-inverting driver output
	7		B		Inverting receiver input and inverting driver output
	8	VCC			Supply voltage

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Truth tables					ST485EB - ST485EC - ST485EX
2	Truth tables
Table 3.	Truth table (driver)
		Inputs				Outputs
RE		DE	DI		B		A
X		H	H		L		H
X		H	L		H		L
X		L	X		Z		Z
Note:	X = Don’t care; Z = High impedance
Table 4.	Truth table (receiver)
		Inputs				Outputs
RE		DE	A-B			RO
L		L	≥ +0.2V			H
L		L	≤ -0.2V			L
L		L	Inputs open			H
H		L	X			Z
Note:	X = Don’t care; Z = High impedance

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ST485EB - ST485EC - ST485EX				Maximum ratings
3	Maximum ratings
Table 5.	Absolute maximum ratings
Symbol			Parameter	Value	Unit
VCC	Supply voltage			7	V
VI	Control input voltage		DE)	-0.5 to (VCC + 0.5)	V
		(RE,
VDI	Driver input voltage (DI)			-0.5 to (VCC + 0.5)	V
VDO	Driver output voltage (A, B)			± 14	V
VRI	Receiver input voltage (A, B)			± 14	V
VRO	Receiver output voltage (RO)			-0.5 to (VCC + 0.5)	V
Note:	Absolute maximum ratings are those values beyond which damage to the device may occur.
	Functional operation under these is not implied.

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Electrical characteristics

ST485EB - ST485EC - ST485EX

4

Electrical characteristics

Table 6.

ESD performance: transmitter outputs, receiver inputs

Symbol

Parameter

Test conditions

Min.

Typ.

Max.

Unit

ESD

ESD protection voltage

Human body model

±15

kV

ESD

ESD protection voltage

IEC-1000-4-2

±8

kV

VCC = 5 V ± 5 %, TA = TMIN to TMAX, unless otherwise specified. Typical values are referred

to TA = 25 °C

Table 7.

DC electrical characteristics

Symbol

Parameter

Test conditions (1)

Min.

Typ.

Max.

Unit

VOD1

Differential driver output (no

5

V

load)

VOD2

Differential driver output

RL = 27 Ω (RS-485) (Figure 2)

1.5

5

V

(with load)

RL = 50 Ω (RS-422) (Figure 2.)

5

V

Change in magnitude of

VOD

driver differential output

RL = 27 Ω or 50 Ω (Figure 2)

0.2

V

voltage for complementary

output states

V

Driver common-mode output

R

L

= 27 Ω or 50 Ω (Figure 2)

3

V

OC

voltage

Change in magnitude of

V

driver common-mode output

R

L

= 27 Ω or 50 Ω (Figure 2)

0.2

V

OC

voltage for complementary

output states

VIH

Input high voltage

DE, DI

2.0

V

RE,

VIL

Input low voltage

DE, DI

0.8

V

RE,

IIN1

Input current

DE, DI

± 2

µA

RE,

VCM = 0 V or 5.25 V, VDE = 0 V

1

mA

IIN2

Input current (A, B)

VIN = 12 V

VIN = -7 V

-0.8

mA

VTH

Receiver differential

VCM = -7 to 12 V

-0.2

0.2

V

threshold voltage

VTH

Receiver input hysteresis

VCM = 0 V

70

mV

VOH

Receiver output high voltage

IO = -4 mA, VID = 200 mV

3.5

V

VOL

Receiver output low voltage

IO = 4 mA, VID = -200 mV

0.4

V

IOZR

3-State (high impedance)

VO = 0.4 to 2.4 V

± 1

µA

output current at receiver

RIN

Receiver input resistance

VCM = -7 to 12 V

96

kΩ

No load supply current (2)

VRE = 0V or VCC

400

900

µA

I

V

DE

= V

CC

CC

VDE = 0 V

300

500

µA

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