ST ST3485EB, ST3485EC User Manual

3.3 V powered, 15 kV ESD protected,

up to 12 Mbps RS-485/RS-422 transceiver

Features

■ ESD protection

– ±15 kV human body model
– ±8 kV IEC 1000-4-2 contact discharge

■ Operate from a single 3.3 V supply - no charge

pump required

■ Interoperable with 5 V logic

■ 1 µA low current shutdown mode max

■ Guaranteed 12 Mbps data rate

■ -7 to 12 V common mode input voltage range

■ Half duplex versions available

■ Industry standard 75176 pinout

■ Current limiting and thermal shutdown for

driver overload protection

■ Guaranteed high receiver output state for

floating inputs with no signal present

■ Allow up to 64 transceivers on the bus

ST3485EB
ST3485EC

DIP-8

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

SO-8

Description

The ST3485E is ±15 kV ESD protected, 3.3 V low
power transceiver for RS-485 and RS-422
communications. The device contains one driver
and one receiver in half duplex configuration. The
ST3485E transmits and receives at a guaranteed
data rate of at least 12 Mbps.

All transmitter outputs and receiver inputs are
protected to ±15 kV using Human Body Model.

Table 1. Device summary

Order code Temperature range Package Packaging

ST3485ECN 0 to 70 °C DIP-8 50 parts per tube / 40 tube per box

ST3485ECDR 0 to 70 °C SO-8 (tape and reel) 2500 parts per reel

ST3485EBDR -40 to 85 °C SO-8 (tape and reel) 2500 parts per reel

November 2007 Rev 5 1/22

www.st.com

22

Contents ST3485EB - ST3485EC

Contents

1 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Test circuits and typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 9

6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2/22

ST3485EB - ST3485EC Pin configuration

1 Pin configuration

Figure 1. Pin connections

Table 2. Pin description

Pin n° Symbol Name and function

1 RO Receiver output. If A>B by 200mV, RO will be high; if A<B by 200mV, RO will be low

2RE

3DE

4DI

5 GND Ground

6 A Non-inverting receiver input and non-inverting driver output

7 B Inverting receiver input and inverting driver output

8V

CC

Receiver output enable. RO is enabled when RE is low; RO is high impedance when RE
is high. If RE is high and DE is low, the device will enter a low power shutdown mode.

Driver output enable. The driver outputs are enabled by bringing DE high. They are high
impedance when DE is low. If RE is high DE is low, the device will enter a low-power
shutdown mode. If the driver outputs are enabled, the part functions as line driver, while
they are high impedance, it functions as line receivers if RE is low.

Driver input. A low on DI forces output A low and output B high. Similarly, a high on DI
forces output A high and output B low

Supply voltage: VCC= 3V to 3.6V

3/22

Truth tables ST3485EB - ST3485EC

2 Truth tables

Table 3. Truth table (driver)

Inputs Outputs

Mode

RE DE DI B A

XHHLH Normal

XHLHL Normal

LLXZZ Normal

H L X Z Z Shutdown

Note: X= Don’t care; Z=High impedance

Table 4. Truth table (receiver)

Inputs Output

Mode

RE DE A-B RO

LL ≥ 0.2V H Normal

LL ≤ -0.2V L Normal

L L Inputs Open H Normal

H L X Z Shutdown

Note: X= Don’t care; Z=High impedance

4/22

ST3485EB - ST3485EC Maximum ratings

3 Maximum ratings

Table 5. Absolute maximum ratings

Symbol Parameter Value Unit

V

CC

V

I

V

DI

V

DO

V

RI

V

RO

Supply voltage 7 V

Control input voltage (RE, DE) -0.3 to 7 V

Driver input voltage (DI) -0.3 to 7 V

Driver output voltage (A, B) ± 14 V

Receiver input voltage (A, B) ± 14 V

Receiver output voltage (RO) -0.3 to (VCC + 0.3) V

Note: Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these condition is not implied.

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 Contact discharge ± 8kV

5/22

Electrical characteristics ST3485EB - ST3485EC

4 Electrical characteristics

Table 7. Electrical characteristics

= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred

V

CC

to T

= 25 °C)

A

Symbol Parameter Test conditions Min. Typ. Max. Unit

I

SUPPLYVCC

I

SHDN

Shutdown supply current DE=0V, RE=VCC, DI=0V or VCC 0.002 1 µA

Power supply current No Load, DI=0V or V

DE=VCC,
RE=0V or V

CC

DE=0V,
RE

CC

=0V

1.3 2.2 mA

1.2 1.9 mA

Table 8. Logic input electrical characteristics

V

= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred

CC

to T

= 25 °C)

A

Symbol Parameter Test conditions Min. Typ. Max. Unit

Input logic threshold low DE, DI, RE 1.3 0.8 V

IL

Input logic threshold high DE, DI, RE 2 V

IH

Logic input current DE, DI, RE ± 2.0 µA

V

=12V 1 mA

Input current (A, B) DE=0V, VCC= 0 or 3.6V

IN

V

=-7V -0.8 mA

IN

V

I

I

V

IN1

IN2

Table 9. Transmitter electrical characteristics

V

= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred

CC

to T

= 25°C)

A

Symbol Parameter Test conditions Min. Typ. Max. Unit

R

= 100Ω (RS-422) (Figure 1)2 V

L

V

Differential drive output

OD

= 54Ω (RS-485) (Figure 1)1.5 V

R

L

R

= 60Ω (RS-485) (Figure 2)1.5 V

L

Change in magnitude of driver

ΔV

differential output voltage for

OD

complementary output states

= 54Ω or 100Ω (Figure 1)0.2V

R

L

(Note: 1)

V

Driver common mode output

OC

voltage

= 54Ω or 100Ω (Figure 1)3V

R

L

Change in magnitude of driver

ΔV

common mode output voltage

OC

= 54Ω or 100Ω (Figure 1)0.2V

R

L

(Note: 1)

I

OSD

Driver short circuit output
current

6/22

± 250 mA

ST3485EB - ST3485EC Electrical characteristics

Table 10. Receiver electrical characteristics

V

= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred

CC

to T

= 25°C)

A

Symbol Parameter Test conditions Min. Typ. Max. Unit

V

ΔV

V

V

I

R

I

TH

TH

OH

OL

OZR

RIN

OSR

Receiver differential
threshold voltage

Receiver input hysteresis VCM = 0V 70 V

Receiver output high
voltage

Receiver output low
voltage

3-State (high impedance)
output current at receiver

Receiver input resistance VCM = -7V to 12V 24 kΩ

Receiver short-circuit
current

V

= -7V to 12V, DE = 0 -0.2 0.2 V

CM

I

= -4mA, VID = 200mV

OUT

(Figure 8 and Figure 9)

= 4mA, VID = -200mV, (Figure 3)0.4V

I

OUT

= 3.6V, VO = 0V to V

V

CC

V

RO

= 0V to V

CC

CC

2V

± 1µA

760mA

Table 11. Driver switching characteristics

V

= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred

CC

to T

= 25 °C)

A

Symbol Parameter Test conditions Min. Typ. Max. Unit

D

t

DD

t

TD

Maximum data rate 12 15 Mbps

R

= 60Ω, CL = 15pF, (Figure 4 and

R

Differential output delay

Differential output
transition time

L

Figure 5)

RL= 60Ω, CL = 15pF, (Figure 4 and

Figure 5)

18 30 ns

12 20 ns

t

PLH

t

PHL

t

PDS

t

PZL

t

PZH

t

PHZ

t

PLZ

t

SKEW

t

ZH(SHDN)

t

ZL(SHDN)

R

= 27Ω, CL = 15pF, (Figure 8 and

Propagation delay

|t

PLH - tPHL

| Propagation

delay skew (Note 2)

L

Figure 9)

RL= 27Ω, CL = 15pF, (Figure 8 and

Figure 9)

18 30 ns

25ns

Output enable time RL= 110Ω, (Figure 10 and Figure 11)1935ns

Output enable time RL= 110Ω, (Figure 6 and Figure 7)3050ns

Output disable time RL= 110Ω, (Figure 6 and Figure 7)1935ns

Output disable time RL= 110Ω, (Figure 10 and Figure 11)3050ns

Differential output delay
skew

Driver enable from
shutdown to output high

Driver enable from
shutdown to output low

13ns

30 50 ns

19 35 ns

7/22