MAX485

1

MAX485 Low Power, Slew-Rate-Limited RS-485/RS-422 Transceiver DESCRIPTION The MAX485 is low-power transceivers for RS-485 and RS-422 communication. IC contains one driver and one receiver. The driver slew rates of the MAX485 is not limited, allowing them to transmit up to 2.5Mbps. These transceivers draw between 120µA and 500µA of supply current when unloaded or fully loaded with disabled drivers. All parts operate from a single 5V supply. Drivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if the input is open circuit. The MAX485 is designed for half-duplex applications

ORDERING INFORMATION PART NO. Temp. Range (°C) Package

MAX485CPA 0 to 70 8 Pin DIP MAX485CSA 0 to 70 8 Pin SOP MAX485EPA -40 to 85 8 Pin DIP MAX485ESA -40 to 85 8 Pin SOP

PINOUT TYPICAL APPLICATION

APPLICATIONS Low-Power RS-485 Transceivers Low-Power RS-422 Transceivers Level Translators Transceivers for EMI-Sensitive Applications Industrial-Control Local Area Networks

FEATURES Low Quiescent Current: 300µA -7V to +12V Common-Mode Input Voltage Range Three-State Outputs 30ns Propagation Delays, 5ns Skew Full-Duplex and Half-Duplex Versions Available Operate from a Single 5V Supply Allows up to 32 Transceivers on the Bus Data rate: 2,5 Mbps Current-Limiting and Thermal Shutdown for Driver Overload Protection

DIP8 / SOP8

1

2

3

4

8

7

6

5

TOP VIEW

VCC

B

A

GND

R

D

RO

RE

DE

DI

VCC1

GND1

RRO1

RE1

DE1

DI1 D

VCC2

GND2

RRO2

RE2

DE2

DI2 D

Rt

Rt

MAX485

2

PIN DESCRIPTIONS

Pin No. PIN NAME DESCRIPTION

01 RO Receiver Output. If the receiver output is enabled(RE low), then if A > B by 200mV, RO will be high. If A < B by 200mV, then RO will be low.

02

RE Receiver Output Enable. A low enables the receiver output, RO. A high input forces the receiver output into a high impedance state.

03 DE

Driver Outputs Enable. A high on DE enables the driver output. A and B, and the chip will function as a line driver. A low input will force the driver outputs into a high impedance state and the chip will function as a line receiver.

04 DI Driver Input. If the driver outputs are enabled (DE high), then a low on DI forces the outputs A low and B high. A high on DI with the driver outputs enabled will force A high and B low.

05 GND Ground Connection. 06 A Driver Output/Receiver Input. 07 B Driver Output/Receiver Input. 08 Vcc Positive Supply; 4.75 < Vcc < 5.25.

ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC) …………………………………………………………………………..…..12V Control Input Voltage………………………………………………………......-0.5V to (VCC +0.5V) Driver Input Voltage (DI)………………………………………………………-0.5V to (VCC +0.5V) Driver Output Voltage (A, B)………………………………………………………..… -8V to +12.5V Receiver Input Voltage (A, B)…………………………………………………………. -8V to +12.5V Receiver Output Voltage (RO)…………………………………………….…-0.5V to (VCC +0.5V) Continuous Power Dissipation…………………………………………………………. (TA= +70°C) 8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) …………………………….………..727mW 8-Pin SO (derate 5.88mW/°C above +70°C) ………………………………………………471mW Storage Temperature Range………………………………………………….……-65°C to +160°C Lead Temperature (soldering, 10sec)……………………………………………….……… +300°C

DC ELECTRICAL CHARACTERISTICS (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSDifferential Driver Output (no load) VOD1 5 V

R = 50Ω (RS-422) 2 Differential Driver Output (with load)

VOD2 R = 27Ω (RS-485), Figure 4 1.5 5

V

Change in Magnitude of Driver Differential Output Voltage for Complementary Output States

∆VOD R = 27Ω or 50Ω, Figure 4 0.2 V

Driver Common-Mode Output Voltage

VOC R = 27Ω or 50Ω, Figure 4 3 V

Change in Magnitude of Driver Common-Mode Output Voltage for Complementary Output States

∆VOD R = 27Ω or 50Ω, Figure 4 0.2 V

Input High Voltage VIH DE, DI, RE 2.0 V Input Low Voltage VIL DE, DI, RE 0.8 V Input Current IIN1 DE, DI, RE ±2 µA

DE = 0V; VIN = 12V 1.0 Input Current (A, B)

IIN2 VCC = 0V or 5.25V, VIN = -7V -0.8

mA

Receiver Differential Threshold Voltage

VTH -7V ≤ VCM ≤12V -0.2 0.2 V

Receiver Input Hysteresis ∆VTH VCM = 0V 70 mV Receiver Output High Voltage VOH IO = -4mA, VID = 200mV 3.5 V Receiver Output Low Voltage VOL IO = 4mA, VID = -200mV 0.4 V

MAX485

3

DC ELECTRICAL CHARACTERISTICS (continued) (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSThree-State (high impedance) Output Current at Receiver

IOZR 0.4V ≤ VO ≤ 2.4V ±1 µA

Receiver Input Resistance RIN -7V ≤ VCM ≤ 12V 12 kΩ DE = VCC 500 900 No-Load Supply Current

(Note 3) ICC

RE = 0V or VCC DE = 0V 300 500 µA Driver Short-Circuit Current, VO = High

IOSD1 -7V ≤ VO ≤ 12V (Note 4) 35 250 mA

Driver Short-Circuit Current, VO = Low

IOSD2 -7V ≤ VO ≤ 12V (Note 4) 35 250 mA

Receiver Short-Circuit Current IOSR 0V ≤ VO ≤ VCC 7 95 mA SWITCHING CHARACTERISTICS (VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITStPLH RDIFF = 54Ω 10 30 60 Driver Input to Output tPHL CL1 = CL2 = 100pF 10 30 60

ns

Driver Output Skew to Output tSKEW RDIFF = 54Ω, CL1 = CL2 = 100pF 5 10 ns Driver Enable to Output High tZH CL= 100pF, S2 closed 40 70 ns Driver Enable to Output Low tZL CL= 100pF, S1 closed 40 70 ns Driver Disable Time from Low tLZ CL= 15pF, S1 closed 40 70 ns Driver Disable Time from High tHZ CL= 15pF, S2 closed 40 70 ns | tPLH - tPHL | Differential Receiver Skew

tSKD RDIFF = 54Ω 13 ns

Receiver Enable to Output Low tZL CRL = 15pF, S1 closed 20 50 ns Receiver Enable to Output High tZH CRL = 15pF, S2 closed 20 50 ns Receiver Disable Time from Low

tLZ CRL = 15pF, S1 closed 20 50 ns

Receiver Disable Time from High

tHZ CRL = 15pF, S2 closed 20 50 ns

Maximum Data Rate fMAX 2.5 MbpsNote 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device

ground unless otherwise specified. Note 2: All typical specifications are given for VCC = 5V and TA = +25°C. Note 3: Supply current specification is valid for loaded transmitters when DE = 0V. Note 4: Applies to peak current. See Typical Operating Characteristics.

MAX485

4

TESTING CIRCUITS

3V

DEA

B

DIRDIFF

CL1

CL2

RO

15pF

A

BRE

OUTPUTUNDER TEST

CL

S1

S2

VCC500Ω

Figure 3. Driver/Receiver Timing Test Circuit Figure 4. Driver Timing Test Load #2

RECEIVEROUTPUT

CRL15pF

1k

S1

S2

TEST POINTVCC

1k

VOD

A

B

R

R VOC

Figure 1. Driver DC Test Load Figure 2. Receiver Timing Test Load

SWITCHING TIME WAVEFORMS

DI3V

1.5V

tPLH

tr

tSKEW1/2 VO

VO

80%10%

0V

B

A

VO

–VO

0V90%

1.5V

tPHL

tSKEW

1/2 VO

f = 1MHz, tr ≤ 10ns, t f ≤ 10ns

20%

tf

VDIFF = V(A) – V(B)

Figure 5. Driver Propagation Delays

1.5V

tZL

2.3V

2.3V

tZH

1.5V

tLZ

0.5V

0.5V

tHZ

f = 1MHz, tr ≤ 10ns, t f ≤ 10ns

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

3V

0VDE

5V

VOL

VOH

0V

A, B

A, B

Figure 6. Driver Enable and Disable Times

MAX485

5

SWITCHING TIME WAVEFORMS

1.5V

tPHL f = 1MHz, tr ≤ 10ns, t f ≤ 10ns

R

–VOD2

A, B 0V

1.5V

tPLH

OUTPUT

INPUT

VOD2

VOL

VOH

Figure 7. Receiver Propagation Delays

Figure 8. Receiver Enable and Disable Times

1.5V

tZL

1.5V

1.5V

tZH

1.5V

tLZ

0.5V

0.5V

tHZ

f = 1MHz, tr ≤ 10ns, t f ≤ 10ns

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

3V

0VRE

5V

0V

R

R

TransmittingINPUTS OUTPUTS

RE DE DI B A

X 1 1 No Fault 0 1

X 1 0 No Fault 1 0

X 0 X X Z Z

X 1 X Fault Z Z

LINECONDITION

Receiving INPUTS OUTPUTS

RE DE A – B R

0 0 ≥0.2V 1

0 0 ≤– 0.2V 0

0 0 Inputs Open 1

1 0 X Z

FUNCTION TABLES

MAX485

6

(Narrow .300 Inch)

(Narrow .150 Inch)

0.100(2.54)BSC

0.065(1.651)

TYP

0.045 – 0.065(1.143 – 1.651)

0.130 ± 0.005(3.302 ± 0.127)

0.020(0.508)

MIN0.018 ± 0.003(0.457 ± 0.076)

0.125(3.175)

MIN

1 2 3 4

8 7 6 5

0.255 ± 0.015*(6.477 ± 0.381)

0.400*(10.160)

MAX

0.009 – 0.015(0.229 – 0.381)

0.300 – 0.325(7.620 – 8.255)

0.325+0.035–0.015+0.889–0.3818.255( )

0.016 – 0.050(0.406 – 1.270)

0.010 – 0.020(0.254 – 0.508)

× 45°

0°– 8° TYP0.008 – 0.010

(0.203 – 0.254)

0.053 – 0.069(1.346 – 1.752)

0.014 – 0.019(0.355 – 0.483)

TYP

0.004 – 0.010(0.101 – 0.254)

0.050(1.270)

BSC

1 2 3 4

0.150 – 0.157**(3.810 – 3.988)

8 7 6 5

0.189 – 0.197*(4.801 – 5.004)

0.228 – 0.244(5.791 – 6.197)

DIP8 Package

SOP8 Package

PACKAGE