Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsInterface ICsInterface IC - transceivers RS485 1/1 SOIC 8 N

40Mbps, +3.3V, RS-485 Half-Duplex

Transceivers

MAX14840E/MAX14841E

19-5131; Rev 0; 2/10

Ordering Information/Selector Guide

General Description

The MAX14840E/MAX14841E are +3.3V ESD-protected

transceivers intended for half-duplex RS-485 communi-

cation up to 40Mbps. These transceivers are optimized

for high speeds over extended cable runs while maximiz-

ing tolerance to noise.

The MAX14840E features symmetrical fail-safe and larg-

er receiver hysteresis, providing improved noise rejec-

tion and improved recovered signals in high-speed and

long cable applications. The MAX14841E has true fail-

safe receiver inputs guaranteeing a logic-high receiver

output when inputs are shorted or open.

The MAX14840E/MAX14841E transceivers draw 1.5mA

(typ) supply current when unloaded or when fully loaded

with the drivers disabled. Hot-swap capability eliminates

undesired transitions on the bus during power-up or hot

insertion.

The MAX14840E/MAX14841E are available in 8-pin SO

and small, 8-pin (3mm x 3mm) TDFN-EP packages. Both

devices operate over the -40NC to +125NC automotive

temperature range.

Applications

Motion Controllers

Fieldbus Networks

Industrial Control Systems

Backplane Buses

HVAC Networks

Features

S Half-Duplex RS-485 Transceivers

S +3.3V Supply Voltage

S 40Mbps Maximum Data Rate

S Large (170mV) Receiver Hysteresis on

MAX14840E

S Symmetrical Fail-Safe Receiver Input on

MAX14840E

S Fail-Safe Receiver Input (MAX14841E)

S Hot-Swap Capability

S Short-Circuit Protected Outputs

S Thermal Self-Protection

S Low 10µA (max) Shutdown Current

S Extended ESD Protection for RS-485 I/O Pins

±35kV Human Body Model (HBM)

±20kV Air-Gap Discharge per IEC 61000-4-2

±12kV Contact Discharge per IEC 61000-4-2

S Automotive -40°C to +125°C Operating

Temperature Range

S Available in Industry-Standard 8-Pin SO or

Space-Saving, 8-Pin TDFN-EP (3mm x 3mm)

Packages

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

PART FAIL SAFE TEMP RANGE PIN-PACKAGE

MAX14840EASA+ Symmetrical

-40NC to +125NC

8 SO

MAX14840EATA+ Symmetrical

-40NC to +125NC

8 TDFN-EP*

MAX14841EASA+ True

-40NC to +125NC

8 SO

MAX14841EATA+ True

-40NC to +125NC

8 TDFN-EP*

For pricing, delivery, and ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

Summary of content (15 pages)

PAGE 1
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers General Description The MAX14840E/MAX14841E are +3.3V ESD-protected transceivers intended for half-duplex RS-485 communication up to 40Mbps. These transceivers are optimized for high speeds over extended cable runs while maximizing tolerance to noise. The MAX14840E features symmetrical fail-safe and larger receiver hysteresis, providing improved noise rejection and improved recovered signals in high-speed and long cable applications.
PAGE 2
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers ABSOLUTE MAXIMUM RATINGS (Voltages referenced to GND.) VCC ...................................................................... -0.3V to +6.0V RE, RO ................................................... -0.3V to +(VCC + 0.3V) DE, DI................................................................... -0.3V to +6.0V A, B..................................................................... -8.0V to +13.
PAGE 3
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers DC ELECTRICAL CHARACTERISTICS (continued) (VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.
PAGE 4
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers SWITCHING CHARACTERISTICS (continued) (VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.
PAGE 5
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers Test and Timing Diagrams A VCC DE RL 2 A DI VOD B VOD RL 2 RL CL VOC B Figure 1. Driver DC Test Load Figure 2. Driver Timing Test Circuit f = 1MHz, tLH = 3ns, tHL = 3ns VCC 1.5V 1.5V 0 tDPHL tDPLH B A VOD VOD = [VA - VB] VO VOD 90% 90% 0 10% -VO 10% tLH tHL tDSKEW = tDPLH - tDPHL Figure 3. Driver Propagation Delays A GND OR VCC DI D B S1 VCC OUT CL 50pF RL = 110I DE 1.
PAGE 6
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers Test and Timing Diagrams (continued) VCC 0 OR VCC A DI RL = 110I S1 OUT D B DE GENERATOR 50I VCC DE tDZL, tDZL(SHDN) 1.5V 0 tDLZ VCC OUT 1.5V VOL 0.25V Figure 5. Driver Enable and Disable Times (tDLZ, tDZL) A ATE R VID RECEIVER OUTPUT B Figure 6. Receiver Propagation Delay Test Circuit f = 1MHz, tLH P 3ns, tHL P 3ns A 1V B VOH RO VOL -1V tRPHL tRPLH VCC 2 VCC 2 tRSKEW = tRPHL - tRPLH Figure 7.
PAGE 7
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers Test and Timing Diagrams (continued) +1.5V S3 -1.5V VID R RE GENERATOR RO R 1kI S1 VCC S2 CL 15pF 50I VCC 1.5V RE tRZH, tRZH(SHDN) 0 VCC S1 OPEN S2 CLOSED S3 = +1.5V 1.5V RE 0 S1 CLOSED S2 OPEN S3 = -1.5V tRZL, tRZL(SHDN) RO VOH VCC 2 0 VCC 1.5V RE 0 VCC 2 0.25V VOL RO VCC S1 OPEN S2 CLOSED S3 = +1.5V 1.5V S1 CLOSED S2 OPEN S3 = -1.5V 0 RE tRLZ tRHZ RO VCC VCC VOH 0 RO 0.25V VOL Figure 8.
PAGE 8
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers Typical Operating Characteristics (VCC = +3.3V, TA = +25NC, unless otherwise noted.) NO-LOAD SUPPLY CURRENT vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE 2 1 2 1 RE = GND AND DE = VCC, OR RE = VCC AND DE = VCC -15 10 35 60 85 110 125 10 35 60 85 NO LOAD 40 0 110 125 0 10 20 30 40 TEMPERATURE (°C) DATA RATE (Mbps) RECEIVER OUTPUT HIGH VOLTAGE vs. OUTPUT CURRENT RECEIVER OUTPUT LOW VOLTAGE vs.
PAGE 9
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers Typical Operating Characteristics (continued) (VCC = +3.3V, TA = +25NC, unless otherwise noted.) DIFFERENTIAL DRIVER SKEW (tDSKEW) vs. TEMPERATURE tDPHL 10 5 1.5 RL = 54I, CL = 50pF 8 TIME (ns) 15 10 MAX14840E toc11 tDPLH RL = 54I, CL = 50pF DRIVER OUTPUT SKEW (ns) 20 2.0 MAX14840E toc10 DRIVER PROPAGATION DELAY (ns) 25 DRIVER OUTPUT RISE AND FALL TIME vs. TEMPERATURE MAX14840E toc12 DRIVER PROPAGATION DELAY vs.
PAGE 10
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers Pin Configurations TOP VIEW VCC B A GND 8 7 6 5 MAX14840E MAX14841E *EP + 1 2 3 4 RO RE DE DI RO 1 RE 2 DE 3 DI 4 MAX14840E MAX14841E 8 VCC 7 B 6 A 5 GND SO TDFN *CONNECT EXPOSED PAD (EP) TO GND. Pin Descriptions PIN NAME 1 RO Receiver Output. See the Function Table. 2 RE Active-Low Receiver-Output Enable. Drive RE low to enable RO. RO is high impedance when RE is high.
PAGE 11
MAX14840E/MAX14841E 40Mbps, +3.
PAGE 12
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers normal conditions, where UART signaling is used, this means that the state on the line prior to all drivers being disabled is a logic-high (i.e., a UART STOP bit). Detailed Description The MAX14840E/MAX14841E are +3.3V ESD-protected RS-485 transceivers intended for high-speed, half-duplex communications. A hot-swap capability eliminates false transitions on the bus during power-up or hot insertion.
PAGE 13
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers How-Swap Input Circuitry The MAX14840E/MAX14841E DE and RE enable inputs feature hot-swap capability. At the input, there are two nMOS devices, M1 and M2 (Figure 10). When VCC ramps from 0V, an internal 15Fs timer turns on M2 and sets the SR latch that also turns on M1. Transistors M2 (a 1mA current sink) and M1 (a 100FA current sink) pull DE to GND through a 5.6kI resistor.
PAGE 14
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers ESD Test Conditions ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, test methodology, and test results. Human Body Model Figure 11 shows the HBM, and Figure 12 shows the current waveform it generates when discharged into a low-impedance state.
PAGE 15
MAX14840E/MAX14841E 40Mbps, +3.3V, RS-485 Half-Duplex Transceivers 120Ω 120Ω DE B B DI D D DI DE RO A B A B A A R R RO RE RE R R D D MAX14840E MAX14841E DI DE RO RE DI DE RO RE Figure 15. Typical Half-Duplex RS-485 Network immediate protection against short circuits over the whole common-mode voltage range (see the Typical Operating Characteristics).