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19-2218; Rev 1; 5/02
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package
General Description
The MAX3362 low-power, high-speed transceiver for RS-485/RS-422 communication operates from a single +3.3V power supply. The device contains one differential transceiver consisting of a line driver and receiver. The transceiver operates at data rates up to 20Mbps, with an output skew of less than 6ns. Driver and receiver propagation delays are guaranteed below 50ns. This fast switching and low skew make the MAX3362 ideal for multidrop clock/data distribution applications. The output level is guaranteed at +1.5V with a standard 54 load, compliant with RS-485 specifications. The transceiver draws 1.7mA supply current when unloaded or fully loaded with the drivers disabled. Additionally, the MAX3362 has a low-power shutdown mode, reducing the supply current to 1A. The MAX3362 has a 1/8-unit-load receiver input impedance, allowing up to 256 transceivers on the bus. The MAX3362 is designed for half-duplex communication. The device has a hot-swap feature that eliminates false transitions on the data cable during circuit initialization. The drivers are short-circuit current limited, and a thermal shutdown circuit protects against excessive power dissipation. The MAX3362 is available in an 8-pin SOT package and specified over industrial and automotive temperature ranges. o Space-Saving 8-Pin SOT Package o Guaranteed 20Mbps Data Rate o Operates from a Single +3.3V Supply o 6ns (max) Transmitter and Receiver Skew o Hot-Swap Feature o Interoperable with +5V Logic o Allows up to 256 Transceivers on the Bus o 1A Low-Power Shutdown Mode o 1.7mA Operating Supply Current o -7V to +12V Common-Mode Range o Current Limiting and Thermal Shutdown o Half-Duplex Operation o Automotive Temperature Range Variants
Features
MAX3362
Ordering Information
PART MAX3362EKA MAX3362AKA TEMP RANGE -40C to +85C -40C to +125C PINTOP MARK PACKAGE 8 SOT23 8 SOT23 AAJL AALL
Applications
Clock/Data Distribution Telecom Equipment Security Equipment Point-of-Sale Equipment Industrial Controls
Pin Configuration and Functional Diagram appear at end of data sheet.
120 DI D B
Typical Operating Circuit
120 B D DE
DE
A R
B
A
B
A
A R
DI
RO RE
RO RE
R
R D
MAX3362
D
DI
DE
RO
RE
DI
DE
RO
RE
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
ABSOLUTE MAXIMUM RATINGS
All voltages with respect to GND. VCC, RE, DE, DI ......................................................-0.3V to +6V Receiver Input Voltages, Driver Output Voltages (A, B) .......................................................-8V to +13V Receiver Input Current, Driver Output Current (A, B) .................................................................250mA |VA - VB|..................................................................................+8V Receiver Output Voltage (RO)....................-0.3V to (VCC + 0.3V) Continuous Power Dissipation (TA = +70C) 8-Pin SOT (derate 9.7mW/C above +70C) ............... 777mW Operating Temperature Range MAX3362E__ .................................................. -40C to +85C MAX3362A__ ................................................ -40C to +125C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(VCC = +3.3V 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25C.) (Notes 1, 2)
PARAMETER DRIVER Figure 1, RL = 100 (RS-422) (extended temperature range) Differential Driver Output VOD Figure 1, RL = 100 (automotive temperature range) Figure 1, RL = 54 (RS-485) (extended temperature range) Change in Magnitude of Differential Output Voltage Driver Common-Mode Output Voltage Change In Magnitude of Common-Mode Voltage Input High Voltage Input Low Voltage Input Hysteresis Input Current (DE, DI, RE) Driver Short-Circuit Output Current Driver Short-Circuit Foldback Output Current VOD VOC VOC VIH VIL VHYS IIN IOSD IOSDF Figure 1, RL = 54 or 100 (Note 3) Figure 1, RL = 54 or 100 Figure 1, RL = 54 or 100 (Note 3) DE, DI, RE DE, DI, RE DE, DI, RE 0 < VIN < 5V 0 < VOUT < 12V (Note 4) -7V < VOUT < VCC (Note 4) (VCC - 1V) < VOUT < 12V (Note 4) -7V < VOUT < 1V (Note 4) -250 +25 -25 50 1 +250 2.0 0.8 2.0 1.5 1.5 0.2 3 0.2 V V V V V mV A mA mA V SYMBOL CONDITIONS MIN TYP MAX UNITS
2
_______________________________________________________________________________________
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3.3V 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25C.) (Notes 1, 2)
PARAMETER Thermal Shutdown Threshold Thermal Shutdown Hysteresis RECEIVER Receiver Differential Threshold Voltage Receiver Input Hysteresis Receiver Output High Voltage Receiver Output Low Voltage Three-State Output Current at Receiver Receiver Input Resistance Receiver Input Current Receiver Output Short-Circuit Current POWER SUPPLY Supply Voltage Supply Current in Normal Operation (Static Condition) Supply Current in Shutdown Mode VCC IQ ISHDN No load, DI = VCC or GND DE = GND, RE = VCC 3.135 3.300 1.7 1 3.465 3 10 V mA A VTH VTH VOH VOL IOZR RIN IIN IOSR -7V < VCM < 12V V A + VB = 0 IO = -1mA, VA - VB = VTH IO = 1mA, VA - VB = -VTH 0 < VO < VCC VCM = 12V DE = GND, VCC = GND or 3.465V 0 < VRO < VCC VIN = +12V VIN = -7V -100 150 96 125 VCC - 0.4 0.4 1 -200 0 25 +200 mV mV V V A k A mA SYMBOL VTS VTSH CONDITIONS MIN TYP 150 10 MAX UNITS C C
MAX3362
SWITCHING CHARACTERISTICS (MAX3362E_ _ only)
(VCC = +3.3V 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25C.) (Note 1)
PARAMETER Driver Propagation Delay Driver Differential Output Rise or Fall Time Driver Output Skew Maximum Data Rate Driver Enable to Output Low Driver Disable Time from Low Driver Disable Time from High SYMBOL tPDLH tPDHL tDR tDF tDSKEW fMAX tPDZL tPDLZ tPDHZ Figure 4, RL = 500, CL = 50pF Figure 4, RL = 500, CL = 50pF Figure 5, RL = 500, CL = 50pF CONDITIONS Figures 2 and 3, RL = 54, CL = 50pF Figures 2 and 3, RL = 54, CL = 50pF Figures 2 and 3, RL = 54, CL = 50pF tDSKEW = |tPDLH - tPDHL| 20 100 100 100 MIN TYP MAX 50 50 12.5 12.5 6 UNITS ns ns
ns Mbps ns ns ns
_______________________________________________________________________________________
3
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
SWITCHING CHARACTERISTICS (MAX3362E_ _ only) (continued)
(VCC = +3.3V 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25C.) (Note 1)
PARAMETER Driver Enable to Output High Receiver Propagation Delay Receiver Output Skew Receiver Enable to Output Low Receiver Enable to Output High Receiver Disable Time from Low Receiver Disable Time from High Time to Shutdown Driver Enable from Output High to Shutdown Driver Enable from Output Low to Shutdown Receiver Enable from Output High to Shutdown Receiver Enable from Output Low to Shutdown Time to Normal Operation Driver Enable from Shutdown to Output High Driver Enable from Shutdown to Output Low Receiver Enable from Shutdown to Output High Receiver Enable from Shutdown to Output Low SYMBOL tPDZH tPRLH tPRHL tRSKEW tPRZL tPRZH tPRLZ tPRHZ tSD tPDHS tPDLS tPRHS tPRLS tNO tPDSH tPDSL tPRSH tPRSL (Note 6) Figure 5 RL = 500, CL = 50pF Figure 4 RL = 500, CL = 50pF Figure 7 RL = 1k, CL = 15pF Figure 7 RL = 1k, CL = 15pF CONDITIONS Figure 5, RL = 500, CL = 50pF Figure 6, CL = 15pF Figure 6, CL = 15pF tRSKEW = |tPRLH - tPRHL| Figure 7, RL = 1k, CL = 15pF Figure 7, RL = 1k, CL = 15pF Figure 7, RL = 1k, CL = 15pF Figure 7, RL = 1k, CL = 15pF (Note 5) 50 50 50 50 50 1500 1500 1500 1500 1500 MIN TYP MAX 100 50 50 6 100 100 100 100 600 600 600 600 600 3000 3000 3000 3000 3000 UNITS ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
Note 1: Devices production tested at +25C. Over-temperature limits are guaranteed by design. Note 2: All currents into the device are positive; all currents out of the device are negative. All voltages are referenced to device ground, unless otherwise noted. Note 3: VOD and VOC are the changes in VOD and VOC, respectively, when the DI input changes state. Note 4: The short-circuit output current applies to peak current just prior to foldback-current limiting; the short-circuit foldback output current applies during current limiting to allow a recovery from bus contention. Note 5: Shutdown is enabled by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns, the device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 600ns, the device is guaranteed to have entered shutdown. Note 6: Transition time from shutdown mode to normal operation.
4
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3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package
Typical Operating Characteristics
(VCC = +3.3V, TA = +25C, unless otherwise noted.)
OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTAGE
MAX3362 toc01
MAX3362
OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTAGE
MAX3362 toc02
RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE
RECEIVER OUTPUT HIGH VOLTAGE (V)
MAX3362 toc03
40 35 OUTPUT CURRENT (mA) 30 25 20 15 10 5 0 0 0.5 1.0 1.5 2.0 2.5 3.0
0 -5 OUTPUT CURRENT (mA) -10 -15 -20 -25 -30
3.26
3.25
3.24
3.23
3.22 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) RECEIVER OUTPUT HIGH VOLTAGE (V)
3.5
RECEIVER OUTPUT LOW VOLTAGE (V)
RECEIVER OUTPUT LOW VOLTAGE vs. TEMPERATURE
MAX3362 toc04
DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX3362 toc05
DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
MAX3362 toc06
0.05 RECEIVER OUTPUT LOW VOLTAGE (V)
75 DRIVER OUTPUT CURRENT (mA)
3.0 2.5 2.0 1.5 1.0 0.5 RL = 54 0
0.04
60
0.03
45
0.02
30
0.01
15
0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 DIFFERENTIAL OUTPUT VOLTAGE (V)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
DRIVER OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE
130 120 110 100 90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 DRIVER OUTPUT LOW VOLTAGE (V) 10 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 -140
MAX3362 toc07
DRIVER OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE
MAX3362 toc08
SUPPLY CURRENT vs. TEMPERATURE
1.75 1.74 ICC (mA) 1.73 1.72 1.71 1.70 1.69 1.68 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
MAX3362 toc09
1.76
DRIVER OUTPUT CURRENT (mA)
9 10 11 12
DRIVER OUTPUT CURRENT (mA)
-7 -6 -5 -4 -3 -2 -1 0
1
2
3
4
5
DRIVER OUTPUT HIGH VOLTAGE (V)
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5
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
Typical Operating Characteristics (continued)
(VCC = +3.3V, TA = +25C, unless otherwise noted.)
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX3362 toc10
DRIVER OUTPUT SKEW vs. TEMPERATURE
0.26 0.24 0.22 0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0 TEMPERATURE (C)
MAX3362 toc11
RECEIVER PROPAGATION DELAY vs. TEMPERATURE
RECEIVER PROPAGATION DELAY (ns)
MAX3362 toc12
1.4 1.2 1.0 ISHDN (A) 0.8 0.6 0.4 0.2 0
35
DRIVER OUTPUT SKEW (ns)
33
31
29
27
25 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
UNLOADED DRIVER OUTPUT WAVEFORM
MAX3362 toc13
LOADED DRIVER OUTPUT WAVEFORM
MAX3362 toc14
A
3.3V A
2V
B B 0
0
fDIN = 16Mbps
20ns/div
fDIN = 16Mbps RL = 54
20ns/div
DRIVER PROPAGATION DELAY
MAX3362 toc15
RECEIVER PROPAGATION DELAY
MAX3362 toc16
3.3V DIN 0
A
2V/div
B
A 2V/div B
RO 2V/div
fDIN = 16Mbps
20ns/div
fDIN = 16Mbps
20ns/div
6
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3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package
Pin Description
PIN 1 2 NAME RO RE DESCRIPTION Receiver Output. RO is high if the receiver input differential (A-B) 200mV and the receiver is enabled (RE is low). RO is low if the receiver input differential (A-B) -200mV and the receiver is enabled. Receiver Output Enable. Driving RE low enables RO. RO is high impedance when RE is high. Drive RE high and DE low (disable both receiver and driver outputs) to enter low-power shutdown mode. Driver Output Enable. Driving DE high enables driver outputs. These outputs are high impedance when DE is low. Drive RE high and DE low (disable both receiver and driver outputs) to enter lowpower shutdown mode. Driver Input. Driving DI low forces the noninverting output low and inverting output high, when the driver is enabled (DE is high). Driving DI high forces the noninverting output high and inverting output low. Ground Noninverting Receiver Input and Noninverting Driver Output Inverting Receiver Input and Inverting Driver Output Supply Voltage. VCC = 3.3V 5%. Bypass VCC to GND with a 0.1F capacitor.
MAX3362
3
DE
4 5 6 7 8
DI GND A B VCC
RL/2 D VOD RL/2 VCC VOC
VCC CL = 50pF RL = 54 D CL RL OUT
Figure 1. Driver DC Test Load
Figure 2. Driver Timing Test Circuit
VCC
VCC DI 0 VCC /2
tri
tfi
tri = 5ns tfi = 5ns
S1 0 or 3V D
RL = 500 OUT CL = 50pF
tPDLH B (A+B)/2 A
tPDHL
GENERATOR
50
90% A-B 10% tDR tDF
IN tPDSL, tPDZL tPDLZ VOM = (VOL + VCC) /2 VOL 0.25V VCC VCC/2 0 VCC
Figure 3. Driver Propagation Delay
OUT
Figure 4. Driver Enable and Disable Times (tPDSL, tPDZL, tPDLS, tPDLZ) _______________________________________________________________________________________ 7
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
S1 0 or 3V D CL = 50pF OUT RL = 500
GENERATOR
50
VCC VCC/2 IN tPDSH, tPDZH VOM = (VOH) /2 OUT tPDHZ VOL 0 0.25V VCC
Figure 5. Driver Enable and Disable Times (tPDSH, tPDZH, tPDHS, tPDHZ)
VID GENERATOR 50
R
OUT CL = 15pF
1.5V 0
VOM =
VCC 2
3.0V IN 1.5V tPRLH OUT VOL VOM 1.5V tPRHL VOM 0 0 VCC
Figure 6. Receiver Propagation Delays
8
_______________________________________________________________________________________
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
1.5V -1.5V S3 VID R CL S2 RL = 1k S1 VCC
GENERATOR
50
3V 1.5V IN tPRZH tPRSH 0 VOH OUT S1 OPEN S2 CLOSED S3 = 1.5V 0 S1 CLOSED S2 OPEN S3 = -1.5V IN tPRZL tPRSL 1.5V 1.5V
3V
0 VOC
OUT
VOL
3V 1.5V IN tPRHZ 0.25V OUT 0 S1 OPEN S2 CLOSED S3 = 1.5V 0 VOH OUT 0.25V S1 CLOSED S2 OPEN S3 = -1.5V IN tPRLZ 1.5V
3V
0 VOH
0
Figure 7. Receiver Enable and Disable Times
Detailed Description
The MAX3362 low-power, high-speed transceiver for RS-485/RS-422 communication operates from a single +3.3V power supply. The device contains one differential line driver and one differential line receiver. The driver and receiver may be independently enabled. When disabled, outputs enter a high-impedance state. The transceiver guarantees data rates up to 20Mbps, with an output skew of less than 6ns. This low skew time makes the MAX3362 ideal for multidrop clock/data
distribution applications, such as cellular base stations. Driver and receiver propagation delays are below 50ns. The output level is guaranteed at 1.5V on a standard 54 load. The device has a hot-swap feature that eliminates false transitions on the data cable during circuit initialization. Also, drivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry.
_______________________________________________________________________________________
9
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
Table 1. Transmitter Functional Table
TRANSMITTING INPUTS RE X X 0 1 DE 1 1 0 0 DI 1 0 X X A 1 0 High Z Shutdown OUTPUTS B 0 1 High Z
Drive RE high and DE low (disable both receiver and driver outputs) to enter low-power shutdown mode.
Hot-Swap Capability
Hot-Swap Input When circuit boards are inserted into a hot or powered backplane, disturbances to the enable and differential receiver inputs can lead to data errors. Upon initial circuit board insertion, the processor undergoes its power-up sequence. During this period, the output drivers are high impedance and are unable to drive the DE input of the MAX3362 to a defined logic level. Leakage currents up to 10A from the high-impedance output could cause DE to drift to an incorrect logic state. Additionally, parasitic circuit board capacitance could cause coupling of VCC or GND to DE. These factors could improperly enable the driver. When VCC rises, an internal pulldown circuit holds DE low for at least 10s and until the current into DE exceeds 200A. After the initial power-up sequence, the pulldown circuit becomes transparent, resetting the hot-swap tolerable input. Hot-Swap Input Circuitry The MAX3362 enable inputs feature hot-swap capability. At the input there are two NMOS devices, M1 and M2 (Figure 8). When VCC ramps from 0, an internal 10s timer turns on M2 and sets the SR latch, which also turns on M1. Transistors M2, a 300A current sink, and M1, a 30A current sink, pull DE to GND through an 8k resistor. M2 is designed to pull DE to the disabled state against an external parasitic capacitance up to 100pF that may drive DE high. After 10s, the timer deactivates M2 while M1 remains on, holding DE low against threestate leakages that may drive DE high. M1 remains on until an external source overcomes the required input current. At this time, the SR latch resets and M1 turns off. When M1 turns off, DE reverts to a standard, highimpedance CMOS input. Whenever VCC drops below 1V, the hot-swap input is reset. For RE there is a complimentary circuit employing two PMOS devices pulling RE to VCC. Hot-Swap Line Transient The circuit of Figure 9 shows a typical offset termination used to guarantee a greater than 200mV offset when a line is not driven (the 50pF represents the minimum parasitic capacitance that would exist in a typical application). During a hot-swap event when the driver is
Table 2. Receiver Functional Table
RECEIVING INPUTS RE 0 0 1 1 DE X X 1 0 A-B 200mV -200mV X X OUTPUT RO 1 0 High-Z Shutdown
The MAX3362 has a 1/8-unit-load receiver input impedance, allowing up to 256 transceivers to be connected simultaneously on a bus. The MAX3362 is designed for half-duplex communication.
Driver
The driver transfers single-ended input (DI) to differential outputs (A, B). The driver enable (DE) input controls the driver. When DE is high, driver outputs are enabled. These outputs are high impedance when DE is low. When the driver is enabled, setting DI low forces the noninverting output (A) low and inverting output (B) high. Conversely, drive DI high to force noninverting output high and inverting output low (Table 1). Drive RE high and DE low (disable both receiver and driver outputs) to enter low-power shutdown mode.
Receiver
The receiver reads differential inputs from the bus lines (A, B) and transfers this data as a single-ended output (RO). The receiver enable (RE) input controls the receiver. Drive RE low to enable the receiver. Driving RE high places RO into a high-impedance state. When the receiver is enabled, RO is high if (A-B) 200mV. RO is low if (A-B) -200mV.
10
______________________________________________________________________________________
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
VCC 10s TIMER TIMER
8k DE 300A M2
DE (HOT SWAP)
30A M1
Figure 8. Simplified Structure of the Driver Enable Input (DE)
3.3V VCC Y A TIN VCC OR GND Z 1k 0.1k 50pF B 1k
3.3V
VCC
0
10mV/div AC-COUPLED
10mV/div AC-COUPLED 10mV/div
A-B 10s/div
Figure 9. Differential Power-Up Glitch (Hot Swap)
Figure 10. Differential Power-Up Glitch (0.1V/s)
______________________________________________________________________________________
11
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
3.3V VCC A 3.3V
VCC A
0
0
10mV/div AC-COUPLED
50mV/div AC-COUPLED
B
10mV/div AC-COUPLED 10mV/div
B
50mV/div AC-COUPLED 10mV/div
A-B 1s/div
A-B 200ns/div
Figure 11. Differential Power-Up Glitch (1V/s)
Figure 12. Differential Power-Up Glitch (10V/s)
connected to the line and is powered up the driver must not cause the differential signal to drop below 200mV. Figures 10, 11, and 12 show the results of the MAX3362 during power-up for three different VCC ramp rates (0.1V/s, 1V/s, and 10V/s). The photos show the VCC ramp, the single-ended signal on each side of the 100 termination, as well as the differential signal across the termination.
256 Transceivers on the Bus
The standard RS-485 receiver input impedance is 12k (one-unit load), and a standard driver can drive up to 32 unit loads. The MAX3362 transceiver has a 1/8-unitload receiver input impedance (96k), allowing up to 256 transceivers to be connected in parallel on one communication line. Any combination of these devices and/or other RS-485 transceivers with a total of 32 unit loads or less can be connected to the line.
Low-Power Shutdown Mode
Low-power shutdown mode is initiated by bringing both RE high and DE low. In shutdown, the MAX3362 typically draws only 1A supply current. RE and DE may be driven simultaneously; the device is guaranteed not to enter shutdown if RE is high and DE is low for less than 50ns. If the inputs are in this state for at least 600ns, the device will enter shutdown. Enable times t PDZH, t PDZL, t PRZH and t PRZL in the Switching Characteristics table assume the device was not in a low-power shutdown state. Enable times tPDSH, tPDSL, tPRSH, and tPRSL assume the device was shut down. Drivers and receivers take longer to become enabled from low-power shutdown mode than from driver/receiver disable mode.
Driver Output Protection
Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. The first, a foldback current limit on the output stage, provides immediate protection against short circuits over the whole common-mode voltage range (see Typical Operating Characteristics). The second, a thermal shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature becomes excessive.
Typical Applications
The MAX3362 transceiver is designed for bidirectional data communications on multipoint bus transmission lines. The Typical Operating Circuit shows a typical network applications circuit. To minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible.
Applications Information
Propagation Delays
Figures 5 and 6 show the typical propagation delays. Skew time is simply the difference between the low-tohigh and high-to-low propagation delay. Small driver/receiver skew times help maintain a symmetrical mark-space ratio (50% duty cycle). Both the receiver skew time and driver skew time are under 6ns.
12
______________________________________________________________________________________
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package
Pin Configuration
TOP VIEW
DE
Functional Diagram
VCC
MAX3362
RO RE DE
1 2
8 7
VCC
DI D
MAX3362
B A GND
RD RE R
MAX3362
3 6 5 DI 4
A B
SOT23
GND
Chip Information
TRANSISTOR COUNT: 708 PROCESS: BiCMOS
______________________________________________________________________________________
13
3.3V, High-Speed, RS-485/RS-422 Transceiver in SOT Package MAX3362
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
SOT23, 8L.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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