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MAX13085E
User Manual
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MAXIM MAX13085E User Manual

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19-6016; Rev 0; 10/11
+5.0V, ±15kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
General Description
The MAX13085E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps.
The MAX13085E is ideal for half-duplex communications and it draws 1.2mA of supply current when unloaded or when fully loaded with the drivers disabled. The MAX13085E has a 1/8-unit load receiver input imped­ance, allowing up to 256 transceivers on the bus.
The MAX13085E is available in an 8-pin SO and PDIP packages.
MAX13085E
Features
S +5.0V Operation
S Extended ESD Protection for RS-485/RS-422 I/O
Pins ±15kV Human Body Model
S True Fail-Safe Receiver While Maintaining
EIA/TIA-485 Compatibility
S Hot-Swap Input Structures on DE and RE
S Enhanced Slew-Rate Limiting Facilitates Error-
Free Data Transmission
S Low-Current Shutdown Mode
S Allow Up to 256 Transceivers on the Bus
S Available in Industry-Standard 8-Pin SO and PDIP
Packages
Applications
Utility Meters
Lighting Systems
Industrial Control
Ordering Information
PART TEMP RANGE PIN-PACKAGE
MAX13085EESA+
+Denotes a lead(Pb)-free/RoHS-compliant package.
-40NC to +85NC
8 SO
Telecom
Security Systems
Instrumentation
Profibus
Typical Operating Circuit
0.1µF
+
1
RO
RE
DE
DI
R
2
3
4
D
8
V
CC
B
7
6
5
TYPICAL HALF-DUPLEX OPERATING CIRCUIT
Rt
A
GND
MAX13085E
DE
DI
B
Rt
A
D
RO
R
RE
_______________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
+5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.)
Supply Voltage (VCC) ........................................................... +6V
Control Input Voltage (RE, DE) ...............................-0.3V to +6V
Driver Input Voltage (DI) .........................................-0.3V to +6V
Driver Output Voltage (A, B) ....................................-8V to +13V
Receiver Input Voltage (A, B) ..................................-8V to +13V
Receiver Output Voltage (RO) ................. -0.3V to (VCC + 0.3V)
Driver Output Current .................................................... ±250mA
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
MAX13085E
maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(VCC = +5.0V ±10%, TA = T
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DRIVER
VCC Supply-Voltage Range V
Differential Driver Output V
Change in Magnitude of Differential Output Voltage
Driver Common-Mode Output Voltage
Change in Magnitude of Common-Mode Voltage
Input-High Voltage V Input-Low Voltage V Input Hysteresis V Input Current I
Input Impedance First Transition at Power-Up
Input Impedance on First Transition after POR Delay
Driver Short-Circuit Output Current
Driver Short-Circuit Foldback Output Current
Thermal-Shutdown Threshold T Thermal-Shutdown Hysteresis T
Input Current (A and B) I
RECEIVER
Receiver Differential Threshold Voltage
Receiver Input Hysteresis
MIN
to T
, unless otherwise noted. Typical values are at VCC = +5.0V and TA = +25NC.) (Note 1)
MAX
CC
RL = 100I (RS-422), Figure 1 RL = 54I (RS-485), Figure 1 No load V
RL = 100I or 54I, Figure 1 (Note 2)
OD
RL = 100I or 54I, Figure 1
RL = 100I or 54I, Figure 1 (Note 2)
OC
DE, DI, RE
IH
DE, DI, RE
IL
DE, DI, RE DE, DI, RE
VDE, VRE = VRE = 2V
VDE = VRE = 2V
ft
0 P V
-7V P V (VCC - 1V) P V
-7V P V
VDE = 0V, VCC = 0V or V
-7V P VCM P +12V
VA + VB = 0V 15 mV
TH
P +12V (Note 3)
OUT
P VCC (Note 3)
OUT
P +1V (Note 3)
OUT
DV
V
DV
R
PWUP
I
OSD
I
OSDF
A, B
V
DV
OD
OC
HYS
IN1
R
TS
TSH
TH
Continuous Power Dissipation (TA = +70°C)
SO (derate 5.9mW/°C above +70°C) ..........................471mW
Operating Temperature Range .......................... -40°C to +85°C
Junction Temperature .....................................................+150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................+300°C
Soldering Temperature (reflow) ......................................+260°C
4.5 5.5 V
P +12V (Note 3)
OUT
VIN = +12V 125
CC
VIN = -7V -100
3 V 2 V
VCC/2 3 V
3 V
100 mV
3.65 8.8
7 60 kΩ
40 250
-250 -40 20
175
15
-200 -125 -50 mV
CC
CC
CC
0.2 V
0.2 V
0.8 V
Q1 FA
-20
V
kI
mA
mA
NC NC
FA
2 ______________________________________________________________________________________
+5.0V, ±15kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = +5.0V ±10%, TA = T
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
RO Output-High Voltage V
RO Output-Low Voltage V
Three-State Output Current at Receiver
Receiver Input Resistance R
Receiver Output Short-Circuit Current
SUPPLY CURRENT
Supply Current I
Supply Current in Shutdown Mode
ESD PROTECTION
ESD Protection for A and B
MIN
to T
, unless otherwise noted. Typical values are at VCC = +5.0V and TA = +25NC.) (Note 1)
MAX
OH
OL
I
OZR
I
OSR
CC
I
SHDN
IO = -1mA
IO = 1mA 0.4 V
0 P VO P VCC P 1 FA
-7V P VCM P +12V
IN
0V P VRO P V
No load, VRE = 0V, DE = V No load, RE = VCC, DE = V No load, VRE = 0V, VDE = 0V
RE = VCC, VDE = 0V
Human Body Model
Contact Discharge IEC 61000-4-2, level 4
Air-Gap Discharge IEC 61000-4-2
CC
CC
CC
VCC -
0.6
96
P 110
1.2 1.8
1.2 1.8
1.2 1.8
2.8 10
Q15
Q8
Q15
MAX13085E
V
kI
mA
mA
FA
kV
DRIVER SWITCHING CHARACTERISTICS WITH INTERNAL SRL (500kbps)
(VCC = +5.0V ±10%, TA = T
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Driver Propagation Delay
Driver Differential Output Rise or Fall Time
Differential Driver Output Skew |t
- t
DPHL
|
_______________________________________________________________________________________ 3
DPLH
Maximum Data Rate 500 kbps Driver Enable to Output High t Driver Enable to Output Low t Driver Disable Time from Low t Driver Disable Time from High t
Driver Enable from Shutdown to Output High
Driver Enable from Shutdown to Output Low
Time to Shutdown t
MIN
to T
, unless otherwise noted. Typical values are at VCC = +5.0V and TA = +25NC.) (Note 1)
MAX
t
DPLH
t
DPHL
t
R , tF
t
DSKEW
DZH
DZL
DLZ
DHZ
t
DZH(SHDN)
t
DZL(SHDN)
SHDN
CL = 50pF, RL = 54I, Figures 2 and 3
CL = 50pF, RL = 54I, Figures 2 and 3
CL = 50pF, RL = 54I, Figures 2 and 3
Figure 4 2500 ns Figure 5 2500 ns Figure 5 100 ns Figure 4 100 ns
Figure 4 5500 ns
Figure 5 5500 ns
200 1000 200 1000
250 900 ns
140 ns
50 340 700 ns
ns
+5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver
RECEIVER SWITCHING CHARACTERISTICS WITH INTERNAL SRL (500kbps)
(VCC = +5.0V ±10%, TA = T
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Receiver Propagation Delay
Receiver Output Skew |t
- t
RPLH
RPHL
|
Maximum Data Rate 500 kbps Receiver Enable to Output Low t
MAX13085E
Receiver Enable to Output High t Receiver Disable Time from Low t Receiver Disable Time from High t
Receiver Enable from Shutdown to Output High
Receiver Enable from Shutdown to Output Low
Time to Shutdown t
Note 1: All currents into the device are positive. All currents out of the device are negative. All voltages are referred to device
ground, unless otherwise noted.
Note 2: ΔVOD and ΔVOC are the changes in VOD and VOC, respectively, when the DI input changes state. Note 3: 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.
MIN
to T
, unless otherwise noted. Typical values are at VCC = +5.0V and TA = +25NC.) (Note 1)
MAX
t
RPLH
t
RPHL
t
RSKEW
RZL
RZH
RLZ
RHZ
t
RZH(SHDN)
t
RZL(SHDN)
SHDN
CL = 15pF, Figures 6 and 7
CL = 15pF, Figures 6 and 7 30 ns
Figure 8 50 ns Figure 8 50 ns Figure 8 50 ns Figure 8 50 ns
Figure 8 5500 ns
Figure 8 5500 ns
50 340 700 ns
200 200
ns
Test Circuits and Waveforms
B
RL/2
V
OD
R
L
A
Figure 1. Driver DC Test Load
V
CC
DE
DI
B
V
A
Figure 2. Driver Timing Test Circuit
V
/2
OC
R
OD
L C
L
V
CC
DI
VCC/2
0
Z
V
O
Y
1/2 V
O
V
O
V
DIFF
0
10%
-V
O
t
R
t
SKEW
t
90%
DPLH
= |
V
= V (B) - V (A)
DIFF
t
DPLH
-
Figure 3. Driver Propagation Delays
t
DPHL
t
DPHL
|
1/2 V
O
90%
t
F
10%
4 ______________________________________________________________________________________
+5.0V, ±15kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Test Circuits and Waveforms (continued)
S1
0 OR V
CC
D
C
L
50pF
R
= 500Ω
L
OUT
MAX13085E
GENERATOR
DE
t
, t
DZH
DZH(SHDN)
OUT
Figure 4. Driver Enable and Disable Times (t
0 OR V
VOM = (0 + VOH)/2
, t
DHZ
DZH
CC
50Ω
, t
DZH(SHDN)
D
V
CC
VCC/2
0
0.25V
t
DHZ
V
OH
0
)
V
CC
R
= 500Ω
S1
C
L
50pF
L
OUT
GENERATOR
DE
t
, t
DZL
DZL(SHDN)
V
CC
OUT
V
OL
Figure 5. Driver Enable and Disable Times (t
_______________________________________________________________________________________ 5
50Ω
VOM = (VOL + VCC)/2
, t
DZL
DLZ, tDLZ(SHDN)
V
CC
VCC/2
0
t
DLZ
0.25V
)
+5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver
Test Circuits and Waveforms (continued)
A
RECEIVER
B
ATE
Figure 6. Receiver Propagation Delay Test Circuit Figure 7. Receiver Propagation Delays
MAX13085E
RE
RO
V
ID
+1.5V
-1.5V
S1 OPEN
S2 CLOSED
= +1.5V
V
S3
R
A
S3
GENERATOR
t
RZH
OUTPUT
, t
RZH(SHDN)
V
ID
VOH / 2
50Ω
V
0
V
0
CC
OH
B
t
V
OH
VCC/2
V
RO
C 15pF
OL
THE RISE TIME AND FALL TIME OF INPUTS A AND B < 4ns
1kΩ
L
RE
RO
RPLH
S1
S2
S1 CLOSED
S2 OPEN
= -1.5V
V
S3
t
RZL
V
CC
, t
RZL(SHDN)
VCC/2
(VOL + VCC)/2
+1V
-1V
t
RPHL
V
CC
0
V
CC
V
OL
S1 OPEN
S2 CLOSED
= +1.5V
V
S3
/250% 50%
V
RE
0.25V
RO
CC
t
RHZ
10%
V
CC
0
V
OH
0
RE
t
RLZ
10%
RO
S1 CLOSED
S2 OPEN
V
= -1.5V
S3
V
/2
CC
0.25V
Figure 8. Receiver Enable and Disable Times
6 ______________________________________________________________________________________
V
CC
0
V
CC
V
OL
+5.0V, ±15kV ESD-Protected, Fail-Safe,
01
12345
345
45
Hot-Swap, RS-485/RS-422 Transceiver
Typical Operating Characteristics
(VCC = +5.0V, TA = +25°C, unless otherwise noted.)
MAX13085E
SUPPLY CURRENT vs. TEMPERATURE
1.60
1.50
1.40
1.30
1.20
1.10
SUPPLY CURRENT (mA)
1.00
0.90
0.80
-40 -10 520-25 35 50 9580 11065 125 TEMPERATURE (°C)
RECEIVER OUTPUT-HIGH VOLTAGE
vs. TEMPERATURE
5.4
5.2
5.0
4.8
4.6
4.4
OUTPUT HIGH VOLTAGE (V)
4.2
4.0
-40 -10 520-25 35 50 9580 11065 125
TEMPERATURE (°C)
NO LOAD
DE = V
DE = 0
IO = -1mA
OUTPUT CURRENT
vs. RECEIVER OUTPUT-HIGH VOLTAGE
60
50
MAX13085E toc01
40
CC
30
20
OUTPUT CURRENT (mA)
10
0
0213
OUTPUT HIGH VOLTAGE (V)
MAX13085E toc02
RECEIVER OUTPUT-LOW VOLTAGE
vs. RECEIVER OUTPUT-LOW VOLTAGE
70
60
50
40
30
OUTPUT CURRENT (mA)
20
10
0
021
DRIVER DIFFERENTIAL OUTPUT CURRENT
vs. TEMPERATURE
0.8
0.7
MAX13085E toc04
0.6
0.5
0.4
0.3
OUTPUT LOW VOLTAGE (V)
0.2
0.1
0
-40 -10 520-25 35 50 9580 11065 125
IO = 1mA
TEMPERATURE (°C)
160
140
MAX13085E toc05
120
100
80
60
40
DIFFERENTIAL OUTPUT CURRENT (mA)
20
0
0
OUTPUT CURRENT
MAX13085E toc03
OUTPUT LOW VOLTAGE (V)
vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX13085E toc06
DIFFERENTIAL OUTPUT VOLTAGE (V)
DRIVER DIFFERENTIAL OUTPUT
VOLTAGE vs. TEMPERATURE
4.8
4.4
4.0
3.6
3.2
2.8
DIFFERENTIAL OUTPUT VOLTAGE (V)
2.4
2.0
-40 -10 520-25 35 50 9580 11065 125 TEMPERATURE (°C)
_______________________________________________________________________________________ 7
RL = 54Ω
200
180
MAX13085E toc07
160
140
120
100
80
60
OUTPUT CURRENT (mA)
40
20
0
-7 -5 -4-6 -3 -2 -1 0 123 54
OUTPUT CURRENT vs. TRANSMITTER
OUTPUT-HIGH VOLTAGE
OUTPUT HIGH VOLTAGE (V)
200
180
160
MAX13085E toc08
140
120
100
80
60
OUTPUT CURRENT (mA)
40
20
0
042681
OUTPUT CURRENT vs. TRANSMITTER
OUTPUT-LOW VOLTAGE
MAX13085E toc09
2
OUTPUT-LOW VOLTAGE (V)
+5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver
Typical Operating Characteristics (continued)
(VCC = +5.0V, TA = +25°C, unless otherwise noted.)
SHUTDOWN CURRENT
vs. TEMPERATURE
10
9
8
7
MAX13085E
6
5
4
3
SHUTDOWN CURRENT (µA)
2
1
0
-40 -10 520-25 35 50 9580 11065 125 TEMPERATURE (°C)
RECEIVER PROPAGATION DELAY
(500kbps)
DRIVER PROPAGATION DELAY vs. TEMPERATURE (500kbps)
600
550
MAX13085E toc10
500
450
400
DRIVER PROPAGATION DELAY (ns)
350
300
-40 -10 520-25 35 50 9580 11065 125
MAX13085E toc13
RL = 100
VA - V
B
5V/div
RO 2V/div
TEMPERATURE (°C)
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE (500kbps)
180
160
MAX13085E toc11
t
DPHL
t
DPLH
DRIVER PROPAGATION DELAY (500kbps)
140
120
100
80
60
40
RECEIVER PROPAGATION DELAY (ns)
20
0
-40 -10 520-25 35 50 9580 11065 125
MAX14780E toc14
RL = 100
TEMPERATURE (°C)
DI 2V/div
VY - V
Z
5V/div
t
DPLH
t
DPHL
MAX13085E toc12
200ns/div
400ns/div
8 ______________________________________________________________________________________
+5.0V, ±15kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Pin Configuration
+
RO
1
R
RE
2
DE
3
DI
D
4
SO
Pin Description
PIN NAME FUNCTION
1 RO
2
3 DE
4 DI
5 GND Ground 6 A Noninverting Receiver Input and Noninverting Driver Output 7 B Inverting Receiver Input and Inverting Driver Output 8 V
RE
CC
Receiver Output. When RE is low and if (A - B) R -50mV, RO is high; if (A - B) P -200mV, RO is low. Receiver Output Enable. Drive RE low to enable RO; RO is high impedance when RE is high. Drive
RE high and DE low to enter low-power shutdown mode. RE is a hot-swap input (see the Hot-Swap Capability section for details).
Driver Output Enable. Drive DE high to enable driver outputs. These outputs are high impedance when DE is low. Drive RE high and DE low to enter low-power shutdown mode. DE is a hot-swap input (see the Hot-Swap Capability section for details).
Driver Input. With DE high, a low on DI forces noninverting output low and inverting output high. Similarly, a high on DI forces noninverting output high and inverting output low.
Positive Supply V
= +5.0V Q10%. Bypass VCC to GND with a 0.1FF capacitor.
CC
V
8
CC
B
7
6
A
5
GND
MAX13085E
Function Tables
TRANSMITTING
INPUTS OUTPUTS
RE
X 1 1 0 1 X 1 0 1 0
0 0 X High-Z High-Z 1 0 X Shutdown
DE DI B A
_______________________________________________________________________________________ 9
RE
0 X 0 X 0 X Open/shorted 1 1 1 X High-Z 1 0 X Shutdown
RECEIVING
INPUTS OUTPUTS
DE A-B RO
R -50mV
P -200mV
1 0
+5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver
Detailed Description
The MAX13085E high-speed transceiver for RS-485/ RS-422 communication contains one driver and one receiver. This device features fail-safe circuitry, which guarantees a logic-high receiver output when the receiv­er inputs are open or shorted, or when they are con­nected to a terminated transmission line with all drivers disabled (see the Fail-Safe section). The MAX13085E also features a hot-swap capability allowing line inser­tion without erroneous data transfer (see the Hot-Swap
MAX13085E
Capability section). The MAX13085E features reduced slew-rate drivers that minimize EMI and reduce reflec­tions caused by improperly terminated cables, allowing error-free data transmission up to 500kbps.
The MAX13085E is a half-duplex transceiver and oper­ates from a single +5.0V supply. Drivers are output short-circuit current limited. Thermal-shutdown circuitry protects drivers against excessive power dissipation. When activated, the thermal-shutdown circuitry places the driver outputs into a high-impedance state.
Fail-Safe
The MAX13085E guarantees a logic-high receiver output when the receiver inputs are shorted or open, or when they are connected to a terminated transmission line with all drivers disabled. This is done by setting the receiver input threshold between -50mV and -200mV. If the dif­ferential receiver input voltage (A - B) is greater than or equal to -50mV, RO is logic-high. If (A - B) is less than or equal to -200mV, RO is logic-low. In the case of a ter­minated bus with all transmitters disabled, the receiver’s differential input voltage is pulled to 0V by the termina­tion. With the receiver threshold of the MAX13085E, this results in a logic-high with a 50mV minimum noise margin. Unlike previous fail-safe devices, the -50mV to
-200mV threshold complies with the ±200mV EIA/TIA­485 standard.
Additionally, parasitic circuit board capacitance could cause coupling of VCC or GND to the enable inputs. Without the hot-swap capability, these factors could improperly enable the transceiver’s driver or receiver.
When VCC rises, an internal pulldown circuit holds DE low and RE high. After the initial power-up sequence, the pulldown circuit becomes transparent, resetting the hot-swap tolerable input.
Hot-Swap Input Circuitry
The enable inputs feature hot-swap capability. At the input there are two nMOS devices, M1 and M2 (Figure 9). When VCC ramps from zero, an internal 7μs timer turns on M2 and sets the SR latch, which also turns on M1. Transistors M2, a 500μA current sink, and M1, a 100μA current sink, pull DE to GND through a 5kΩ resistor. M2 is designed to pull DE to the disabled state against an external parasitic capacitance up to 100pF that can drive DE high. After 7μs, the timer deactivates M2 while M1 remains on, holding DE low against three-state leak­ages that can 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, high-impedance
V
CC
10µs
TIMER
SR LATCH
TIMER
Hot-Swap Capability
Hot-Swap Inputs
When circuit boards are inserted into a hot or powered backplane, differential disturbances to the data bus
DE
5kΩ
can lead to data errors. Upon initial circuit board inser­tion, the data communication processor undergoes its own power-up sequence. During this period, the processor’s logic-output drivers are high impedance
100µA
500µA
M2M1
and are unable to drive the DE and RE inputs of these devices to a defined logic level. Leakage currents up to ±10μA from the high-impedance state of the proces­sor’s logic drivers could cause standard CMOS enable inputs of a transceiver to drift to an incorrect logic level.
10 _____________________________________________________________________________________
Figure 9. Simplified Structure of the Driver Enable Pin (DE)
DE (HOT SWAP)
+5.0V, ±15kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
CMOS input. Whenever VCC drops below 1V, the hot­swap input is reset.
For RE there is a complementary circuit employing two pMOS devices pulling RE to VCC.
±30kV ESD Protection
As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The driver output and receiver input of the MAX13085E have extra protection against static electricity. Maxim’s engineers have developed state-of-the-art structures to protect these pins against ESD of ±15kV without dam­age. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. After an ESD event, the MAX13085E keeps working without latchup or damage.
ESD protection can be tested in various ways. The trans­mitter output and receiver input of the MAX13085E are characterized for protection to the following limits:
• ±15kVusingtheHumanBodyModel
• ±8kVusingtheContactDischargemethodspecified
in IEC 61000-4-2
• ±15kVusingtheAir-GapDischargemethodspecified
in IEC 61000-4-2
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
MAX13085E
Figure 10a shows the Human Body Model, and Figure 10b shows the current waveform it generates when dis­charged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device through a
1.5kΩ resistor.
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and performance of finished equipment. However, it does not specifically refer to integrated circuits. The MAX13085E helps you design equipment to meet IEC 61000-4-2, with­out the need for additional ESD-protection components.
The major difference between tests done using the Human Body Model and IEC 61000-4-2 is higher peak current in IEC 61000-4-2 because series resistance is lower in the IEC 61000-4-2 model. Hence, the ESD withstand voltage measured to IEC 61000-4-2 is gen­erally lower than that measured using the Human Body Model. Figure 10c shows the IEC 61000-4-2 model, and Figure 10d shows the current waveform for IEC 61000-4-2 ESD Contact Discharge test.
Machine Model
The machine model for ESD tests all pins using a 200pF storage capacitor and zero discharge resistance. The objective is to emulate the stress caused when I/O pins are contacted by handling equipment during test and assembly. Of course, all pins require this protection, not just RS-485 inputs and outputs.
R
C
1MΩ
CHARGE-CURRENT-
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
SOURCE
Figure 10a. Human Body ESD Test Model Figure 10b. Human Body Current Waveform
C
s
100pF
______________________________________________________________________________________ 11
R
D
1500Ω
DISCHARGE
RESISTANCE
STORAGE CAPACITOR
DEVICE UNDER
TEST
AMPS
IP 100%
90%
36.8%
10%
PEAK-TO-PEAK RINGING
I
r
(NOT DRAWN TO SCALE)
0
0
t
RL
TIME
t
DL
CURRENT WAVEFORM
+5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver
R
C
50MΩ TO 100MΩ
CHARGE-CURRENT-
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
SOURCE
150pF
C
s
MAX13085E
Figure 10c. IEC 61000-4-2 ESD Test Model Figure 10d. IEC 61000-4-2 ESD Generator Current Waveform
Applications Information
The standard RS-485 receiver input impedance is 12kΩ (1-unit load), and the standard driver can drive up to 32-unit loads. The MAX13085E has a 1/8-unit load receiver input impedance (96kΩ), allowing up to 256 transceivers to be connected in parallel on one commu­nication line. Any combination of the MAX13085E, as well as other RS-485 transceivers with a total of 32-unit loads or fewer, can be connected to the line.
Reduced EMI and Reflections
The MAX13085E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improp­erly terminated cables, allowing error-free data transmis­sion up to 500kbps.
Low-Power Shutdown Mode
Low-power shutdown mode is initiated by bringing both RE high and DE low. In shutdown, the devices typically draw only 2.8μA of supply current.
RE and DE can be driven simultaneously; the devices are guaranteed not to enter shutdown if RE is high and
R
D
330Ω
DISCHARGE
RESISTANCE
STORAGE CAPACITOR
DEVICE UNDER
TEST
I
100%
90%
PEAK
I
10%
tr = 0.7ns TO 1ns
30ns
60ns
Enable times tZH and tZL (see the Switching Characteristics section) assume the devices were not in
a low-power shutdown state. Enable times t t
ZL(SHDN)
assume the devices were in shutdown state.
ZH(SHDN)
It takes drivers and receivers longer to become enabled from low-power shutdown mode (t
ZH(SHDN)
, t
than from driver/receiver-disable mode (tZH, tZL).
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 the Typical Operating Characteristics). The second, a thermal-shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature exceeds +175°C (typ).
Line Length
The RS-485/RS-422 standard covers line lengths up to 4000ft. For line lengths greater than 4000ft, it may be
necessary to implement a line repeater. DE is low for less than 50ns. If the inputs are in this state for at least 700ns, the devices are guaranteed to enter shutdown.
t
and
ZL(SHDN)
)
12 _____________________________________________________________________________________
+5.0V, ±15kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
MAX13085E
120Ω 120Ω
DI
D
DE
RO
RE
Figure 11. Typical Half-Duplex RS-485 Network
R
MAX13085E
B
BB
R
D
DI RO DE
DE
Typical Applications
The MAX13085E transceiver is designed for bidirectional data communications on multipoint bus transmission lines. Figure 11 shows a typical network applications circuit.
To minimize reflections, terminate the line at both ends in its characteristic impedance, and keep stub lengths off the main line as short as possible. The slew-rate-limited MAX13085E is more tolerant of imperfect termination.
Chip Information
PROCESS: BiCMOS
B
D
AAA
R
D
DI
RO
A
R
RERE
DE
DI
RO RE
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
8 SO S8+4
PACKAGE
CODE
OUTLINE
NO.
21-0041 90-0096
LAND
PATTERN
NO.
______________________________________________________________________________________ 13
+5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver
Revision History
REVISION
NUMBER
0 10/11 Initial release —
REVISION
DATE
MAX13085E
DESCRIPTION
PAGES
CHANGED
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
©
2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
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