Maxim MAX22501E 100mbps half-duplex rs-485/rs-422 transceivers for long cable Datasheet

EVALUATION KIT AVAILABLE
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
General Description
Benefits and Features
The MAX22500E features integrated preemphasis circuitry
that extends the distance and increases the data rate of
reliable communication by reducing inter-symbol interference
(ISI) caused by long cables. The MAX22500E features a
flexible logic interface down to 1.6V.
●● Integrated Protection Increases Robustness
• -15V to +15V Common Mode Range
• ±15kV ESD Protection (Human Body Model)
• ±7kV IEC 61000-4-2 Air-Gap ESD Protection
• ±6kV IEC 61000-4-2 Contact Discharge ESD
Protection
• Driver Outputs are Short-Circuit Protected
The MAX22500E/MAX22501E half-duplex ESD-protected
RS-485/RS-422 transceivers are optimized for highspeed (up to 100Mbps) communication over long cables.
These transceivers feature integrated hot-swap protection
and a fail-safe receiver, ensuring a logic-high on the
receiver output when input signals are shorted or open for
longer than 10μs (typ).
The MAX22501E operates without preemphasis and is
powered from a 3V to 5.5V supply.
The MAX22500E is available in a 10-pin TDFN-EP package.
The MAX22501E is available in a 8-pin TDFN-EP package.
Both transceivers operate over the -40°C to +125°C ambient
temperature range.
Applications
●● Motion Control
●● High-Speed Operation Over Long Distances
• Up to 100Mbps Data Rate
• Integrated Preemphasis Extends Cable Length
(MAX22500E)
• High Receiver Sensitivity
• Wide Receiver Bandwidth
• Symmetrical Receiver Thresholds
●● Flexibility for Many Different Applications
• 3V to 5.5V Supply Range
• Low Voltage Logic Supply Down to 1.6V
(MAX22500E)
• Low 5μA (max) Shutdown Current
• Available in 8-pin or 10-pin TDFN Package
• -40°C to +125°C Operating Temperature Range
●● Encoder Interfaces
●● Field Bus Networks
●● Industrial Control Systems
Ordering Information appears at end of data sheet.
●● Backplane Busses
Simplified Block Diagram
VL
VCC
RO
DI
PSET
RO
R
RE
DE
SHUTDOWN
B
RE
A
DE
DI
D
MAX22500E
GND
19-100073; Rev 0; 6/17
VCC
R
B
SHUTDOWN
D
MAX22501E
GND
A
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Absolute Maximum Ratings
VCC.........................................................................-0.3 V to +6 V
RE, DE, DI, VL .....................................................-0.3 V to +6 V
RO (MAX22500E only)............................... -0.3 V to (VL + 0.3) V
RO (MAX22501E only).............................. -0.3V to (VCC + 0.3)V
PSET......................................................... -0.3 V to (VCC+0.3) V
A, B..........................................................................-15V to +15V
Short-Circuit Duration (RO, A, B) to GND..................Continuous
Continuous Power Dissipation (TA = +70°C) (8-Pin TDFN
(derate 24.4mW/°C above +70°C) )...........................1951mW
Continuous Power Dissipation (TA = +70°C) (10-Pin TDFN
(derate 24.4mW/°C above +70°C) )...........................1951mW
Operating Temperature Range ......................... -40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (Soldering 10sec) .............................. +300°C
Reflow Temperature ........................................................ +270ºC
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.
Package Information
TDFN8
PACKAGE CODE
T833-2
Outline Number
21-0137
Land Pattern Number
90-0059
Thermal Resistance, Single-Layer Board:
Junction to Ambient (θJA)
54°C/W
Junction to Case (θJC)
8°C/W
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θJA)
41°C/W
Junction to Case (θJC)
8°C/W
TDFN10
PACKAGE CODE
T1033-2
Outline Number
21-0137
Land Pattern Number
90-0061
Thermal Resistance, Single-Layer Board:
Junction to Ambient (θJA)
54°C/W
Junction to Case (θJC)
9°C/W
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θJA)
41°C/W
Junction to Case (θJC)
9°C/W
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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 thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board.
For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
www.maximintegrated.com
Maxim Integrated │ 2
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Electrical Characteristics
(VCC = 3V to 5.5V, VL = 1.6V to VCC (MAX22500E only), VL ≤ VCC, TA = TMIN to TMAX, unless otherwise noted (Notes 1, 2))
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
POWER
Supply Voltage
VCC
MAX22500E
Preemphasis
disabled
3.0
Preemphasis
enabled
4.5
5
5.5
MAX22500E
12.7
16.5
MAX22501E
4
5.6
MAX22501E
Supply Current
Shutdown Supply Current
ICC
ISHDN
DE = high,
RE= low, no load
5.5
3.0
5.5
5
DE = low, RE= high
Logic Supply Voltage
VL
MAX22500E only
Logic Supply Current
IL
MAX22500E only, no load on RO
V
1.6
16.4
mA
µA
VCC
V
23
µA
DRIVER
Differential Driver Output
RL = 54Ω
1.5
RL = 100Ω
2.0
RL= 54Ω
1.33
1.37
1.41
RL= 100Ω
1.33
1.37
1.41
VOD
Figure 1, Figure 2
Differential Driver
Preemphasis Ratio
DPRE
MAX22500E only,
preemphasis enabled,
4.5V ≤ VCC ≤ 5.5V
(Note 3)
Change in Magnitude of
Differential Output Voltage
ΔVOD
RL = 54Ω, Figure 1 (Note 4)
VOC
RL = 54Ω, Normal mode and
preemphasis, Figure 1
Driver Common-Mode
Output Voltage
Change In Magnitude of
Common-Mode Voltage
ΔVOC
V
VCC/2
RL = 100Ω or 54Ω, Figure 1 (Note 4)
Single-Ended Driver Output
High
VOH
A or B output, IOUT = -20mA
Single-Ended Driver Output
Low
VOL
A or B output, IOUT = +20mA
Differential Output
Capacitance
COD
DE = RE= high, f = 4MHz
Driver Short-Circuit Output
Current
|IOST|
-15V ≤ VOUT ≤ +15V
Input Current (A and B)
IA,B
DE = GND, VCC =
GND, +3.6V or 5.5V
Differential Input
Capacitance
CA,B
Between A and B, DE = GND, f = 2MHz
Common Mode Voltage
Range
VCM
V/V
0.2
V
3
V
0.2
V
2.2
V
0.8
50
V
pF
250
mA
RECEIVER
Receiver Differential
Threshold High
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VTH_H
-15V ≤ VCM ≤ +15V
VIN = +12V
VIN = -7V
+1350
-1100
50
μA
pF
-15
+15
V
+50
+200
mV
Maxim Integrated │ 3
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Electrical Characteristics (continued)
(VCC = 3V to 5.5V, VL = 1.6V to VCC (MAX22500E only), VL ≤ VCC, TA = TMIN to TMAX, unless otherwise noted (Notes 1, 2))
PARAMETER
SYMBOL
CONDITIONS
Receiver Differential
Threshold Low
VTH_L
-15V ≤ VCM ≤ +15V
Receiver Input Hysteresis
ΔVTH
VCM = 0V, time from last transition is
less than tD_FS
Differential Input
Fail-Safe Level
VTH_FS
MIN
TYP
-200
-15V ≤ VCM ≤ +15V
MAX
UNITS
-50
mV
250
-50
mV
+50
mV
LOGIC INTERFACE (RE, RO, DE, DI)
MAX22500E
2/3xVL
MAX22501E
2/3 x
VCC
Input Voltage High
VIH
DE, DI, RE
Input Voltage Low
VIL
DE, DI, RE
Input Current
IIN
DI and DE, RE (after first transition)
V
MAX22500E
1/3 x VL
MAX22501E
1/3 x
VCC
V
+2
μA
10
kΩ
Input Impedance on First
Transition
RIN_FT
RO Output High Voltage
VOH
RE = GND, (VA - VB) >
200mV, IOUT = -1mA
RO Output Low Voltage
VOL
RE = GND, (VA – VB) < -200mV,
IOUT = +1mA
Three-State Output Current
at Receiver
IOZR
RE= high, 0 ≤ VRO ≤ VCC
Thermal Shutdown
Threshold
TSH
Temperature rising
Thermal Shutdown
Hysteresis
TSH_HYS
-2
DE, RE
MAX22500E
VL – 0.4
MAX22501E
VCC - 0.4
V
-1
0.4
V
+1
μA
PROTECTION
ESD Protection
(A and B Pins)
ESD Protection
(All Other Pins)
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+160
°C
10
°C
Human Body Model
±15
IEC61000-4-2 Air Gap Discharge to
GND
±7
IEC61000-4-2 Contact Discharge to
GND
±6
Human Body Model
±2
kV
kV
Maxim Integrated │ 4
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Electrical Characteristics - Switching
(VCC = 3V to 5.5V, VL = 1.6V to VCC (MAX22500E only), VL ≤ VCC, TA = TMIN to TMAX, unless otherwise noted (Notes 1, 2))
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DRIVER (Note 5)
Driver Propagation Delay
Differential Driver Output Skew
Driver Differential Output
Rise and Fall Time
Data Rate
tDPLH
RL = 54Ω, CL = 50pF, Figures 3, 4
20
tDPHL
RL = 54Ω, CL = 50pF, Figures 3, 4
20
tDSKEW
tHL, tLH
|tDPLH – tDPHL|,
RL = 54Ω,
CL= 50pF,
Figures 3, 4 (Note 6)
MAX22501E
1.2
MAX22500E,
VL = VCC,
VCC ≥ 3V
1.2
MAX22500E,
VL ≠ VCC
1.6
RL = 54Ω, CL = 50pF, Figure 4
(Note 6)
DR
ns
ns
3
ns
100
Mbps
Driver Enable to Output High
tDZH
RL = 500Ω, CL = 50pF, Figures 5, 6
30
ns
Driver Enable to Output Low
tDZL
RL = 500Ω, CL = 50pF, Figures 5, 6
30
ns
Driver Disable Time from Low
tDLZ
RL = 500Ω, CL = 50pF, Figures 5, 6
30
ns
Driver Disable Time from High
tDHZ
RL = 500Ω, CL = 50pF, Figures 5, 6
30
ns
Driver Enable from Shutdown
to Output High
tDZH(SHDN)
RL = 1kΩ, CL = 15pF, Figures 5, 6
100
µs
Driver Enable from Shutdown
to Output Low
tDZL(SHDN)
RL = 1kΩ, CL = 15pF, Figures 5, 6
100
µs
800
ns
Time to Shutdown
Driver Preemphasis Interval
tSHDN
tPRE
(Notes 7, 8)
50
MAX22500E only,
RPSET = 4kΩ
4.5V ≤ VCC ≤ 5.5V,
RL = 100Ω, Figure 2 RPSET = 400kΩ
10
13
16
ns
0.8
1
1.2
μs
RECEIVER (Note 5)
Delay to Fail-Safe Operation
Receiver Propagation Delay
Receiver Output Skew
Data Rate
tD_FS
10
tRPLH,tRPHL CL = 15pF, Figure 7, Figure 8
tRSKEW
|tRPHL - tRPLH|, CL= 15pF,
Figures 7, 8 (Note 6)
DR
µs
20
ns
2.5
ns
100
Mbps
Receiver Enable to Output
High
tRZH
RL = 1kΩ, CL = 15pF, Figure 9
30
ns
Receiver Enable to Output
Low
tRZL
RL = 1kΩ, CL = 15pF, Figure 9
30
ns
Receiver Disable Time from
Low
tRLZ
RL = 1kΩ, CL = 15pF, Figure 9
30
ns
Receiver Disable Time from
High
tRHZ
RL = 1kΩ, CL = 15pF, Figure 9
30
ns
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Maxim Integrated │ 5
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Electrical Characteristics - Switching (continued)
(VCC = 3V to 5.5V, VL = 1.6V to VCC (MAX22500E only), VL ≤ VCC, TA = TMIN to TMAX, unless otherwise noted (Notes 1, 2))
PARAMETER
SYMBOL
Receiver Enable from
Shutdown to Output High
tRZH(SHDN)
Receiver Enable from
Shutdown to Output Low
tRZL(SHDN)
Time to Shutdown
tSHDN
CONDITIONS
MIN
MAX
UNITS
RL=1kΩ, CL=15pF, Figure 9
100
μs
RL=1kΩ, CL=15pF, Figure 9
100
μs
800
ns
(Notes 7, 8)
TYP
50
Note 1: All devices are 100% production tested at TA = +25°C. Specifications for all 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: VODP is the differential voltage between A and B during the preemphasis interval on the MAX22500E, and is the differential
voltage when preemphasis is disabled. VODP = DPRE x VOD.
Note 4: ΔV­OD and ΔVOC are the changes in VOD and VOC, respectively, when the DI input changes state.
Note 5: Capacitive load includes test probe and fixture capacitance.
Note 6: Not production tested. Guaranteed by design.
Note 7: Shutdown is enabled by driving RE high and DE low. The device is guaranteed to have entered shutdown after tSHDN has
elapsed.
Note 8: The timing parameter refers to the driver or receiver enable delay, when the device has exited the initial hot-swap protect
state and is in normal operating mode.
Test Circuits/Diagrams
A
VOD
VODP
B
RL
2
RL
2
VOC
Figure 1: Driver DC Test Load
A OR B
VOD
B OR A
VODP
50%
tPRE
MAX22500E only, preemphasis enabled
VODP = DPRE x VOD
Figure 2: Driver Preemphasis Timing
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Maxim Integrated │ 6
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
VCC
DE
A
VOD
VODP
B
RL
CL
Figure 3: Driver Timing Test Circuit
f = 1MHz, tLH = 3ns, tHL = 3ns
DI
50%
VL OR VCC
50%
0
tDPLH
tDPHL
B
A
VOD
VOD = (VA - VB)
VO
90%
90%
0
VOD
10%
10%
-VO
tHL
tLH
tDSKEW = |tDPLH - tDPHL|
Figure 4: Driver Propagation Delays
GND OR VCC
DI
A
B
CL
RL
OUT
DE
50%
tDZH, tDZH(SHDN)
0.25V
GENERATOR
50Ω
OUT
50%
tDHZ
VL OR VCC
0V
VOH
0V
Figure 5: Driver Enable and Disable Times (tDZH, tDHZ)
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Maxim Integrated │ 7
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
V CC
RL
GND OR V CC
DI
A
B
DE
50%
tDZL, tDZL(SHDN)
VL OR VCC
50Ω
GENERATOR
VL OR VCC
OUT
CL
0V
tDLZ
50%
OUT
0.25V
V OL
Figure 6: Driver Enable and Disable Times (tDZL, tDLZ)
A
ATE
R
VID
B
Figure 7: Receiver Propagation Delay Test Circuit
A
+1V
B
RO
-1V
tRPLH
tRPHL
50%
VOH
50%
tRSKEW = |tRPHL – tRPHL|
VOL
Figure 8: Receiver Propagation Delays
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Maxim Integrated │ 8
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
S3
+1.5V
-1.5V
R
V IO
RO
RL
1kΩ
S1
CL
15pF
VL OR VCC
S2
50Ω
GENERATOR
VL OR VCC
VL OR VCC
RE
RE
50%
tRZH, tRZH(SHDN)
0V
V OH
tRZL, tRZL(SHDN)
S1 OPEN
S2 CLOSED
S3 = +1.5V
50%
RO
50%
V OH
RO
V OL
VL OR VCC
VL OR VCC
50%
tRHZ
RE
0V
V OH
RO
0.25V
S1 OPEN
S2 CLOSED
S3 = +1.5V
50%
0V
tRLZ
S1 CLOSED
S2 OPEN
S3 = -1.5V
VL OR VCC
RO
0V
S1 CLOSED
S2 OPEN
S3 = -1.5V
50%
0V
RE
0V
0.25V
V OL
Figure 9: Receiver Enable and Disable Times
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Maxim Integrated │ 9
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Typical Operating Characteristics
VCC = 5V, VL = VCC (MAX22500E only), 60Ω termination between A and B, TA = 25°C, unless otherwise noted.
MAX22500E SUPPLY CURRENT vs. DATA RATE
(PREEMPHASIS DISABLED)
MAX22500E SUPPLY CURRENT vs. DATA RATE
(PREEMPHASIS ENABLED)
toc01
125
ICC (mA)
ICC (mA)
54Ω LOAD
75
125
100
VCC = 5V, 54Ω LOAD
75
VCC = 3.3V, 54Ω LOAD
50
50
25
SQUARE WAVE ON DI (50% DUTY CYCLE)
125
100
VCC = 5V, 54Ω LOAD
100
VCC = 5V, NO LOAD
25
VCC = 3.3V, NO LOAD
0
0
0.1
VCC = 3.3V, 54Ω LOAD
75
50
VCC = 5V, NO LOAD
VCC = 3.3V, NO LOAD
25
NO LOAD
toc03
150
SQUARE WAVE ON DI (50% DUTY CYCLE)
SQUARE WAVE ON DI (50% DUTY CYCLE)
PSET RESISTOR ADJUSTED FOR EACH
DATA RATE
ICC (mA)
150
MAX22501E SUPPLY CURRENT
vs. DATA RATE
toc02
150
1
10
0.01
100
0.1
1
10
RO OUTPUT VOLTAGE LOW
vs. LOAD CURRENT
0.1
1
10
DATA RATE (Mbps)
100
toc05
5.5
(VA - VB) > +200mV
(VA - VB) < -200mV
5.0
0.40
0.35
VCC = 3.3V
4.5
0.30
VOH (V)
VOL (V)
0.01
RO OUTPUT VOLTAGE HIGH
vs. LOAD CURRENT
toc04
0.50
0.45
0
100
DATA RATE (Mbps)
DATA RATE (Mbps)
0.25
VCC = 5V
4.0
0.20
VCC = 3.3V
3.5
VCC = 5V
0.15
0.10
3.0
0.05
0.00
2.5
0
10
20
30
40
50
0
-10
SINK CURRENT (mA)
DIFFERENTIAL DRIVER OUTPUT VOLTAGE
vs. LOAD CURRENT
-50
toc07
VCC = 5V
4.0
3.5
3.0
4
VCC = 3.3V
3
VOD (V)
VOD (V)
-40
4.5
VCC = 5V
5
-30
DIFFERENTIAL DRIVER OUTPUT VOLTAGE
vs. TEMPERATURE
toc06
6
-20
SOURCE CURRENT (mA)
VCC = 3.3V
2.5
2.0
1.5
2
1.0
1
0.5
RL = 54Ω
0.0
0
0
25
50
75
LOAD CURRENT (mA)
www.maximintegrated.com
100
-40 -25 -10 5
20 35 50 65 80 95 110 125
TEMPERATURE (ºC)
Maxim Integrated │ 10
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Typical Operating Characteristics (continued)
VCC = 5V, VL = VCC (MAX22500E only), 60Ω termination between A and B, TA = 25°C, unless otherwise noted.
DRIVER OUTPUT VOLTAGE HIGH
vs. LOAD CURRENT
DRIVER OUTPUT VOLTAGE LOW
vs. LOAD CURRENT
toc08
1.0
DI = VCC
4.5
0.8
0.7
DRIVER OUTPUT VOLTAGE HIGH (V)
DRIVER OUTPUT VOLTAGE LOW (V)
toc09
5.0
DI = GND
0.9
VCC = 3.3V
0.6
0.5
0.4
VCC = 5V
0.3
0.2
0.1
0.0
0
25
50
75
100
125
4.0
VCC = 5V
3.5
VCC = 3.3V
3.0
2.5
2.0
150
0
-25
-50
-75
-100
-125
SOURCE CURRENT (mA)
SINK CURRENT (mA)
DRIVER PROPAGATION DELAY
vs. TEMPERATURE
20
DRIVER PROPAGATION DELAY SKEW
vs. TEMPERATURE
toc10
4.5
16
14
toc11
5.0
RL = 54Ω
CL = 50pF
RL = 54Ω
CL = 50pF
4.0
VCC = 3.3V, tDPHL
VCC = 3.3V, tDPLH
3.5
tDSKEW (ns)
DRIVER PROPAGATION DELAY (ns)
18
12
10
3.0
2.5
8
2.0
6
1.5
4
VCC = 3.3V
1.0
2
VCC = 5V, tDPHL
VCC = 5V, tDPLH
0.5
0
VCC = 5V
0.0
-40 -25 -10 5
20 35 50 65 80 95 110 125
-40 -25 -10 5
TEMPERATURE (ºC)
20 35 50 65 80 95 110 125
TEMPERATURE (ºC)
DRIVER PREMPHASIS
(MAX22500E)
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE
toc13
toc12
20
VCC = 3.3V, tRPHL
18
RECEIVER PROPAGATION DELAY (ns)
-150
VCC = 3.3V, tRPLH
16
DI
5V/div
14
12
VCC = 5V, tRPHL
10
8
VA-VB
2V/div
VCC = 5V, tRPLH
6
4
2
0
RL = 54Ω, CL = 10pF, RSET = 8kΩ
CL = 15pF
-40 -25 -10 5
20 35 50 65 80 95 110 125
TEMPERATURE (ºC)
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0
1
0
1
1 0
20ns/div
1
0
0
1
Maxim Integrated │ 11
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Pin Configuration
TOP VIEW
TOP VIEW
VCC
B
A
10
9
8
GND PSET
7
VCC
B
A
GND
8
7
6
5
6
MAX22500E
MAX22501E
EP
+
+
1
2
3
4
5
1
2
3
4
VL
RO
DE
RE
DI
RO
RE
DE
DI
TDFN-EP
3mm x 3mm
TDFN-EP
3mm x 3mm
Pin Description
PIN
NAME
FUNCTION
-
VL
Logic Supply Input. VL defines the interface logic levels on DE, DI and RO. Apply a
voltage between 1.6V to 5.5V to VL. Bypass VL to ground with a 0.1μF capacitor as
close to the device as possible.
2
1
RO
Receiver Output. See the Receiving Function Table for more information.
3
3
DE
Driver Output Enable. Force DE high to enable driver. Pull DE low to three-state the
driver output.
4
2
RE
Receiver Enable. Pull RE high to disable and the receiver and tri-state RO. The
device is in low-power shutdown when RE = high and DE = low.
5
4
DI
Driver Input. See the Transmitting Function Table for more information.
MAX22500E
MAX22501E
1
6
-
PSET
Preemphasis Select Control Input. Connect a resistor from PSET to GND to select
the preemphasis duration. See the Layout Recommendations in the Applications
Information section for more information. To disable preemphasis, connect PSET to
GND or VCC.
7
5
GND
Ground
8
6
A
Noninverting Receiver Input/Driver Output
9
7
B
Inverting Receiver Input/Driver Output
10
8
VCC
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Supply Input. Bypass VCC to ground with a 0.1μF ceramic capacitor as close to the
device as possible.
Maxim Integrated │ 12
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Functional Tables
Transmitting Function Table
INPUTS
OUTPUTS
RE
DE
DI
A
B
X
1
1
1
0
X
1
0
0
1
0
0
X
High Impedance
1
0
X
High Impedance
Shutdown. A and B are high impedance
X = Don’t care
Receiving Function Table
INPUTS
OUTPUTS
RE
DE
(VA - VB)
Time from Last
A-B Transition
0
X
≥ +200mV
Always
1
RO
0
X
-200mV < (VA - VB) < +200mV
< tD_FS
Indeterminate
RO is latched to previous value
0
X
-50mV < (VA - VB) < +50mV
> tD_FS
1
0
X
≤ -200mV
Always
0
0
X
Open/Shorted
> tD_FS
1
1
1
X
X
High Impedance
1
0
X
X
Shutdown. RO is high impedance
Functional Diagrams
Half-Duplex Application Circuit
5V
3.3V
RE
RE
RO
RO
R
B
DE
DI
A
D
PSET
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VCC
VCC
120Ω
MICROCONTROLLER
MICROCONTROLLER
VL
3.3V
3.3V
R
B
DE
DI
A
120Ω
D
MAX22500E
MAX22501E
GND
GND
Maxim Integrated │ 13
MAX22500E/MAX22501E
Detailed Description
The MAX22500E/MAX22501E ESD-protected RS-485/
RS-422 transceivers are optimized for high-speed, halfduplex communications over long cables. Both transceivers
feature integrated hot-swap functionality to eliminate false
transitions on the driver during power-up or during a hotplug event. These transceivers also feature fail-safe receiver
inputs, guaranteeing a logic-high on the receiver output
when inputs are shorted or open for longer than 10µs (typ).
Receiver Threshold Voltages
The MAX22500E and MAX22501E receivers feature
large threshold hysteresis of 250mV (typ) for increased
differential noise rejection.
Additionally, the receivers feature symmetrical threshold
voltages. Symmetric thresholds have the advantage that
recovered data at the RO output does not have duty cycle
distortion. Typically, fail-safe receivers, which have unipolar
(non-symmetric) thresholds, show some duty cycle distortion
at high signal attenuation due to long cable lengths.
Preemphasis (MAX22500E only)
The MAX22500E features integrated driver preemphasis
circuitry, which strongly improves signal integrity at high data
rates over long distances by reducing inter-symbol interference
(ISI) caused by long cables. Preemphasis is set by connecting
a resistor (RPSET) between PSET and ground.
Long cables attenuate the high-frequency content of
transmitted signals due to the cable's limited bandwidth.
This causes signal/pulse distortion at the receiving end,
resulting in ISI. ISI causes jitter in data and clock recovery
circuits. ISI can be visualized by considering the following
cases: If a series of ones (1's) is transmitted, followed
by a zero (0), the transmission-line voltage has risen to
a high value by the end of the string of ones. It takes
longer for the signal to move toward the '0' state because
the starting voltage on the line is so far from the zero
crossing. Similarly, if a data pattern has a string of zeros
followed by a one and then another zero, the one-to-zero
transition starts from a voltage that is much closer to the
zero-crossing (VA - VB = 0) and it takes much less time
for the signal to reach the zero crossing.
Preemphasis reduces ISI by boosting the differential
signal amplitude at every transition edge, counteracting
the high frequency attenuation of the cable. When the
DI input changes from a logic-low to a logic-high, the
differential output (VA - VB) is driven high to VODP. At the
end of the preemphasis interval, the differential voltage
returns to a lower level (VOD). The preemphasis differential
high voltage (VODP) is typically 1.37 the VOD voltage.
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100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
If DI switches back to a logic-low state before the preemphasis
interval ends, the differential output switches directly from
the 'strong' VODP high to a 'strong' low (-VODP).
Driver behavior is similar when the DI input changes from
a logic-high to a logic-low. When this occurs, the differential
output is pulled low to -VODP until the end of the preemphasis
interval, at which point VA - VB = -VODP.
Setting the Preemphasis Interval
Connect a resistor (RPSET) between PSET and GND to
set the preemphasis time interval on the MAX22500E.
An optimum preemphasis interval ranges from 1 to 1.5
unit intervals (bit time). Use the following equation to
calculate the resistance needed on PSET to achieve a 1.2
preemphasis interval:
RPSET = 400x109/DR
where DR is the data rate and 1Mbps ≤ DR ≤ 100Mbps.
Preemphasis only minimally degrades the jitter on the eye
diagram when using short cables, making it reasonable to
permanently enable preemphasis on systems where cable
lengths may vary or change. Figure 10 and Figure 11
are eye diagrams taken at 100Mbps over a 10m Cat-5e
cable. Note that the eye varies only slightly as preemphasis
is enabled or disabled.
Figure 12 and Figure 13 show the driver eye diagrams
over a long cable length. The MAX22500E was used as
the driver and the eye diagrams were taken at the receiver input after a length of 100m Cat-5e cable. Figure 12
shows the signal at the receiver when the driver preemphasis is disabled. Figure 13 shows the receiver signal
when preemphasis is enabled.
Fail-Safe Functionality
The MAX22500E/MAX22501E feature fail-safe receiver
inputs, guaranteeing a logic-high on the receiver output
(RO) when the receiver inputs are shorted or open for
longer than 10μs (typ). When the differential receiver
input voltage is greater than -50mV [(VA - VB) ≥ -50mV]
for more than 10μs (typ), RO is logic-high. For example, in
the case of a terminated bus with all transmitters disabled,
the receiver’s differential input voltage is pulled to 0V by
the termination resistor, so (VA - VB = 0V) > -50mV and
RO is guaranteed to be a logic-high after 10μs (typ).
Driver Single-Ended Operation
The A and B outputs on the MAX22500E/MAX22501E
can be used in the standard differential operating mode
or as single-ended outputs. Because the driver outputs
swing rail-to-rail, they can also be used as individual
standard TTL logic outputs.
Maxim Integrated │ 14
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
EYE DIAGRAM
PREEMPHASIS DISABLED
EYE DIAGRAM
PREEMPHASIS ENABLED
VA - VB
1V/div
VA - VB
1V/div
100Mbps, 10m Cat-5e Cable 2.5ns/div
Preemphasis Enabled
100Mbps, 10m Cat-5e Cable 2.5ns/div
Preemphasis Disabled
Figure 10: Eye Diagram, 100Mbps Over 10m Cat-5e Cable,
Preemphasis Disabled
Figure 11: Eye Diagram, 100Mbps Over 10m Cat-5e Cable,
Preemphasis Enabled
EYE DIAGRAM
PREEMPHASIS ENABLED
EYE DIAGRAM
PREEMPHASIS DISABLED
VA - VB
700mV/div
VA - VB
700mV/div
50Mbps, 100m Cat-5e Cable 5ns/div
Preemphasis Disabled
Figure 12: Eye Diagram, 50Mbps Over 100m Cat-5e Cable,
Preemphasis Disabled
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50Mbps, 100m Cat-5e Cable 5ns/div
Preemphasis Enabled
Figure 13: Eye Diagram, 50Mbps Over 100m Cat-5e Cable,
Preemphasis Enabled
Maxim Integrated │ 15
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Hot-Swap Capability
is not needed. Pull the RE input high and the DE input
low to put the device in low-power shutdown mode. If
the inputs are in this state for at least 800ns, the parts
are guaranteed to enter shutdown. The MAX22500E/
MAX22501E draw 5μA (max) of supply current when the
device is in shutdown.
The DE and RE enable inputs feature hot-swap functionality.
At each input there are two NMOS devices, M1 and M2
(Figure 14). When VCC ramps from zero, an internal 10ms
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 10μs, 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 CMOS input.
Whenever VCC drops below 1V, the hot-swap input is reset.
The RE and DE inputs can be driven simultaneously. The
MAX22500E/MAX22501E are guaranteed not to enter
shutdown if RE is high and DE is low for less than 50ns.
Applications Information
Layout Recommendations
Ensure that the preemphasis set resistor (RPSET) is located
close to the PSET and GND pins in order to minimize
interference by other signals. Minimize the trace length
to the PSET resistor. Additionally, place a ground plane
under RPSET and surround it with ground connections/
traces to minimize interference from the A and B switching
signals. See Figure 15.
There is a complimentary circuit for RE that uses two
PMOS devices to pull RE to VCC.
Driver Output Protection
Network Topology
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus contention.
The first, a current limit on the output stage provides
immediate protection against short circuits over the whole
common-mode voltage range. The second, a thermal-shutdown
circuit, forces the driver outputs into a high-impedance
state if the die temperature exceeds +160°C (typ).
The MAX22500E/MAX22501E transceivers are designed
for high-speed bidirectional RS-485/RS-422 data
communications. Multidrop networks can cause impedance
discontinuities which affect signal integrity. Maxim recommends using a point-to-point network topology (Figure 16),
instead of a multidrop topology, when communicating with
high data rates. Terminate the transmission line at both
ends with the cable’s characteristic impedance to reduce
reflections.
Low-Power Shutdown Mode
The MAX22500E/MAX22501E feature a low-power
shutdown mode to reduce supply current when the transceiver
VCC
10µs
TIMER
TIMER
5kΩ
DE
(HOT-SWAP)
DE
100µA
500µA
Figure 14: Simplified Structure of the Driver Enable (DE) Pin
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Maxim Integrated │ 16
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Figure 15. Sample PSET Resistor Placement
3.3V
5V
5V
0.1µF
0.1µF
VL
VCC
VCC
RE
MICROCONTROLLER
RE
RO
R
DE
DI
B
B
A
A
RO
R
DE
D
D
DI
PSET
PSET
MAX22500E
GND
MAX22500E
GND
Figure 16: Point-to-Point Half-Duplex Communication for High Speeds
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Maxim Integrated │ 17
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Ordering Information
PREEMPHASIS
LOGIC
SUPPLY
PIN-PACKAGE
PIN-PITCH
PACKAGE
CODE
MAX22500EATB+
Y
Y
TDFN10-EP*
5mm
T1033+2
MAX22500EATB+T
Y
Y
TDFN10-EP*
5mm
T1033+2
MAX22501EATA+
N
N
TDFN8-EP*
6.5mm
T833+2
MAX22501EATA+T
N
N
TDFN8-EP*
6.5mm
T833+2
PART
+ Denotes a lead (Pb)-free/RoHS-compliant package.
* EP = Exposed Pad
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Maxim Integrated │ 18
MAX22500E/MAX22501E
100Mbps Half-Duplex RS-485/RS-422
Transceivers for Long Cables
Revision History
REVISION
NUMBER
REVISION
DATE
0
6/17
DESCRIPTION
Initial release
PAGES
CHANGED
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For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2017 Maxim Integrated Products, Inc. │ 19