MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
General Description
The MAX3440E–MAX3444E fault-protected RS-485 and
J1708 transceivers feature ±60V protection from signal
faults on communication bus lines. Each device contains
one differential line driver with three-state output and one
differential line receiver with three-state input. The 1/4-unitload receiver input impedance allows up to 128 transceivers on a single bus. The devices operate from a 5V supply
at data rates of up to 10Mbps. True fail-safe inputs guarantee a logic-high receiver output when the receiver inputs
are open, shorted, or connected to an idle data line.
Hot-swap circuitry eliminates false transitions on the data
bus during circuit initialization or connection to a live
backplane. Short-circuit current-limiting and thermal shutdown circuitry protect the driver against excessive power
dissipation, and on-chip ±15kV ESD protection eliminates
costly external protection devices.
The MAX3440E–MAX3444E are available in 8-pin SO
and PDIP packages and are specified over industrial and
automotive temperature ranges.
Applications
●●
●●
●●
●●
●● ±15kV ESD Protection
●● ±60V Fault Protection
●● Guaranteed 10Mbps Data Rate
(MAX3441E/MAX3443E)
●● Hot Swappable for Telecom Applications
●● True Fail-Safe Receiver Inputs
●● Enhanced Slew-Rate-Limiting Facilitates
Error-Free Data Transmission
(MAX3440E/MAX3442E/MAX3444E)
●● Allow Up to 128 Transceivers on the Bus
●● -7V to +12V Common-Mode Input Range
●● Automotive Temperature Range (-40°C to +125°C)
●● Industry-Standard Pinout
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
8 SO
MAX3440EEPA+
-40°C to +85°C
8 PDIP
MAX3440EASA+
-40°C to +125°C
8 SO
MAX3440EESA+
RS-422/RS-485 Communications
Industrial Networks
Telecommunications Systems
HVAC Controls
Selector Guide
PART
Features
TYPE
MAX3440EAPA+
-40°C to +125°C
8 PDIP
+Denotes a lead(Pb)-free/RoHS-compliant package.
Ordering Information continued at end of data sheet.
DATA RATE
(Mbps)
LOW-POWER
SHUTDOWN
RECEIVER/DRIVER
ENABLE
TRANSCEIVERS
ON BUS
HOT SWAP
MAX3440E
RS-485
0.25
No
Yes
128
Yes
MAX3441E
RS-485
2.5 to 10
No
Yes
128
Yes
MAX3442E
RS-485
0.25
Yes
Yes
128
Yes
MAX3443E
RS-485
2.5 to 10
Yes
Yes
128
Yes
MAX3444E
J1708
0.25
Yes
Yes
128
Yes (only RE)
Pin Configurations and Typical Operating Circuits
TOP VIEW
FAULT 1
RO 2
+
R
DE/RE 3
DI
4
D
DIP/SO
8
VCC FAULT 1
7
B
6
A
5
GND
RO 2
DE/RE
+
R
3
DI 4
D
DIP/SO
8 VCC
7 B
Rt
6
A
5 GND
Pin Configurations and Typical Operating Circuits continued at end of data sheet.
19-2666; Rev 3; 4/14
DE/RE
MAX3440E
MAX3441E
Rt
D
B
A
DI
RO
R
FAULT
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Absolute Maximum Ratings
Voltages Referenced to GND
VCC.........................................................................................+7V
FAULT, DE/RE, RE, DE, DE, DI, TXD....... -0.3V to (VCC + 0.3V)
A, B (Note 1)........................................................................±60V
RO............................................................. -0.3V to (VCC + 0.3V)
Short-Circuit Duration (RO, A, B)...............................Continuous
Continuous Power Dissipation (TA = +70°C)
SO (derate 5.9mW/°C above +70°C)...........................471mW
PDIP (derate 9.09mW/°C above +70°C)......................727mW
Operating Temperature Ranges
MAX344_EE_ _............................................... -40°C to +85°C
MAX344_EA_ _............................................. -40°C to +125°C
Storage Temperature Range............................. -65°C to +150°C
Junction Temperature.......................................................+150°C
Lead Temperature (soldering, 10s).................................. +300°C
Soldering Temperature (reflow)........................................+260°C
Note 1: A, B must be terminated with 54Ω or 100Ω to guarantee ±60V fault protection.
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 = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DRIVER
Differential Driver Output
Change in Magnitude of
Differential Output Voltage
Driver Common-Mode
Output Voltage
Change in Magnitude of
Common-Mode Voltage
VOD
∆VOD
VOC
∆VOC
Figure 1, RL = 100Ω
Figure 1, RL = 54Ω
2
VCC
1.5
VCC
Figure 1, RL = 100Ω or 54Ω (Note 2)
Figure 1, RL = 100Ω or 54Ω
VCC / 2
Figure 1, RL = 100Ω or 54Ω (Note 2)
V
0.2
V
3
V
0.2
V
DRIVER LOGIC
Driver Input High Voltage
Driver Input Low Voltage
Driver Input Current
VDIH
2
V
VDIL
IDIN
Driver Short-Circuit Output Current
(Note 3)
IOSD
Driver Short-Circuit Foldback
Output Current
IOSDF
0V ≤ VOUT ≤ +12V
-7V ≤ VOUT ≤ VCC
(VCC - 1V) ≤ VOUT ≤ +12V (Note 3)
0.8
V
±2
µA
+350
-350
+25
-7V ≤ VOUT ≤ +1V (Note 3)
-25
mA
mA
RECEIVER
Input Current
Receiver Differential Threshold
Voltage
Receiver Input Hysteresis
www.maximintegrated.com
VCC = GND, VA, B = 12V
IA,B
A, B
VTH
-7V ≤ VCM ≤ +12V
∆VTH
250
VA, B = -7V
-150
VA, B = ±60V
-200
25
µA
±6
mA
-50
mV
mV
Maxim Integrated │ 2
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
DC Electrical Characteristics (continued)
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RECEIVER LOGIC
VCC –
0.6
Output High Voltage
VOH
Figure 2, IOH = -1.6mA
V
Output Low Voltage
VOL
Figure 2, IOL = 1mA
0.4
V
Three-State Output Current at
Receiver
IOZR
0V ≤ VA, B ≤ VCC
±1
µA
Receiver Input Resistance
RIN
-7V ≤ VCM ≤ +12V
Receiver Output Short-Circuit
Current
IOSR
0V ≤ VRO ≤ VCC
VCIH
DE, DE, RE, DE/RE
48
kW
±95
mA
CONTROL
Control Input High Voltage
Input Current Latch During First
Rising Edge
IIN
2
DE, DE/RE, RE
V
90
µA
SUPPLY CURRENT
Normal Operation
IQ
ISHDN
Supply Current in Shutdown Mode
Supply Current with Output Shorted
to ±60V
ISHRT
No load,
DI = VCC
or GND
MAX3440E (DE/RE = VCC),
MAX3442E (DE = VCC,
RE = GND),
MAX3444E (DE = RE = GND)
MAX3441E (DE/RE = VCC),
MAX3443E (DE = VCC,
RE = GND)
30
mA
10
DE = GND, RE = VCC (MAX3442E/
MAX3443E)
20
DE = GND, RE = VCC, TA = +25°C
(MAX3442E/MAX3443E)
10
DE = RE = VCC (MAX3444E)
100
DE = RE = VCC, TA = +25°C (MAX3444E)
10
DE = GND, RE = GND, no load
output in three-state (MAX3443E)
±15
µA
mA
Protection Specifications
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
Overvoltage Protection
A, B; RSOURCE = 0, RL = 54Ω
ESD Protection
A, B
MIN
TYP
MAX
±60
Human Body Model
UNITS
V
±15
kV
FAULT DETECTION
Receiver Differential Threshold
FDIPH
VCM = 0V, high limit
270
450
mV
Receiver Differential Threshold
FDIPL
VCM = 0V, low limit
-450
-270
mV
Fault-Detection Common-Mode
Input Voltage Positive
Fault-Detection Common-Mode
Input Voltage Negative
www.maximintegrated.com
12
V
-7
V
Maxim Integrated │ 3
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Switching Characteristics (MAX3440E/MAX3442E/MAX3444E)
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
Driver Propagation Delay
SYMBOL
tPLHA,
tPLHB
CONDITIONS
MIN
MAX3440E/MAX3442E,
Figure 3, RL = 54Ω, CL = 50pF
TYP
MAX
UNITS
2000
ns
2000
ns
2000
ns
350
ns
200
ns
MAX3444E, RDIFF = 60Ω, CDIFF = 100pF
Driver Differential Propagation Delay
tDPLH,
tDPHL
Figure 4, RL = 54Ω, CL = 50pF
Driver Differential Output
Transition Time
tLH,tHL
Figure 4, RL = 54Ω, CL = 50pF
Driver Output Skew
RL = 54Ω, CL = 50pF,
tSKEWAB,
t
= |tPLHA - tPHLB|,
tSKEWBA SKEWAB
tSKEWBA = |tPLHB - tPHLA|
Differential Driver Output Skew
tDSKEW
200
RL = 54Ω, CL = 50pF,
tDSKEW = |tDPLH - tDPHL|
Maximum Data Rate
fMAX
Driver Enable Time to Output High
tPDZH
Figure 5, RL = 500Ω, CL = 50pF
250
2000
kbps
ns
Driver Disable Time from Output High
tPDHZ
Figure 5, RL = 500Ω, CL = 50pF
2000
ns
Driver Enable Time from Shutdown to
Output High
tPDHS
Figure 5, RL = 500Ω, CL = 50pF
(MAX3442E/MAX3444E)
4.2
µs
Driver Enable Time to Output Low
tPDZL
Figure 6, RL = 500Ω, CL = 50pF
2000
ns
Driver Disable Time from Output Low
tPDLZ
Figure 6, RL = 500Ω, CL = 50pF
2000
ns
Driver Enable Time from Shutdown to
Output Low
tPDLS
Figure 6, RL = 500Ω, CL = 50pF
(MAX3442E/MAX3444E)
4.2
µs
Driver Time to Shutdown
tSHDN
RL = 500Ω, CL = 50pF
(MAX3442E/MAX3444E)
800
ns
Receiver Propagation Delay
tRPLH,
tRPHL
Figure 7, CL = 20pF, VID = 2V, VCM = 0V
2000
ns
CL = 20pF, tRSKEW = |tRPLH - tRPHL|
200
ns
Receiver Output Skew
tRSKEW
Receiver Enable Time to Output High
tRPZH
Figure 8, RL = 1kΩ, CL = 20pF
2000
ns
Receiver Disable Time from Output
High
tRPHZ
Figure 8, RL = 1kΩ, CL = 20pF
2000
ns
Receiver Wake Time from Shutdown
tRPWAKE
Figure 8, RL = 1Ω, CL = 20pF
(MAX3442E/MAX3444E)
4.2
µs
Receiver Enable Time to Output Low
tRPZL
Figure 8, RL = 1kΩ, CL = 20pF
2000
ns
Receiver Disable Time from Output Low
tRPLZ
Figure 8, RL = 1Ω, CL = 20pF
2000
ns
Receiver Time to Shutdown
tSHDN
RL = 50Ω, CL= 50pF
(MAX3442E/MAX3444E)
800
ns
www.maximintegrated.com
Maxim Integrated │ 4
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Switching Characteristics (MAX3441E/MAX3443E)
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
SYMBOL
MAX
UNITS
Figure 3, RL = 27Ω, CL = 50pF
60
ns
tDPLH,
tDPHL
Figure 4, RL = 54Ω, CL = 50pF
60
ns
tLH,tHL
Figure 4, RL = 54Ω, CL = 50pF
25
ns
10
ns
10
ns
Driver Propagation Delay
tPLHA,
tPLHB
Driver Differential Propagation Delay
Driver Differential Output
Transition Time
Driver Output Skew
Differential Driver Output Skew
CONDITIONS
MIN
RL = 54Ω, CL = 50pF,
tSKEWAB,
t
= |tPLHA - tPHLB|,
tSKEWBA SKEWAB
tSKEWBA = |tPLHB - tPHLA|
tDSKEW
RL = 54Ω, CL = 50pF,
tDSKEW = |tDPLH - tDPHL|
TYP
Maximum Data Rate
fMAX
Driver Enable Time to Output High
tPDZH
Figure 5, RL = 500Ω, CL = 50pF
1200
ns
Driver Disable Time from Output High
tPDHZ
Figure 5, RL = 500Ω, CL = 50pF
1200
ns
Driver Enable Time from Shutdown to
Output High
tPDHS
Figure 5, RL = 500Ω, CL = 50pF (MAX3443E)
4.2
µs
Driver Enable Time to Output Low
tPDZL
Figure 6, RL = 500Ω, CL = 50pF
1200
ns
Driver Disable Time from Output Low
tPDLZ
Figure 6, RL = 500Ω, CL = 50pF
1200
ns
Driver Enable Time from Shutdown to
Output Low
tPDLS
Figure 6, RL = 500Ω, CL = 50pF (MAX3443E)
4.2
µs
Driver Time to Shutdown
tSHDN
Figure 6, RL = 500Ω, CL = 50pF (MAX3443E)
800
ns
Receiver Propagation Delay
tRPLH,
tRPHL
Figure 7, CL = 20pF, VID = 2V, VCM = 0V
85
ns
Receiver Output Skew
Mbps
CL = 20pF, tRSKEW = |tRPLH - tRPHL|
15
ns
Receiver Enable Time to Output High
tRPZH
Figure 8, RL = 1kΩ, CL = 20pF
400
ns
Receiver Disable Time from Output
High
tRPHZ
Figure 8, RL = 1kΩ, CL = 20pF
400
ns
4.2
µs
Receiver Wake Time from Shutdown
Receiver Enable Wake Time from
Shutdown
tRSKEW
10
tRPWAKE Figure 8, RL = 1kΩ, CL= 20pF (MAX3443E)
tRPSH
Figure 8, RL = 1kΩ, CL = 20pF
400
ns
Receiver Disable Time from Output Low
tRPLZ
Figure 8, RL = 1kΩ, CL= 20pF
400
ns
Receiver Time to Shutdown
tSHDN
RL = 500Ω, CL= 50pF (MAX3443E)
800
ns
Note 2: ∆VOD and ∆VOC 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 before foldback current limiting; the short-circuit foldback output
current applies during current limiting to allow a recovery from bus contention.
www.maximintegrated.com
Maxim Integrated │ 5
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Typical Operating Characteristics
(VCC = +5V, TA = +25°C, unless otherwise noted.)
DRIVER DISABLED,
RECEIVER ENABLED
3
2
1
16
12
8
DRIVER DISABLED,
RECEIVER ENABLED
RECEIVER OUTPUT VOLTAGE
vs. TEMPERATURE
15
10
5
35
30
25
20
15
10
5
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
5.0
RECEIVER OUTPUT VOLTAGE (V)
20
RECEIVER OUTPUT CURRENT (mA)
25
40
MAX3443E toc05
RECEIVER OUTPUT CURRENT
vs. OUTPUT HIGH VOLTAGE
MAX3443E toc04
RECEIVER OUTPUT CURRENT
vs. OUTPUT LOW VOLTAGE
4.5
4.0
VOH, IOUT = +10mA
3.5
3.0
2.5
2.0
1.5
VOL, IOUT = -10mA
1.0
0.5
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
-40 -25 -10 5 20 35 50 65 80 95 110 125
OUTPUT HIGH VOLTAGE (V)
TEMPERATURE (°C)
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
A, B CURRENT
vs. A, B VOLTAGE (TO GROUND)
50
40
30
20
10
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
DIFFERENTIAL OUTPUT VOLTAGE (VA - VB) (V)
www.maximintegrated.com
3.0
RL = 100Ω
2.5
2.0
1.5
RL = 54Ω
1.0
1200
MAX3441E/MAX3443E
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
RL = 54Ω
800
400
0
-400
-800
-1200
0.5
0
1600
A, B CURRENT (µA)
60
DIFFERENTIAL OUTPUT VOLTAGE (V)
70
2000
MAX3443E toc09
OUTPUT LOW VOLTAGE (V)
3.5
MAX3443E toc06
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
MAX3443E toc07
RECEIVER OUTPUT CURRENT (mA)
DRIVER OUTPUT CURRENT (mA)
-40 -25 -10 5 20 35 50 65 80 95 110 125
MAX3442E/MAX3443E/MAX3444E
TEMPERATURE (°C)
30
0
0.01
WTEMPERATURE (°C)
35
80
0.1
MAX3440E/MAX3442E/MAX3444E
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
40
0
1
4
MAX3441E/MAX3443E
0
MAX3443E toc03
DRIVER AND RECEIVER
ENABLED
SUPPLY CURRENT (A)
4
20
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
10
MAX3443E toc08
SUPPLY CURRENT (mA)
5
24
MAX3440E toc02
DRIVER AND RECEIVER
ENABLED
SUPPLY CURRENT (mA)
6
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
MAX3440E toc01
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
-1600
-2000
DRIVER DISABLED,
RECEIVER ENABLED
-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60
A, B VOLTAGE (V)
Maxim Integrated │ 6
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Test Circuits and Waveforms
RL
2
A
DI
VOD
D
B
RL
VCC
VOC
2
Figure 1. Driver VOD and VOC
A
VID
RO
R
B
0
VOL
IOL
(+)
VOH
IOH
(-)
Figure 2. Receiver VOH and VOL
3V
VOM
A
DI
GENERATOR
(NOTE 4)
S1
B
0
CL = 50pF
(NOTE 5)
VCC
VOM =
1.5V
1.5V
tPLHA
OUT
D
50Ω
DI
RL
2
tPHLA
VOH
VOM
A
VOM
VOL
tPHLB
VOH + VOL
ª 1.5V
2
tPLHB
VOH
B
VOM
VOM
VOL
Figure 3. Driver Propagation Times
3V
DI
GENERATOR
(NOTE 4)
50Ω
A
D
RL
B
0
OUT
(A–B)
CL = 50pF (NOTE 5)
tDPHL
tDPLH
VCC
CL
1.5V
1.5V
DI
CL
50%
10%
tLH
90%
90%
ª 2.0V
50%
10%
ª -2.0V
tHL
Figure 4. Driver Differential Output Delay and Transition Times
www.maximintegrated.com
Maxim Integrated │ 7
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Test Circuits and Waveforms (continued)
0 OR 3V
DI
A
DE
GENERATOR
(NOTE 4)
3V
S1
A, B
D
DE
RL = 500W
CL = 50pF
(NOTE 5)
1.5V
1.5V
tPDZH
B
tPDHS
0
tPDHZ
50W
0.25V
A, B
VOM =
VOH
VOM
VOH + VOL
ª 1.5V
2
0
Figure 5. Driver Enable and Disable Times
VCC
0 OR 3V
DI
A
GENERATOR
(NOTE 4)
S1
tPDLS
B
CL = 50pF
(NOTE 5)
1.5V
1.5V
tPDZL
DE
A, B
D
DE
3V
RL = 500Ω
0
tPDLZ
VCC
A, B
50Ω
VOM
0.25V
VOL
Figure 6. Driver Enable and Disable Times
A
GENERATOR
(NOTE 4)
VID
50Ω
R
B
2.0V
RO
(A–B)
CL = 20pF
(NOTE 5)
1.0V
1.0V
0
tRPLH
tRPHL
VCC
1.0V
0
RO
VOM
VOM
0
Figure 7. Receiver Propagation Delay
www.maximintegrated.com
Maxim Integrated │ 8
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Test Circuits and Waveforms (continued)
S3
1.5V
S1
A
-1.5V
VID
R
RO
VCC
1kΩ
S2
B
GENERATOR
(NOTE 4)
CL = 20pF
(NOTE 5)
50Ω
3V
RE
1.5V
0
tRPZH
tRPSH
tRPWAKE
RO
S1 OPEN
S2 CLOSED
VS3 = 1.5V
3V
RE
1.5V
VOH
VCC
RO
1.5V
1.5V
0
3V
RE
1.5V
0
VOL
S1 OPEN
S2 CLOSED
VS3 = 1.5V
3V
RE
1.5V
0
tRPHZ
RO
0.5V
tRPLZ
VOH
RO
0
0
tRPZL
tRPSL
S1 CLOSED
S2 OPEN
VS3 = -1.5V
S1 CLOSED
S2 OPEN
VS3 = -1.5V
VCC
0.5V
VOL
Figure 8. Receiver Enable and Disable Times
Note 4: The input pulse is supplied by a generator with the following characteristics: f = 5MHz, 50% duty cycle; tr ≤ 6ns; Z0 = 50Ω.
Note 5: CL includes probe and stray capacitance.
www.maximintegrated.com
Maxim Integrated │ 9
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Pin Description
PIN
MAX3440E
MAX3441E
MAX3442E
MAX3443E
MAX3444E
NAME
FUNCTION
Fault output. 1 = fault; 0 = normal operation
A or B under the following conditions:
• A-B differential