High-ESD Profibus RS-485 Transceiver
MAX14770E
General Description
The MAX14770E is a half-duplex, Q35kV high ESD-
protected transceiver for PROFIBUS-DP and RS-485
applications. In addition, it can be used for RS-422/V.11
communications. The MAX14770E is designed to meet
IEC 61158-2, TIA/EIA-422-B, TIA/EIA-485-A, V.11, and
X.27 standards.
The MAX14770E operates from a +5V supply and has
true fail-safe circuitry that guarantees a logic-high receiv-
er output when the receiver inputs are open or shorted.
The MAX14770E features a 1/4 standard-unit load
receiver input impedance, allowing up to 128 1/4 unit
load transceivers on the bus. Drivers are short-circuit
current limited and are protected against excessive
power dissipation by thermal-shutdown circuitry.
The MAX14770E is available in an 8-pin SO and an 8-pin
FMAX® specified over the extended (-40NC to +105NC) tem-
perature range. It is also available in a tiny TDFN (3mm x
3mm) package and specified over the automotive (-40NC
to +125NC) temperature range.
Applications
PROFIBUS-DP Networks
Industrial Fieldbuses
Motion Controllers
RS-485 Networks
Machine Encoders
Features
S Meets EIA 61158-2 Type 3 PROFIBUS-DP
S +4.5V to +5.5V Supply Voltage
S 20Mbps Data Rate
S Short-Circuit Protected
S True Fail-Safe Receiver
S Thermal-Shutdown Protected
S Hot Swappable
S High ESD Protection
±35kV Human Body Model (HBM)
±20kV IEC 61000-4-2 Air Gap
±10kV IEC 61000-4-2 Contact
S -40NC to +125NC Automotive Temperature Range
in Tiny 8-Pin (3mm x 3mm) TDFN
19-5017; Rev 3; 10/12
Functional Diagram
Ordering Information
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
The PROFI BUS PROCESS FIELD BUS logo is a registered
trademark of PROFIBUS and PROFINET International (PI).
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Typical PROFIBUS-DP Operating Circuit appears at end of
data sheet.
DI
DE
RO
A
D
R
SHUTDOWN
B
RE
MAX14770E
PART TEMP RANGE PIN-
PACKAGE
TOP
MARK
MAX14770EGUA+T -40NC to +105NC 8 FMAX —
MAX14770EGSA+T -40NC to +105NC8 SO —
MAX14770EATA+T -40NC to +125NC8 TDFN-EP* BMG
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
2 Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
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.
(Voltages referenced to GND.)
VCC ....................................................................... -0.3V to +6.0V
RE, RO .......................................................-0.3V to (VCC + 0.3V)
DE, DI ...................................................................-0.3V to +6.0V
A, B .....................................................................-8.0V to +13.0V
Short-Circuit Duration (RO, A, B) to GND .................Continuous
Continuous Power Dissipation (TA = +70NC)
SO (derate 7.6mW/NC above +70NC) .........................606mW
TDFN (derate 24.4mW/NC above +70NC) .................1951mW
FMAX (derate 4.8mW/NC above +70NC) .................. 387.8mW
Operating Temperature Range
FMAX.............................................................-40NC to +105NC
SO ................................................................. -40NC to +105NC
TDFN ............................................................. -40NC to +125NC
Storage Temperature Range ............................ -65NC to +150NC
Junction Temperature Range ........................... -40NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
ELECTRICAL CHARACTERISTICS
(VCC = +5V Q10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25NC.) (Note 2)
ABSOLUTE MAXIMUM RATINGS
Note 1: 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.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
SO
Junction-to-Ambient Thermal Resistance (qJA) ........ 132°C/W
Junction-to-Case Thermal Resistance (qJC)...............38°C/W
µMAX
Junction-to-Ambient Thermal Resistance (qJA) ..... 206.3°C/W
Junction-to-Case Thermal Resistance (qJC)...............42°C/W
TDFN
Junction-to-Ambient Thermal Resistance (qJA) .......... 41°C/W
Junction-to-Case Thermal Resistance (qJC).................8°C/W
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Power-Supply Range VCC 4.5 5.5 V
Supply Current ICC
DE = 1, RE = 0 or
DE = 0, RE = 0 or
DE = 1, RE = 1; no load
2.5 4 mA
Shutdown Supply
Current ISH DE = 0, RE = 1 15 FA
DRIVER
Differential Driver
Output |VOD|RL = 54I, DI = VCC or GND; Figure 1 2.1 V
Differential Driver
Peak-to-Peak Output VODPP Figure 2 (Note 3) 4.0 6.8 V
Change in Magnitude
of Differential Output
Voltage
DVOD RL = 54I; Figure 1 (Note 4) -0.2 0 +0.2 V
Driver Common-
Mode Output Voltage VOC RL = 54I; Figure 1 1.8 3 V
Change in Common-
Mode Voltage DVOC RL = 54I; Figure 1 (Note 4) -0.2 +0.2 V
Driver Short-Circuit
Output Current
(Note 5)
IOSD
0V P VOUT P +12V; output low +250
mA
-7V P VOUT P VCC; output high -250
3Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +5V Q10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25NC.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Driver Short-Circuit
Foldback Output
Current (Note 5)
IOSDF
(VCC - 1V) P VOUT P +12V; output low -15
mA
-7V P VOUT P +1V; output high +15
LOGIC INPUTS
Driver Input High
Voltage VIH DE, DI, RE 2.0 V
Driver Input Low
Voltage VIL DE, DI, RE 0.8 V
Driver Input
Hysteresis VHYS DE, DI, RE 50 mV
Driver Input Current IIN DE, DI, RE -1 +1 FA
Input Impedance in
Hot Swap
RDE Figure 11 until the first low-to-high transition of DE
occurs
1 5.6 10 kW
RRE Figure 11 until the first high-to-low transition of RE
occurs
RECEIVER
Input Current (A, B) IA, IBDE = GND, VCC = VGND or
+5.5V
VIN = 12V +250 FA
VIN = -7V -200
Differential Input
Capacitance CAB Between A and B, DE = RE = GND at 6MHz 8 pF
Receiver Differential
Threshold Voltage VTH -7V P VCM P 12V -200 -125 -50 mV
Receiver Input
Hysteresis DVTH VCM = 0V 15 mV
LOGIC OUTPUT
Output High Voltage VOH IOUT = -6mA, VA - VB = VTH 4 V
Output Low Voltage VOL IOUT = 6mA, VA - VB = -VTH 0.4 V
Three-State Receiver
Output Current IOZR 0V P VOUT P VCC -1 +1 FA
Receiver Input
Resistance RIN -7V P VCM P 12V 48 kI
Receiver Output
Short-Circuit Current IOSR 0V P VRO P VCC -110 +110 mA
PROTECTION SPECIFICATIONS
Thermal-Shutdown
Threshold VTS +160 NC
Thermal-Shutdown
Hysteresis VTSH 15 NC
ESD Protection, A
and B Pins
HBM ±35
kVIEC 61000-4-2 Air-Gap Discharge to GND ±20
IEC 61000-4-2 Contact Discharge to GND ±10
4 Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +5V Q10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25NC.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
ESD Protection, All
Other Pins HBM ±2kV
DRIVER SWITCHING CHARACTERISTICS
Driver Propagation
Delay
tDPLH RL = 54I, CL = 50pF; Figures 3 and 4 15 28 ns
tDPHL
Differential Driver
Output Skew |tDPLH
- tDPHL|
tDSKEW RL = 54I, CL = 50pF; Figures 3 and 4 1.2 ns
Driver Output
Transition Skew
|tt(MLH)|, |tt(MHL)|
tTSKEW RL = 54I, CL = 50pF; Figures 3 and 5 2 ns
Driver Differential
Output Rise or Fall
Time
tLH, tHL RL = 54I, CL = 50pF; Figures 3 and 4 7 15 ns
Maximum Data Rate 20 Mbps
Driver Enable to
Output High tDZH RL = 500I, CL = 50pF; Figure 6 25 48 ns
Driver Enable to
Output Low tDZL RL = 500I, CL = 50pF; Figure 7 25 48 ns
Driver Disable Time
from Low tDLZ RL = 500I, CL = 50pF; Figure 7 20 40 ns
Driver Disable Time
from High tDHZ RL = 500I, CL = 50pF, Figure 6 20 40 ns
Driver Enable Skew
Time |tZL - tZH|RL = 500I, CL = 50pF; Figures 6 and 7 8 ns
Driver Disable Skew
Time |tLZ - tHZ|RL = 500I, CL = 50pF; Figures 6 and 7 8 ns
Driver Enable High—
Propagation Delay
Difference
tDZH -
tDPHL 8 20 ns
Driver Enable Low—
Propagation Delay
Difference
tDZL - tDPHL 10 20 ns
Driver Enable from
Shutdown to Output
High
tDZL(SHDN) RL = 500I, CL = 50pF; Figure 7 (Note 6) 46 100 Fs
Driver Enable from
Shutdown to Output
Low
tDZH(SHDN) RL = 500I, CL = 50pF; Figure 6 (Note 6) 46 100 Fs
Time to Shutdown tSHDN (Note 6) 50 800 ns
5Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +5V Q10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25NC.) (Note 2)
Note 2: Devices are production tested at TA = +25NC. Specifications over temperature limits are guaranteed by design.
Note 3: VODPP is the difference in VOD, with the DI at high and DI at low.
Note 4: DVOD and DVOC are the changes in |VOD| and |VOC|, respectively, with the DI at high and DI at low.
Note 5: The short-circuit output current applies to peak current just prior to foldback current limiting; the short-circuit foldback out-
put current applies during current limiting to allow a recovery from bus contention.
Note 6: 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 800ns, the device is guaranteed to
have entered shutdown.
Note 7: Capacitive load includes test probe and fixture capacitance.
Note 8: Guaranteed by characterization; not production tested.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
RECEIVER SWITCHING CHARACTERISTICS
Receiver Propagation
Delay
tRPLH CL = 15pF; Figures 8 and 9 (Note 7) 28 ns
tRPHL
Receiver Output
Skew tRSKEW CL = 15pF; Figures 8 and 9 (Notes 7, 8) 2 ns
Maximum Data Rate 20 Mbps
Receiver Enable to
Output High tRZH S2 closed; RL = 1kI, CL = 15pF; Figure 10 30 ns
Receiver Enable to
Output Low tRZL S1 closed; RL = 1kI, CL = 15pF; Figure 10 30 ns
Receiver Disable
Time from Low tRLZ S1 closed; RL = 1kI, CL = 15pF; Figure 10 30 ns
Receiver Disable
Time from High tRHZ S2 closed; RL = 1kI, CL = 15pF; Figure 10 30 ns
Receiver Enable from
Shutdown to Output
High
tRZL(SHDN) S1 closed; RL = 1kI, CL = 15pF; Figure 10
(Notes 6, 7) 100 Fs
Receiver Enable from
Shutdown to Output
Low
tRZH(SHDN) S2 closed; RL = 1kI, CL = 15pF; Figure 10
(Notes 6, 7) 100 Fs
Time to Shutdown tSHDN (Note 6) 50 800 ns
6 Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Figure 1. Driver DC Test Load
Figure 3. Driver Timing Test Circuit
Figure 4. Driver Propagation Delays
Figure 2. VODPP Swing Under Profibus Equivalent Load Test
VOD
A
B
VOC
RL
2
RL
2
RLCL
VID
VCC
DI
DE
A
B
VCC
DI
DE
A
B
VCC
195I
110IVOD
195I
1.5V 1.5V
0
DI
B
A
20%
80%
20%
80%
0
VO
-VO
VDIFF
tDSKEW = |tDPLH - tDPHL|
VDIFF = VA - VB
VCC f = 1MHz, tLH P 3ns, tHL P 3ns
1/2 VO
tDPLH
tLH tHL
tDPHL
VO
1/2 VO
7Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Figure 5. Driver Transition Skew
Figure 6. Driver Enable and Disable Times
Figure 7. Driver Enable and Disable Times
A
B
50%
50% 50%
50%
tt(MLH) tt(MHL)
0
0
0.25V
1.5V
tDZH, tDZH(SHDN)
tDHZ
DE
VCC
VOH
1.5V
OUT
RL = 500I
50I
OUT
S1
A
B
D
DI
0 OR VCC
GENERATOR
DE
CL
50pF
RL = 500I
50I
OUT
0
0.25V
1.5V
tDZL, tDZL(SHDN)
tDLZ
DE
S1
A
B
D
DI
0 OR VCC
VCC
VCC
1.5V
VCC
OUT
VOL
GENERATOR
DE
8 Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Figure 8. Receiver Propagation Delay Test Circuit
Figure 9. Receiver Propagation Delays
Figure 10. Receiver Enable and Disable Times
VID
B
A
RECEIVER
OUTPUT
ATE R
A
B
VOH
VOL
RO
tRPHL
tRSKEW = |tRPHL - tRPLH|
t = 1MHz, tLH P 3ns, tHL P 3ns
tRPLH
-1V
1V
2
VCC
2
VCC
GENERATOR 50I
R
1kI
CL
15pF
R
-1.5V
+1.5V
RO
S1 VCC
S2
S3
VID
RE
RE
RO
RE
RO
RE
RE
RO
RO
0
tRHZ tRLZ
0.25V
0.25V
1.5V 1.5V
0 0
2
S1 OPEN
S2 CLOSED
S3 = +1.5V
S1 OPEN
S2 CLOSED
S3 = +1.5V
S1 CLOSED
S2 OPEN
S3 = -1.5V
S1 CLOSED
S2 OPEN
S3 = -1.5V
VOH
0
0
VOH
VCC
VCC
VCC
1.5V1.5V
VCC
tRZL, tRZL(SHDN)
VOL
0
VCC
VCC
VCC
VOL
tRZH, tRZH (SHDN)
2
VCC
9Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Typical Operating Characteristics
(VCC = +5V, TA = +25NC, unless otherwise noted.)
DIFFERENTIAL OUTPUT VOLTAGE VOD
vs. TEMPERATURE
MAX14770E toc09
TEMPERATURE (°C)
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
11095-25 -10 5 35 50 6520 80
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.0
-40 125
RL = 54Ω
DIFFERENTIAL OUTPUT VOLTAGE VOD
vs. OUTPUT CURRENT
MAX14770E toc08
OUTPUT CURRENT (mA)
DIFFERENTIAL OUTPUT VOLTAGE (V)
604020
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0
0 80
DRIVER PROPAGATION DELAY
vs. TEMPERATURE
MAX14770E toc07
TEMPERATURE (°C)
DRIVER PROPAGATION DELAY (ns)
1109580655035205-10-25
5
10
15
20
25
0
-40 125
RL = 54Ω, CL = 50pF
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE
MAX14770E toc06
TEMPERATURE (°C)
RECEIVER PROPAGATION DELAY (ns)
1109580655035205-10-25
5
10
15
20
25
0
-40 125
RECEIVER OUTPUT RO CURRENT
vs. OUTPUT HIGH VOLTAGE
MAX14770E toc05
OUTPUT HIGH VOLTAGE (V)
OUTPUT CURRENT (mA)
4.54.03.53.02.52.01.5
10
20
30
40
50
60
0
1.0 5.0
RECEIVER OUTPUT RO CURRENT
vs. OUTPUT LOW VOLTAGE
MAX14770E toc04
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT (mA)
3.53.02.52.01.51.00.5
10
20
30
40
50
60
0
0 4.0
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX14770E toc03
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT (µA)
1109580655035205-10-25
0.5
1.0
1.5
2.0
2.5
3.0
0
-40 125
SUPPLY CURRENT
vs. DATA RATE
MAX14770E toc02
DATA RATE (kbps)
SUPPLY CURRENT (mA)
15,00010,0005,000
5
10
15
20
25
30
35
40
45
50
55
60
0
0 20,000
PROFIBUS EQUIVALENT LOAD
NO LOAD
NO-LOAD DC SUPPLY CURRENT
vs. TEMPERATURE
MAX14770E toc01
TEMPERATURE (°C)
NO-LOAD SUPPLY CURRENT (mA)
1109580655035205-10-25
0.5
1.0
1.5
2.0
2.5
0
-40 125
DE = VCC
DE = GND
10 Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Typical Operating Characteristics (continued)
(VCC = +5V, TA = +25NC, unless otherwise noted.)
DRIVER DISABLE TIME
FROM HIGH tDHZ
MAX14770E toc18
10ns/div
DE
2V/div
A
2V/div
DI = VCC, RL = 500Ω, CL = 50pF
DRIVER DISABLE TIME
FROM LOW tDLZ
MAX14770E toc17
10ns/div
DE
2V/div
B
2V/div
DI = VCC, RL = 500Ω, CL = 50pF
DRIVER ENABLE TO
OUTPUT LOW tDZL
MAX14770E toc16
10ns/div
DE
2V/div
B
2V/div
DI = VCC, RL = 500Ω, CL = 50pF
DRIVER ENABLE TO
OUTPUT HIGH tDZH
MAX14770E toc15
10ns/div
DE
2V/div
A
2V/div
DI = VCC, RL = 500Ω, CL = 50pF
DRIVER OUTPUT RISE AND FALL TIME
vs. TEMPERATURE
MAX14770E toc14
TEMPERATURE (°C)
TIME (ns)
11095-25 -10 5 35 50 6520 80
2
4
6
8
10
12
14
16
0
-40 125
RL = 54Ω, CL = 50pF FALL TIME
RISE TIME
DRIVER OUTPUT TRANSITION SKEW
vs. TEMPERATURE
MAX14770E toc13
TEMPERATURE (°C)
DRIVER OUTPUT TRANSITION SKEW (ns)
1109580655035205-10-25
1
2
3
4
5
0
-40 125
RL = 54Ω, CL = 50pF
DRIVER DIFFERENTIAL SKEW tDSKEW
vs. TEMPERATURE
MAX14770E toc12
TEMPERATURE (°C)
DRIVER OUTPUT SKEW (ns)
1109580655035205-10-25
1
2
3
4
5
0
-40 125
RL = 54Ω, CL = 50pF
DRIVER OUTPUT CURRENT
vs. OUTPUT HIGH VOLTAGE
MAX14770E toc11
OUTPUT HIGH VOLTAGE (V)
OUTPUT CURRENT (mA)
31-1-3-5
20
40
60
80
100
120
140
0
-7 5
DRIVER OUTPUT CURRENT
vs. OUTPUT LOW VOLTAGE
MAX14770E toc10
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT (mA)
963
20
40
60
80
100
120
140
0
0 12
11Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Pin Configurations
Pin Description
PIN NAME FUNCTION
1 RO Receiver Output. When RE is low and (A - B) R -50mV, RO is high; if (A - B) P -200mV, RO is low.
2RE Receiver 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.
3 DE Driver Enable. Drive DE high to enable driver output. The driver outputs are high impedance when
DE is low. Drive RE high and DE low to enter low-power shutdown mode.
4 DI
Driver Input. With DE high, a low on DI forces the noninverting output, A, low and the inverting out-
put, B, high. Similarly, a high on DI forces the noninverting output, A, high and the inverting output,
B, low.
5 GND Ground
6 A Noninverting Receiver Input and Noninverting Driver Output
7 B Inverting Receiver Input and Inverting Driver Output
8 VCC Positive Supply. Bypass VCC to GND with a 0.1FF ceramic capacitor as close as possible to the
device.
— EP Exposed Pad (TDFN Only). Connect EP to GND.
MAX14770E
+
TOP VIEW
A
GND
8
7
VCC
B
SO/µMAX
6
5
DE
DI
1
2
RO
3
4
RE
1
+
4
3
8
6
5
VCC
MAX14770E
27B
A
GND
DI
RO
DE
TDFN
(3mm × 3mm)
*CONNECT EXPOSED PAD TO GND.
*EP
RE
12 Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Detailed Description
The MAX14770E is a half-duplex, Q35kV high ESD-
protected transceiver for PROFIBUS-DP, RS-485, and
RS-422 communications. The device features true fail-
safe circuitry that guarantees a logic-high receiver
output when the receiver inputs are open or shorted,
or when they are connected to a terminated transmis-
sion line with all drivers disabled (see the True Fail-Safe
section). The MAX14770E supports data rates up to
20Mbps.
The MAX14770E operates from a single +4.5V to +5.5V
supply. Drivers are output short-circuit current limit-
ed. Thermal-shutdown circuitry protects drivers against
excessive power dissipation. When activated, the ther-
mal-shutdown circuitry places the driver outputs into
a high-impedance state. The MAX14770E has a hot-
swap input structure that prevents disturbances on the
differential signal lines when the MAX14770E is powered
up (see the Hot-Swap Capability section).
True Fail-Safe
The MAX14770E 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 having the receiver
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 thresholds of the MAX14770E, this results
in a logic-high with a 50mV minimum noise margin. The
-50mV to -200mV threshold complies with the Q200mV
EIA/TIA-485 standard.
Hot-Swap Capability
Hot-Swap Inputs
When circuit boards are inserted into a hot or powered
backplane, disturbances to the enable inputs and differ-
ential receiver inputs can lead to data errors. Upon initial
circuit board insertion, the processor undergoes its pow-
er-up sequence. During this period, the processor out-
put drivers are high impedance and are unable to drive
the DE and RE inputs of the MAX14770E to a defined
logic level. Leakage currents up to 10FA from the high-
impedance output of a controller could cause DE and RE
to drift to an incorrect logic state. Additionally, parasitic
circuit board capacitance could cause coupling of VCC
or GND to DE and RE. These factors could improperly
enable the driver or receiver. However, the MAX14770E
has hot-swap inputs that avoid these potential problems.
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 inputs.
Hot-Swap Input Circuitry
The MAX14770E DE and RE enable inputs feature
hot-swap capability. At the input, there are two NMOS
devices, M1 and M2 (Figure 11). When VCC ramps from
0, an internal 15Fs timer turns on M2 and sets the SR
latch that also turns on M1. Transistors M2, a 1mA cur-
rent sink, and M1, a 100FA current sink, pull DE to GND
through a 5.6kI resistor. M2 is designed to pull DE to
the disabled state against an external parasitic capaci-
tance up to 100pF that can drive DE high. After 15Fs, 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.
For RE, there is a complementary circuit employing two
PMOS devices pulling RE to VCC.
Table 1. Functional Table (Transmitting)
Table 2. Functional Table (Receiving)
X = Don’t care.
X = Don’t care.
TRANSMITTING
INPUTS OUTPUTS
RE DE DI B A
X 1 1 0 1
X 1 0 1 0
0 0 X High-Z High-Z
1 0 X High-Z and shutdown
RECEIVING
INPUTS OUTPUT
RE DE A-B RO
0 X R -0.05V 1
0 X P -0.2V 0
0 X Open/shorted 1
1 1 X High-Z
1 0 X High-Z and
shutdown
13Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Thermal-Shutdown Protection
The MAX14770E features thermal-shutdown circuitry.
The internal switch turns off when the junction tempera-
ture exceeds +160NC (typ) and immediately goes into a
fault mode. The device exits thermal shutdown after the
junction temperature cools by 15NC (typ).
Applications Information
128 Transceivers on the Bus
The standard RS-485 receiver input impedance is one
unit load, and a standard driver can drive up to 32 unit
loads. The MAX14770E transceiver has a 1/4 unit load
receiver, which allows up to 128 transceivers connected
in parallel on one communication line. Connect any com-
bination of these devices, and/or other RS-485 devices,
for a maximum of 32 unit loads to the line.
Low-Power Shutdown Mode
Low-power shutdown mode is initiated by bringing both
RE high and DE low. In shutdown, the devices draw only
15FA (max) of supply current. RE and DE can be driven
simultaneously; the devices are 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 800ns, the devices
are guaranteed to enter shutdown.
Driver Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus conten-
tion. The first, a foldback current limit on the output
stage, provides immediate protection against short cir-
cuits 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
+160NC (typ).
Typical Application
The MAX14770E transceivers are designed for bidirectional
data communications on multipoint bus transmission lines.
Figure 12 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.
Profibus Termination
The MAX14770E is designed for driving PROFIBUS-DP
termination networks. With a worst-case loading of two
termination networks with 220I termination impedance
and 390I pullups/pulldowns, the drivers can drive
V(A - B) > 2.1V output.
Figure 11. Simplified Structure of the Driver Enable Pin (DE)
VCC
TIMER
DE
TIMER
5.6kI
15Fs
100FA1mA
M2M1
DRIVER
ENABLE
(HOT SWAP)
14 Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
Extended ESD Protection
ESD protection structures are incorporated on all pins
to protect against electrostatic discharges up to Q2kV
(HBM) encountered during handling and assembly.
A and B are further protected against high ESD up
to Q35kV (HBM) without damage. The A and B pins
are also protected against Q20kV Air-Gap and Q10kV
Contact IEC61000-4-2 ESD events. The ESD structures
withstand high ESD both in normal operation and when
the device is powered down. After an ESD event, the
MAX14770E continues to function without latchup.
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents test
setup, test methodology, and test results.
Human Body Model
Figure 13 shows the HBM. Figure 14 shows the current
waveform it generates when discharged into a low-
impedance state. This model consists of a 100pF capaci-
tor charged to the ESD voltage of interest that is then
discharged into the device through a 1.5kI resistor.
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and
performance of finished equipment. It does not spe-
cifically refer to integrated circuits. The MAX14770E
is specified for Q20kV Air-Gap Discharge and Q10kV
Contact Discharge IEC 61000-4-2 on the A and B pins.
The main difference between tests done using the HBM
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
Figure 12. Typical Half-Duplex RS-485 Network
Figure 13. Human Body ESD Test Model Figure 14. Human Body Current Waveform
DI
R
D
DE RO RE
DI
R
DE RO RE
D
B
B
120I120I
A
A
BA DI
R
D
DE
RO
RE
DI
DE
RO
RE
B
A
R
D
MAX14770E
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
CS
100pF
RC
1MI
RD
1.5kI
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
IP 100%
90%
36.8%
tRL TIME
tDL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
IR
10%
0
0
AMPERES
15Maxim Integrated
High-ESD Profibus RS-485 Transceiver
MAX14770E
ESD test model (Figure 15), the ESD-withstand voltage
measured to this standard is generally lower than that
measured using the HBM. Figure 16 shows the current
waveform for the Q10kV IEC 61000-4-2 Level 4 ESD
Contact Discharge test. The Air-Gap Discharge test
involves approaching the device with a charged probe.
The Contact Discharge method connects the probe to
the device before the probe is energized.
Chip Information
PROCESS: BiCMOS
Figure 15. IEC61000-4-2 ESD Test Model Figure 16. IEC61000-4-2 ESD Generator Current Waveform
Typical PROFIBUS-DP Operating Circuit
Package Information
For the latest package outline information and land patterns, 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.
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
CS
150pF
RC
50MI TO 100MIRD
330I
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
60ns
30ns
tR = 0.7ns
TO 1ns
t
10%
90%
IPEAK
100%
VCC
GND
GND
DI
DE
RE
RO
220I
390I
390I
A
D
R
SHUTDOWN
B
MAX14770E
0.1FF0.1FF
VCC
DI
DE
RO
220I
390I
390I
A
D
R
SHUTDOWN
PROFIBUS B LINE
PROFIBUS A LINE
B
RE
MAX14770E
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN
NO.
8 SO S8+4 21-0041 90-0096
8 TDFN-EP T833+2 21-0137 90-0059
8 FMAX U8+1 21-0036 90-0092
High-ESD Profibus RS-485 Transceiver
MAX14770E
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.
16 Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
© 2012 Maxim Integrated Products, Inc. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 10/09 Initial release —
1 4/10 Switched the position of the pins DE and DI (TDFN) in the Pin Configurations 11
2 1/11
Updated logic output specifications, TOC 15, and the Typical PROFIBUS-DP
Operating Circuit, added the “Driver Enable High/Low—Propagation Delay
Difference” parameters and updated various typical values in the Electrical
Characteristics table
3, 4, 10, 15
3 10/12 Added FMAX and new SOIC packaging to data sheet 1, 2, 11, 15
