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PDF MAX14945 Data sheet ( Hoja de datos )
| Número de pieza | MAX14945 | |
| Descripción | 2.75kVRMS Isolated 500kbps Half-Duplex RS-485/RS-422 Transceiver | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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MAX14945
EVALUATION KIT AVAILABLE
2.75kVRMS Isolated 500kbps Half-Duplex RS-485/
RS-422 Transceiver with ±30kV ESD Protection
General Description
The MAX14945 isolated RS-485/RS-422 transceiver provides
2750VRMS (60s) of galvanic isolation between the cable
side (RS-485/RS-422 driver/receiver side) and the UART
side of the device. Isolation improves communication by
breaking ground loops and reduces noise when there
are large differences in ground potential between ports.
Signals are passed across the isolation barrier through
integrated high-voltage capacitors. This device allows for
robust communication at any speed up to 500kbps.
The device includes one half-duplex drive/receive channel.
The receiver is 1/8-unit load, allowing up to 256 transceivers
on a common bus.
Integrated true fail-safe circuitry ensures a logic-high on the
receiver output when inputs are shorted or open. Undervoltage
lockout disables the driver when the cable side or UART side
power supplies are below functional levels.
The driver outputs/receiver inputs are protected from
±30kV electrostatic discharge (ESD) to GNDB on the
cable side, as specified by the Human Body Model (HBM).
The MAX14945 is available in a wide body 16-pin
SO package and operates over the -40°C to +85°C
temperature range.
Benefits and Features
●● High-Performance Transceiver Enables Flexible Designs
• Integrated LDO for Cable-Side Power
• Compliant with RS-485 EIA/TIA-485 Standard
• 500kbps Maximum Data Rate
• Allows Up to 256 Devices on the Bus
●● Integrated Protection Ensures Robust Communication
• ±30kV ESD (HBM) on Driver Outputs/Receiver Inputs
• 2.75kVRMS Withstand-Isolation Voltage for 60s (VISO)
• 630VPEAK Maximum Repetitive Peak-Isolation
Voltage (VIORM)
• 445VRMS Maximum Working-Isolation Voltage (VIOWM)
• > 30 Years Lifetime at Rated Working Voltage
• Withstands ±10kV Surge per IEC 61000-4-5
• Thermal Shutdown
Safety Regulatory Approvals Pending
●● UL According to UL1577
●● cUL According to CSA Bulletin 5A
●● VDE 0884-10
Applications
●● Industrial Automation Equipment
●● Programmable Logic Controllers
●● HVAC
●● Power Meters
Functional Diagram
VDDA
VLDO
Ordering Information/Selector Guide appears at end of data
sheet.
MAX14945
LDO VDDB
SBA
RE
RXD A
TXD B
DE
GNDA
GNDB
19-7967; Rev 0; 11/15
1 page  
MAX14945
2.75kVRMS Isolated 500kbps Half-Duplex RS-485/
RS-422 Transceiver with ±30kV ESD Protection
Switching Electrical Characteristics
(VDDA – VGNDA = 1.71V to 5.5V, VDDB – VGNDB = 4.5V to 5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at
VDDA – VGNDA = 3.3V, VDDB – VGNDB = 5V, VGNDA = VGNDB, and TA = +25°C.) (Note 7)
PARAMETER
DYNAMIC
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Common Mode Transient
Immunity
CMTI
(Note 8)
35 kV/μs
Glitch Rejection
TXD, DE, RXD
10 17 29 ns
DRIVER
Driver Propagation Delay
tDPLH, tDPHL
RL = 54Ω, CL = 50pF, Figure 2 and
Figure 3
1040
ns
Differential Driver Output Skew
|tDPLH - tDPHL|
tDSKEW
RL = 54Ω, CL = 50pF, Figure 2 and
Figure 3
144 ns
Driver Differential Output Rise
or Fall Time
tLH, tHL
RL = 54Ω, CL = 50pF, Figure 2 and
Figure 3
900 ns
Maximum Data Rate
DRMAX
500 kbps
Driver Enable to Output High
tDZH
RL = 500Ω, CL = 50pF, Figure 4
2540
ns
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
RECEIVER
tDZL
tDLZ
tDHZ
RL = 500Ω, CL = 50pF, Figure 5
RL = 500Ω, CL = 50pF, Figure 5
RL = 500Ω, CL = 50pF, Figure 4
2540
140
140
ns
ns
ns
Receiver Propagation Delay
tRPLH, tRPHL CL = 15pF, Figure 6 and 7 (Note 9)
240 ns
Receiver Output Skew
|tRPLH - tRPHL|
tRSKEW
CL = 15pF, Figure 6 and 7
(Note 9)
34 ns
Maximum Data Rate
Receiver Enable to Output High
Receiver Enable to Output Low
Receiver Disable Time From Low
DRMAX
tRZH
tRZL
tRLZ
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8
RL = 1kΩ, CL = 15pF, S1 closed,
Figure 8
RL = 1kΩ, CL = 15pF, S1 closed,
Figure 8
500
kbps
20 ns
30 ns
20 ns
Receiver Disable Time From High
tRHZ
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8
20 ns
Note 2: All devices are 100% production tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Note 3: All currents into the device are positive. All currents out of the device are negative. All voltages are referenced to their
respective ground (GNDA or GNDB), unless otherwise noted.
Note 4: VLDO max indicates voltage capability of the circuit. Power dissipation requirements may limit VLDO max to a lower value.
Note 5: ΔVOD and ΔVOC are the changes in VOD and VOC, respectively, when the TXD input changes state.
Note 6: The short circuit output current applies to the peak current just prior to foldback current limiting.
Note 7: Not production tested. Guaranteed by design.
Note 8: CMTI is the maximum sustainable common-mode voltage slew rate while maintaining the correct output states. CMTI
applies to both rising and falling common-mode voltage edges. Tested with the transient generator connected between
GNDA and GNDB.
Note 9: Capacitive load includes test probe and fixture capacitance.
www.maximintegrated.com
Maxim Integrated │ 5
5 Page 
MAX14945
2.75kVRMS Isolated 500kbps Half-Duplex RS-485/
RS-422 Transceiver with ±30kV ESD Protection
Typical Operating Characteristics (continued)
(VDDA – VGNDA = 3.3V, VDDB – VGNDB = 5V, VGNDA = VGNDB, and TA = +25°C, unless otherwise noted.)
DRIVER ENABLE/DISABLE
500 DELAY vs. TEMPERATURE toc10
450
400
350
300
250 tDZL
200
tDZH
150
100 tDLZ tDHZ
50
0
-45 -30 -15 0 15 30 45 60 75 90
TEMPERATURE (°C)
DRIVER
PROPAGATION DELAY
RL = 54Ω
CL = 50pF
toc11
TXD
2V/div
0V
A
2V/div
B
2V/div
200ns/div
RECEIVER
PROPAGATION DELAY
CL = 15pF
toc12
RXD
2V/div
0V
A
2V/div
200ns/div
B
2V/div
VDDA SUPPLY CURRENT
8
vs. DATA RATE
toc13
7
6
5
4
3
2
1
0
0 100 200 300 400 500
DATA RATE (kbps)
90
80
70
60
50
40
30
20
10
0
0
VDDB SUPPLY
CURRENT vs. DATA RATE
54Ω LOAD
toc14
120Ω LOAD
NO LOAD
100 200 300 400 500
DATA RATE (kbps)
www.maximintegrated.com
Maxim Integrated │ 11
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet MAX14945.PDF ] | |
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