ISL4485E Datasheet, PDF (8/11 Pages) Intersil Corporation – ±15kV ESD Protected, 20Mbps, 5V, Low Power, RS-485/RS-422 Transceiver

ISL4485E
temperature drops about 15 degrees. If the contention
persists, the thermal shutdown / reenable cycle repeats until
the fault is cleared. Receivers stay operational during
thermal shutdown.
ESD Protection
All pins on these interface devices include class 3 Human
Body Model (HBM) ESD protection structures, but the
RS-485 pins (driver outputs and receiver inputs) incorporate
advanced structures allowing them to survive ESD events in
excess of ±15kV HBM. The RS-485 pins are particularly
vulnerable to ESD damage because they typically connect to
an exposed port on the exterior of the finished product.
Simply touching the port pins, or connecting a cable, can
cause an ESD event that might destroy unprotected ICs.
These new ESD structures protect the device whether or not
it is powered up, protect without allowing any latchup
mechanism to activate, and without degrading the RS-485
common mode range of -7V to +12V. This built-in ESD
protection eliminates the need for board level protection
structures (e.g., transient suppression diodes), and the
associated, undesirable capacitive load they present.
Human Body Model Testing
As the name implies, this test method emulates the ESD
event delivered to an IC during human handling. The tester
delivers the charge stored on a 100pF capacitor through a
1.5kΩ current limiting resistor into the pin under test. The
HBM method determines an ICs ability to withstand the ESD
events typically present during handling and manufacturing.
The RS-485 pin survivability on this high ESD device has
been characterized to be in excess of ±15kV, for discharges
to GND.
Typical Performance Curves V_CC = 5V, T_A = 25^oC; Unless Otherwise Specified
DI
5
RO
0
DI
5
5
0
0
5
RO
0
DRIVER+CABLE DELAY (~450ns)
3
1.5
0
A-B
-1.5
-3
TIME (20ns/DIV)
FIGURE 7. DRIVER AND RECEIVER WAVEFORMS DRIVING
300 FEET OF CABLE (DOUBLE TERMINATED)
DRIVER+CABLE DELAY (~650ns)
3
1.5
0
A-B
-1.5
-3
TIME (20ns/DIV)
FIGURE 8. DRIVER AND RECEIVER WAVEFORMS DRIVING
450 FEET OF CABLE (DOUBLE TERMINATED)
30
R_DIFF = 54Ω
25
20
15
10
5
0
500 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
DIFFERENTIAL CAPACITANCE (pF)
FIGURE 9. DATA RATE vs DIFFERENTIAL CAPACITANCE
750
700
DE = V_CC, RE = X
650
600
550
500
DE = GND, RE = X
450
400
-40 -25
0
25
50
TEMPERATURE (^oC)
75 85
FIGURE 10. SUPPLY CURRENT vs TEMPERATURE
8