±15kV ESD Protection

As with all Maxim devices, ESD-protection structures

are incorporated on all pins to protect against ESD

encountered during handling and assembly. The

MAX3440E–MAX3444E receiver inputs/driver outputs

(A, B) have extra protection against static electricity

found in normal operation. Maxim’s engineers have

developed state-of-the-art structures to protect these

pins against ±15kV ESD without damage. After an ESD

event, the MAX3440E–MAX3444E continue working

without latchup.

ESD protection can be tested in several ways. The

receiver inputs are characterized for protection to

±15kV using the Human Body Model.

ESD Test Conditions

ESD performance depends on a number of conditions.

Contact Maxim for a reliability report that documents

test setup, methodology, and results.

Human Body Model

Figure 9a shows the Human Body Model, and Figure

9b shows the current waveform it generates when dis-

charged into a low impedance. This model consists of

a 100pF capacitor charged to the ESD voltage of inter-

est, which is then discharged into the device through a

1.5k

Ω resistor.

Driver Output Protection

Two mechanisms prevent excessive output current and

power dissipation caused by faults or bus contention.

The first, a foldback current limit on the driver output

stage, provides immediate protection against short cir-

cuits over the whole common-mode voltage range. The

second, a thermal shutdown circuit, forces the driver out-

puts into a high-impedance state if the die temperature

exceeds +160°C. Normal operation resumes when the

die temperature cools to +140°C, resulting in a pulsed

output during continuous short-circuit conditions.

±15kV ESD-Protected, ±60V Fault-Protected,

10Mbps, Fail-Safe RS-485/J1708 Transceivers

______________________________________________________________________________________

13

CHARGE-CURRENT-

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

100pF

1M

9

1.5k

9

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 9a. Human Body ESD Test Model

90%

36.8%

TIME

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

(NOT DRAWN TO SCALE)

Ir

10%

0

0

AMPERES

Figure 9b. Human Body Model Current Waveform