_______________Detailed Description

±15kV ESD Protection

As with all Maxim devices, ESD-protection structures are

incorporated on all pins to protect against ESDs encoun-

tered

during

handling

and

assembly.

The

MAX3093E/MAX3094E receiver inputs 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

MAX3093E/MAX3094E continue working without latchup.

ESD protection can be tested in several ways. The

receiver inputs are characterized for protection to the

following:

• ±15kV using the Human Body Model

• ±8kV using the Contact Discharge Method specified

in IEC 1000-4-2 (formerly IEC 801-2)

• ±15kV using the Air-Gap Method specified in

IEC 1000-4-2 (formerly IEC 801-2)

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 4a shows the Human Body Model, and Figure

4b 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 interest,

which is then discharged into the device through a

1.5k

Ω resistor.

IEC 1000-4-2

Since January 1996, all equipment manufactured and/or

sold in the European community has been required to

meet the stringent IEC 1000-4-2 specification. The IEC

1000-4-2 standard covers ESD testing and performance

of finished equipment; it does not specifically refer to inte-

grated circuits. The MAX3093E/MAX3094E help you

design equipment that meets Level 4 (the highest level) of

IEC 1000-4-2, without additional ESD-protection compo-

nents.

The main difference between tests done using the

Human Body Model and IEC 1000-4-2 is higher peak

current in IEC 1000-4-2. Because series resistance is

lower in the IEC 1000-4-2 ESD test model (Figure 5a), the

ESD-withstand voltage measured to this standard is gen-

erally lower than that measured using the Human Body

Model. Figure 5b shows the current waveform for the

±8kV IEC 1000-4-2 Level 4 ESD Contact Discharge test.

The Air-Gap test involves approaching the device with a

charge probe. The Contact-Discharge method connects

the probe to the device before the probe is energized.

Machine Model

The Machine Model for ESD testing uses a 200pF stor-

age capacitor and zero-discharge resistance. It mimics

the stress caused by handling during manufacturing

and assembly. All pins (not just RS-485 inputs) require

this protection during manufacturing. Therefore, the

Machine Model is less relevant to the I/O ports than are

the Human Body Model and IEC 1000-4-2.

Low-Power Shutdown Mode

The function tables show the functionality of the enable

inputs. The MAX3093E/MAX3094E enter shutdown

when ENAC and ENBD are low. In shutdown, all out-

puts go high impedance and the devices typically draw

less than 1nA. The devices exit shutdown by taking

either ENAC or ENBD high. The typical shutdown exit

time is 600ns.

±15kV ESD-Protected, 10Mbps, 3V/5V,

Low-Power Quad RS-422/RS-485 Receivers

Function Tables

OUTPUT

YA OR YC

DEVICE

MODE

ENAC

ENBD

(IN+ - IN-)

On

1

X

≥ 200mV

1

On

1

X

≤ -200mV

0

1

X

Open

1

On

0

1

X

High-Z

On

0

0

X

High

Shutdown

X = don’t care, High-Z = high impedance

8

_______________________________________________________________________________________

OUTPUT

YB OR YD

DEVICE

MODE

ENBD

ENAC

(IN+ - IN-)

On

1

X

≥ 200mV

1

On

1

X

≤ -200mV

0

1

X

Open

1

On

0

1

X

High-Z

On

0

0

X

High-Z

Shutdown