High-input impedance is guaranteed from -13.0V to

+13.0V, when the receiver is in high-input-impedance

mode. The receiver is able to withstand the RS-232

maximum input voltage of ±25V.

Shutdown Mode

Supply current falls to less than 10µA when the

MAX3322E/MAX3323E are placed in shutdown mode

(logic low). When in shutdown mode, the devices’

pulled to ground, the transmitter outputs and the

receiver outputs are disabled (high impedance), and

the receiver inputs are in high impedance (Table 1).

The time required to exit shutdown is typically 50µs, as

mode is not used.

Unlike other RS-232 interface devices, in which the

MAX3322E/MAX3323E feature a separate logic supply

sets thresholds for the transmit and shutdown inputs.

This feature allows a great deal of flexibility in interfac-

ing to many types of systems with different logic levels.

Connect this input to the host logic supply (1.65V

≤ 5.5V).

±15kV ESD Protection

To protect the MAX3322E/MAX3323E against ESD,

transmitters and receivers have extra protection against

static electricity to protect the device up to ±15kV. The

ESD structures withstand high ESD in all states: normal

operation, shutdown, and powered down. ESD protec-

tion can be tested in various ways; the transmitter and

receiver pins are characterized for protection to the fol-

lowing limits:

• ±15kV using the Human Body Model

• ±8kV using the IEC 1000-4-2 Contact Discharge

method

• ±15kV using the IEC 1000-4-2 Air-Gap method

Note: ESD performance depends on many conditions.

Contact Maxim for a reliability report that documents

test setup, test methodology, and test results.

Human Body Model

Figure 5 shows the Human Body Model, and Figure 6

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 test device

through a 1.5k

Ω resistor.

±15kV ESD-Protected, RS-232 Transceivers for

Multidrop Applications

_______________________________________________________________________________________

7

TXENABLE

RENABLE

SHDN

TRANSMITTER OUTPUT

RECEIVER OUTPUT

RECEIVER INPUT

1

1

0

High-Z

High-Z

High-Z

1

1

1

Active

Enabled

5k

Ω

1

0

0

High-Z

High-Z

High-Z

1

0

1

Active

Enabled

High-Z

0

1

0

High-Z

High-Z

High-Z

0

1

1

High-Z

Enabled

5k

Ω

0

0

0

High-Z

High-Z

High-Z

0

0

1

High-Z

Enabled

High-Z

Table 1. Tx/Rx Logic

50

µs/div

T2

T1

5V/div

2V/div

C1–C4 = 0.1

µF

Figure 4. Transmitter Outputs when Exiting Shutdown