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 10A when the
MAX3322E/MAX3323E are placed in shutdown mode
(logic low). When in shutdown mode, the devices’
charge pumps are turned off, V+ decays to VCC, V- is
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 device enters shutdown when VL or VCC is absent.
The time required to exit shutdown is typically 50s, as
shown in Figure 4. Connect SHDN to VCC if shutdown
mode is not used.
VL Logic Supply Input
Unlike other RS-232 interface devices, in which the
receiver outputs swing between 0 and VCC, the
MAX3322E/MAX3323E feature a separate logic supply
input (VL) that sets VOUT for the receiver outputs and
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
≤ VL
≤ 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
resistor.
MAX3322E/MAX3323E
±15kV ESD-Protected, RS-232 Transceivers for
Multidrop Applications
_______________________________________________________________________________________
7
TXENABLE
RENABLE
SHDN
TRANSMITTER OUTPUT
RECEIVER OUTPUT
RECEIVER INPUT
1
0
High-Z
1
Active
Enabled
5k
1
0
High-Z
1
0
1
Active
Enabled
High-Z
0
1
0
High-Z
0
1
High-Z
Enabled
5k
0
High-Z
0
1
High-Z
Enabled
High-Z
Table 1. Tx/Rx Logic
50
s/div
T2
T1
5V/div
2V/div
VCC = 3.3V
C1–C4 = 0.1
F
Figure 4. Transmitter Outputs when Exiting Shutdown