MAX3238E/MAX3248E
+3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
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Tables 1 and 2 and Figure 3 summarize the MAX3238E/
MAX2348Es’ operating modes. FORCEON and FORCE-
OFF override the automatic circuitry and force the
transceiver into its normal operating state or into its low-
power standby state. When neither control is asserted,
the IC enters AutoShutdown Plus mode and selects
between these states automatically, based on the last
receiver or transmitter input edge received.
When shut down, the devices’ charge pumps turn off,
V+ decays to V
CC,
V- decays to ground, and the trans-
mitter outputs are disabled (high impedance). The time
required to recover from shutdown is typically 25µs
(Figure 4b).
Software-Controlled Shutdown
If direct software control is desired, use INVALID to
indicate DTR or Ring Indicator signal. Tie FORCEOFF
and FORCEON together to bypass the AutoShutdown
Plus feature so the line acts like a SHDN input.
ESD Protection
As with all Maxim devices, ESD protection structures
are incorporated to protect against electrostatic dis-
charges (ESDs) encountered during handling and
assembly. The MAX3238E/MAX3248E RS-232 transmit-
ters and receivers, as well as the I/O have extra protec-
tion against static electricity found in normal operation.
Maxim’s engineers developed state-of-the-art struc-
tures to protect these pins against ESD of ±15kV with-
out damage. After an ESD event, the MAX3238E/
MAX3248E keep working without latchup.
ESD protection can be tested in various ways. The pins
are characterized for protection to ±15kV and ±8kV
(see Electrical Characteristics).
ESD Test Conditions
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
Human Body Model
Figure 5a shows the Human Body Model, and Figure
5b 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-
Table 2. INVALID Truth Table
* POWER DOWN IS ONLY AN INTERNAL SIGNAL.
