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Maxim > Design Support > Technical Documents > Application Notes > Interface Circuits > APP 654
Maxim > Design Support > Technical Documents > Application Notes > Protection and Isolation > APP 654
Keywords: RS-232, rs232, EIA/TIA-232, ESD protected, +/-15kV, IEC 801-2, auto shutdown, auto wakeup,
low power, 3V operation, charge pumps, EIA/TIA-562, ESD protection, rs-232 transceivers
APPLICATION NOTE 654
New RS-232 ICs Feature 1µA Supply Current,
±15kV ESD Protection, and 3V Operation
Aug 16, 2002
Abstract: Application note briefly describing important features of Maxim's RS-232 transceivers with special
characteristics. Several families are described with separate and/or overlapping features: 5V only operation
through use of internal charge pumps, 3V only operation using high-efficiency internal charge pumps,
automatic shutdown to 1µA supply current when not in use and automatic wakeup when signals are
received, ±15kV ESD protection, high-efficiency driver for 50% power savings, and/or controllable DTE or
DCE function without special null-modem cable. IEC 801-2 test methods are treated, and a list of ESD-
testing DO's and DON'Ts is provided.
Maxim pioneered the use of charge-pump DC/DC converters for RS-232 interface ICs, and now offers
more than 54 such products. Maxim's first products operated from +5V, and produced outputs greater than
±5V as required by the RS-232 standard. New products feature improvements such as 3V operation (using
only four 0.1µF external capacitors), ±15kV ESD protection, and 1µA no-load supply current.
Many digital systems have moved towards 3V operation in order to increase density while decreasing
power consumption. Maxim has responded with RS-232 interface ICs that operate at 3.0V and 3.3V, many
of which use only four 0.1µF capacitors (Table 1).
Table 1. 3V and 3.3V RS-232 ICs
Device
Supply-
Voltage
Range
No. of
Drivers/
Receivers
Shutdown: No. of
Receivers
Active/Current Drawn
(mA max)
No-Load
Supply Current
(mA typ/max)
DC-DC
Converter
Architecture
Mouse
Driver
Auto
SHDN
RS-
232
(V)
RS-
562
(V)
MAX212
3 to
3.6
>
3.0 3/5 5/15 1.5/3 Inductor
Y N
MAX3212
2.7
to
3.6
>
2.7 3/5 5/15 1mA/10mA Inductor
Y Y
MAX3232
3 to
3.6
>
2.7 2/2 2/10 0.3/1
Regulated
Capacitor
Doubler
N/A N
3 to
Regulated
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