AN654 Datasheet, PDF (1/8 Pages) Maxim Integrated Products – New RS-232 ICs Feature 1uA Supply Current, 15kV ESD Protection, and 3V Operation

INTERFACE CIRCUITS
Application Note 654: Mar 31, 2000
New RS-232 ICs Feature 1µA Supply Current, ±15kV
ESD Protection, and 3V Operation
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
Maxim is the only RS-232 IC manufacturer to specify and achieve ±15kV ESD protection using both the
human body model and the IEC 801-2 air-gap discharge method (see sidebar). Maxim's extended ESD
protection eliminates the need for costly external protection devices such as TransZorbs™, while
preventing expensive field failures.
To further simplify RS-232 applications, Maxim has recently introduced transceivers that shut down
automatically when not in use, reducing supply current to 1µA-a thousand-fold improvement over other
parts. This action helps extend battery life in portable equipment such as notebook computers, palmtop
computers, and bar-code scanners.
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