The MAX3318 is a dual-driver, dual-receiver, RS-232 compatible transceiver. The device
features auto-power-down plus and enhanced electrostatic discharge (ESD) protection integrated into
the chip. Driver output and receiver input are protected to ±8 kV using the IEC 61000-4-2 Air-Gap
Discharge method, ±8 kV using the IEC 61000-4-2 Contact Discharge method, and ±15 kV using the
Human-Body Model (HBM).
The device operates at a data rate of 460 kbps. The transceiver has a proprietary
low-dropout driver output stage enabling RS-232-compatible operation from a 2.25-V to 3-V supply
with a dual charge pump. The charge pump requires only four 0.1-μF capacitors and features a
logic-level output (READY) that asserts when the charge pump is regulating and the device is ready
to begin transmitting.
The MAX3318 achieves a 1-μA supply current using the auto-power-down feature. This device
automatically enters a low-power power-down mode when the RS-232 cable is disconnected or the
drivers of the connected peripherals are inactive for more than 30 s. The device turns on again
when it senses a valid transition at any driver or receiver input. Auto power down saves power
without changes to the existing BIOS or operating system.
This device is available in two space-saving packages: 20-pin SSOP and 20-pin
Flexible control options for power management are featured when the serial port and
driver inputs are inactive. The auto-power-down plus feature functions when FORCEON is low and
FORCEOFF is high. During this mode of operation, if the device does not
sense valid signal transitions on all receiver and driver inputs for approximately 30 s, the
built-in charge pump and drivers are powered down, reducing the supply current to 1 μA. By
disconnecting the serial port or placing the peripheral drivers off, auto-power-down plus can be
disabled when FORCEON and FORCEOFF are high. With auto-power-down plus
enabled, the device activates automatically when a valid signal is applied to any receiver or
driver input. INVALID is high (valid data) if any receiver input voltage is
greater than 2.7 V or less than –2.7 V, or has been between –0.3 V and 0.3 V for less than 30 μs
(typical number). INVALID is low (invalid data) if all receiver input
voltage are between –0.3 V and 0.3 V for more than 30 μs (typical number).
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