MAX3316–MAX3319
2.5V, 1µA, 460kbps,
RS-232-Compatible Transceivers
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Pin Description (continued)
Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3316–MAX3319s’ internal power supply con-
sists of a regulated dual charge pump that provides
output voltages of +4.4V (doubling charge pump) and
-4.3V (inverting charge pump), over the +2.25V to
+3.0V input voltage range. The charge pump operates
in discontinuous mode: if the output voltages are less
than 4.4V, the charge pump is enabled; if the output
voltages exceed 4.4V, the charge pump is disabled.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies.
The READY output (MAX3318/MAX3319) is low when
the charge pumps are disabled in shutdown mode. The
READY signal asserts high when V- goes below -2.75V.
RS-232-Compatible Transmitters
The MAX3316–MAX3319s’ transmitters are inverting
level translators that convert CMOS-logic levels to
RS-232-compatible voltage levels. They guarantee a
460kbps data rate with worst-case loads of 3kΩ in parallel
with 1000pF, providing compatibility with PC-to-PC
communication software (such as LapLink™).
The MAX3317’s transmitters are turned off (high imped-
ance) when SHDN is asserted low, putting the device in
shutdown mode. The MAX3318/MAX3319s’ transmitters
are turned off (high impedance) when FORCEOFF is
asserted low, or when the AutoShutdown Plus circuitry
senses that all receiver and transmitter inputs are inac-
tive for more than 30 seconds.
The transmitter outputs can be driven to ±12V when
power is off. The transmitter inputs do not have internal
pullup resistors. Connect unused inputs to GND or V
CC
.
Figure 1a shows an RS-232-compatibility circuit and
Figure 1b shows MAX3316–MAX3319 transmitter output
compatibility with an RS-232 receiver.
RS-232 Receivers
The MAX3316–MAX3319s’ receivers convert RS-232
signal levels into CMOS-logic output levels. The
receivers are rated to receive signals up to ±25V. The
MAX3316/MAX3318/MAX3319s’ receivers feature
inverting outputs that always remain active (Table 1).
The MAX3317’s receivers have inverting, three-state
outputs. In shutdown, the receivers can be active or
inactive (Table 2).
The MAX3318/MAX3319 feature an INVALID output that
is asserted low when no valid RS-232 voltage levels
have been detected on all receiver inputs. Because
INVALID indicates the receiver’s input condition, it
is independent of the states of FORCEON and
FORCEOFF.
LapLink is a trademark of Traveling Software.
PIN
MAX3316
MAX3317
SSOP/
TSSOP
MAX3318
SSOP/
TSSOP
MAX3319
SSOP
NAME FUNCTION
Shutdown Control, Active Low
Ready to Transmit Output, Active High. READY is
enabled high when V- goes below -2.75V and the
device is ready to transmit.
Valid Signal Detector Output, Active Low. A logic
high indicates that a valid RS-232 level is present
on a receiver input.
Force-On Input, Active High. Drive high to override
AutoShutdown Plus, keeping transmitters and
receivers on (FORCEOFF must be high) (Table 1).
Force-Off Input, Active Low. Drive low to shut
down transmitters, receivers, and charge pump.
This overrides AutoShutdown Plus and FORCEON
(Table 1).
FORCEOFF
FORCEON
INVALID
READY
SHDN
—
1
10
12
1620
14
11
1
—20
—
—
—
——
—
—
—
——
—
—
—
—
SSOP TSSOP
