MAX3316E–MAX3319E
±15kV ESD-Protected, 2.5V, 1µA, 460kbps,
RS-232 Compatible Transceivers
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Pin Description (continued)
Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3316E–MAX3319Es’ internal power supply
consists 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 range. The charge pump operates in discontinu-
ous 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 (MAX3318E/MAX3319E) 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 MAX3316E–MAX3319Es’ 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 MAX3317E’s transmitters are turned off (high
impedance) when SHDN is asserted low, putting the
device in shutdown mode. The MAX3318E/MAX3319Es’
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 inactive for more than 30 seconds.
The transmitter outputs can be driven to ±12V when
power is off. The transmitter inputs do not have internal
pull-up resistors. Connect unused inputs to GND or V
CC
.
RS-232 Receivers
The MAX3316E–MAX3319Es’ receivers convert ±3.7V
to ±13.2V RS-232 signal levels into CMOS-logic output
levels. The receivers are rated to receive signals up to
±25V. The MAX3316E/MAX3318E/MAX3319Es’
receivers feature inverting outputs that always remain
active (Table 1). The MAX3317E’s receivers have
inverting, three-state outputs. In shutdown, the
receivers can be active or inactive (Table 2).
The MAX3318E/MAX3319E 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.
MAX3317E Shutdown Mode
Supply current falls to less than 1µA in shutdown mode
(SHDN = low). When shut down, the device’s charge
pumps are turned off, V+ is pulled down to V
CC
, V- is
pulled to ground, and the transmitter outputs are dis-
abled (high impedance). The time required to exit shut-
LapLink is a trademark of Traveling Software.
PIN
MAX3316E
MAX3317E MAX3318E MAX3319E
NAME FUNCTION
Shutdown Control, Active Low
Ready to Transmit Output, Active High. READY is
enabled high when V- goes below -3.5V 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
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1
10
12
1620
14
11
1
—20
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SSOP TSSOP
