Datasheet
MAX3316–MAX3319
2.5V, 1µA, 460kbps,
RS-232-Compatible Transceivers
8 _______________________________________________________________________________________
MAX3317 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 disabled
(high impedance). The time required to exit shutdown is
typically 30µs, as shown in Figure 2. Connect SHDN to
V
CC
if the shutdown mode is not used; SHDN has no
effect on R_OUT.
MAX3318/MAX3319
AutoShutdown Plus Mode
Maxim’s AutoShutdown Plus feature on the MAX3318/
MAX3319 allows the supply current to fall to 1µA. These
devices will enter the AutoShutdown Plus mode if
FORCEOFF is high, FORCEON is low, and they do not
sense a valid signal transition on any receiver or trans-
mitter input for 30 seconds. This may occur if the RS-232
cable is disconnected or if the peripheral transmitters
are turned off, and the UART driving the transmitter
inputs is inactive. The system turns on again when a
valid transition is applied to any RS-232 receiver or
transmitter input. As a result, the system saves power
without changes to the existing BIOS or operating system.
Figure 4a depicts valid and invalid RS-232 receiver volt-
age levels. INVALID indicates the receiver input’s condi-
tion and is independent of FORCEON and FORCEOFF
states. Figure 3 and Table 1 summarize the operating
modes of the MAX3318/MAX3319. FORCEON and
FORCEOFF override AutoShutdown Plus circuitry. When
neither control is asserted, the IC selects between these
states automatically, based on the last receiver or trans-
mitter edge received.
X
X
X
X
VALID RECEIVER
LEVEL
Active
Active
Active
Active
R_OUT
No
Yes
X
X
RECEIVER OR
TRANSMITTER
EDGE WITHIN
30s
High-Z
Active
Active
High-Z
T_OUT
Shutdown
(AutoShutdown Plus)
0 1
Normal Operation
(AutoShutdown Plus)
0 1
Normal Operation
(Forced On)
1 1
Shutdown (Forced
Off)
X 0
OPERATION
STATUS
FORCEON
FORCEOFF
No
Yes
No
X
Yes
Active
Active
Active
Active
Active
X
X
No
Yes
X
High-Z
Active
High-Z
Active
Active
Shutdown
(AutoShutdown)
INVALID** INVALID**
Normal Operation
(AutoShutdown)
INVALID** INVALID**
Shutdown
INVALID*
1
Normal Operation
INVALID*
1
Normal Operation
INVALID*
1
Table 1. Output Control Truth Table (MAX3318/MAX3319)
Table 2. Shutdown and Enable Control
Truth Table (MAX3317)
X = Don’t care
*
INVALID
connected to FORCEON
**
INVALID
connected to FORCEON and
FORCEOFF
SHDN EN
T_OUT R_OUT
0 0 High-Z Active
0 1 High-Z High-Z
1 0 Active Active
1 1 Active High-Z