Datasheet

MAX3316E–MAX3319E
±15kV ESD-Protected, 2.5V, 1µA, 460kbps,
RS-232 Compatible Transceivers
8 _______________________________________________________________________________________
down 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.
MAX3318E/MAX3319E
AutoShutdown Plus Mode
Maxim’s AutoShutdown Plus feature on the MAX3318E/
MAX3319E 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 MAX3318E/MAX3319E. 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.
When shut down, the device’s charge pumps turn off,
V+ is pulled to V
CC
, V- is pulled to ground, the transmitter
outputs are high impedance, and READY is driven low.
The time required to exit shutdown is typically 30µs
(Figure 2).
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 (MAX3318E/MAX3319E)
Table 2. Shutdown and Enable Control
Truth Table (MAX3317E)
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