MAX3226EAAE+T Maxim Integrated, MAX3226EAAE+T Datasheet - Page 7

• Manufacturer Part Number: MAX3226EAAE+T
• Description: RS-232 Interface IC
• Manufacturer: Maxim Integrated
• Series: MAX3224E, MAX3225E, MAX3226E, MAX3227E, MAX3244E, MAX3245Er

Specifications of MAX3226EAAE+T

• Data Rate: 250 Kbps
• Operating Supply Voltage: 3 V to 5.5 V
• Supply Current: 1 mA
• Operating Temperature Range: 0 C to + 70 C
• Function: Transceiver
• Number Of Drivers: 1
• Number Of I/os: 4
• Number Of Receivers: 1
• Propagation Delay Time Ns: 0.15 us
• Shutdown: Yes

232 output levels do not change if V
sudden current draw causing the supply voltage to drop
slightly. The outputs return to RS-232-compliant levels
(±5.5V) when V
The MAX3230E/AE and MAX3231E/AE transmitters
guarantee a 250kbps data rate with worst-case loads of
3kΩ in parallel with 1000pF.
When FORCEOFF is driven to ground, the transmitters
and receivers are disabled and the outputs become
high impedance. When the AutoShutdown circuitry
senses that all receiver and transmitter inputs are inac-
tive for more than 30µs, the transmitters are disabled
and the outputs go to a high-impedance state. When
the power is off, the MAX3230E/AE and MAX3231E/AE
permit the transmitter outputs to be driven up to ±12V.
The transmitter inputs do not have pullup resistors.
Connect unused inputs to GND or V
The MAX3230E/AE and MAX3231E/AE receivers con-
vert RS-232 signals to logic-output levels. All receivers
have inverting tri-state outputs and can be active or
inactive. In shutdown (FORCEOFF = low) or in
AutoShutdown, the MAX3230E/AE and MAX3231E/AE
receivers are in a high-impedance state (Table 2).
The MAX3230E/AE and MAX3231E/AE feature an
INVALID output that is enabled low when no valid RS-232
Table 1. Operating Supply Options
Table 2. Output Control Truth Table
X = Don’t care.
† = INVALID output state is determined by R_IN input levels.
Shutdown (AutoShutdown)
Shutdown (Forced Off)
Normal Operation (Forced On)
Normal Operation (AutoShutdown)
Regulated Voltage Only
Regulated Voltage Only
TRANSCEIVER STATUS
SYSTEM SUPPLY (V)
3 NiCad/NiMh Cells
(V
(V
1 Li+ Cell
CC
CC
falling)
falling)
CC
_______________________________________________________________________________________
rises above approximately +3.5V.
RS-232 Transceivers in UCSP and WLP
±15kV ESD-Protected +2.5V to +5.5V
RS-232 Receivers
+2.4 to +4.2
+2.4 to +3.8
+3.0 to +5.5
+2.5 to +3.0
L
CC
.
V
CC
FORCEON
is noisy or has a
(V)
High
Low
Low
X
Regulated system voltage
Regulated system voltage
FORCEOFF
signal levels have been detected on any receiver inputs.
INVALID is functional in any mode (Figures 2 and 3).
The MAX3230E/AE and MAX3231E/AE achieve a 1µA
supply current with Maxim’s AutoShutdown feature,
which operates when FORCEON is low and FORCEOFF
is high. When these devices sense no valid signal lev-
els on all receiver inputs for 30µs, the on-board charge
pump and drivers are shut off, reducing V
current to 1µA. This occurs if the RS-232 cable is dis-
connected or the connected peripheral transmitters are
turned off. The device turns on again when a valid level
is applied to any RS-232 receiver input. As a result, the
system saves power without changes to the existing
BIOS or operating system.
Table 2 and Figure 2c summarize the MAX3230E/AE
and MAX3231E/AE operating modes. FORCEON and
FORCEOFF override AutoShutdown. When neither con-
trol is asserted, the IC selects between these states
automatically, based on receiver input levels. Figures
2a, 2b, and 3a depict valid and invalid RS-232-receiver
levels. Figures 3a and 3b show the input levels and tim-
ing diagram for AutoShutdown operation.
A system with AutoShutdown can require time to wake
up. Figure 4 shows a circuit that forces the transmitters
on for 100ms, allowing enough time for the other
system to realize that the MAX3230E/AE and
+3.0 to +5.5
+2.5 to +3.0
High
High
High
Low
V
L
(V)
RECEIVER STATUS
High impedance
High impedance
Active
Active
Compliant/Compatible
Compliant/Compatible
RS-232 MODE
Compatible
Compliant
AutoShutdown
INVALID
High
Low
CC
†
†
supply
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