MAX3238CAI+T Maxim Integrated Products, MAX3238CAI+T Datasheet - Page 7

• Manufacturer Part Number: MAX3238CAI+T
• Description: IC TXRX RS-232 TRUE 28-SSOP
• Manufacturer: Maxim Integrated Products
• Type: Transceiverr

Specifications of MAX3238CAI+T

• Number Of Drivers/receivers: 5/3
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Tables 1 and 2 and Figure 3 summarize the MAX3238’s
operating modes. FORCEON and FORCEOFF override
the automatic circuitry and force the transceiver into its
normal operating state or into its low-power standby
state. When neither control is asserted, the IC enters
AutoShutdown Plus mode and selects between these
states automatically, based on the last receiver or
transmitter input edge received.
When shut down, the device’s charge pumps turn off,
V+ decays to V
mitter outputs are disabled (high impedance). The time
required to exit shutdown is typically 25 s (Figure 4b).
If direct software control is desired, use INVALID to
indicate DTR or Ring Indicator signal. Tie FORCEOFF
and FORCEON together to bypass the AutoShutdown
feature so the line acts like a SHDN input.
The capacitor type used for C1–C4 is not critical for
proper operation; polarized or nonpolarized capacitors
can be used. The charge pump requires 0.1µF capaci-
tors for 3.3V operation. For other supply voltages, see
Table 3 for required capacitor values. Do not use val-
ues smaller than those listed in Table 3. Increasing the
capacitor values (e.g., by a factor of 2) reduces ripple
on the transmitter outputs and slightly reduces power
consumption. C2, C3, and C4 can be increased without
changing C1’s value. However, do not increase C1
without also increasing the values of C2, C3, C4,
and C
other capacitors).
Table 2. I I N N V V A A L L I I D D Truth Table
__________Applications Information
RS-232 SIGNAL PRESENT AT
ANY RECEIVER INPUT
BYPASS
RS-232 Transceiver with AutoShutdown Plus
Yes
, to maintain the proper ratios (C1 to the
No
CC,
Software-Controlled Shutdown
+3.0V to +5.5V, 1µA, up to 250kbps, True
_______________________________________________________________________________________
V- decays to ground, and the trans-
Capacitor Selection
I I N N V V A A L L I I D D OUTPUT
H
L
Figure 3a. INVALID Functional Diagram, INVALID Low
Figure 3b. INVALID Functional Diagram, INVALID High
Figure 3c. AutoShutdown Plus Logic
Figure 3d. Power-Down Logic
+0.3V
-0.3V
+2.7V
-2.7V
R_IN
R_IN
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30 s.
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
R_IN
T_IN
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30 s.
AUTOSHDN
FORCEOFF
FORCEON
DETECT
DETECT
EDGE
EDGE
FORCEON
FORCEOFF
TIMER
30sec
S
R
TIMER
TIMER
30µs
30µs
R
R
POWERDOWN*
AUTOSHDN
INVALID
INVALID
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