MAX3228EBV-T Maxim Integrated, MAX3228EBV-T Datasheet - Page 9

• Manufacturer Part Number: MAX3228EBV-T
• Description: RS-232 Interface IC 2.5-5.5V Transceiver
• Manufacturer: Maxim Integrated
• Series: MAX3228, MAX3229r

Specifications of MAX3228EBV-T

• Data Rate: 250 Kbps
• Operating Supply Voltage: 2.5 V to 5.5 V
• Supply Current: 10 uA
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Package / Case: UCSP-20 6 x 5
• Number Of Drivers: 2
• Number Of Receivers: 2

Table 3. Output Control Truth Table
X = Don’t care.
† = I NVALID output state is determined by R_IN input levels.
MAX3228/MAX3229 feature a separate logic supply
input (V
outputs. The transmitter inputs (T_IN), FORCEON and
FORCEOFF, are also referred to V
maximum flexibility in interfacing to different systems
and logic levels. Connect V
ply voltage (+1.65V to +5.5V), and bypass it with a
0.1µF capacitor to GND. If the logic supply is the same
as V
enabling the V
equal to the V
If direct software control is desired, connect FORCEOFF
and FORCEON together to disable AutoShutdown. The
microcontroller then drives FORCEOFF and FORCEON
like a SHDN input, INVALID can be used to alert the
microcontroller to indicate serial data activity.
The capacitor type used for C1–C4 is not critical for
proper operation; either polarized or nonpolarized
capacitors may be used. However, ceramic chip
capacitors with an X7R or X5R dielectric work best. The
charge pump requires 0.1µF capacitors for 3.3V opera-
tion. For other supply voltages, refer to Table 4 for
required capacitor values. Do not use values smaller
than those listed in Table 4. Increasing the capacitor
values (e.g., by a factor of 2) reduces ripple on the
Table 4. Required Capacitor Values
Shutdown (AutoShutdown)
Shutdown (Forced Off)
Normal Operation (Forced On)
Normal Operation (AutoShutdown)
2.5 to 3.0
3.0 to 3.6
4.5 to 5.5
3.0 to 5.5
CC
V
TRANSCEIVER STATUS
CC
, connect V
L
) that sets V
(V)
L
L
supply.
Applications Information
Software-Controlled Shutdown
supply. V
_______________________________________________________________________________________
L
C1, C
to V
OH
BYPASS
CC
0.047
0.22
0.22
for the receiver and INVALID
0.1
CC
. Always enable V
L
+2.5V to +5.5V RS-232 Transceivers
to the system’s logic sup-
Capacitor Selection
must be greater than or
( F)
L
. This feature allows
FORCEON
C2, C3, C4 ( F)
High
Low
Low
X
0.22
0.33
0.1
CC
1
before
FORCEOFF
transmitter outputs and slightly reduces power con-
sumption. 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, and C4
to maintain the proper ratios (C1 to the other capac-
itors).
When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capaci-
tors with a larger nominal value. The capacitor’s equiv-
alent series resistance (ESR) usually rises at low
temperatures and influences the amount of ripple on
V+ and V-.
In most circumstances, a 0.1µF V
is adequate. In applications that are sensitive to power-
supply noise, use a capacitor of the same value as the
charge-pump capacitor C1. Connect bypass capaci-
tors as close to the IC as possible.
Figure 5. Transmitter Outputs Exiting Shutdown or Powering Up
High
High
High
Low
FORCEON =
FORCEOFF
T
OUT
RECEIVER STATUS
High-Z
High-Z
Active
Active
Power-Supply Decoupling
4µs/div
CC
in UCSP
bypass capacitor
INVALID
5V/div
0
2V/div
0
H
L
†
†
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