MAX221EEUE+ Maxim Integrated Products, MAX221EEUE+ Datasheet - Page 7

• Manufacturer Part Number: MAX221EEUE+
• Description: IC TXRX RS-232 5V 16-TSSOP
• Manufacturer: Maxim Integrated Products
• Type: Transceiverr

Specifications of MAX221EEUE+

• Number Of Drivers/receivers: 1/1
• Protocol: RS232
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 4. AutoShutdown with Initial Turn-On to Wake Up a
Mouse or Another System
Figure 3. AutoShutdown Trip Levels
RECEIVER
VOLTAGE
OUTPUT
INVALID
INPUT
MANAGEMENT
b)
a)
(V)
(V)
+2.7V
+0.3V
POWER-
-0.3V
-2.7V
V
V
UNIT
CC
V+
CC
V-
0
0
0
AUTOSHUTDOWN, TRANSMITTER DISABLED,
TRANSMITTER ENABLED, INVALID HIGH
TRANSMITTER ENABLED, INVALID HIGH
1 A SUPPLY CURRENT, INVALID LOW
MASTER SHDN LINE
_______________________________________________________________________________________
t
INVL
INDETERMINATE
INDETERMINATE
FORCEOFF
+5V, 1µA, Single RS-232 Transceiver
MAX221
0.1 F
FORCEON
1M
t
INVH
INVALID
REGION
t
WU
INVALID indicates when an RS-232 signal is present at
the receiver input, and therefore when the port is in use.
INVALID can be used in alternative shutdown control
schemes where it relieves the processor from constantly
polling the port for activity.
The capacitor type used for C1–C4 is not critical for
proper operation; either polarized or nonpolarized
capacitors are acceptable. If polarized capacitors are
used, connect polarity as shown in the Typical Operating
Circuit . The charge pump requires 0.1µF capacitors.
Increasing the capacitor values (e.g., by a factor of 2)
reduces ripple on the transmitter output and slightly
reduces power consumption. C2, C3, and C4 can be
increased without changing C1’s value. However, do not
increase C1’s value without also increasing the values of
C2, C3, and C4 to maintain the proper ratios (C1 to the
other capacitors).
When using the minimum 0.1µF capacitors, make sure
the capacitance does not degrade excessively with
temperature. If in doubt, use capacitors with a larger
nominal value. The capacitor’s equivalent series resis-
tance (ESR) usually rises at low temperatures and influ-
ences 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 shows the transmitter output when exiting shut-
down mode. The transmitter is loaded with 3kΩ in paral-
lel with 2500pF. The transmitter output displays no
ringing or undesirable transients as the MAX221 comes
out of shutdown. Note that the transmitter is enabled only
when the magnitude of V- exceeds approximately 3V.
The MAX221 maintains the RS-232 ±5.0V minimum
transmitter output voltage even at high data rates.
Figure 6 shows a transmitter loopback test circuit.
Figure 7 shows the loopback test result at 120kbps,
and Figure 8 shows the same test at 250kbps.
with AutoShutdown
Applications Information
Power-Supply Decoupling
Transmitter Output when
Capacitor Selection
Exiting Shutdown
CC
High Data Rates
Using INVALID
bypass capacitor
7