ICL3217ECB Intersil, ICL3217ECB Datasheet - Page 7

• Manufacturer Part Number: ICL3217ECB
• Description: IC TXRX RS-232 3-5.5V ESD 24SOIC
• Manufacturer: Intersil
• Type: Transceiverr

Specifications of ICL3217ECB

• Number Of Drivers/receivers: 5/3
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

This automatic powerdown feature provides additional
system power savings without changes to the existing
operating system or hardware.
Utilizing power management circuitry, to power down the
rest of the communication circuitry (e.g., the UART) when
the ICL3217E powers down, produces even greater power
savings. Connecting a transition detector to the V- pin (see
Figure 3) is an easy way for the power management logic to
determine when the ICL3217E enters and exits powerdown.
Capacitor Selection
The charge pumps require 0.1µF, or greater, capacitors for
3.3V operation. With 0.1µF capacitors, five percent tolerance
supplies (e.g., 3.14V minimum) deliver greater than ±5V
transmitter swings at full data rate, while ten percent
tolerance supplies (e.g., 2.97V minimum) deliver ±4.95V
transmitter swings. If greater than ±5V transmitter swings
are required with a 10% tolerance 3.3V supply, 0.22µF
capacitors are recommended (see Table 3). Existing 5V
applications typically utilize either 0.1µF or 1µF capacitors,
and the ICL32X7E works well with either value. New 5V
designs should use 0.22µF capacitors for the best results.
For other supply voltages refer to Table 3 for capacitor
values. Do not use values smaller than those listed in
Table 3. Increasing the capacitor values (by a factor of two)
TRANSMITTER
FIGURE 5. AUTOMATIC POWERDOWN TIMING DIAGRAM
FIGURE 4. DEFINITION OF VALID RS-232 RECEIVER
-0.3V
-2.7V
2.7V
0.3V
RECEIVER
OUTPUTS
INPUTS
V
CC
INVALID LEVEL - POWERDOWN OCCURS AFTER 30µs
V+
VALID RS-232 LEVEL - ICL3217E IS ACTIVE
VALID RS-232 LEVEL - ICL3217E IS ACTIVE
INDETERMINATE - POWERDOWN MAY OR
V-
INDETERMINATE - POWERDOWN MAY OR
0
LEVELS
AUTOPWDN
MAY NOT OCCUR
MAY NOT OCCUR
7
PWR UP (t
}
ICL3207E, ICL3217E
INVALID
REGION
WU
)
reduces ripple on the transmitter outputs and slightly
reduces power consumption. C
increased without increasing C
increase C
maintain the proper ratios (C
When using minimum required capacitor values, make sure
that capacitor values do not degrade excessively with
temperature. If in doubt, use capacitors with a larger nominal
value. The capacitor’s equivalent series resistance (ESR)
usually rises at low temperatures and it influences the
amount of ripple on V+ and V-
Power Supply Decoupling
In most circumstances a 0.1µF bypass capacitor is
adequate. In applications that are particularly sensitive to
power supply noise, decouple V
capacitor of the same value as the charge-pump capacitor C
Connect the bypass capacitor as close as possible to the IC.
Transmitter Outputs when Exiting
Powerdown
Figure 6 shows the response of two ICL3217E transmitter
outputs when exiting powerdown mode. As they activate, the
two transmitter outputs properly go to opposite RS-232
levels, with no glitching, ringing, nor undesirable transients.
Each transmitter is loaded with 3kΩ in parallel with 2500pF.
Note that the transmitters enable only when the magnitude
of the supplies exceed approximately 3V.
.
5V/DIV
2V/DIV
FIGURE 6. TRANSMITTER OUTPUTS WHEN EXITING
3.15 to 3.6
3.0 to 3.6
4.5 to 5.5
3.0 to 5.5
V
CC
V
C1 - C4 = 0.1µF
TABLE 3. REQUIRED CAPACITOR VALUES
CC
1
(V)
without also increasing C
= +3.3V
POWERDOWN (ICL3217E ONLY)
RX
IN
0.1 to 1.0
C
TIME (20µs/DIV.)
1
1
0.22
0.22
0.1
.
(µF)
to the other capacitors).
1
2
’s value, however, do not
CC
, C
3
to ground with a
, and C
2
, C
0.22
0.1 to 1.0
0.22
3
C
, and C
4
2
, C
can be
3
0.1
, C
4
T1
T2
4
to
(µF)
1
.