ICL3238EIAZ Intersil, ICL3238EIAZ Datasheet - Page 9

• Manufacturer Part Number: ICL3238EIAZ
• Description: IC TXRX RS232 3-5.5V 28SSOP
• Manufacturer: Intersil
• Type: Transceiverr

Specifications of ICL3238EIAZ

• Number Of Drivers/receivers: 5/3
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Peak Reflow Compatible (260 C): Yes
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Emulating Standard Automatic Powerdown
If enhanced automatic powerdown isn’t desired, the user can
implement the standard automatic powerdown feature
(mimics the function on the ICL3221, ICL3223, ICL3243E)
by connecting the INVALID output to the FORCEON and
FORCEOFF inputs, as shown in Figure 9. After 60
invalid receiver levels, INVALID switches low and drives the
ICL3238E into a forced powerdown condition. INVALID
switches high as soon as a receiver input senses a valid RS-
232 level, forcing the ICL3238E to power on. See the
“INVALID DRIVING FORCEON AND FORCEOFF” section
of Table 2 for an operational summary. This operational
mode is perfect for handheld devices that communicate with
another computer via a detachable cable. Detaching the
cable allows the internal receiver pull-down resistors to pull
the inputs to GND (an invalid RS-232 level), causing the
60µs timer to time-out and drive the IC into powerdown.
Reconnecting the cable restores valid levels, causing the IC
to power back up.
TRANSMITTER
TRANSMITTER
FIGURE 9. CONNECTIONS FOR AUTOMATIC POWERDOWN
RECEIVER
OUTPUTS
OUTPUT
INVALID
INPUTS
INPUTS
CPU
V
CC
V+
V-
0
WHEN NO VALID RECEIVER SIGNALS ARE
PRESENT
t
INVL
UART
I/O
FIGURE 8. ENHANCED AUTOMATIC POWERDOWN, AND INVALID TIMING DIAGRAMS
9
t
INVH
ICL3238E
t
AUTOPWDN
µ
s of
ICL3238E
Hybrid Automatic Powerdown Options
For devices which communicate only through a detachable
cable, connecting INVALID to FORCEOFF (with FORCEON
= 0) may be a desirable configuration. While the cable is
attached INVALID and FORCEOFF remain high, so the
enhanced automatic powerdown logic powers down the RS-
232 device whenever there is 30 seconds of inactivity on the
receiver and transmitter inputs. Detaching the cable allows
the receiver inputs to drop to an invalid level (GND), so
INVALID switches low and forces the RS-232 device to
power down. The ICL3238E remains powered down until the
cable is reconnected (INVALID = FORCEOFF = 1) and a
transition occurs on a receiver or transmitter input (see
Figure 7). For immediate power up when the cable is
reattached, connect FORCEON to FORCEOFF through a
network similar to that shown in Figure 5.
Capacitor Selection
The charge pumps require 0.1
3.3V (5% tolerance) operation. 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 2) reduces ripple on the transmitter
outputs and slightly reduces power consumption. C
and C
however, do not increase C
and C
capacitors).
3.0 to 3.6 (3.3V ±10%)
3.15 to 3.6 (3.3V ±5%)
t
WU
4
4
4.5 to 5.5
3.0 to 5.5
can be increased without increasing C
to maintain the proper ratios (C
V
CC
TABLE 3. REQUIRED CAPACITOR VALUES
(V)
t
AUTOPWDN
C
1
0.047
1
0.22
0.22
without also increasing C
0.1
µ
(µF)
F, or greater, capacitors for
t
WU
1
to the other
C
2
, C
1
’s value,
0.22
0.33
3
0.1
, C
1
}
2
4
INVALID
REGION
, C
(µF)
2
3
, C
,
3
,