icl3237e Intersil Corporation, icl3237e Datasheet - Page 7

• Manufacturer Part Number: icl3237e
• Description: ?15kv Esd Protected, 1?a Supply-current, +3v To +5.5v, 250kbps Or 1000kbps, Rs-232 Transmitters/receivers
• Manufacturer: Intersil Corporation

Receiver ENABLE Control
This device also features an EN input to control the receiver
outputs. Driving EN high disables all the inverting (standard)
receiver outputs placing them in a high impedance state.
This is useful to eliminate supply current, due to a receiver
output forward biasing the protection diode, when driving the
input of a powered down (V
Figure 2). The enable input has no effect on transmitter nor
monitor (R
FIGURE 3. DISABLED RECEIVERS PREVENT POWER DRAIN
SHDN INPUT EN INPUT
POWERED
FIGURE 2. POWER DRAIN THROUGH POWERED DOWN
DOWN
UART
POWERED
H
H
L
L
DOWN
V
UART
WAKE-UP
GND
CC
LOGIC
OUTB
V
TO
CC
R
T
PERIPHERAL
X
X
SHDN = GND, EN = V
) outputs.
TRANSITION
DETECTOR
Rx
Tx
H
H
L
L
V
CC
V
SHDN = GND
OUT
R1
V
R1
OUT
= HI-Z
V
OUTB
TRANSMITTER OUTPUTS
CC
T1
CC
OUT
= V
IN
7
= GND) peripheral (see
CC
CC
TABLE 2. POWERDOWN AND ENABLE LOGIC TRUTH TABLE
High-Z
High-Z
Active
Active
ICL3237E
RS-232 CHIP
OLD
V
CURRENT
FLOW
CC
R1
T1
RECEIVER OUTPUTS
OUT
IN
ICL3237E
High-Z
High-Z
Active
Active
MegaBaud Selection
In normal operating mode (MBAUD = GND), the ICL3237E
transmitters guarantee a 250kbps data rate with worst-case
loads of 3kΩ in parallel with 1000pF. This provides
compatibility with PC-to-PC communication software, such
as Laplink™.
For higher speed serial communications, the ICL3237E
features MegaBaud operation. In MegaBaud operating mode
(MBAUD = V
1Mbps data rate with worst-case loads of 3kΩ in parallel with
250pF for 3.0V < V
ICL3237E transmitters guarantee a 1Mbps data rate with
worst-case loads of 3kΩ in parallel with 1000pF.
Capacitor Selection
The charge pumps require 0.1µF capacitors for 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
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.
3.0 to 3.6 (3.3V ±10%)
3.15 to 3.6 (3.3V ±5%)
R
4.5 to 5.5
3.0 to 5.5
OUTB
V
TABLE 3. REQUIRED CAPACITOR VALUES
(V)
CC
1
Active
Active
Active
Active
without also increasing C
CC
OUTPUT
), the ICL3237E transmitters guarantee a
CC
Laplink® is a registered trademark of Traveling Software.
< 4.5V. For 5V
Manual Powerdown
Manual Powerdown w/Rcvr. Disabled
Normal Operation
Normal Operation w/Rcvr. Disabled
0.047
1
(µF)
0.22
0.22
0.1
C
to the other capacitors).
MODE OF OPERATION
1
1
2
’s value, however, do not
CC
, C
3
to ground with a
, and C
±
2
10% operation, the
, C
3
, and C
4
C
can be
2
, C
0.22
0.33
(µF)
0.1
1.0
3
4
, C
to
4
1
.