ISL4260E Intersil Corporation, ISL4260E Datasheet - Page 6

• Manufacturer Part Number: ISL4260E
• Description: QFN Packaged, 15kV Esd Protected, +3V to +5.5V, 150nA, 250kbps, RS-232 Transmitters/receivers With Separate Logic Supply
• Manufacturer: Intersil Corporation

(there are no pull-up resistors), and may cause I
increases. Connect unused inputs to GND for the best
performance.
Receivers
The ISL4260E contains standard inverting receivers that
convert RS-232 signals to CMOS output levels and accept
inputs up to ±25V while presenting the required 3kΩ to 7kΩ
input impedance (see Figure 1) even if the power is off
(V
hysteresis to increase noise immunity and decrease errors
due to slow input signal transitions. Receiver outputs swing
from GND to V
Low Power Operation
This 3V device requires a nominal supply current of 0.3mA,
even at V
powerdown mode). This is considerably less than the 11mA
current required by comparable 5V RS-232 devices, allowing
users to reduce system power simply by replacing the old
style device with the ISL4260E in new designs.
Powerdown Functionality
The already low current requirement drops significantly
when the device enters powerdown mode. In powerdown,
supply current drops to 150nA, because the on-chip charge
pump turns off (V+ collapses to V
and the transmitter and receiver outputs tristate. This micro-
power mode makes these devices ideal for battery powered
and portable applications.
Software Controlled (Manual) Powerdown
The ISL4260E may be forced into its low power, standby
state via a simple shutdown (SHDN) pin (see Figure 2).
Driving this pin high enables normal operation, while driving
it low forces the IC into its powerdown state. The time
required to exit powerdown, and resume transmission is less
than 100µs. Connect SHDN to V
function isn’t needed.
INPUT
SHDN
CC
H
L
= 0V). The receivers’ Schmitt trigger input stage uses
-25V ≤ V
TRANSMITTER
CC
TABLE 2. POWERDOWN TRUTH TABLE
OUTPUTS
FIGURE 1. RECEIVER CONNECTIONS
= 5.5V, during normal operation (not in
High-Z
RIN
Active
R
GND
L
, and tristate in powerdown.
XIN
V
≤ +25V
L
RECEIVER
OUTPUTS MODE OF OPERATION
5kΩ
High-Z
Active
6
CC
CC
if the powerdown
, V- collapses to GND),
Manual Powerdown
Normal Operation
GND ≤ V
R
XOUT
ROUT
CC
≤ V
L
ISL4260E
V
Unlike other RS-232 interface devices where the CMOS
outputs swing between 0 and V
separate logic supply input (V
V
to a host logic supply lower than V
ISL4260E outputs from forward biasing the input diodes of a
logic device powered by that lower supply. Connecting V
a logic supply greater than V
output levels are compatible even with the CMOS input V
of AC, HC, and CD4000 devices. Note that the V
current increases to 100µA with V
(see Figure 11). V
inputs, thereby setting their switching thresholds to levels
compatible with the logic supply. This separate logic supply
pin allows a great deal of flexibility in interfacing to systems
with different logic supplies. If logic translation isn’t required,
connect V
Capacitor Selection
The ISL4260E charge pumps only require 0.1µF capacitors
for the full operational voltage range. Table 3 lists other
acceptable capacitor values for various supply voltage
ranges. 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.
CC
L
FIGURE 2. CONNECTIONS FOR MANUAL POWERDOWN
Logic Supply Input
) that sets V
3.0 to 3.6
4.5 to 5.5
3.0 to 5.5
CPU
V
LOGIC
TABLE 3. REQUIRED CAPACITOR VALUES
(V)
L
PWR
MGT
CC
to the ISL4260E V
OH
L
also powers the transmitter and logic
for the receiver outputs. Connecting V
UART
I/O
V
CC
I/O CHIP
POWER SUPPLY
SHDN
0.047
CC
(µF)
0.22
0.1
C
L
CC
; 1.8V to 5V, regardless of
1
CC
ensures that the receiver
.
L
, the ISL4260E features a
CC
= 5V and V
V
, prevents the
L
ISL4260E
C
2
CC
, C
0.33
(µF)
0.1
L
1
3
supply
= 3.3V
, C
4
L
IH
to
L