ISL83384E Intersil Corporation, ISL83384E Datasheet - Page 5

• Manufacturer Part Number: ISL83384E
• Description: 15kV ESD Protected/ +3V to +5.5V/ 1 Microamp/ 250Kbps/ RS-232 Transmitter/Receiver
• Manufacturer: Intersil Corporation

All the receivers convert RS-232 signals to CMOS output
levels and accept inputs up to ±30V while presenting the
required 3kΩ to 7kΩ input impedance (see Figure 1) even if
the power is off (V
input stage uses hysteresis to increase noise immunity and
decrease errors due to slow input signal transitions.
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 ISL83384E.
Low Power, Pin Compatible Replacement
Pin compatibility with existing 5V products (e.g., MAX222),
coupled with the wide operating supply range, make the
ISL83384E a potential lower power, higher performance
drop-in replacement for existing 5V applications. As long as
the ±5V RS-232 output swings are acceptable, and
transmitter pull-up resistors aren’t required, the ISL83384E
should work in most 5V applications.
When replacing a device in an existing 5V application, it is
acceptable to terminate C
Operating Circuit”. Nevertheless, terminate C
possible, as slightly better performance results from this
configuration.
Powerdown Functionality
The already low current requirement drops significantly
when the device enters powerdown mode. In powerdown,
supply current drops to 1µA, because the on-chip charge
pump turns off (V+ collapses to V
and the transmitter and receiver outputs three-state. This
micro-power mode makes these devices ideal for battery
powered and portable applications.
Software Controlled (Manual) Powerdown
The ISL83384E may be forced into its low power, standby
state via a simple shutdown (SHDN) pin (see Figure 4).
Driving this pin high enables normal operation, while driving
it low forces the IC into it’s powerdown state. The time
required to exit powerdown, and resume transmission is less
than 50µs. Connect SHDN to V
isn’t needed.
FIGURE 1. INVERTING RECEIVER CONNECTIONS
-25V ≤ V
CC
= 5.5V, during normal operation (not in
RIN
R
GND
V
XIN
CC
≤ +25V
CC
= 0V). The receivers’ Schmitt trigger
3
5kΩ
to V
5
CC
CC
CC
if the powerdown function
as shown on the “Typical
, V- collapses to GND),
GND ≤ V
R
XOUT
ROUT
3
to GND if
≤ V
CC
ISL83384E
FIGURE 3. DISABLED RECEIVERS PREVENT POWER DRAIN
POWERED
FIGURE 2. POWER DRAIN THROUGH POWERED DOWN
FIGURE 4. CONNECTIONS FOR MANUAL POWERDOWN
DOWN
UART
POWERED
CPU
DOWN
V
UART
WAKE-UP
GND
CC
LOGIC
LOGIC
PWR
MGT
V
TO
CC
PERIPHERAL
R
T
X
X
TRANSITION
DETECTOR
Rx
Tx
V
CC
V
UART
SHDN = GND
OUT
I/O
V
OUT
= HI-Z
V
SHDN
CC
= V
CC
V-
RS-232 CHIP
ISL83384E
ISL83384E
V
OLD
CURRENT
FLOW
CC