ICL3238EIA Intersil, ICL3238EIA Datasheet - Page 7

• Manufacturer Part Number: ICL3238EIA
• Description: IC 5DRVR/3RCVR RS232 3V 28-SSOP
• Manufacturer: Intersil
• Type: Transceiverr

Specifications of ICL3238EIA

• Number Of Drivers/receivers: 5/3
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

even during manual powerdown making it extremely useful
for RING INDICATOR monitoring. Standard receivers driving
powered down peripherals must be disabled to prevent
current flow through the peripheral’s protection diodes (see
Figures 2 and 3). This renders them useless for wake up
functions, but the corresponding monitor receiver can be
dedicated to this task as shown in Figure 3.
Powerdown Functionality
This 3V RS-232 interface device requires a nominal supply
current of 0.3mA during normal operation (not in powerdown
mode). This is considerably less than the 5mA to 11mA
FIGURE 3. DISABLED RECEIVERS PREVENT POWER DRAIN
POWERED
FIGURE 2. POWER DRAIN THROUGH POWERED DOWN
DOWN
UART
FIGURE 1. INVERTING RECEIVER CONNECTIONS
POWERED
-25V ≤ V
DOWN
V
UART
WAKE-UP
GND
CC
LOGIC
V
TO
CC
RIN
R
T
PERIPHERAL
X
X
FORCEOFF = GND
R
GND
V
XIN
CC
≤ +25V
TRANSITION
DETECTOR
Rx
Tx
V
CC
V
SHDN = GND
OUT
R1
V
R1
OUT
= HI-Z
5kΩ
V
OUTB
T1
CC
OUT
= V
IN
7
CC
GND ≤ V
ICL3238E
RS-232 CHIP
R
OLD
XOUT
V
CURRENT
FLOW
CC
ROUT
≤ V
CC
R1
T1
OUT
IN
ICL3238E
current required by 5V RS-232 devices. The already low
current requirement drops significantly when the device
enters powerdown mode. In powerdown, supply current
drops to 10nA, because the on-chip charge pump turns off
(V+ collapses to V
transmitter outputs three-state. This micro-power mode
makes this device ideal for battery powered and portable
applications.
Software Controlled (Manual) Powerdown
The ICL3238E allows the user to force the IC into the low
power, standby state, and utilizes a two pin approach where
the FORCEON and FORCEOFF inputs determine the IC’s
mode. For always enabled operation, FORCEON and
FORCEOFF are both strapped high. To switch between
active and powerdown modes, under logic or software
control, only the FORCEOFF input need be driven. The
FORCEON state isn’t critical, as FORCEOFF dominates
over FORCEON. Nevertheless, if strictly manual control over
powerdown is desired, the user must strap FORCEON high
to disable the enhanced automatic powerdown circuitry.
ICL3238E inverting (standard) receiver outputs also disable
when the device is in manual powerdown, thereby
eliminating the possible current path through a shutdown
peripheral’s input protection diode (see Figures 2 and 3).
Connecting FORCEOFF and FORCEON together disables
the enhanced automatic powerdown feature, enabling them
to function as a manual SHUTDOWN input (see Figure 4).
With any of the above control schemes, the time required to
exit powerdown, and resume transmission is only 25µs.
When using both manual and enhanced automatic
powerdown (FORCEON = 0), the ICL3238E won’t power up
from manual powerdown until both FORCEOFF and
FORCEON are driven high, or until a transition occurs on a
receiver or transmitter input. Figure 5 illustrates a circuit for
ensuring that the ICL3238E powers up as soon as
FIGURE 4. CONNECTIONS FOR MANUAL POWERDOWN
CPU
LOGIC
PWR
MGT
WHEN NO VALID RECEIVER SIGNALS ARE
PRESENT
CC
, V- collapses to GND), and the
UART
I/O
FORCEOFF
FORCEON
INVALID
ICL3238E