ISL4238EIR Intersil, ISL4238EIR Datasheet - Page 9

• Manufacturer Part Number: ISL4238EIR
• Description: IC 5DRVR/3RCVR RS232 3V 32-QFN
• Manufacturer: Intersil
• Type: Transceiverr

Specifications of ISL4238EIR

• Number Of Drivers/receivers: 5/3
• Protocol: RS232
• Voltage - Supply: 2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 32-VQFN Exposed Pad, 32-HVQFN, 32-SQFN, 32-DHVQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

GND for the best performance. ISL4238E transmitter inputs
incorporate an active positive feedback resistor that
maintains the last input state in the absence of a forcing
signal, so unused transmitter inputs may be left
unconnected.
Receivers
ISL4238E, ISL4244E, ISL4245 devices contain standard
inverting receivers which can tristate via the FORCEOFF
control line. Additionally, they include a noninverting
(monitor) receiver (denoted by the R
always active, regardless of the state of any control lines.
Both receiver types 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
input stage uses hysteresis to increase noise immunity and
decrease errors due to slow input signal transitions.
The ISL4238E, ISL4244E, ISL4245 inverting receivers
disable during forced (manual) power-down, but not during
automatic power-down (see Table 2). Conversely, the
monitor receiver remains active even during manual power-
down 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
NOTE:
INVALID DRIVING FORCEON AND FORCEOFF (EMULATES AUTOMATIC POWER-DOWN)
8. Input is connected to INVALID Output.
WITHIN 30
RCVR OR
XMTR
EDGE
SEC?
YES
YES
NO
NO
NO
NO
X
X
X
X
FIGURE 1. INVERTING RECEIVER CONNECTIONS
-25V ≤ V
RIN
FORCEOFF
R
GND
V
XIN
CC
INPUT
Note 8
Note 8
≤ +25V
CC
H
H
H
H
H
H
L
L
= 0V). The receivers’ Schmitt trigger
FORCEON
5kΩ
INPUT
Note 8
Note 8
9
H
H
X
X
L
L
L
L
OUTB
GND ≤ V
TRANSMITTER
OUTPUTS
R
TABLE 2. POWER-DOWN LOGIC TRUTH TABLE
High-Z
High-Z
High-Z
High-Z
High-Z
XOUT
Active
Active
Active
Active
Active
label) that is
ISL4238E, ISL4244E, ISL4245E
ROUT
≤ V
CC
RECEIVER
OUTPUTS
High-Z
High-Z
High-Z
Active
Active
Active
Active
Active
Active
Active
OUTPUTS
R
Active
Active
Active
Active
Active
Active
Active
Active
Active
Active
OUTB
renders them useless for wake up functions, but the
corresponding monitor receiver can be dedicated to this task
as shown in Figure 3.
Low Power Operation
These 3V devices require a nominal supply current of
0.3mA, even at V
power-down mode). This is considerably less than the 5mA
to 11mA current required by comparable 5V RS-232 devices,
allowing users to reduce system power simply by switching
to this new family.
FIGURE 2. POWER DRAIN THROUGH POWERED DOWN
POWERED
DOWN
RECEIVER
UART
PRESENT
GND
INPUT?
RS-232
LEVEL
V
Yes
Yes
Yes
Yes
Yes
AT
No
No
No
No
No
CC
PERIPHERAL
CC
Rx
Tx
V
= 5.5V, during normal operation (not in
OUTPUT
INVALID
CC
SHDN = GND
H
H
H
H
H
L
L
L
L
L
V
OUT
= V
Normal Operation (Enhanced
Auto Power-down Disabled)
Normal Operation (Enhanced
Auto Power-down Enabled)
Power-down Due to Enhanced
Auto Power-down Logic
Manual Power-down
Normal Operation
Forced Auto Power-down
CC
MODE OF OPERATION
RS-232 CHIP
V
OLD
CURRENT
FLOW
CC
May 13, 2010
FN8038.5