ISL3241E Datasheet, PDF (9/16 Pages) Intersil Corporation – QFN Packaged, ±15kV ESD Protected, +2.7V to +3.6V, 250kbps, RS-232 Transmitters/Receivers with Separate Logic Supply Pin

ISL3241E, ISL3243E
TABLE 2. POWER-DOWN AND ENABLE LOGIC TRUTH TABLE (NOTE: “H” = V_L)
RS-232
SIGNAL
PRESENT
AT
RECEIVER
INPUT?
SHDN OR
FORCEOFF FORCEON EN TRANSMITTER RECEIVER R_OUTB
INPUT
INPUT INPUT OUTPUTS OUTPUTS OUTPUTS
INVALID
OUTPUT
MODE OF OPERATION
ISL3241E
N/A
L
N/A
L
High-Z
Active
Active
N/A Manual Power-down
N/A
L
N/A
H
High-Z
High-Z
Active
N/A Manual Power-down w/Rcvr. Disabled
N/A
H
N/A
L
Active
Active
Active
N/A Normal Operation
N/A
H
N/A
H
Active
High-Z
Active
N/A Normal Operation w/Rcvr. Disabled
ISL3243E
NO
H
H
N.A.
Active
Active
Active
L
Normal Operation
(Auto Powerdown Disabled)
YES
H
L
N.A.
Active
Active
Active
H
Normal Operation
(Auto Power-down Enabled)
NO
H
L
N.A.
High-Z
Active
Active
L
Power-down Due to Auto Power-down
Logic
YES
L
X
N.A.
High-Z
High-Z
Active
H
Manual Power-down
NO
L
X
N.A.
High-Z
High-Z
Active
L
Manual Power-down
ISL324xE monitor receivers remain active even during
manual powerdown, making them 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 5
and 6). This renders them useless for wake up functions, but
the corresponding monitor receiver can be dedicated to this
task as shown in Figure 6.
Low Power Operation
These 3V devices require a nominal supply current of
0.3mA, even at V_CC = 3.6V, during normal operation (not in
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.
Power-down Functionality
The already low current requirement drops significantly
when the device enters powerdown mode. In powerdown,
supply current drops to less than 1µA, because the on-chip
charge pump turns off (V+ collapses to V_CC, V- collapses to
GND), and the transmitter outputs three-state. Inverting
receiver outputs disable only in manual powerdown
(ISL3243E) or when EN = V_L (ISL3241E); refer to Table 2 for
details. This micro-power mode makes the ISL324xE ideal
for battery powered and portable applications.
V_CC
V_CC
V_CC
POWERED
DOWN
UART
GND
V_OUT = V_CC
Rx
Tx
SHDN = GND
CURRENT
FLOW
OLD
RS-232 CHIP
FIGURE 5. POWER DRAIN THROUGH POWERED DOWN
PERIPHERAL
9
FN6768.1
May 13, 2010