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ICL3221CA View Datasheet(PDF) - Intersil

Part NameICL3221CA Intersil
Intersil Intersil
Description1 Microamp Supply-Current, +3V to +5.5V, 250kbps, RS-232 Transmitters/Receivers
ICL3221CA Datasheet PDF : 28 Pages
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ICL3221, ICL3222, ICL3223, ICL3232, ICL3241, ICL3243
The INVALID output always indicates whether or not a valid
RS-232 signal is present at any of the receiver inputs (See
Table 2), giving the user an easy way to determine when the
interface block should power down. In the case of a
disconnected interface cable where all the receiver inputs
are floating (but pulled to GND by the internal receiver pull
down resistors), the INVALID logic detects the invalid levels
and drives the output low. The power management logic
then uses this indicator to power down the interface block.
Reconnecting the cable restores valid levels at the receiver
inputs, INVALID switches high, and the power management
logic wakes up the interface block. INVALID can also be
used to indicate the DTR or RING INDICATOR signal, as
long as the other receiver inputs are floating, or driven to
GND (as in the case of a powered down driver). Connecting
FORCEOFF and FORCEON together disables the
automatic powerdown feature, enabling them to function as
a manual SHUTDOWN input (See Figure 4).
VCC
VCC
VCC
CURRENT
FLOW
POWERED
DOWN
UART
GND
VOUT = VCC
Rx
Tx
SHDN = GND
OLD
RS-232 CHIP
FIGURE 2. POWER DRAIN THROUGH POWERED DOWN
PERIPHERAL
VCC
TRANSITION
DETECTOR
TO
WAKE-UP
LOGIC
VCC
R2OUTB
RX
POWERED
DOWN
UART
TX
VOUT = HI-Z
R2OUT
T1IN
ICL324X
FORCEOFF = GND
OR SHDN = GND, EN = VCC
R2IN
T1OUT
FIGURE 3. DISABLED RECEIVERS PREVENT POWER DRAIN
PWR
MGT
LOGIC
FORCEOFF
FORCEON
INVALID
ICL3221/23/43
CPU
I/O
UART
FIGURE 4. CONNECTIONS FOR MANUAL POWERDOWN
WHEN NO VALID RECEIVER SIGNALS ARE
PRESENT
With any of the above control schemes, the time required to
exit powerdown, and resume transmission is only 100µs. A
mouse, or other application, may need more time to wake up
from shutdown. If automatic powerdown is being utilized, the
RS-232 device will reenter powerdown if valid receiver levels
aren’t reestablished within 30µs of the ICL32XX powering
up. Figure 5 illustrates a circuit that keeps the ICL32XX from
initiating automatic powerdown for 100ms after powering up.
This gives the slow-to-wake peripheral circuit time to
reestablish valid RS-232 output levels.
POWER
MANAGEMENT
UNIT
MASTER POWERDOWN LINE
0.1µF
1M
FORCEOFF FORCEON
ICL3221/23/43
FIGURE 5. CIRCUIT TO PREVENT AUTO POWERDOWN FOR
100ms AFTER FORCED POWERUP
Automatic Powerdown (ICL3221/23/43 Only)
Even greater power savings is available by using the
devices which feature an automatic powerdown function.
When no valid RS-232 voltages (See Figure 6) are sensed
on any receiver input for 30µs, the charge pump and
transmitters powerdown, thereby reducing supply current to
1µA. Invalid receiver levels occur whenever the driving
peripheral’s outputs are shut off (powered down) or when the
RS-232 interface cable is disconnected. The ICL32XX
powers back up whenever it detects a valid RS-232 voltage
level on any receiver input. This automatic powerdown
feature provides additional system power savings without
changes to the existing operating system.
12
FN4805.21
March 1, 2006
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One Microamp Supply-Current, +3V to +5.5V, 250kbps, RS-232 Transmitters/Receivers


The Intersil ICL32XX devices are 3.0V to 5.5V powered RS-232 transmitters/receivers which meet ElA/TIA-232 and V.28/V.24 specifications, even at VCC= 3.0V. Targeted applications are PDAs, Palmtops, and notebook and laptop computers where the low operational, and even lower standby, power consumption is critical. Efficient on-chip charge pumps, coupled with manual and automatic powerdown functions (except for the ICL3232), reduce the standby supply current to a 1µA trickle. Small footprint packaging, and the use of small, low value capacitors ensure board space savings as well. Data rates greater than 250kbps are guaranteed at worst case load onditions. This family is fully compatible with3.3V only systems, mixed 3.3V and 5.0V systems, and 5.0V only systems.

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