FN4900.9 February 27, 2006 When using both manual and enhanced automatic powerdown (FORCEON = 0), the ICL32XXE won’t power up from manual power" />
參數(shù)資料
型號(hào): ICL3245ECV
廠商: Intersil
文件頁數(shù): 2/20頁
文件大小: 0K
描述: IC 3DRVR/5RCVR RS232 3V 28-TSSOP
標(biāo)準(zhǔn)包裝: 50
類型: 收發(fā)器
驅(qū)動(dòng)器/接收器數(shù): 3/5
規(guī)程: RS232
電源電壓: 3 V ~ 5.5 V
安裝類型: 表面貼裝
封裝/外殼: 28-TSSOP(0.173",4.40mm 寬)
供應(yīng)商設(shè)備封裝: 28-TSSOP
包裝: 管件
10
FN4900.9
February 27, 2006
When using both manual and enhanced automatic
powerdown (FORCEON = 0), the ICL32XXE 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 ICL32XXE powers up as soon as
FORCEOFF switches high. The rising edge of the Master
Powerdown signal forces the device to power up, and the
ICL32XXE returns to enhanced automatic powerdown mode
an RC time constant after this rising edge. The time constant
isn’t critical, because the ICL32XXE remains powered up for
30 seconds after the FORCEON falling edge, even if there
are no signal transitions. This gives slow-to-wake systems
(e.g., a mouse) plenty of time to start transmitting, and as
long as it starts transmitting within 30 seconds both systems
remain enabled.
INVALID Output
The INVALID output always indicates (see Table 2) whether
or not 30
s have elapsed with invalid RS-232 signals (see
Figures 6 and 8) persisting on all of the receiver inputs,
giving the user an easy way to determine when the interface
block should power down. Invalid receiver levels occur
whenever the driving peripheral’s outputs are shut off
(powered down) or when the RS-232 interface cable is
disconnected. 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).
Enhanced Automatic Powerdown
Even greater power savings is available by using these devices
which feature an enhanced automatic powerdown function.
When the enhanced powerdown logic determines that no
transitions have occurred on any of the transmitter nor receiver
inputs for 30 seconds, the charge pump and transmitters
powerdown, thereby reducing supply current to 1
A. The
ICL32XXE automatically powers back up whenever it detects a
transition on one of these inputs. This automatic powerdown
feature provides additional system power savings without
changes to the existing operating system.
Enhanced automatic powerdown operates when the
FORCEON input is low, and the FORCEOFF input is high.
Tying FORCEON high disables automatic powerdown, but
manual powerdown is always available via the overriding
FORCEOFF input. Table 2 summarizes the enhanced
automatic powerdown functionality.
Figure 7 illustrates the enhanced powerdown control logic.
Note that once the ICL32XXE enters powerdown (manually
or automatically), the 30 second timer remains timed out
FIGURE 4. CONNECTIONS FOR MANUAL POWERDOWN
WHEN NO VALID RECEIVER SIGNALS ARE
PRESENT
PWR
FORCEOFF
INVALID
CPU
I/O
FORCEON
ICL32XXE
MGT
LOGIC
UART
FIGURE 5. CIRCUIT TO ENSURE IMMEDIATE POWER UP
WHEN EXITING FORCED POWERDOWN
FORCEOFF
FORCEON
POWER
MASTER POWERDOWN LINE
1M
0.1
F
MANAGEMENT
UNIT
ICL32XXE
FIGURE 6. DEFINITION OF VALID RS-232 RECEIVER LEVELS
0.3V
-0.3V
-2.7V
2.7V
INVALID LEVEL - INVALID = 0
VALID RS-232 LEVEL - INVALID = 1
INDETERMINATE
FIGURE 7. ENHANCED AUTOMATIC POWERDOWN LOGIC
30s
TIMER
S
R
FORCEOFF
AUTOSHDN
FORCEON
R_IN
T_IN
EDGE
DETECT
EDGE
DETECT
ICL3225E, ICL3227E, ICL3245E
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