Electronic Components Datasheet Search |
|
ISL4221EIR-T Datasheet(PDF) 7 Page - Intersil Corporation |
|
ISL4221EIR-T Datasheet(HTML) 7 Page - Intersil Corporation |
7 / 13 page 7 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 automatic powerdown circuitry. Connecting FORCEOFF and FORCEON together disables the automatic powerdown feature, enabling them to function as a manual SHUTDOWN input (see Figure 4). The time to recover from automatic powerdown mode is typically 100 µs. Automatic Powerdown Even greater power savings is available by using the automatic powerdown function. When no valid RS-232 voltages (see Figure 6) are sensed on any receiver input for 30 µs, the charge pump and transmitters powerdown, thereby reducing supply current to 10nA. 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 ISL422XE 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. 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 automatic powerdown functionality. Some applications 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 30 µs of the ISL422XE powering up. Figure 5 illustrates a circuit that keeps the ISL422XE TABLE 2. POWERDOWN AND ENABLE LOGIC TRUTH TABLE RS-232 SIGNAL PRESENT AT RECEIVER INPUT? FORCEOFF INPUT FORCEON INPUT EN INPUT TRANSMITTER OUTPUTS RECEIVER OUTPUTS INVALID OUTPUT MODE OF OPERATION NO H H L Active Active L Normal Operation (Auto Powerdown Disabled) NO H H H Active High-Z L YES H L L Active Active H Normal Operation (Auto Powerdown Enabled) YES H L H Active High-Z H NO H L L High-Z Active L Powerdown Due to Auto Powerdown Logic NO H L H High-Z High-Z L YES L X L High-Z Active H Manual Powerdown YES L X H High-Z High-Z H Manual Powerdown w/Rcvr. Disabled NO L X L High-Z Active L Manual Powerdown NO L X H High-Z High-Z L Manual Powerdown w/Rcvr. Disabled FIGURE 4. CONNECTIONS FOR MANUAL POWERDOWN WHEN NO VALID RECEIVER SIGNALS ARE PRESENT PWR FORCEOFF INVALID CPU I/O FORCEON ISL422XE MGT LOGIC UART FIGURE 5. CIRCUIT TO PREVENT AUTO POWERDOWN FOR 100ms AFTER FORCED POWERUP ISL422XE FORCEOFF FORCEON POWER MASTER POWERDOWN LINE 1M Ω 0.1 µF MANAGEMENT UNIT ISL4221E, ISL4223E |
Similar Part No. - ISL4221EIR-T |
|
Similar Description - ISL4221EIR-T |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |