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ICL3227 Datasheet(PDF) 8 Page - Intersil Corporation |
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ICL3227 Datasheet(HTML) 8 Page - Intersil Corporation |
8 / 20 page 8 Powerdown Functionality This 3V family of RS-232 interface devices requires a nominal supply current of 0.3mA during normal operation (not in powerdown mode). This is considerably less than the 5mA to 11mA current required of 5V RS-232 devices. The already low current requirement drops significantly when the device enters powerdown mode. In powerdown, supply current drops to 1 µA, because the on-chip charge pump turns off (V+ collapses to VCC, V- collapses to GND), and the transmitter outputs three-state. Inverting receiver outputs may or may not disable in powerdown; refer to Table 2 for details. This micro-power mode makes these devices ideal for battery powered and portable applications. Software Controlled (Manual) Powerdown These three devices allow the user to force the IC into the low power, standby state, and utilize a two pin approach where the FORCEON and FORCEOFF inputs determine the IC’s 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 enhanced automatic powerdown circuitry. ICL3245 inverting (standard) receiver outputs also disable when the device is in powerdown, thereby eliminating the possible current path through a shutdown peripheral’s input protection diode (see Figures 2 and 3). Connecting FORCEOFF and FORCEON together disables the enhanced automatic powerdown feature, enabling them to function as a manual SHUTDOWN input (see Figure 4). TABLE 2. POWERDOWN LOGIC TRUTH TABLE RCVR OR XMTR EDGE WITHIN 30s? FORCEOFF INPUT FORCEON INPUT TRANSMITTER OUTPUTS RECEIVER OUTPUTS (NOTE 5) ROUTB OUTPUTS RS-232 LEVEL PRESENT AT RECEIVER INPUT? INVALID OUTPUT MODE OF OPERATION ICL3225, ICL3227 NO H H Active Active N.A. No L Normal Operation (Enhanced Auto Powerdown Disabled) NO H H Active Active N.A. Yes H YES H L Active Active N.A. No L Normal Operation (Enhanced Auto Powerdown Enabled) YES H L Active Active N.A. Yes H NO H L High-Z Active N.A. No L Powerdown Due to Enhanced Auto Powerdown Logic NO H L High-Z Active N.A. Yes H X L X High-Z Active N.A. No L Manual Powerdown X L X High-Z Active N.A. Yes H ICL322X - INVALID DRIVING FORCEON AND FORCEOFF (EMULATES AUTOMATIC POWERDOWN) X NOTE 6 NOTE 6 Active Active N.A. Yes H Normal Operation X NOTE 6 NOTE 6 High-Z Active N.A. No L Forced Auto Powerdown ICL3245 NO H H Active Active Active No L Normal Operation (Enhanced Auto Powerdown Disabled) NO H H Active Active Active Yes H YES H L Active Active Active No L Normal Operation (Enhanced Auto Powerdown Enabled) YES H L Active Active Active Yes H NO H L High-Z Active Active No L Powerdown Due to Enhanced Auto Powerdown Logic NO H L High-Z Active Active Yes H X L X High-Z High-Z Active No L Manual Powerdown X L X High-Z High-Z Active Yes H ICL3245 - INVALID DRIVING FORCEON AND FORCEOFF (EMULATES AUTOMATIC POWERDOWN) X NOTE 6 NOTE 6 Active Active Active Yes H Normal Operation X NOTE 6 NOTE 6 High-Z High-Z Active No L Forced Auto Powerdown NOTES: 5. Applies only to the ICL3245. 6. Input is connected to INVALID Output. ICL3225, ICL3227, ICL3245 |
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