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ICL3222CA Datasheet(PDF) 10 Page - Intersil Corporation |
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ICL3222CA Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 28 page 10 FN4805.21 March 1, 2006 Detailed Description ICL32XX interface ICs operate from a single +3V to +5.5V supply, guarantee a 250kbps minimum data rate, require only four small external 0.1 µF capacitors, feature low power consumption, and meet all ElA RS-232C and V.28 specifications. The circuit is divided into three sections: charge pump, transmitters and receivers. Charge-Pump Intersil’s new ICL32XX family utilizes regulated on-chip dual charge pumps as voltage doublers, and voltage inverters to generate ±5.5V transmitter supplies from a VCC supply as low as 3.0V. This allows these devices to maintain RS-232 compliant output levels over the ±10% tolerance range of 3.3V powered systems. The efficient on-chip power supplies require only four small, external 0.1 µF capacitors for the voltage doubler and inverter functions at VCC = 3.3V. See the Capacitor Selection section, and Table 3 for capacitor recommendations for other operating conditions. The charge pumps operate discontinuously (i.e., they turn off as soon as the V+ and V- supplies are pumped up to the nominal values), resulting in significant power savings. Transmitters The transmitters are proprietary, low dropout, inverting drivers that translate TTL/CMOS inputs to EIA/TIA-232 output levels. Coupled with the on-chip ±5.5V supplies, these transmitters deliver true RS-232 levels over a wide range of single supply system voltages. Except for the ICL3232, all transmitter outputs disable and assume a high impedance state when the device enters the powerdown mode (See Table 2). These outputs may be driven to ±12V when disabled. All devices guarantee a 250kbps data rate for full load conditions (3k Ω and 1000pF), VCC ≥ 3.0V, with one transmitter operating at full speed. Under more typical conditions of VCC ≥ 3.3V, RL =3kΩ, and CL = 250pF, one transmitter easily operates at 900kbps. Transmitter inputs float if left unconnected, and may cause ICC increases. Connect unused inputs to GND for the best performance. Receivers All the ICL32XX devices contain standard inverting receivers that three-state (except for the ICL3232) via the EN or FORCEOFF control lines. Additionally, the two ICL324X products include noninverting (monitor) receivers (denoted by the ROUTB label) that are always active, regardless of the state of any control lines. All the receivers convert RS-232 signals to CMOS output levels and accept inputs up to ±25V while presenting the required 3k Ω to 7kΩ input impedance (See Figure 1) even if the power is off (VCC = 0V). The receivers’ Schmitt trigger input stage uses hysteresis to increase noise immunity and decrease errors due to slow input signal transitions. The ICL3221/22/23/41 inverting receivers disable only when EN is driven high. ICL3243 receivers disable during forced (manual) powerdown, but not during automatic powerdown (See Table 2). ICL324X monitor receivers remain active even during manual powerdown and forced receiver disable, 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 2 and 3). This renders them useless for wake up functions, but the corresponding monitor receiver can be dedicated to this task as shown in Figure 3. Low Power Operation These 3V devices require a nominal supply current of 0.3mA, even at VCC = 5.5V, during normal operation (not in powerdown 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. Pin Compatible Replacements For 5V Devices The ICL3221/22/32 are pin compatible with existing 5V RS-232 transceivers - see the Features section on the front page for details. This pin compatibility coupled with the low Icc and wide operating supply range, make the ICL32XX potential lower power, higher performance drop-in replacements for existing 5V applications. As long as the ±5V RS-232 output swings are acceptable, and transmitter input pull-up resistors aren’t required, the ICL32XX should work in most 5V applications. When replacing a device in an existing 5V application, it is acceptable to terminate C3 to VCC as shown on the Typical Operating Circuit. Nevertheless, terminate C3 to GND if possible, as slightly better performance results from this configuration. Powerdown Functionality (Except ICL3232) 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. RXOUT GND ≤ VROUT ≤ VCC 5k Ω RXIN -25V ≤ VRIN ≤ +25V GND VCC FIGURE 1. INVERTING RECEIVER CONNECTIONS ICL3221, ICL3222, ICL3223, ICL3232, ICL3241, ICL3243 |
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Similar Description - ICL3222CA |
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