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ISL3241EIRZ-T 数据表(PDF) 11 Page - Intersil Corporation |
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ISL3241EIRZ-T 数据表(HTML) 11 Page - Intersil Corporation |
11 / 16 page 11 FN6768.1 May 13, 2010 receiver output high voltage, to values compatible with the logic device’s I/O levels. Tailoring the ISL324XE’s logic pin input switching points and output levels to the supply voltage of the UART, ASIC, or µcontroller eliminates the need for a level shifter/translator between the two ICs. VL may range from 1.6V to VCC, and Table 3 indicates the ISL324xE’s typical VIH and VIL levels for several VL values. Note that the VL supply current increases significantly when VL exceeds VCC (see Figure 20). If logic translation isn’t required, connect VL to VCC. INVALID Output (ISL3243E Only) The INVALID output always indicates whether or not a valid RS-232 signal (see Figure 10) 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. 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). INVALID switches low after invalid levels have persisted on all of the receiver inputs for more than 20µs (see Figure 11). INVALID switches back high 1µs after detecting a valid RS-232 level on a receiver input. INVALID operates in all modes (forced or automatic power-down, or forced on), so it is also useful for systems employing manual power-down circuitry. When automatic powerdown is utilized, INVALID = 0 indicates that the ISL3243E is in powerdown mode. Automatic Power-down (ISL3243E Only) Even greater power savings is available by using the ISL3243E which features an automatic power-down function. When no valid RS-232 voltages (see Figure 11) are sensed on any receiver input for 20µs, the charge pump and TABLE 3. VIH AND VIL vs VL FOR VCC = 3.3V VL (V) VIH (V) VIL (V) 1.6 0.85 0.8 1.8 0.95 0.9 2.5 1.25 1.2 FIGURE 9. USING VL PIN TO ADJUST LOGIC LEVELS GND TXD RXD VCCL = +1.8V UART/PROCESSOR GND TIN ROUT VCCI = +3.3V RS-232 IC WITH NO VOH ≥ 3V GND TXD VCCL = +1.8V UART/PROCESSOR GND VL VCCI = +3.3V ISL324xE VOH ≤ 1.8V VIH ≤ 1V VOH ≤ 1.8V VIH ≥ 2V VOH ≤ 1.8V VL PIN TIN ROUT RXD INPUT DIODE INPUT DIODE FIGURE 10. DEFINITION OF VALID RS-232 RECEIVER LEVELS 0.3V -0.3V -2.7V 2.7V INVALID LEVEL - POWER-DOWN OCCURS AFTER 20 μs VALID RS-232 LEVEL - ISL3243E IS ACTIVE VALID RS-232 LEVEL - ISL3243E IS ACTIVE INDETERMINATE - POWERDOWN MAY OR INDETERMINATE - POWERDOWN MAY OR MAY NOT OCCUR MAY NOT OCCUR RECEIVER INPUTS TRANSMITTER OUTPUTS INVALID OUTPUT V+ VCC 0 V- VL 0 tINVL tINVH INVALID REGION } FIGURE 11. AUTOMATIC POWERDOWN AND INVALID TIMING DIAGRAMS AUTOPWDN PWR UP ISL3241E, ISL3243E |
类似零件编号 - ISL3241EIRZ-T |
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类似说明 - ISL3241EIRZ-T |
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