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ISL23512WFRU10Z-TK Folha de dados(PDF) 8 Page - Intersil Corporation |
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ISL23512WFRU10Z-TK Folha de dados(HTML) 8 Page - Intersil Corporation |
8 / 9 page 8 FN6590.0 November 27, 2007 Power-Up and Power-Down Requirements There are no restrictions on the power-up or power-down conditions of VCC and the voltages applied to the potentiometer pins provided that VCC is always more positive than or equal to VRH and VRL, i.e., VCC ≥ VRH,VRL. The VCC ramp rate specification is always in effect. Pin Descriptions RH and RL The RH and RL pins of the ISL23512 are equivalent to the fixed terminals of a mechanical potentiometer. The minimum voltage is VSS and the maximum is VCC. The terminology of RH and RL references the relative position of the terminal in relation to wiper movement direction. RW The RW pin is the wiper terminal of the potentiometer, which is equivalent to the movable terminal of a mechanical potentiometer. The default wiper position at power-up is at 0tap. PU The debounced PU input is used to increment the wiper position. An on-chip pull-up holds the PU input HIGH. A switch closure to ground or a LOW logic level will, after a debounce time, move the wiper to the next adjacent higher tap position. PD The debounced PD input is used to decrement the wiper position. An on-chip pull-up holds the PD input HIGH. A switch closure to ground or a LOW logic level will, after a debounce time, move the wiper to the next adjacent lower tap position. Device Operation There are three sections of the ISL23512: the input control, the counter and decode section and the resistor array. The input control section operates just like an up/down counter. The output of this counter is decoded to turn on a single electronic switch, connecting a point on the resistor array to the wiper output. The resistor array is comprised of 15 individual resistors connected in series. At either end of the array and between each resistor is an electronic switch that transfers the potential at that point to the wiper. The ISL23512 is designed to interface directly to two push button switches for effectively moving the wiper up or down. The PU and PD inputs increment or decrement a 4-bit counter respectively. The output of this counter is decoded to select one of the sixteen wiper positions along the resistive array. The wiper increment input, PU and the wiper decrement input, PD are both connected to an internal pull-up so that they normally remain HIGH. When pulled LOW by an external push button switch or a logic LOW level input, the wiper will be switched to the next adjacent tap position. Internal debounce circuitry prevents inadvertent switching of the wiper position if PU or PD remain LOW for less than 15ms, typical. Each of the buttons can be pushed either once for a single increment/decrement or continuously for a multiple increments/decrements. The number of increments/decrements of the wiper position depend on how long the button is being pushed. When making a continuous push, after the first second, the increment/decrement speed increases. For the first second, the device will be in the slow scan mode. Then, if the button is held for longer than 1s, the device will go into the fast scan mode. As soon as the button is released, the ISL23512 will return to a stand-by condition. If both PU and PD buttons are pulled low more than 15ms from each other, all commands are ignored upon release of ALL buttons. The wiper, when at either fixed terminal, acts like its mechanical equivalent and does not move beyond the last position. That is, the counter does not wrap around when clocked to either extreme. Shutdown Mode The ISL23512 enters into Shutdown Mode if both PU and PD inputs are kept LOW for 2 seconds. In this mode, the resistors array is totally disconnected from its RH pin and the wiper is moved to the position closest to the RL pin, as shown in Figure 13. Note that PU and PD inputs must be pulled LOW within tDB time window of 15ms (see “Shutdown Mode Timing” on page 5.) otherwise all commands will be ignored until both inputs are released. Holding either PU or PD input LOW for more than 15ms will exit shutdown mode and return wiper to prior shutdown position. If PU or PD will be held LOW for more than 250ms, the ISL23512 will start auto-increment or auto-decrement of wiper position. RTOTAL with VCC Removed The end to end resistance of the array will fluctuate once VCC is removed. RL RW RH FIGURE 13. DCP CONNECTION IN SHUTDOWN MODE ISL23512 |
Nº de peça semelhante - ISL23512WFRU10Z-TK |
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Descrição semelhante - ISL23512WFRU10Z-TK |
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