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ISL45042IR Datasheet(PDF) 5 Page - Intersil Corporation |
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ISL45042IR Datasheet(HTML) 5 Page - Intersil Corporation |
5 / 8 page 5 FN6072.8 July 9, 2008 needed to program the non-volatile memory is given in Figure 2. It then takes a maximum of 100ms for the programming to be completed inside the device.. When the part is programmed, the counter setting is loaded into the non-volatile memory. This value will be loaded from the nonvolatile memory during initial power-up or when the CE pin is pulled low. Once the programming is completed, it is recommended that the user float the CLT pin. The CTL pin is internally tied to a resistor network connected to ground. If left floating, the voltage at the CTL pin will equal VDD/2. Under these conditions, no additional pulses will be seen by the Up/Down counter via the CTL pin. To prevent further programming, ground the CE pin. CTL should have a noise filter to reduce bouncing or noise on the input that could cause unwanted counting when the CE pin is high. The board should have an additional ESD protection circuit, with a series 1k Ω resistor and a shunt 0.01µF capacitor connected on the CTL pin (see Figure 3) To avoid unintentional adjustment, the ISL45042 guarantees to reject CTL pulses shorter than 20µs. During Initial Power-up (only), to avoid the possibility of a false pulse (since the internal comparators come up in an unknown state), the very first CTL pulse is ignored. See Figure 7 for the timing information. CE Pin To adjust the output voltage, the CE pin must be pulled high (VDD). The CE pin has an internal pull-down resistor to prevent unwanted reprogramming of the EEPROM. The impedance of this resistor is 400k Ω to 500kΩ (see RINTERNAL in Figure 6). Transitions of the CE pin are recommended to be less than 10µs. Replacing Existing Mechanical Potentiometer Circuits Figure 4 shows the common adjustment mechanical circuits and equivalent replacement with the ISL45042. Expected Output Voltage The ISL45042 provides an output sink current, which lowers the voltage on the external voltage divider (VCOM output voltage). Equations 1 and 2 can be used to calculate the output current (IOUT) and output voltage (VOUT) values. Where, setting is an integer between 1 and 128. CTL VOLTAGE TIME 4.9V CTLPT FIGURE 2. EEPROM PROGRAMMING >200µs FIGURE 3. EXTERNAL ESD PROTECTION ON CTL PIN ISL45042 CTL 0.01µF 1k Ω I OUT Setting 128 --------------------- x AV DD 20 R SET () --------------------------- = V OUT R 2 R 1 R 2 + --------------------- ⎝⎠ ⎜⎟ ⎛⎞ AV DD 1 Setting 128 --------------------- x R 1 20 R SET () --------------------------- – ⎝⎠ ⎜⎟ ⎛⎞ = (EQ. 1) (EQ. 2) - + Ra Rb Rc RSET - + ISL45042 SET OUT AVDD R1 R2 AVDD VCOM VCOM AVDD R1 = Ra R2 = Rb + Rc RSET = (Ra(Rb + Rc))/20Rb FIGURE 4. EXAMPLE OF THE REPLACEMENT FOR THE MECHANICAL POTENTIOMETER CIRCUIT USING THE ISL45042 ISL45042 |
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