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MAX6420 Datasheet(PDF) 8 Page - Maxim Integrated Products |
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MAX6420 Datasheet(HTML) 8 Page - Maxim Integrated Products |
8 / 12 page Interfacing to Other Voltages for Logic Compatibility The open-drain outputs of the MAX6414/MAX6417/ MAX6420 can be used to interface to µPs with other logic levels. As shown in Figure 5, the open-drain out- put can be connected to voltages from 0 to 5.5V. This allows for easy logic compatibility to various micro- processors. Negative-Going VCC Transients In addition to issuing a reset to the µP during power-up, power-down, and brownout conditions, these supervisors are relatively immune to short-duration negative-going transients (glitches). The Maximum Transient Duration vs. Reset Threshold Overdrive graph in the Typical Operating Characteristics shows this relationship. The area below the curve of the graph is the region in which these devices typically do not generate a reset pulse. This graph was generated using a negative- going pulse applied to VCC, starting above the actual reset threshold (VTH) and ending below it by the magni- tude indicated (reset-threshold overdrive). As the mag- nitude of the transient decreases (farther below the reset threshold), the maximum allowable pulse width decreases. Typically, a VCC transient that goes 100mV below the reset threshold and lasts 50µs or less will not cause a reset pulse to be issued. Ensuring a Valid RESET or RESET Down to VCC = 0V When VCC falls below 1V, RESET/RESET current sink- ing (sourcing) capabilities decline drastically. In the case of the MAX6412, MAX6415, and MAX6418, high- impedance CMOS-logic inputs connected to RESET can drift to undetermined voltages. This presents no problems in most applications, since most µPs and other circuitry do not operate with VCC below 1V. In those applications where RESET must be valid down to 0, adding a pulldown resistor between RESET and ground sinks any stray leakage currents, holding RESET low (Figure 6). The value of the pulldown resis- tor is not critical; 100k Ω is large enough not to load RESET and small enough to pull RESET to ground. For applications using the MAX6413, MAX6416, and MAX6419, a 100k Ω pullup resistor between RESET and VCC will hold RESET high when VCC falls below 1V (Figure 7). Open-drain RESET versions are not recom- mended for applications requiring valid logic for VCC down to 0V. Low-Power, Single/Dual-Voltage µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay MAX6412–MAX6420 8 Maxim Integrated MAX6414 MAX6417 MAX6420 VCC GND 3.3V 5.0V RESET 10k Ω 5V SYSTEM Figure 5. MAX6414/MAX6417/MAX6420 Open-Drain RESET Output Allows use with Multiple Supplies MAX6412 MAX6415 MAX6418 GND VCC VCC RESET 100k Ω Figure 6. Ensuring RESET Valid to VCC = 0V MAX6413 MAX6416 MAX6419 GND VCC VCC RESET 100k Ω Figure 7. Ensuring RESET Valid to VCC = 0V |
Similar Part No. - MAX6420_12 |
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Similar Description - MAX6420_12 |
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