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CAT8710JTD-GT3 Datasheet(PDF) 5 Page - ON Semiconductor |
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CAT8710JTD-GT3 Datasheet(HTML) 5 Page - ON Semiconductor |
5 / 7 page CAT8710 http://onsemi.com 5 Detailed Description The CAT8710 is a space-saving, low-power, quad voltage microprocessor supervisory circuit designed to monitor 4 voltage supplies. The CAT8710 has 2 factory preset thresholds for monitoring standard power supply voltages of 3.3 V, 3.0 V, 2.5 V, or 1.8 V, and 2 adjustable thresholds for monitoring voltages as low as 0.62 V. Each internal voltage comparator has a typical hysteresis of 0.3% with respect to its reset threshold, which improves immunity to ambient noise without significantly reducing threshold accuracy. CAT8710 is designed to ignore short transients. Applications Information Reset Output CAT8710 provides an extended reset signal 120 ms (typ) in duration. The output is open drain and requires an external pull-up resistor to an external power supply. This supply can be less than or greater than VDD, but should not exceed 5.5 V. When the external pull−up voltage is greater than VDD reverse current flow from the external pull−up voltage to VDD is prevented by CAT8710’s internal circuitry. The CAT8710 is powered by VDD, which is also a monitored voltage. When any supply drops below its threshold, the reset output asserts low and remains low as long as VDD is above 1.0 V. Figure 9. RESET Output Timing Diagram Figure 10. Interfacing to Different Logic−Supply Voltage 3.3 V 5 V V3 GND V4MON V1MON CAT8710 RESET RESET mP V2/VDD Adjustable Thresholds CAT8710 allows users to create 2 custom voltage thresholds. The threshold voltage at each adjustable input is typically 0.62 V. Monitoring of voltages greater than 0.62 V requires a resistor-divider network to be connected to the circuit (Figure 11). VIN + 0.62 V (R1 ) R2) R2 or, written in terms of R1: R1 + R2 VIN 0.62 V * 1 Because the CAT8710 has a guaranteed input current of less than 50 nA on the adjustable inputs, resistor values up to 1000 k W can be used for R2 with < 1% error. Unused Inputs Connect unused monitor inputs to a supply voltage greater in magnitude than their specified threshold voltages; use VDD for normal operation (device power−supply pin). Do not connect unused monitor inputs to ground or allow them to float. Adding Manual Reset Capability Figure 12 illustrates how to add manual reset to the CAT8710. Depressing the pushbutton switch short−circuits the analog input to ground and initiates a RESET pulse. This technique can be used on either the V1 or V4 inputs. The switch must be open for at least 120 ms in order to deassert the RESET output. No external switch debounce is required. A small capacitor across R2 will improve noise immunity when using long leads from the pushbutton switch to the adjustable input. POR Applying power to the CAT8710 activates a POR circuit which activates the reset output (active LOW). At power−up POR prevents the system microprocessor from starting to operate with insufficient voltage and prior to stabilization of the clock oscillator. It ensures that operation is precluded until internal registers are properly loaded, FPGA’s have downloaded their configuration data. The reset signal remains active until all monitored power supplies have risen above their minimum preset voltage levels. Power−Supply Bypassing All monitored inputs are immune to short supply transients. For applications where higher immunity is required, connect a 0.1 mF bypass capacitor from each input pin to ground very close to CAT8710’s package. |
Similar Part No. - CAT8710JTD-GT3 |
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Similar Description - CAT8710JTD-GT3 |
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