Electronic Components Datasheet Search |
|
ASM690AEPA Datasheet(PDF) 7 Page - ON Semiconductor |
|
ASM690AEPA Datasheet(HTML) 7 Page - ON Semiconductor |
7 / 12 page ASM690A/692A, ASM802L/802M, ASM805L http://onsemi.com 7 that the capacitor voltage remain below the maximum voltages shown in Table 6. Although the circuit of Figure 6 shows the most simple way to connect the SuperCap, this circuit cannot insure that an over voltage condition will not occur since the capacitor will ultimately charge up to VCC. To insure that an over voltage condition does not occur, the circuit of Figure 7 is preferred. In this circuit configuration, the diode−resistor pair clamps the capacitor voltage at one diode drop below VCC. VCC itself should be regulated within ±5% of 5 V for the ASM692A/802M or within ±10% of 5 V for the ASM690A/802L/805L to insure that the storage capacitor does not achieve an over voltage state. Figure 6. Capacitor as a Backup Power Source Figure 7. Capacitor as a Backup Power Source Voltage Clamped to 0.5 V below VCC Operation without a Backup Power Source When operating without a back−up power source, the VBATT pin should be connected to GND and VOUT should be connected to VCC, since power source switchover will not occur. Connecting VOUT to VCC eliminates the voltage drop due to the ON−resistance of the PMOS switch. Power−Fail Comparator The Power Fail feature is an independent voltage monitoring function that can be used for any number of monitoring activities. The PFI function can provide an early sensing of power supply failure by sensing the voltage of the unregulated DC ahead of the regulated supply sensing seen by the backup−battery switchover circuitry. The PFI pin is compared to a 1.25 V internal reference. If the voltage at the PFI pin is less than this reference voltage, the PFO pin goes low. By sensing the voltage of the raw DC power supply, the microprocessor system can prepare for imminent power−loss, especially if the battery backup supply is not enabled. The input voltage at the PFI pin results from a simple resistor voltage divider as shown in Figure 8. Figure 8. Simple Voltage Divider Sets PFI Trip Point Power Fail Hysteresis A noise margin can be added to the simple monitoring circuit of Figure 8 by adding positive feedback from the PFO pin. The circuit of Figure 9 adds this positive “latching” effect by means of an additional resistor R3 connected between PFO and PFI which helps in pulling PFI in the direction of PFO and eliminating an indecision at the trip point. Resistor R3 is normally about 10 times higher in resistance than R2 to keep the hysteresis band reasonable and should be larger than 10 k W to avoid excessive loading on the PFO pin. The calculations for the correct values of resistors to set the hysteresis thresholds are given in Figure 9. A capacitor can be added to offer additional noise rejection by low−pass filtering. |
Similar Part No. - ASM690AEPA |
|
Similar Description - ASM690AEPA |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |