công cụ tìm kiếm bảng dữ liệu linh kiện điện tử |
|
ADM708RAR-REEL bảng dữ liệu(PDF) 11 Page - Analog Devices |
|
ADM708RAR-REEL bảng dữ liệu(HTML) 11 Page - Analog Devices |
11 / 16 page ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T Rev. C | Page 11 of 16 POWER-FAIL COMPARATOR INPUT POWER TO MICROPROCESSOR NMI R3 3.3V The power-fail comparator is an independent comparator that can be used to monitor the input power supply. The inverting input of the comparator is internally connected to a 1.25 V reference voltage. The noninverting input is available at the PFI input. This input is used to monitor the input power supply via a resistive divider network. When the voltage on the PFI input drops below 1.25 V, the comparator output (PFO) goes low, indicating a power failure. For early warning of power failure, the comparator is used to monitor the preregulator input simply by choosing an appropriate resistive divider network. The PFO output is used to interrupt the processor so that a shutdown procedure is implemented before the power is lost. INPUT POWER R1 R2 POWER-FAIL INPUT 1.25V PFI PFO POWER-FAIL OUTPUT ADM706P/ADM706R/ ADM706S/ADM706T/ ADM708R/ADM708S/ ADM708T Figure 17. Power-Fail Comparator ADDING HYSTERESIS TO THE POWER-FAIL COMPARATOR For increased noise immunity, hysteresis can be added to the power-fail comparator. Because the comparator circuit is noninverting, hysteresis is added simply by connecting a resistor between the PFO output and the PFI input as shown in . When Figure 18 PFO is low, Resistor R3 sinks current from the summing junction at the PFI pin. When PFO is high, Resistor R3 sources current into the PFI summing junction. This results in differing trip levels for the comparator. Further noise immunity is achieved by connecting a capacitor between PFI and GND. VCC R1 R2 1.25V PFI PFO ADM663A – + 3.3V 0V 0V VL VIN VH PFO ADM706P/ADM706R/ ADM706S/ADM706T/ ADM708R/ADM708S/ ADM708T Figure 18. Adding Hysteresis to the Power-Fail Comparator ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ × + + = R1 R3 R2 R3 R2 V H 1 25 . 1 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − − + = R3 V R2 R1 V CC L 25 . 1 25 . 1 25 . 1 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + = R2 R2 R1 V MID 25 . 1 VALID RESET BELOW 1 V VCC The ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ ADM708T are guaranteed to provide a valid reset level with VCC as low as 1 V. Refer to the Typical Performance Characteristics section. As VCC drops below 1 V, the internal transistor does not have sufficient drive to hold it on so the voltage on RESET is no longer held at 0 V. A pull-down resistor, as shown in , can be connected externally to hold the line low if it is required. Figure 19 GND RESET R1 ADM706R/ADM706S/ ADM706T/ADM708R/ ADM708S/ADM708T Figure 19. RESET Valid Below 1 V |
Số phần tương tự - ADM708RAR-REEL |
|
Mô tả tương tự - ADM708RAR-REEL |
|
|
Link URL |
Chính sách bảo mật |
ALLDATASHEET.VN |
Cho đến nay ALLDATASHEET có giúp ích cho doanh nghiệp của bạn hay không? [ DONATE ] |
Alldatasheet là | Quảng cáo | Liên lạc với chúng tôi | Chính sách bảo mật | Trao đổi link | Tìm kiếm theo nhà sản xuất 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 |