Diodes Incorporated

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Processor Supervisory Circuits

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The APX823/APX824/APX825A family of supervisors provides circuit initialization and timing supervision, primarily for DSP and processor-based systems.

During power-on, RESET is asserted when supply voltage VCC becomes higher than 1.1V. Thereafter, the supply voltage supervisor monitors VCC and keeps RESET active as long as VCC remains below the threshold voltage VTH- . An internal timer delays the return of the output to the inactive state (high) to ensure proper system reset. The delay time, td starts after VCC has risen above the threshold voltage VTH- . When the supply voltage drops below the threshold voltage VTH- , the output becomes active (low) again. No external components are required. All the devices of this family have a fixed-sense threshold voltage VTH- set by an internal voltage divider.

The APX823/APX825A devices incorporate a manual reset input, MR. A low level at MR causes RESET to become active. The APX824/APX825A devices include a high-level output RESET. APX823/APX824/APX825A have a watchdog timer that is periodically triggered by a positive or negative transition at WDI. When the supervising system fails to retrigger the watchdog circuit within the time-out interval, ttout, RESET becomes active for the time period td. This event also reinitializes the watchdog timer. Leaving WDI unconnected disables the watchdog.

In applications where the input to the WDI pin may be active (transitioning high and low) when the APX823/APX824/APX825A asserting RESET the APX823/APX824/APX825A does not return to a non-reset state when the input voltage is above Vt. The product spectrum is designed for supply voltage of 2.5V, 3V, 3.3V and 5V. The circuits are available in a SOT25 and SOT26 packages. The APX823/APX824/APX825A devices are characterized for operation over a temperature range of -40°C to 105°C.


  • Power-on reset generator with fixed delay time of 200ms Typ
  • Manual reset input (APX823/APX825A)
  • Reset output available in active-low (APX823/APX824/APX825A), active-high (APX824/APX825A)
  • Supply voltage supervision range 2.5V, 3V, 3.3V, 5V
  • Watchdog timer
  • Supply current of 30μA (Typ.)
  • Temperature range: -40°C to 85°C
  • Lead-Free Finish; RoHS Compliant (Notes 1 & 2)
  • Halogen and Antimony Free. “Green” Device (Note 3)
  • For automotive applications requiring specific change control (i.e. parts qualified to AEC-Q100/101/104/200, PPAP capable, and manufactured in IATF 16949 certified facilities), please contact us or your local Diodes representative. https://www.diodes.com/quality/productdefinitions/


  • Applications using DSPs, microcontrollers, or microprocessors
  • Industrial equipment
  • Programmable controls
  • Portable/battery-powered equipment
  • Intelligent instruments
  • Wireless communications systems
  • Notebook/desktop computers


Product Specifications

Product Parameters

Fixed Detect Voltages (V) 2.25, 2.63, 2.93, 3.08, 4, 4.38, 4.63 V
Adjustable Detect Voltage Reference Voltage (V) N/A V
Number of Channels 1
Minimum Operating Voltage (V) 1 V
Maximum Input Voltage (V) 5.5 V
Quiescent Current (µA) 30 µA
Typical Time Delay (µs) 20 µs
Reset Period (ms) 200 ms
RESET Output (Active High) Yes (Active High)
RESET Output (Active Low) Yes (Active Low)
Manual RESET Yes
Watchdog Yes
Watchdog Time (s) None s
Power Fail Comparator Threshold (V) None V
Reset Output Topology Push-Pull
Ambient Temperature Range  (°C) -40 to 85 °C

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Technical Documents

Recommended Soldering Techniques


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Product Change Notices (PCNs)

A PCN may only apply to specific orderable part numbers in this datasheet. Please refer to the corresponding PCN to see the exact orderable part number(s) affected.

PCN # Issue Date Implementation Date Subject
PCN-2651 2023-11-13 2023-11-13 Qualified Additional Fab Source, Assembly Test Sites, Die Revision, BOM, Datasheet, Tape and Reel Packing Quantity.