TPS3823A-33DBVR Integrated Circuits (ICs)

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1. Description

The TPS3823A-33DBVR family of supervisors provide circuit initialization and timing supervision, primarily for DSP and processor-based systems. During power on, RESET asserts when the supply voltage VDD becomes greater than 1.1 V. Thereafter, the supply voltage supervisor monitors VDD and keeps RESET active low as long as VDD remains less than the threshold voltage, VIT−. 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 VDD has risen above the threshold voltage (VIT−+ VHYS). When the supply voltage drops below the threshold voltage VIT−, the output becomes active (low) again. No external components are required. All the devices of this family have a fixed-sense threshold voltage, VIT– , set by an internal voltage divider. The TPS382x family also offers watchdog time out options of 200 ms (TPS3820) and 1.6 s (TPS3823/4/8).

2. Features

    1. Power-On reset generator with fixed delay time of 200 ms or 25 ms 

    2. Manual reset input 

    3. Reset output available in active-low, active-high, and open drain 

    4. Supply voltage supervision range: 2.5 V, 3 V, 3.3 V, 5 V

    5. Watchdog timer 

    6. Supply current of 15 μA 

    7. 5-Pin SOT-23 package

    8. Temperature range: −40°C to 85°C 

3. Applications

    1. DSPs, microcontrollers, or microprocessors

    2. Industrial equipment

    3. Programmable controls

    4. Automotive systems

    5. Portable and battery-powered equipment

    6. Intelligent instruments

    7. Wireless communications systems

    8. Notebook and desktop computers

4. Pin Configuration

5. Pin Functions

6. Feature Description

    1. Manual Reset (MR)

        The MR input allows an external logic signal from processors, logic circuits, and/or discrete sensors to force a reset signal regardless of VDD with respect to VIT– or the state of the watchdog timer. A low level at MR causes the reset signals to become active.

    2. Active-High or Active-Low Output

        All TPS382x devices have an active-low logic output (RESET), while the TPS3824/5 devices also include an active-high logic output (RESET).

    3. Push-Pull or Open-Drain Output

        All TPS382x devices, except for TPS3828, have push-pull outputs. TPS3828 devices have an open-drain output.

    4. Watchdog Timer (WDI)

        The TPS3820, TPS3823, TPS3824, and TPS3828 devices have a watchdog timer that must be periodically triggered by either a positive or negative transition at WDI to avoid a reset signal being issued. 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. The watchdog timer can be disabled by disconnecting the WDI pin from the system. If the WDI pin detects that it is in a high impedance state, the TPS3820, TPS3823, TPS3824, or TPS3828 will generate its own WDI pulse to ensure that RESET does not assert. If this behavior is not desired, place a 1-kΩ resistor from WDI to ground. This resistor will help ensure that the TPS3820, TPS3823, TPS3824, or TPS3828 detects that WDI is not in a high-impedance state. In applications where the input to the WDI pin is active (transitioning high and low) and the TPS3820, TPS3823, TPS3824, or TPS3828 is asserting RESET, RESET is stuck at a logic low after the input voltage returns above VIT–. If the application requires that input to WDI be active when the reset signal is asserted, then either the A version of the device or a FET should be used to decouple the WDI signal. The A version does not latch the reset signal to the asserted state if a WDI pulse is received while RESET is asserted. An external FET decouples the WDI signal by disconnecting the WDI input when RESET is asserted. For more details on this, see Decoupling WDI During Reset Event. The A version of the device does not require this FET, but it does operate in circuits that have it. Therefore, the A version is backwards-compatible with the non-A versions.

7. Application Information

The TPS382x family of devices are very small supervisory circuits that monitor fixed supply voltages of 2.5 V, 3 V, 3.3 V, and 5 V. The TPS382x family operates from 1.1 V to 5.5 V. Orderable options include versions with either push-pull or open-drain outputs, versions that use active-high or active-low logic for output signals, versions with a manual reset pin, and versions with a watchdog timer.