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STM6779：Dual/triple ultra-low voltage supervisors with push-button reset (with delay option)

The STM6717/18/19/20 and STM6777/78/79/80 supervisors are a family of low-voltage/low-supply current processor (micro or DSP) supervisors, designed to monitor two (or three) system power supply voltages. They are targeted at applications such as set-top boxes (STBs), portable, battery-powered systems, networking, and communication systems.

All device options have a push-button-type manual reset input (MR). The STM6777/78/79/80 also includes an option which enables the user to delay the start of the manual reset process from 6 μs (MRC pin left open) or more with external capacitor. The delay is implemented by connecting the appropriately sized capacitor between the MRC pin and V_SS(typical 4 s delay with a 3.3 μF capacitor).

Two of the three supplies monitored (V_CC1and V_CC2) have fixed (customer-selectable, factory-trimmed) thresholds (V_RST1and V_RST2). The third voltage is monitored using an externally adjustable RSTIN threshold (0.626 V internal reference).

If any of the three monitored voltages drop below its factory-trimmed or adjustable thresholds, or if MRis asserted to logic low, a RSTis asserted (driven low). Once asserted, RSTis maintained at low for a minimum delay period (t_rec) after ALL supplies rise above their respective thresholds and MRreturns to high. These devices are guaranteed to be in the correct reset output logic state when V_CC1and/or V_CC2is greater than 0.8 V.

These devices are available in standard 5-pin or 6-pin SOT23 packages.

Key Features

• Primary supply (VCC1 ) monitor. Fixed (factory-programmed) reset thresholds: 4.63 V to 1.58 V
• Secondary supply (VCC2 ) monitor (STM6717/18/19/20/77/78)
• Fixed (factory-programmed) reset thresholds: 3.08 V to 0.79 V
• Tertiary supply monitor (using externally adjustable RSTIN): 0.626 V internal reference
• RST outputs (push-pull or open drain); state guaranteed if VCC1 or VCC2 ≥ 0.8 V
• Reset delay time (trec ) on power-up: 13.2 ms, 210 ms, 900 ms (typ)
• Manual reset input (MR )
• Optional delayed manual reset input (MRC) with external capacitor (STM6777/78/79/80)
• Low supply current - 11 μA (typ), VCC1 = VCC2 = 3.6 V
• Operating temperature: –40 °C to 85 °C (industrial grade)

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