STM6905 Datasheet, PDF (7/19 Pages) STMicroelectronics – Quintuple, ultralow voltage supervisor with push-button reset

STM6905
2
Pin descriptions
Pin descriptions
2.1
Push-button reset input (MR)
When MR goes low the RST output is driven low, RST remains low as long as MR is low and
for t_REC after MR returns to high. The active-low input has an internal 10k ohm pull-up
resistor to V_CC. It can be driven from a TTL or CMOS logic line, or with open drain/collector
outputs, or connected to V_SS through a switch. If unused, leave this pin open or connect it to
V_CC.
Connect a normally open momentary switch from MR to V_SS; external debounce circuitry is
not required. (If MR is driven from long cables or if the device is used in noisy environments,
connecting a 0.1uF capacitor from MR to V_SS provides additional noise immunity).
2.2
V_CC primary supply voltage monitoring input
The V_CC pin is also the input for the primary reset threshold monitor. Fixed (customer-
selectable, factory programmed) reset thresholds include 3.078 V to 2.866 V.
2.3
V2IN second fixed voltage monitoring input
The V2IN input is the second fixed-voltage input for reset threshold monitoring. Available
fixed (customer-selectable, factory programmed) reset thresholds include 2.333 V to
1.050 V.
2.4
V_SS
This pin is the ground pin for the power supply.
2.5
V3IN, V4IN, and V5IN
The V3IN, V4IN and V5IN are high impedance inputs. RST is driven low when the voltage
(VTRIP) at the pin falls below 600 mV (internal reference voltage at their respective
comparators). The monitored voltage reset threshold is set with an external resistor-divider
network.
2.6
RST active-low, open drain reset output
The reset output (RST) pin is driven low and stays low whenever V_CC or V2IN, or V3IN, or
V4IN, or V5IN falls below its factory-trimmed or adjustable reset threshold or when MR
goes to logic low. It remains low for trec after all supply voltages being monitored rise above
their reset thresholds and MR goes from low to high. Connect an external pull-up resistor to
V_CC. A 10k ohms pull-up resistor should be sufficient for most applications.
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