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STM810MWX6F ,RESET CIRCUITLogic Diagram (STM811/812) . . . . . . 4Table 2. Signal Names . . 4Figure 4. SOT23-3 Co ..
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STM809LWX6F-STM809MWX6F-STM809RWX6F-STM809SWX6F-STM809TWX6F-STM810LWX6F-STM810MWX6F-STM810RWX6F-STM810SWX6F-STM810TWX6F-STM811LW16F-STM811MW16F-STM811RW16F-STM811SW16F-STM811TW16F-STM812LW16F-STM812MW16F-STM812RW16F-STM812SW16F-STM812TW16F
RESET CIRCUIT
1/18November 2004
STM809, STM810
STM811, STM812Reset Circuit
FEATURES SUMMARY PRECISION MONITORING OF 3V, 3.3V, and
5V SUPPLY VOLTAGES TWO OUTPUT CONFIGURATIONS Push-pull RST Output (STM809/811) Push-pull RST Output (STM810/812) 140ms RESET PULSE WIDTH (MIN) LOW SUPPLY CURRENT - 6µA (TYP) GUARANTEED RST/RST ASSERTION
DOWN TO VCC = 1.0V OPERATING TEMPERATURE:
–40°C to 85°C (Industrial Grade) LEAD-FREE, SMALL SOT23 and SOT143
PACKAGE
Table 1. Device Options
STM809/810/811/812
TABLE OF CONTENTS
FEATURES SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Table 1. Device Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Figure 1. Packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
SUMMARY DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Figure 2. Logic Diagram (STM809/810) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Figure 3. Logic Diagram (STM811/812) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Table 2. Signal Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Figure 4. SOT23-3 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Figure 5. SOT143-4 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Figure 6. Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Figure 7. Hardware Hookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Reset Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Push-Button Reset Input (STM811/812) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Negative-Going VCC Transients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Valid /RST Output Down to VCC = 0V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
TYPICAL OPERATING CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Figure 8. Supply Current vs. Temperature, L/M/R/S/T (no load) . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Figure 9. Power-down Reset Delay vs. Temperature - VOD = VTH – VCC (L/M). . . . . . . . . . . . . . . .7
Figure 10.Power-down Reset Delay vs. Temperature - VOD = VTH – VCC (R/S/T) . . . . . . . . . . . . . .8
Figure 11.Power-up trec vs. Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Figure 12.Normalized Reset Threshold vs. Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Figure 13.Max Transient Duration NOT Causing Reset Pulse vs. Reset Comparator Overdrive. . .9
MAXIMUM RATING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Table 3. Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
DC and AC PARAMETERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Table 4. Operating and AC Measurement Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Figure 14.AC Testing Input/Output Waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Figure 15.MR Timing Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Table 5. DC and AC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
PACKAGE MECHANICAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Figure 16.SOT23-3 – 3-lead Small Outline Transistor Package Outline . . . . . . . . . . . . . . . . . . . . .13
Table 6. SOT23-3 – 3-lead Small Outline Transistor Package Mechanical Data . . . . . . . . . . . . .13
Figure 17.SOT143-4 – 4-lead Small Outline Transistor Package Outline. . . . . . . . . . . . . . . . . . . .14
Table 7. SOT143-4 – 4-lead Small Outline Transistor Package Mechanical Data . . . . . . . . . . . .14
PART NUMBERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
3/18
STM809/810/811/812Table 8. Ordering Information Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Table 9. Marking Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
REVISION HISTORY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Table 10. Document Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
STM809/810/811/812
SUMMARY DESCRIPTIONThe STM809/810/811/812 MICROPROCESSOR
RESET Circuits are low-power supervisory devic-
es used to monitor power supplies. They perform
a single function: asserting a reset signal whenev-
er the VCC supply voltage drops below a preset
value and keeping it asserted until VCC has risen
above the preset threshold for a minimum period
of time (trec). The STM811/812 also provide a
push-button reset input (MR).
Figure 6. Block DiagramNote:1. STM811/812 only RST for STM810/812
5/18
STM809/810/811/812
Figure 7. Hardware HookupNote:1. STM809/811 only (RST for STM810/812) STM811/812 only
STM809/810/811/812
OPERATION
Reset OutputThe STM809/810/811/812 MICROPROCESSOR
RESET CIRCUIT asserts a reset signal to the
MCU whenever VCC goes below the reset thresh-
old (VRST), or when the push-button reset input
(MR) is taken low (see Figure 15., page 11). RST
(active high for STM810/812) is guaranteed valid
down to VCC =1V (0° to 70°C).
During power-up, once VCC exceeds the reset
threshold an internal timer keeps RST low for the
reset time-out period, trec. After this interval, RST
returns high.
If VCC drops below the reset threshold, RST goes
low. Each time RST is asserted, it stays low for at
least the reset time-out period. Any time VCC goes
below the reset threshold, the internal timer clears.
The reset timer starts when VCC returns above the
reset threshold. The active-low reset (RST) and
active-high reset (RST) both source and sink cur-
rent.
Push-Button Reset Input (STM811/812)A logic low on MR asserts RST. RST remains as-
serted while MR is low, and for trec after it returns
high. The MR input has an internal 20kΩ pull-up
resistor, allowing it to be left open if not used. This
input can be driven with TTL/CMOS-logic levels or
with open-drain/collector outputs. Connect a nor-
mally open push-button switch from MR to GND to
create a manual reset function; external debounce
circuitry is not required. If the device is used in a
noisy environment, connect a 0.1µF capacitor
from MR to GND to provide additional noise immu-
nity.
Negative-Going VCC TransientsThe STM809/810/811/812 are relatively immune
to negative-going VCC transients (glitches). Figure
13., page 9 shows typical transient duration ver-
sus reset comparator overdrive (for which the
STM809/810/811/812 will NOT generate a reset
pulse). The graph was generated using a negative
pulse applied to VCC, starting at 0.5V above the
actual reset threshold and ending below it by the
magnitude indicated (comparator overdrive). The
graph indicates the maximum pulse width a nega-
tive VCC transient can have without causing a re-
set pulse. As the magnitude of the transient
increases (further below the threshold), the maxi-
mum allowable pulse width decreases. Any com-
bination of duration and overdrive which lies under
the curve will NOT generate a reset signal. Typi-
cally, a VCC transient that goes 100mV below the
reset threshold and lasts 20µs or less will not
cause a reset pulse. A 0.1µF bypass capacitor
mounted as close as possible to the VCC pin pro-
vides additional transient immunity.
Valid /RST Output Down to VCC = 0VWhen VCC falls below 1V, the RST (STM809/811)
output no longer sinks current, but becomes an
open circuit. In most systems this is not a problem,
as most MCUs do not operate below 1V. However,
in applications where RST output must be valid
down to 0V, a pull-down resistor may be added to
hold the RST output low. This resistor must be
large enough to not load the RST output, and still
be small enough to pull the output to ground. A
100KΩ resistor is recommended.
Note: The same situation applies for the active-high RST of the STM810/812. A 100KΩ pull-up re-
sistor to VCC should be used if RST must remain
valid for VCC < 1.0V.
7/18
STM809/810/811/812
STM809/810/811/812
Figure 10. Power-down Reset Delay vs. Temperature - VOD = VTH – VCC (R/S/T)
Figure 11. Power-up trec vs. Temperature
9/18
STM809/810/811/812
Figure 12. Normalized Reset Threshold vs. Temperature
Figure 13. Max Transient Duration NOT Causing Reset Pulse vs. Reset Comparator Overdrive
