Electronic Components Datasheet Search
  English  ▼
ALLDATASHEET.COM

X  

795S Datasheet(PDF) 9 Page - STMicroelectronics

Part # 795S
Description  3V Supervisor with Battery Switchover
Download  32 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  STMICROELECTRONICS [STMicroelectronics]
Direct Link  http://www.st.com
Logo STMICROELECTRONICS - STMicroelectronics

795S Datasheet(HTML) 9 Page - STMicroelectronics

Back Button 795S Datasheet HTML 5Page - STMicroelectronics 795S Datasheet HTML 6Page - STMicroelectronics 795S Datasheet HTML 7Page - STMicroelectronics 795S Datasheet HTML 8Page - STMicroelectronics 795S Datasheet HTML 9Page - STMicroelectronics 795S Datasheet HTML 10Page - STMicroelectronics 795S Datasheet HTML 11Page - STMicroelectronics 795S Datasheet HTML 12Page - STMicroelectronics 795S Datasheet HTML 13Page - STMicroelectronics Next Button
Zoom Inzoom in Zoom Outzoom out
 9 / 32 page
background image
9/32
STM690/704/795/802/804/805/806
OPERATION
Reset Output
The STM690/704/795/802/804/805/806 Supervi-
sor asserts a reset signal to the MCU whenever
VCC goes below the reset threshold (VRST), a
watchdog time-out occurs, or when the Push-but-
ton Reset Input (MR) is taken low. RST is guaran-
teed to be a logic low (logic high for STM804/805)
for 0V < VCC < VRST if VBAT is greater than 1V.
Without a back-up battery, RST is guaranteed val-
id down to VCC =1V.
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 (trec). Any time VCC
goes below the reset threshold the internal timer
clears. The reset timer starts when VCC returns
above the reset threshold.
Push-button Reset Input (STM704/806)
A logic low on MR asserts reset. Reset remains
asserted while MR is low, and for trec (see Figure
37., page 24) after it returns high. The MR input
has an internal 40k
Ω 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 normally open mo-
mentary switch from MR to GND to create a man-
ual reset function; external debounce circuitry is
not required. If MR is driven from long cables or
the device is used in a noisy environment, connect
a 0.1µF capacitor from MR to GND to provide ad-
ditional noise immunity. MR may float, or be tied to
VCC when not used.
Watchdog Input (NOT available on STM704/
795/806)
The watchdog timer can be used to detect an out-
of-control MCU. If the MCU does not toggle the
Watchdog Input (WDI) within tWD (1.6sec typ), the
reset is asserted. The internal watchdog timer is
cleared by either:
1.
a reset pulse, or
2.
by toggling WDI (high-to-low or low-to-high),
which can detect pulses as short as 50ns. If
WDI is tied high or low, a reset pulse is
triggered every 1.8sec (tWD + trec).
The timer remains cleared and does not count for
as long as reset is asserted. As soon as reset is re-
leased, the timer starts counting (see Figure
38., page 24).
Note: Input frequency greater than 20ns (50MHz)
will be filtered.
Back-up Battery Switchover
In the event of a power failure, it may be necessary
to preserve the contents of external SRAM
through VOUT. With a backup battery installed with
voltage VBAT, the devices automatically switch the
SRAM to the back-up supply when VCC falls.
Note: If back-up battery is not used, connect both
VBAT and VOUT to VCC.
This family of Supervisors does not always con-
nect VBAT to VOUT when VBAT is greater than VCC.
VBAT connects to VOUT (through a 100Ω switch)
when VCC is below VSW (2.4V) or VBAT (whichever
is lower). This is done to allow the back-up battery
(e.g., a 3.6V lithium cell) to have a higher voltage
than VCC.
Assuming that VBAT > 2.0V, switchover at VSO en-
sures that battery back-up mode is entered before
VOUT gets too close to the 2.0V minimum required
to reliably retain data in most external SRAMs.
When VCC recovers, hysteresis is used to avoid
oscillation around the VSO point. VOUT is connect-
ed to VCC through a 3Ω PMOS power switch.
Note: The back-up battery may be removed while
VCC is valid, assuming VBAT is adequately decou-
pled (0.1µF typ), without danger of triggering a re-
set.
Table 4. I/O Status in Battery Back-up
Pin
Status
VOUT
Connected to VBAT through internal switch
VCC
Disconnected from VOUT
PFI
Disabled
PFO
Logic Low
E
High impedance
ECON
Logic High
WDI
Watchdog timer is disabled
MR
Disabled
RST
Logic Low
RST
Logic High
VBAT
Connected to VOUT
Vccsw
Logic High (STM795)


Similar Part No. - 795S

ManufacturerPart #DatasheetDescription
logo
Marl International Limi...
795-107-00-51 MARL-795-107-00-51 Datasheet
379Kb / 3P
   LED MODULES
795-107-00-52 MARL-795-107-00-52 Datasheet
379Kb / 3P
   LED MODULES
795-107-00-53 MARL-795-107-00-53 Datasheet
379Kb / 3P
   LED MODULES
logo
Winchester Electronics ...
795-15-9 WINCHESTER-795-15-9 Datasheet
67Kb / 1P
   PLUG, C
logo
Vitesse Semiconductor C...
795-16-9 VITESSE-795-16-9 Datasheet
62Kb / 1P
   PLUG, C
More results

Similar Description - 795S

ManufacturerPart #DatasheetDescription
logo
STMicroelectronics
STM690 STMICROELECTRONICS-STM690 Datasheet
445Kb / 31P
   3V Supervisor with Battery Switchover
STM1403 STMICROELECTRONICS-STM1403 Datasheet
162Kb / 9P
   3V FIPS-140 Security Supervisor with Battery Switchover
STM1404 STMICROELECTRONICS-STM1404 Datasheet
199Kb / 9P
   Security Supervisor with Battery Switchover
STM690A STMICROELECTRONICS-STM690A Datasheet
773Kb / 37P
   5V Supervisor with Battery Switchover
STM690 STMICROELECTRONICS-STM690_10 Datasheet
960Kb / 42P
   3 V supervisor with battery switchover
STM690A STMICROELECTRONICS-STM690A_10 Datasheet
1Mb / 43P
   5 V supervisor with battery switchover
STM1403 STMICROELECTRONICS-STM1403_08 Datasheet
361Kb / 34P
   3 V FIPS-140 security supervisor with battery switchover
STM1404 STMICROELECTRONICS-STM1404_08 Datasheet
370Kb / 35P
   3 V FIPS-140 security supervisor with battery switchover
logo
Micro Analog systems
MCP7952X MAS-MCP7952X Datasheet
946Kb / 50P
   3V SPI Real-Time Clock Calendar with Battery Switchover
logo
Microchip Technology
MCP79510-IMS MICROCHIP-MCP79510-IMS Datasheet
946Kb / 50P
   3V SPI Real-Time Clock Calendar with Battery Switchover
11/29/11
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32


Datasheet Download

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com