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PDF AS1911 Data sheet ( Hoja de datos )
| Número de pieza | AS1911 | |
| Descripción | Dual-Voltage Microprocessor Supervisory Circuits | |
| Fabricantes | austriamicrosystems AG | |
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AS1910 - AS1915
Dual-Voltage Microprocessor Supervisory Circuits
with Manual Reset and Watchdog
Data Sheet
1 General Description
2 Key Features
The AS1910 - AS1915 microprocessor supervisory cir-
cuits were designed to generate a reset when one of the
two monitored supply voltages falls below a factory-
trimmed threshold, and to maintain the reset for a mini-
mum timeout period when both supplies are above their
reset thresholds. Guaranteed to be in the correct state
for VCC higher than +1.0V, these devices are ideal for
multiple-voltage systems with strict monitoring require-
ments.
The AS1913/AS1914/AS1915 feature factory-trimmed
thresholds to monitor a primary voltage between 1.8 and
3.6V, and a secondary voltage between 0.9 and 2.5V.
For the AS1910/AS1911/AS1912, a secondary monitor-
ing voltage can be user-adjusted via an external resistor
divider down to 0.6V.
The devices are available with the reset output types
listed in Table 1.
Table 1. Standard Products
Model
Reset Output Type
AS1910/AS1913
Active-Low Push/Pull
AS1911/AS1914
Active-High Push/Pull
AS1912/AS1915
Active-Low Open-Drain
The AS1910 - AS1915 include a manual-reset input for
systems that never fully power down the microproces-
sor. Additionally, these devices feature a watchdog timer
to help ensure that the processor is operating within
proper code boundaries.
The AS1910 - AS1915 are available in a 6-pin SOT23
package.
Figure 1. Typical Application Diagram
! Primary VCC Supervisory Range: +1.8 to +3.6V
! Secondary VCC Supervisory Range: +0.9 to +2.5V
(AS1913/AS1914/AS1915)
! User-Adjustable Threshold Down to +0.63V
(AS1910/AS1911/AS1912)
! Guaranteed Reset Valid Down to VCC = +1.0V
! Reset Timeout Delay: 215ms
! Manual Reset Input
! Three Reset Output Types
- Active-High Push/Pull
- Active-Low Push/Pull
- Active-Low Open-Drain
! Watchdog Timeout Period: 1.5s
! Immune to Fast Negative VCC Transients
! External Components Not Required
! Operating Temperature Range: -40 to +125°C
! 6-pin SOT23 Package
3 Applications
The devices are ideal for portable and battery-powered
systems, embedded controllers, intelligent instruments,
automotive systems, critical CPU monitoring, and any
multi-supply application.
VCC
VCC2
External
Reset
6
VCC
5
VCC2
3
MRN
AS1913/
AS1915
1
RESETN
4
WDI
GND 2
I/O Supply
Core
Supply
RESETN
CPU
GND
I/O
www.austriamicrosystems.com
Revision 1.00
1 - 15
1 page  
AS1910 - AS1915
Data Sheet - Electrical Characteristics
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Table 4. Electrical Characteristics (Continued)
Symbol
Parameter 1
Reset Threshold
Temperature Coefficient
Conditions
Reset Threshold Hysteresis
VRESETINTH
RESETIN Threshold
VRESETINTH Falling, TAMB = 0 to +85ºC
TAMB = -40 to +125ºC
RESETIN Hysteresis
IRESETIN
tRD
tRP
RESETIN Input Current 2
VCC to Reset
Output Delay
RESETIN to Reset
Output Delay
Reset Timeout Period
VOL
RESETN Output Low
(Push/Pull or Open-Drain)
VOH
RESETN Output High
(Push/Pull Only)
ILKG
Open-Drain RESETN Output
Leakage Current
VOH
RESET Output High
(Push/Pull Only)
VOL
RESET Output Low
(Push/Pull Only)
Manual Reset Input
TAMB = -40 to +85ºC
TAMB = -40 to +125ºC
VCC = VTH to (VTH - 100mV)
VRESETIN = VRESETINTH to
(VRESETINTH - 30mV)
TAMB = -40 to +85ºC
TAMB = -40 to +125ºC
VCC ≥ 1.0V, ISINK = 50µA,
Reset Asserted, TAMB = 0 to +85ºC
VCC ≥ 1.2V, ISINK = 100µA, Reset
Asserted
VCC ≥ 2.55V, ISINK = 1.2mA,
Reset Asserted
VCC ≥ 3.3V, ISINK = 3.2mA,
Reset Asserted
VCC ≥ 1.8V, ISOURCE = 200µA,
Reset Not Asserted
VCC ≥ 3.15V, ISOURCE = 500µA,
Reset Not Asserted
VCC ≥ 3.3V, ISOURCE = 800µA,
Reset Not Asserted
RESETN Not Asserted
TAMB = +25ºC
VCC ≥ 1.0V, ISOURCE = 1µA,
Reset Asserted, TAMB = 0 to +85ºC
VCC ≥ 1.50V, ISOURCE = 100µA,
Reset Asserted
VCC ≥ 2.55V, ISOURCE = 500µA,
Reset Asserted
VCC ≥ 3.3V, ISOURCE = 800µA,
Reset Asserted
VCC ≥ 1.8V, ISINK = 500µA,
Reset Asserted
VCC ≥ 3.15V, ISINK = 1.2mA,
Reset Asserted
VCC ≥ 3.3V, ISINK = 3.2mA,
Reset Asserted
VIL
MRN Input voltage
VIH
Min Typ Max Units
60
ppm/
ºC
8x
VTH
0.615 0.630 0.645
0.61 0.65
mV
V
8x
VTH
mV
-25
-100
+25
nA
+100
55 µs
45 µs
140 215 280
ms
100 320
0.3
0.3
V
0.3
0.8 x
VCC
0.8 x
VCC
0.8 x
VCC
0.8 x
VCC
0.8 x
VCC
0.8 x
VCC
0.8 x
VCC
0.4
V
1.0
µA
0.2
V
0.3
0.3 V
0.4
0.7 x
VCC
0.3 x
VCC
V
www.austriamicrosystems.com
Revision 1.00
5 - 15
5 Page 
AS1910 - AS1915
Data Sheet - Application Information
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9 Application Information
Watchdog Input Current
The watchdog input is driven through an internal buffer and an internal series resistor from the watchdog timer (see
Figure 11 on page 9). When pin WDI is left unconnected (watchdog disabled), the watchdog timer is serviced within the
watchdog timeout period (see tWD on page 6) by a low-high-low pulse from the counter chain. For minimum watchdog
input current (minimum overall power consumption), pull WDI low for most of the watchdog timeout period, pulsing it
low-high-low once within the first 7/8 (87.5%) of the watchdog timeout period to reset the watchdog timer.
Note: If WDI is externally driven high for the majority of the timeout period, up to 160µA can flow into pin WDI.
Interfacing to Bi-Directional CPU Reset Pins
Since the reset outputs of the AS1912 and AS1915 are open drain, these devices interface easily with processors that
have bi-directional reset pins. Connecting the processor reset output directly to the AS1912/AS1915 RESETN pin with
a single pullup resistor (see Figure 14) allows the AS1912/AS1912 to assert a reset.
Figure 14. AS1912 or AS1915 RESETN-to-CPU Bi-Directional Reset Pin
VCC
VCC
CPU
RESETN
GND
1
RESETN
VCC 6
AS1912/
AS1915
Reset
Generator
GND 2
Fast Negative-Going Transients
Fast, negative-going VCC transients normally do not require the CPU to be shutdown. The AS1910 - AS1915 are virtu-
ally immune to such transients. Resets are issued to the CPU during power-up, powerdown, and brownout conditions.
Note: VCC transients that go 100mV below the reset threshold and last ≤ 55µs typically will not assert a reset pulse.
Valid Reset to VCC = 0
The AS1910 - AS1915 are guaranteed to operate properly down to VCC = 1V. For applications requiring valid reset lev-
els down to VCC = 0, a pulldown resistor to active-low outputs (push/pull only) and a pullup resistor to active-high out-
puts (push/pull only) will ensure that the reset line is valid during the interval where the reset output can no longer sink
or source current.
Watchdog Tips
Careful consideration should be taken when implementing the AS1910 - AS1915 watchdog feature.
One method of supervising software code execution is to set/reset the watchdog input at different places in the code,
rather than pulsing the watchdog input high-low-high or low-high-low. This method avoids a loop condition in which the
watchdog timer would continue to be reset inside the loop, preventing the watchdog from ever timing out.
Figure 15 shows a flowchart where the input/output driving the watchdog is set high at the beginning of the routine, set
low at the beginning of every subroutine, then set high again when the routine returns to the beginning. If the routine
should hang in a subroutine, the problem would quickly be corrected, since the I/O is continually set low and the watch-
dog timer is allowed to time out, causing a reset or interrupt to be issued (see Watchdog Input Current on page 11).
This method results in higher averaged WDI input current over time than a case where WDI is held low for the majority
(87.5%) of the timeout period and periodically pulsing it low-high-low.
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Revision 1.00
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| PDF Descargar | [ Datasheet AS1911.PDF ] | |
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