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AS1916 - AS1918
M i c r o p r o c e s s o r S u p e r v i s o r y C i r c u i ts w i t h M a n u a l R e s e t a n d Wa t c h d o g
D a ta S he e t
1 General Description
The AS1916 - AS1918 microprocessor supervisory circuits were designed to generate a reset when the monitored supply voltage falls below a factory-trimmed threshold. The reset remains asserted for a minimum timeout period after the supply voltage stabilizes. Guaranteed to be in the correct state for VCC higher than +1.0V, these devices are ideal for portable and batterypowered systems with strict monitoring requirements. The devices feature factory-trimmed thresholds to monitor a supply voltage between 1.8 and 3.6V. The devices are available with the reset output types listed in Table 1. Table 1. Standard Products Model AS1916 AS1917 AS1918 Reset Output Type Active-Low Push/Pull Active-High Push/Pull Active-Low Open-Drain
2 Key Features
! ! ! ! !
VCC Supervisory Range: +1.8 to +3.6V Guaranteed Reset Valid Down to VCC = +1.0V Reset Timeout Delay: 215ms Manual Reset Input Three Reset Output Types - Active-Low Push/Pull (AS1916) - Active-High Push/Pull (AS1917) - Active-Low Open-Drain (AS1918) Watchdog Timeout Period: 1.5s Immune to Fast Negative VCC Transients External Components Not Required Operating Temperature Range: -40 to +125C 5-pin SOT23 Package
! ! ! ! !
The AS1916 - AS1918 include a manual-reset input for systems that never fully power down the microprocessor. Additionally, these devices feature a watchdog timer to help ensure that the processor is operating within proper code boundaries. The AS1916 - AS1918 are available in a 5-pin SOT23 package.
3 Applications
The devices are ideal for portable and battery-powered systems, embedded controllers, intelligent instruments, automotive systems, and critical CPU monitoring applications.
Figure 1. Typical Application Diagram
I/O Supply
VCC
5
1 RESETN RESETN
VCC
AS1916/ AS1918
3 External Reset MRN 4 WDI GND 2 I/O
CPU
GND
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AS1916 - AS1918
Data Sheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
RESETN/RESET 1
5 VCC
GND 2
AS1916 AS1918
MRN 3
4 WDI
Pin Descriptions
Table 2. Pin Descriptions Pin Number Pin Name Description
1
Active-Low Reset Output (AS1916, AS1918). The RESETN signal toggles from high to low when VCC, or MRN is pulled low, or the watchdog triggers a reset. This output signal remains RESETN low for the reset timeout period after all supervised voltages exceed their reset threshold, or MRN goes low to high, or the watchdog triggers a reset. Active-High Reset Output (AS1917). The RESET signal toggles from low to high when VCC, or MRN is pulled low, or the watchdog triggers a reset. This output signal remains high for the reset timeout period (see tRP on page 4) after all supervised voltages exceed their reset threshold, or MRN goes low to high, or the watchdog triggers a reset. Ground Active-Low Manual Reset Input. Pulling this pin low asserts a reset. This pin is connected to the internal 50k pullup to VCC. This reset remains active as long as MRN is low and for the reset timeout period (see tRP on page 4) after MRN goes high. Note: If the manual reset feature is not used, this pin should be unconnected or connected to VCC. Watchdog Input. If WDI remains high or low for longer than the watchdog timeout period (see tWD on page 5), the internal watchdog timer period expires and a reset is triggered for the reset timeout period (see tRP on page 4). The internal watchdog timer clears whenever a reset is a asserted or when WDI senses a rising or falling edge. Note: To disable the watchdog feature, this pin must be unconnected or connected to a tristate buffer output. Supervised Voltage Input. This pin serves as the supervised supply voltage input.
RESET
2
GND
3
MRN
4
WDI
5
VCC
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AS1916 - AS1918
Data Sheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in Table 3 may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in Electrical Characteristics on page 4 is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 3. Absolute Maximum Ratings Parameter VCC to GND Open-Drain RESETN Push/Pull RESET, RESETN MRN, WDI to GND Input Current (VCC) Output Current (RESET, RESETN) Continuous Power Dissipation (TAMB = +70C) Operating Temperature Range Junction Temperature Storage Temperature Range -65 -40 Min -0.3 -0.3 -0.3 -0.3 Max +5.0 +7.0 VCC + 0.3 VCC + 0.3 20 20 696 +125 +150 +150 Units V V V V mA mA mW C C C The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/JEDEC J-STD-020C "Moisture/Reflow Sensitivity Classification for Non-Hermetic Solid State Surface Mount Devices". The lead finish for Pb-free leaded packages is matte tin (100% Sn). Derate 8.7mW/C above +70C Comments
Package Body Temperature
+260
C
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Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
VCC = +2.7 to +3.6V for AS19xx-T/S/R, VCC = +2.1 to +2.75V for AS19xx- Z/Y, VCC = +1.53 to +2.0V for AS19xx-W/V; TAMB = -40 to +125C (unless otherwise specified). Typ values @ TAMB = +25C. Table 4. Electrical Characteristics Symbol VCC Parameter
1
Conditions TAMB = 0 to +85C TAMB = -40 to +125C VCC = +3.6V, No Load, TAMB = -40C to +85C VCC = +3.6V, No Load, TAMB = -40 to +125C TAMB = -40 to +85C TAMB = -40 to +125C TAMB = -40 to +85C TAMB = -40 to +125C TAMB = -40 to +85C TAMB = -40 to +125C AS19xx-T AS19xx-S AS19xx-R AS19xx-Z AS19xx-Y AS19xx-W AS19xx-V
Min 1.0 1.2
Typ
Max 3.6 3.6
Units V
Operating Voltage Range
ICC
VCC Supply Current (MRN and WDI Not Connected)
5.5
12 A 19
2.994 2.972 2.848 2.827 2.556 2.538 2.255 2.239 2.129 2.113 1.623 1.612 1.536 1.525
3.08 2.93 2.63 2.32 2.19 1.67 1.58
3.154 3.179 3.000 3.024 2.693 2.714 2.376 2.394 2.243 2.260 1.710 1.723 1.618 1.631 ppm/ C mV s 280 320 0.3 0.3 V 0.3 0.4 ms V
VTH
VCC Reset Threshold (VCC Falling)
TAMB = -40 to +85C TAMB = -40 to +125C TAMB = -40 to +85C TAMB = -40 to +125C TAMB = -40 to +85C TAMB = -40 to +125C TAMB = -40 to +85C TAMB = -40 to +125C
Reset Threshold Temperature Coefficient Reset Threshold Hysteresis tRD tRP VCC to Reset Output Delay Reset Timeout Period VCC = VTH to (VTH - 100mV) TAMB = -40 to +85C TAMB = -40 to +125C VCC 1.0V, ISINK = 50A, Reset Asserted, TAMB = 0 to +85C VOL RESETN Output Low (Push/Pull or Open-Drain) VCC 1.2V, ISINK = 100A, Reset Asserted VCC 2.55V, ISINK = 1.2mA, Reset Asserted VCC 3.3V, ISINK = 3.2mA, Reset Asserted VCC 1.8V, ISOURCE = 200A, Reset Not Asserted VOH RESETN Output High (Push/Pull Only) VCC 3.15V, ISOURCE = 500A, Reset Not Asserted VCC 3.3V, ISOURCE = 800A, Reset Not Asserted ILKG Open-Drain RESETN Output Leakage Current RESETN Not Asserted TAMB = +25C 0.8 x VCC 0.8 x VCC 0.8 x VCC 140 100
60 8x VTH 55 215
V
1.0 0.2
A
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Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s
Table 4. Electrical Characteristics (Continued) Symbol Parameter
1
Conditions VCC 1.0V, ISOURCE = 1A, Reset Asserted, TAMB = 0 to +85C
Min 0.8 x VCC 0.8 x VCC 0.8 x VCC 0.8 x VCC
Typ
Max
Units
VOH
RESET Output High (Push/Pull Only)
VCC 1.50V, ISOURCE = 100A, Reset Asserted VCC 2.55V, ISOURCE = 500A, Reset Asserted VCC 3.3V, ISOURCE = 800A, Reset Asserted VCC 1.8V, ISINK = 500A, Reset Asserted
V
0.3 0.3 0.4 V
VOL
RESET Output Low (Push/Pull Only)
VCC 3.15V, ISINK = 1.2mA, Reset Asserted VCC 3.3V, ISINK = 3.2mA, Reset Asserted
Manual Reset Input VIL MRN Input voltage VIH MRN Minimum Input Pulse MRN Transient Rejection MRN to Reset Delay MRN Pullup Resistance Watchdog Input tWD tWDI VIL WDI Input Voltage VIH IWDI WDI Input Current WDI = VCC, Time Average WDI = 0, Time Average -20 0.7 x VCC 80 -11 160 Watchdog Timeout Period WDI Pulse Width
2
0.3 x VCC 0.7 x VCC 1 90 130 25 TAMB = -40 to +85C TAMB = -40 to +125C 1.12 0.80 20 0.3 x VCC 50 1.5 75 2.4 2.60
V s ns ns k
s ns
V
A
1. Over-temperature limits are guaranteed by design and not production tested. Devices tested at +25C. 2. Guaranteed by design and not production tested.
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Data Sheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
7 Typical Operating Characteristics
TAMB = +25C (unless otherwise specified). Figure 3. Normalized Reset Threshold Delay vs. Temperature
1.06 1.04 1.02 1 0.98 0.96 0.94 -40 -20 0 20 40 60 80 100 120
Figure 4. VOUT vs. VCC, VTH = 1.58V, Active-Low (Typ)
5.50 5.00 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -0.50 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Reset Threshold (V) e
Output Voltage (V)e
Temperature (C)
Figure 5. Reset Timeout Period vs. Temperature
250
VCC (V)
Figure 6. Supply Current vs. Temperature
10
Reset Timeout Periode (ms)
240 230 220 210 200 190 180 170 160 150 -40 -20 0 20 40 60 80 100 120
VCC Supply Current (A) e
9 8 7 6 5 4 3 -50 -25 0 25 50 75 100 125
VCC = 1.58V V Version VCC = 3.08V T Version
Temperature (C)
Figure 7. VOH vs. ISOURCE; VCC = 3.2V
3.25 3.2 3.15
Temperature (C)
Figure 8. VOL vs. ISINK; VCC = 3.2V
0.5 0.45 0.4 0.35
VOUT (V) ]
VOUT (V) e
0 0.2 0.4 0.6 0.8 1 1.2
3.1 3.05 3 2.95 2.9
0.3 0.25 0.2 0.15 0.1 0.05 0 0 1 2 3 4 5 6 7
ISOURCE (mA)
ISINK (mA)
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Data Sheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS1916 - AS1918 supervisory circuits were designed to generate a reset when the monitored supply voltage falls below its factory-trimmed trip threshold (see VTH on page 4), and to maintain the reset for a minimum timeout period (see tRP on page 4) after the supply has stabilized. The integrated watchdog timer (see Watchdog Input on page 8) helps mitigate against bad programming code or clock signals, and/or poor peripheral response. The active-low manual reset input (see Manual Reset Input on page 8) allows for an externally activated system reset.
RESET/RESETN
Whenever the monitored supply voltage falls below its reset threshold, the RESET output asserts low or the RESETN output asserts high. Once the monitored voltage has stabilized, an internal timer keeps the reset asserted for the reset timeout period (tRP). After the tRP period, the RESET/RESETN output returns to its original state (see Figure 10).
Figure 9. Functional Diagram of VCC Supervisory Application
5 VCC
AS1916 - AS1918
Reset Timeout Delay Generator
1 RESETN/ RESET
+ -
1.26V
VCC
3 MRN
4 WDI
Watchdog Transition Detector
Watchdog Timer
2 GND
Figure 10. Reset Timing Diagram
VCC 1V VTH VTH 1V
RESETN
tRP
tRD
RESET GND
tRP
tRD
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Data Sheet - D e t a i l e d D e s c r i p t i o n
Watchdog Input
The integrated watchdog feature can be used to monitor processor activity via pin WDI, and can detect pulses as short as 50ns. The watchdog requires that the processor toggle the watchdog logic input at regular intervals, within a specified minimum timeout period (1.5s, typ). A reset is asserted for the reset timeout period. As long as reset is asserted, the timer remains cleared and is not incremented. When reset is deasserted, the watchdog timer starts counting (Figure 11).
Note: The watchdog timer can be cleared with a reset pulse or by toggling WDI. Figure 11. Watchdog Timing Relationship
VCC tRST
RESETN
tRP
tWD
tRP
WDI
The RESET signal is the inverse of the RESETN signal.
The watchdog is internally driven low during most (87.5%) of the watchdog timeout period (see tWD on page 5) and high for the rest of the watchdog timeout period. When pin WDI is left unconnected, this internal driver clears the watchdog timer every 1.4s. When WDI is tri-stated or is not connected, the maximum allowable leakage current is 10A and the maximum allowable load capacitance is 200pF.
Note: The watchdog function can be disabled by leaving pin WDI unconnected or connecting it to a tri-state output buffer.
Manual Reset Input
The active-low pin MRN is used to force a manual reset. This input can be driven by CMOS logic levels or with opendrain collector outputs. Pulling MRN low asserts a reset which will remain asserted as long as MRN is kept low, and for the timeout period (see tRP on page 4) after MRN goes high (140ms min). The manual reset circuitry has an internal 50k pullup resistor, thus it can be left open if not used. To create a manual-reset circuit, connect a normally open momentary switch from pin MRN to GND (see Figure 1 on page 1); external debounce circuitry is not required in this configuration. If MRN is driven via long cables or the device is used in a noisy environment, a 0.1F capacitor between pin MRN and GND will provide additional noise immunity.
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
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 8). When pin WDI is left unconnected (watchdog disabled), the watchdog timer is serviced within the watchdog timeout period (see tWD on page 5) 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 160A can flow into pin WDI.
Interfacing to Bi-Directional CPU Reset Pins
Since the reset output of the AS1918 is open drain, this device interfaces easily with processors that have bi-directional reset pins. Connecting the processor reset output directly to the AS1918 RESETN pin with a single pullup resistor (see Figure 12) allows the AS1918 to assert a reset.
Figure 12. AS1918 RESETN-to-CPU Bi-Directional Reset Pin
VCC VCC 5 VCC
AS1918
CPU RESETN 1 RESETN Reset Generator
GND GND 2
Fast Negative-Going Transients
Fast, negative-going VCC transients normally do not require the CPU to be shutdown. The AS1916 - AS1918 are virtually 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 55s typically will not assert a reset pulse.
Valid Reset to VCC = 0
The AS1916 - AS1918 are guaranteed to operate properly down to VCC = 1V. For AS1916 and AS1917 applications requiring valid reset levels down to VCC = 0, a pulldown resistor to active-low outputs and a pullup resistor to active-high outputs 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 AS1916 - AS1918 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.
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Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
Figure 13 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 watchdog timer is allowed to time out, causing a reset or interrupt to be issued (see Watchdog Input Current on page 9). 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.
Figure 13. Example Watchdog Programming Flowchart
Start
Set WDI High Program Code
Subroutine or Program Loop Set WDI Low
Return
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Data Sheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
10 Package Drawings and Markings
The devices are available in an 5-pin SOT23 package.
Figure 14. 5-pin SOT23 Package
Notes:
1. All dimensions in millimeters. 2. Foot length measured at intercept point between datum A and lead surface. 3. Package outline exclusive of mold flash and metal burr. 4. Package outline inclusive of solder plating. 5. Complies with EIAJ SC74. 6. PKG ST 0003 Rev A supersedes SOT23-D-2005 Rev C.
Symbol A A1 A2 b C D E E1 L e e1
Min Max 0.90 1.45 0.00 0.15 0.90 1.30 0.30 0.50 0.09 0.20 2.80 3.05 2.60 3.00 1.50 1.75 0.30 0.55 0.95 REF 1.90 REF 0 8
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Data Sheet - O r d e r i n g I n f o r m a t i o n
11 Ordering Information
The devices are available as the standard products shown in Table 5.
Table 5. Ordering Information Model Marking Description Threshold Delivery Form Package
AS1916S-T AS1916R-T AS1916Z-T AS1916V-T AS1917S-T AS1917R-T AS1917Z-T AS1917V-T AS1918S-T AS1918R-T AS1918Z-T AS1918V-T
ASIO ASIP ASIQ ASIR ASIS ASIT ASIU ASIV ASIW ASIX ASIY ASIZ
Active-Low Push/Pull Supervisory Circuit with Watchdog and Manual Reset Active-Low Push/Pull Supervisory Circuit with Watchdog and Manual Reset Active-Low Push/Pull Supervisory Circuit with Watchdog and Manual Reset Active-Low Push/Pull Supervisory Circuit with Watchdog and Manual Reset Active High Push/Pull Supervisory Circuit with Watchdog and Manual Reset Active High Push/Pull Supervisory Circuit with Watchdog and Manual Reset Active High Push/Pull Supervisory Circuit with Watchdog and Manual Reset Active High Push/Pull Supervisory Circuit with Watchdog and Manual Reset Active-Low Open Drain Supervisory Circuit with Watchdog and Manual Reset Active-Low Open Drain Supervisory Circuit with Watchdog and Manual Reset Active-Low Open Drain Supervisory Circuit with Watchdog and Manual Reset Active-Low Open Drain Supervisory Circuit with Watchdog and Manual Reset
2.93V 2.63V 2.32V 1.58V 2.93V 2.63V 2.32V 1.58V 2.93V 2.63V 2.32V 1.58V
Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel
5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23 5-pin SOT23
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Data Sheet
Copyrights
Copyright (c) 1997-2007, austriamicrosystems AG, Schloss Premstaetten, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered (R). All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. All products and companies mentioned are trademarks or registered trademarks of their respective companies.
Disclaimer
Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. austriamicrosystems AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. austriamicrosystems AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with austriamicrosystems AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or lifesustaining equipment are specifically not recommended without additional processing by austriamicrosystems AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location. The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However, austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of austriamicrosystems AG rendering of technical or other services.
Contact Information
Headquarters austriamicrosystems AG A-8141 Schloss Premstaetten, Austria
Tel: +43 (0) 3136 500 0 Fax: +43 (0) 3136 525 01
For Sales Offices, Distributors and Representatives, please visit: http://www.austriamicrosystems.com/contact
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