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AAT3532
MicroPowerTM Microprocessor Reset Circuit General Description
The AAT3532 PowerManager is a member of AnalogicTech's Total Power Management ICTM (TPMICTM) product family. It is a fully integrated device for monitoring microprocessor activity, external reset, and power supply conditions. The device holds the microprocessor in a reset condition for a minimum of 250ms while VCC is established to ensure correct system start-up. A manual reset can be initiated via a de-bounced input pin. As an additional level of protection, the AAT3532 includes a watchdog timer which requires a periodic strobe input from the microprocessor to ensure correct operation. The AAT3532 has a programmable watchdog timer and voltage tolerance level. The quiescent supply current is extremely low, typically 23A. The AAT3532 is available in a Pb-free, 8-pin SOP package and is specified over the -40C to +85C temperature range.
Features
* * * * * * * * * *
PowerManagerTM
Adjustable 4.5V or 4.75V Voltage Monitor 250ms (min) Reset Pulse Width Low Quiescent Current: Typically 23A Adjustable Watchdog Timer (150ms, 600ms, or 1200ms) De-bounced Manual Reset Input Operates Down to 20ns Strobe Input Pulse Width No External Components Temperature Range: -40 to +85C Standard 8-Pin SOP Package Pin Compatible with MAX1232
Applications
* * * * * * Automotive Computers Controllers Embedded Systems Intelligent Instrumentation Telecom Equipment
Typical Application
VDD
VCC PBRST RST RESET INPUT
VDD
AAT3532
TD
RST
P
I/O
ST TOL GND
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AAT3532
MicroPowerTM Microprocessor Reset Circuit Pin Descriptions
Pin #
1 2 3 4 5
Symbol
PBRST TD TOL GND RST
Function
Push-button reset input. A de-bounced active low input for manual reset. Guaranteed to recognize inputs 20ms or greater. Watchdog time delay set input. See Table 1 for watchdog timeout selections. Tolerance set. Input selects 5% or 10% threshold detection. IC ground connection. Reset output (active high). Activated when either: VCC falls below the reset voltage threshold; PBRST is forced low; ST is not strobed within the minimum timeout period; or during power-up. Reset output (active low, open drain). Inverse of RST. Strobe input to watchdog timer. A pulse is required within the watchdog timeout period to prevent RST and RST entering active state. 5V supply.
6 7 8
RST ST VCC
Pin Programming Selections
Timeout TD Pin
GND Float VCC
Min Typ Max
62.5ms 250ms 500ms
150ms 600ms 1200ms
250ms 1000ms 2000ms
Table 1: TD Pin Programming for Watchdog Timeout Selections.
TOL Pin
VCC GND
Tolerance
10% 5%
Table 2: Reset Voltage Threshold Programming Selections.
Pin Configuration
SOP-8 (Top View)
PBRST TD TOL GND
1 8
VCC ST RST RST
1
2 2
7
3
6
4
5
2
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AAT3532
MicroPowerTM Microprocessor Reset Circuit Absolute Maximum Ratings1
TA = 25C, unless otherwise noted. Symbol
VCC VI/O TA TS TLEAD VESD
Description
VCC to GND Voltage on I/O Pins Relative to GND Operating Temperature Range Storage Temperature Range Maximum Soldering Temperature (at leads) for 10s ESD Rating2--HBM
Value
-0.5 to 6 -0.5 to (VCC+0.5) -40 to 85 -65 to 150 300 2000
Units
V V C C C V
Thermal Characteristics3
Symbol
JA PD
Description
Maximum Thermal Resistance Maximum Power Dissipation
Value
100 1.25
Units
C/W W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. Human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin. 3. Mounted on an FR4 board. 3532.2005.12.1.2
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AAT3532
MicroPowerTM Microprocessor Reset Circuit DC Electrical Characteristics
VIN = 4.5V to 5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C. Symbol
VCC IQ VCCTP IIL IOH IOL VIH VIL IRST
Description
Supply Voltage Quiescent Current1 Reset Threshold 5% Reset Threshold 10% Input Leakage ST, TOL Output Current RST2 Current RST2, RST ST and PBRST Input High ST and PBRST Input Low RST Output Leakage
Conditions
CMOS Levels TTL Levels
Min
4.5
Typ
5.0 23 160 4.62 4.37
Max
5.5 50 500 4.74 4.49 1.0
Units
V A V A mA mA V V A
VCC = 5.5V TOL = GND TOL = VCC VOH = 2.4V VOL = 0.4V
4.50 4.25 -1.0 -8.0 10.0 2.0 -0.3
VOH = VCC
VCC + 0.3 0.8 1.0
AC Electrical Characteristics
VIN = 4.5V to 5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C. Symbol
CIN COUT tPB tPBD tRST tST tTD tf tr tRPD tRPU
Description
Input Capacitance ST, TOL Output Capacitance RST, RST3 PBRST4 PBRST Delay Reset Active Time ST Pulse Width ST Time-out Period VCC VCC VCC VCC Fall Time3 Rise Time3 Detect to RST High and RST Low Detect to RST Low and RST Open
3
Conditions
TA = 25C TA = 25C See Figure 2 See Figure 2 See Figure 3 TD Pin = 0V TD Pin = Open TD Pin = VCC 4.75V to 4.25V 4.25V to 4.75V VCC Falling VCC Rising
Min
Typ
Max
5 7
Units
pF pF ms ms ms ns ms s s s ms
20 1 250 20 62.5 250 500 10 0 250
4 610 150 600 1200 5 610
20 1000 250 1000 2000
50 1000
1. 2. 3. 4.
Measured with outputs open and ST toggling at 100kHz, 50% duty cycle. RST is an open drain output. Guaranteed by design and not subject to production testing. PBRST must remain low for greater than 20ms to guarantee a reset. 3532.2005.12.1.2
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AAT3532
MicroPowerTM Microprocessor Reset Circuit Functional Block Diagram
VCC VCC Tolerance Select
TOL
Reset Generator
RST RST
VREF
PBRST ST TD
De-Bounce Circuit Watchdog Timer Detector Watchdog Timer
GND
Applications Information
Power Monitor
The reset function monitors the VCC supply to ensure a microprocessor is correctly reset and is powered up into a known condition following a power supply failure. RST and RST will remain valid for VCC voltages down to 1.4V. The RST and RST pins are asserted whenever VCC drops below the reset threshold voltage. This volt-
age can be set by programming the TOL pin. Connecting TOL to VCC sets the 10% tolerance of the VCC supply (typically 4.37V for VCC = 5V). Connecting TOL to GND sets the 5% tolerance of the VCC supply (typically 4.62V for VCC = 5V). The reset pin is guaranteed to remain asserted for a minimum period of 250ms after VCC has risen above the reset threshold voltage. (See Figure 1.) RST output is an open drain output. For correct operation, a pull-up resistor of 10k should be connected between this output and VCC.
+5V
+4.75V (5% Trip Point) VCC +4.50V (10% Trip Point)
0V RESET Output Delay (VCC Rising) tRPU RST tRPD RESET Output Delay (VCC Falling)
RST
Figure 1: Reset Output Delay.
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AAT3532
MicroPowerTM Microprocessor Reset Circuit
Manual Reset
The PBRST pin makes it possible to manually reset the system by either directly connecting a mechanical push-button between the PBRST pin and GND or connecting to a logic low output. Internal de-bounce circuitry is provided to reduce the effect of noise glitches at the input. The signal should remain low for a minimum of 20ms for correct operation. Once the PBRST signal is released (or goes to a logic high), RESET (RESET) remains asserted for a minimum of 250ms.
t PB
t PBD PBRST
t RST
RESET
RESET
Figure 2: Push-Button Reset.
Watchdog Timer
The watchdog timer monitors the microprocessor to ensure that the system is functioning correctly. The ST pin of the AAT3532 can be derived from the microprocessor data signals, address signals, and/or I/O signals. The watchdog timer function forces the RST and RST signals into the active state when the ST input is not toggled by a predetermined time. This time period is set by the logic state of the TD pin, as shown in Table 1. The timer
starts once the RST signals become inactive. If the watchdog timer does not receive a high-to-low transition within the specified timeout period, then the RST signals are activated for a minimum 250ms. In normal operation, the timer should receive a transition from the microprocessor within the timeout period, in which case the timer is reset and normal operation continues. The AAT3532 will accept and recognize ST pulses down to a minimum of 20ns wide.
t ST
ST
t TD
Figure 3: Watchdog Input.
6
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AAT3532
MicroPowerTM Microprocessor Reset Circuit Ordering Information
Package
SOP-8
Marking
3532
Part Number (Tape and Reel)1
AAT3532IAS-T1
All AnalogicTech products are offered in Pb-free packaging. The term "Pb-free" means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
SOP-8
3.90 0.10 4.90 0.10
6.00 0.20
0.375 0.125 1.55 0.20
45
0.175 0.075
4 4
0.235 0.045 0.825 0.445
0.42 0.09 x 8
1.27 BSC
All dimensions in millimeters.
1. Sample stock is generally held on all part numbers listed in BOLD. 3532.2005.12.1.2
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AAT3532
MicroPowerTM Microprocessor Reset Circuit
(c) Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech's standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 8
3532.2005.12.1.2

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