Analogic AAT3532 Micropowerâ ¢ microprocessor reset circuit Datasheet

AAT3532
MicroPower™ Microprocessor Reset Circuit
General Description
Features
The AAT3532 PowerManager is a member of
AnalogicTech’s Total Power Management IC™
(TPMIC™) 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 23µA.
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PowerManager™
Adjustable 4.5V or 4.75V Voltage Monitor
250ms (min) Reset Pulse Width
Low Quiescent Current: Typically 23µA
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 +85°C
Standard 8-Pin SOP Package
Pin Compatible with MAX1232
Applications
The AAT3532 is available in a Pb-free, 8-pin SOP
package and is specified over the -40°C to +85°C
temperature range.
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Automotive
Computers
Controllers
Embedded Systems
Intelligent Instrumentation
Telecom Equipment
Typical Application
VDD
VDD
VCC
RST
PBRST
AAT3532
RESET
INPUT
µP
RST
TD
ST
I/O
TOL
GND
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AAT3532
MicroPower™ Microprocessor Reset Circuit
Pin Descriptions
Pin #
Symbol
1
PBRST
2
3
4
5
TD
TOL
GND
RST
6
7
RST
ST
8
VCC
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.
Pin Programming Selections
Timeout
TD Pin
Min
Typ
Max
GND
Float
VCC
62.5ms
250ms
500ms
150ms
600ms
1200ms
250ms
1000ms
2000ms
Table 1: TD Pin Programming for Watchdog Timeout Selections.
TOL Pin
Tolerance
VCC
GND
10%
5%
Table 2: Reset Voltage Threshold Programming Selections.
Pin Configuration
SOP-8
(Top View)
VCC
7
ST
3
6
RST
4
5
RST
TD
2
TOL
GND
2
1
1
2
8
PBRST
3532.2005.12.1.2
AAT3532
MicroPower™ Microprocessor Reset Circuit
Absolute Maximum Ratings1
TA = 25°C, 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
Units
-0.5 to 6
-0.5 to (VCC+0.5)
-40 to 85
-65 to 150
300
2000
V
V
°C
°C
°C
V
Value
Units
100
1.25
°C/W
W
Thermal Characteristics3
Symbol
ΘJA
PD
Description
Maximum Thermal Resistance
Maximum Power Dissipation
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 1.5kΩ resistor into each pin.
3. Mounted on an FR4 board.
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AAT3532
MicroPower™ Microprocessor Reset Circuit
DC Electrical Characteristics
VIN = 4.5V to 5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol
Description
VCC
Supply Voltage
IQ
VCCTP
IIL
IOH
IOL
VIH
VIL
IRST
Conditions
Quiescent Current1
VCC = 5.5V
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
TOL = GND
TOL = VCC
Min
Typ
Max
Units
4.5
5.0
23
160
4.62
4.37
5.5
50
500
4.74
4.49
1.0
V
CMOS Levels
TTL Levels
4.50
4.25
-1.0
-8.0
10.0
2.0
-0.3
VOH = 2.4V
VOL = 0.4V
VCC + 0.3
0.8
1.0
VOH = VCC
µA
V
µA
mA
mA
V
V
µA
AC Electrical Characteristics
VIN = 4.5V to 5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol
CIN
COUT
tPB
tPBD
tRST
tST
tTD
tf
tr
tRPD
tRPU
1.
2.
3.
4.
4
Description
Conditions
3
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
TA = 25ºC
TA = 25ºC
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
20
1
250
20
62.5
250
500
10
0
250
Typ
Max
Units
5
7
pF
pF
ms
ms
ms
ns
4
610
20
1000
150
600
1200
250
1000
2000
5
610
50
1000
ms
µs
µs
µs
ms
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.
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AAT3532
MicroPower™ Microprocessor Reset Circuit
Functional Block Diagram
VCC
VCC
Tolerance
Select
TOL
Reset
Generator
RST
RST
VREF
De-Bounce
Circuit
PBRST
Watchdog
Timer
Detector
ST
Watchdog
Timer
TD
GND
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.)
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.
RST output is an open drain output. For correct
operation, a pull-up resistor of 10kΩ should be connected between this output and VCC.
The RST and RST pins are asserted whenever VCC
drops below the reset threshold voltage. This volt-
+5V
+4.75V (5% Trip Point)
VCC
+4.50V (10% Trip Point)
0V
RESET Output Delay (VCC Falling)
RESET Output Delay (VCC Rising)
tRPU
tRPD
RST
RST
Figure 1: Reset Output Delay.
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AAT3532
MicroPower™ 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.
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AAT3532
MicroPower™ Microprocessor Reset Circuit
Ordering Information
Package
Marking
Part Number (Tape and Reel)1
SOP-8
3532
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
6.00 ± 0.20
3.90 ± 0.10
SOP-8
4.90 ± 0.10
0.42 ± 0.09 × 8
1.27 BSC
45°
4° ± 4°
0.175 ± 0.075
1.55 ± 0.20
0.375 ± 0.125
0.235 ± 0.045
0.825 ± 0.445
All dimensions in millimeters.
1. Sample stock is generally held on all part numbers listed in BOLD.
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AAT3532
MicroPower™ Microprocessor Reset Circuit
© 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
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3532.2005.12.1.2
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