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19-0136; Rev. 1; 6/94
Power-Supply Monitor with Reset
_______________General Description
The MAX709 provides a system reset during power-up, power-down, and brownout conditions. When VCC falls below the reset threshold, RESET goes low and holds the P in reset for 140ms min after VCC rises above the threshold. The RESET output is guaranteed to be in the correct state with V CC down to 1V. The MAX709 provides excellent circuit reliability and low cost by eliminating external components and adjustments when used with +5V, +3.3V, or +3V powered systems. The MAX709 is available 8-pin DIP, MAX, and SO packages.
___________________________Features
o +5V, +3.3V, and +3V Versions o No External Components o Low Cost o Precise Power-Down Reset Threshold o 140ms Min Power-On Reset Delay o Immune to Short Negative VCC Transients o 8-Pin DIP, MAX, and SO Packages o Low Supply Current: 35A - MAX709R/S/T 65A - MAX709L/M
MAX709
______________Ordering Information
PART MAX709_CPA MAX709_CUA MAX709_CSA MAX709_C/D TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 8 Plastic DIP 8 MAX 8 SO Dice 8 Plastic DIP 8 MAX 8 SO
_______________________Applications
Minimum Component Count, Low-Cost Processor Systems
MAX709_EPA MAX709_EUA MAX709_ESA
* Dice are specified at TA = +25C, DC parameters only. Note: This part offers a choice of five different reset threshold voltages. Select the letter corresponding to the desired nominal reset threshold voltage, and insert it into the blank to complete the part number.
RESET THRESHOLD SUFFIX L M T S R VOLTAGE (V) 4.65 4.40 3.08 2.93 2.63
__________Typical Operating Circuit
__________________Pin Configuration
VCC VCC P RESET VCC GND GND GND N.C.
TOP VIEW
N.C.
MAX709
RESET
1 2 3 4
DIP/SO/MAX
8
MAX709
N.C. RESET N.C. N.C.
7 6 5
________________________________________________________________ Maxim Integrated Products
1
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Power-Supply Monitor with Reset MAX709
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND) VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V RESET. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to (VCC + 0.3V) Input Current, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA Output Current, RESET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA Rate-of-Rise, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100V/s Continuous Power Dissipation (TA = +70C) Plastic DIP (derate 9.09mW/C above +70C) . . . . . . . . 727mW MAX (derate 4.10mW/C above +70C) . . . . . . . . . . . . . 330mW SO (derate 5.88mW/C above +70C). . . . . . . . . . . . . . . . . 471mW Operating Temperature Ranges MAX709_C___ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0C to +70C MAX709_E___ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40C to +85C Storage Temperature Range . . . . . . . . . . . . . . . . . . - 65C to +160C Lead Temperature (soldering, 10sec). . . . . . . . . . . . . . . . . . . . +300C
Stresses beyond those listed under "Absolute Maximum Ratings" 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 the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = full range, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER VCC Range MAX709_C MAX709_E MAX709R/S/T only Supply Current (Note 1) All versions MAX709L MAX709M RESET Threshold, VTH MAX709T MAX709S MAX709R VCC to RESET Delay Reset Active Timeout Period VCC = reset threshold max to reset threshold min VCC = reset threshold max, VCC rising ISINK = 1.2mA, VCC = reset threshold min, MAX709R/S/T only ISINK = 3.2mA, VCC = reset threshold min, MAX709L/M only RESET Output Voltage ISINK = 50A, VCC 1.0V, MAX709_C ISINK = 100A, VCC 1.2V, MAX709_E ISOURCE = 500A, VCC reset threshold max, MAX709R/S/T only ISOURCE = 800A, VCC reset threshold max, MAX709L/M only 0.8 x VCC VCC - 1.5 140 MAX709_C, VCC < 3.6V MAX709_E, VCC < 3.6V MAX709_C, VCC < 5.5V MAX709_E, VCC < 5.5V 4.50 4.25 3.00 2.85 2.55 CONDITIONS MIN 1.0 1.2 35 35 65 65 4.65 4.40 3.08 2.93 2.63 20 280 560 0.3 0.4 0.3 0.4 V TYP MAX 5.5 5.5 85 110 150 200 4.75 4.50 3.15 3.00 2.70 s ms V A UNITS V
Note 1: Supply current is measured with VCC = 3.6V for MAX709R/S/T, and VCC = 5.5V for all versions. 2 _______________________________________________________________________________________
Power-Supply Monitor with Reset
__________________________________________Typical Operating Characteristics
MAX709
POWER-UP RESET DELAY vs. TEMPERATURE
300 250 200 150 100 50 0 -60 -20 20 60 100 TEMPERATURE (C) POWER-DOWN RESET DELAY (s) POWER-UP RESET DELAY (ms) VCC = RESET THRESHOLD MAX, VCC RISING 24 20 16 12 8 4 0 -60
POWER-DOWN RESET DELAY vs. TEMPERATURE
VCC STEPPED FROM RESET THRESHOLD MAX TO RESET THRESHOLD MIN -20 20 60 100
TEMPERATURE (C)
SUPPLY CURRENT vs. TEMPERATURE
100 NORMALIZED RESET THRESHOLD NOTE: STEADY-STATE SUPPLY CURRENT IS INDEPENDENT OF RESET OUTPUT STATUS NO LOAD 60 VCC = +5V VCC = +4V 40 VCC = +3V 20 0 VCC = +2V VCC = +1V -60 -20 20 60 100 TEMPERATURE (C) 1.005
NORMALIZED RESET THRESHOLD vs. TEMPERATURE
THE RESET THRESHOLD IS SHOWN NORMALIZED TO 1, REPRESENTING ALL AVAILABLE MAX709 RESET THRESHOLDS
SUPPLY CURRENT (A)
80
1.003
1.001
0.999
0.997 0.995 -60 -20 20 60 100 TEMPERATURE (C)
_________________________________________________________________________________________________
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Power-Supply Monitor with Reset MAX709
MAXIMUM TRANSIENT DURATION (s)
____________________Pin Description
PIN 1, 4, 5, 6, 8 2 3 NAME N.C. VCC GND FUNCTION No Connect. There is no internal connection to this pin. +5V, +3.3V, or +3V Supply Voltage Ground Reset Output remains low while VCC is below the reset threshold, and for 280ms after VCC rises above the reset threshold.
150
TA = +25C
100
MAX709L/M 50 10ns MAX709R/S/T 0 10 100 1k 10k RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)
7
RESET
__________Applications Information
Negative-Going VCC Transients
In addition to issuing a reset to the microprocessor (P) during power-up, power-down, and brownout conditions, the MAX709 is relatively immune to short duration negative-going VCC transients (glitches). Figure 1 shows typical transient duration vs. reset comparator overdrive, for which the MAX709 does not generate a reset pulse. The graph was generated using a negative-going pulse applied to V CC, starting 1.5V above the actual reset threshold and ending below it by the magnitude indicated (reset comparator overdrive). The graph indicates the typical maximum pulse width that a negative-going VCC transient may have without causing a reset pulse to be issued. As the magnitude of the transient increases (goes farther below the reset threshold), the maximum allowable pulse width decreases. Typically, for the MAX709L/MAX709M, a VCC transient that goes 100mV below the reset threshold and lasts 40s or less will not cause a reset pulse to be issued.
Figure 1. Maximum Transient Duration without Causing a Reset Pulse vs. Reset Comparator Overdrive
A 0.1F bypass capacitor mounted as close as possible to pin 2 (VCC) provides additional transient immunity.
Ensuring a Valid RESET Output Down to VCC = 0V
When VCC falls below 1V, the MAX709 RESET output no longer sinks current--it becomes an open circuit. Therefore, high-impedance CMOS logic inputs connected to the RESET output can drift to undermined voltages. This presents no problem in most applications, since most P and other circuitry is inoperative with VCC below 1V. However, in applications where the RESET output must be valid down to 0V, adding a pulldown resistor to the RESET pin will cause any stray leakage currents to flow to ground, holding RESET low (see Figure 2). The resistance value of R1 is not critical. It should be about 100k, which is large enough not to load RESET and small enough to pull RESET to ground.
4
_______________________________________________________________________________________
Power-Supply Monitor with Reset MAX709
BUFFER VCC VCC VCC P RESET BUFFERED RESET TO OTHER SYSTEM COMPONENTS
MAX709
RESET R1 GND GND GND
MAX709
RESET
4.7k
Figure 2. RESET Valid to VCC = Ground Circuit
Figure 3. Interfacing to Ps with Bidirectional Reset I/O
Interfacing to Ps with Bidirectional Reset Pins
Microprocessors with bidirectional reset pins (such as the Motorola 68HC11 series) can contend with the MAX709 reset output. If, for example the MAX709 RESET output is asserted high and the P wants to pull it low, indeterminate logic levels may result. To correct this, connect a 4.7k resistor between the MAX709 RESET output and the P reset I/O (see Figure 3). Buffer the MAX709 RESET output to other system components.
_______________________________________________________________________________________
5
Power-Supply Monitor with Reset MAX709
_____________________________________________________P Supervisory Circuits
Minimum Nominal Reset Reset Pulse Threshold Width (V) (ms)
4.65/4.40 4.65/4.40 Adj. Adj. 4.65/adj. 4.65/4.40 4.65/4.40 2.63 2.63/2.93/ 3.08 4.65/4.40 2.63/2.93/ 3.08 140 140/adj. 35/adj. 35/adj. 200 140 140 140 140 140 140
Part Number
MAX690A/692A MAX691A/693A MAX696 MAX697 MAX700 MAX703/704 MAX705/706 MAX706P MAX706R/S/T MAX707/708 MAX708R/S/T MAX709L/M/ R/S/T MAX791 MAX792L/M/ R/S/T MAX800L/M MAX802L/M MAX805L MAX813L MAX820L/M/ R/S/T MAX1232 MAX1259
Nominal Watchdog Timeout Backup- CE Period Battery Write (sec) Switch Protect
1.6 1.6/adj. 1.6/adj. 1.6/adj. 1.6 1.6 1.6 1 1 1.6/adj. 1.6 1.6 1.6 1 0.15/0.60/1.2 /10ns /10ns /10ns /10ns /10ns
PowerFail Comparator
Manual- Watch- LowReset dog Line Input Output Output
Active- BatteryHigh On Reset Output
4.65/4.40/ 140 2.63/2.93/3.08 4.65 140 4.65/4.40/ 140 2.63/2.93/3.08 4.60/4.40 4.60/4.40 4.65 4.65 140 140 140 140
/2% /2%
4.65/4.40/ 140 2.63/2.93/3.08 4.37/4.62 250 -
/2%
6
_______________________________________________________________________________________
Power-Supply Monitor with Reset
___________________Chip Topography
MAX709
V CC RESET 0.045" (1.143mm)
GND 0.056" (1.422mm)
TRANSISTOR COUNT: 380 SUBSTRATE CONNECTED TO VCC
________________________________________________________Package Information
DIM
C A 0.101mm 0.004 in B A1 L
e
A A1 B C D E e H L
INCHES MAX MIN 0.044 0.036 0.008 0.004 0.014 0.010 0.007 0.005 0.120 0.116 0.120 0.116 0.0256 0.198 0.188 0.026 0.016 6 0
MILLIMETERS MIN MAX 0.91 1.11 0.10 0.20 0.25 0.36 0.13 0.18 2.95 3.05 2.95 3.05 0.65 4.78 5.03 0.41 0.66 0 6
21-0036D
E
H
8-PIN MAX MICROMAX SMALL-OUTLINE PACKAGE
D
_______________________________________________________________________________________
7
Power-Supply Monitor with Reset MAX709
__________________________________________Package Information (continued)
DIM INCHES MAX MIN 0.069 0.053 0.010 0.004 0.019 0.014 0.010 0.007 0.157 0.150 0.050 0.244 0.228 0.050 0.016 MILLIMETERS MIN MAX 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 3.80 4.00 1.27 5.80 6.20 0.40 1.27
D A e B
0.101mm 0.004in.
0-8
A1
C
L
A A1 B C E e H L
E
H
Narrow SO SMALL-OUTLINE PACKAGE (0.150 in.)
DIM PINS D D D 8 14 16
INCHES MILLIMETERS MIN MAX MIN MAX 0.189 0.197 4.80 5.00 0.337 0.344 8.55 8.75 0.386 0.394 9.80 10.00
21-0041A
DIM
E A2 A D A3 E1
A A1 A2 A3 B B1 C D1 E E1 e eA eB L
0-15 A1 L B D1 e B1 eA eB C
Plastic DIP PLASTIC DUAL-IN-LINE PACKAGE (0.600 in.)
INCHES MAX MIN 0.200 - - 0.015 0.175 0.125 0.080 0.055 0.020 0.016 0.065 0.045 0.012 0.008 0.090 0.050 0.625 0.600 0.575 0.525 - 0.100 - 0.600 0.700 - 0.150 0.120
MILLIMETERS MIN MAX - 5.08 0.38 - 3.18 4.45 1.40 2.03 0.41 0.51 1.14 1.65 0.20 0.30 1.27 2.29 15.24 15.88 13.34 14.61 2.54 - 15.24 - - 17.78 3.05 3.81
PKG. DIM PINS P P P D D D 24 28 40
INCHES MILLIMETERS MIN MAX MIN MAX 1.230 1.270 31.24 32.26 1.430 1.470 36.32 37.34 2.025 2.075 51.44 52.71
21-0044A
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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