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FEATURES Precision Supply Voltage Monitor +5 V, +3.3 V, +3 V Power Supply Monitor 35 A Quiescent Current 140 ms (min) Power-On Reset Pulse Low Cost 8-Pin DIP/SO Packages Upgrade for MAX709 APPLICATIONS Microprocessor Systems Computers Controllers Intelligent Instruments Critical P Monitoring Automotive Systems Critical P Power Monitoring GENERAL DESCRIPTION
VCC VTH
Power Supply Monitor with Reset ADM709
FUNCTIONAL BLOCK DIAGRAM
ADM709
RESET GENERATOR RESET
GND
VCC
VCC
ADM709
RESET GND RESET
P
GND
The ADM709 contains a power supply monitor which generates 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. On power-up the RESET output is held low for 140 ms after VCC rises above the threshold. The RESET output remains operational with VCC as low as 1 V. Three supply-voltage threshold levels are available suitable for +5 V, +3.3 V and for +3 V supply monitoring. The actual reset voltage threshold is given below. The ADM709 is available in 8-pin DIP and SOIC packages.
Table I. Reset Threshold
Typical Operating Circuit
ORDERING GUIDE
Model ADM709LAN ADM709LAR ADM709MAN ADM709MAR ADM709TAN ADM709TAR ADM709SAN ADM709SAR ADM709RAN ADM709RAR
Reset Threshold 4.65 V 4.65 V 4.40 V 4.40 V 3.08 V 3.08 V 2.93 V 2.93 V 2.63 V 2.63 V
Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C
Package Option* N-8 SO-8 N-8 SO-8 N-8 SO-8 N-8 SO-8 N-8 SO-8
Suffix L M T S R
Voltage (V) 4.65 4.40 3.08 2.93 2.63
*N = Plastic DIP; SO = SOIC.
REV. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. (c) Analog Devices, Inc., 1995 One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703
ADM709-SPECIFICATIONS (V
Parameter VCC Operating Voltage Range Supply Current Min 1.0 1.2 35 35 65 65 4.5 4.25 3.00 2.85 2.55 4.65 4.40 3.08 2.93 2.63 20 140 280 Typ
CC
= Full Operating Range, TA = TMIN to TMAX unless otherwise noted)
Max 5.5 5.5 85 110 150 200 4.75 4.50 3.15 3.00 2.70 Units V V A A A A V V V V V s 380 0.3 0.4 0.3 0.4 ms V V V V V V Test Conditions/Comments TA = 0C to +70C TA = -40C to +85C VCC < 3.6 V, TA = 0C to +70C VCC < 3.6 V, TA = -40C to +85C VCC < 5.5 V, TA = 0C to +70C VCC < 5.5 V, TA = -40C to +85C ADM709L ADM709M ADM709T ADM709S ADM709R VCC = Reset Threshold max-min VCC = Reset Threshold max, VCC Rising ADM709R/S/T, ISINK = 1.2 mA. VCC = Reset Threshold min ADM709L/M, ISINK = 3.2 mA. VCC = Reset Threshold min ISINK = 50 A. VCC 1.0 V ISINK = 100 A. VCC 1.2 V ADM709R/S/T, ISOURCE = 500 A, VCC Reset Threshold max ADM709L/M, ISOURCE = 800 A, VCC Reset Threshold max
Reset Threshold
VCC to RESET Delay RESET Active Time-Out Period RESET Output Voltage
0.8 x VCC VCC-1.5 V
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS*
(TA = +25C unless otherwise noted)
PIN FUNCTION DESCRIPTION
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 V to +6 V RESET Output . . . . . . . . . . . . . . . . . . . -0.3 V to VCC + 0.3 V VCC Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 mA RESET Output Current . . . . . . . . . . . . . . . . . . . . . . . . 20 mA Power Dissipation, N-8 DIP . . . . . . . . . . . . . . . . . . . . 727 mW JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 135C/W Power Dissipation, SO-8 SOIC . . . . . . . . . . . . . . . . . . 470 mW JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 110C/W Operating Temperature Range Industrial ( A Version) . . . . . . . . . . . . . . . . . -40C to +85C Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . . +300C Vapor Phase (60 secs) . . . . . . . . . . . . . . . . . . . . . . . . . +215C Infrared (15 secs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +220C Storage Temperature Range . . . . . . . . . . . . . -65C to +150C ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . >5 kV
*
Mnemonic Pin No. NC VCC RESET 1, 4, 5, 6, 8 2 7
Function No Connect Pins. +5 V, +3.3 V, +3 V Power Supply Input. Logic Output. It remains low while VCC is below the reset threshold voltage and for 280 ms (typ) after VCC rises above the threshold. Ground, 0 V.
GND
3
PIN CONFIGURATION
Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum ratings for extended periods of time may affect device reliability.
NC 1 VCC 2 GND 3 NC 4
8
NC RESET NC NC
ADM709
TOP VIEW (Not to Scale)
7 6 5
NC = NO CONNECT
-2-
REV. 0
ADM709
ADM709
VCC VTH RESET GENERATOR RESET
RESET at Voltages < 1 V
GND
The ADM709 RESET output is guaranteed to operate with supply voltages as low as 1 V. If it is desired that the RESET output remains low below 1 V, then a pull-down resistor should be connected between the RESET output and GND. A resistor of 100 k is suitable. This is illustrated in Figure 5.
Figure 1. Functional Block Diagram
ADM709
RESET
VCC
VCC
R1 GND
ADM709
RESET GND RESET
P
GND
Figure 5. RESET Valid @ VCC < 1 V
Glitch Immunity
Figure 2. Typical Operating Circuit
CIRCUIT INFORMATION RESET Output
The ADM709 is immune to short transients which may occur on the VCC line. This is important so that spurious resets are not generated as a result of minor glitches on the power supply. Additional glitch immunity may be obtained by connecting a capacitor (0.1 F or greater) as close as possible to the VCC pin on the device.
Microprocessors with Bidirectional I-O
RESET is an active low output which provides a reset signal to the microprocessor whenever the VCC supply voltage is below the reset threshold. An internal timer holds RESET low for 140 ms after the voltage on VCC rises above the threshold. This is intended as a power-on reset signal for the processor. It allows time for the power supply and microprocessor to stabilize after power up. Similarly a power supply brownout will initiate a processor reset. On power-down, the RESET output remains low with VCC as low as 1 V. This ensures that the microprocessor is held in a stable shutdown condition as the power supply drops.
VRT VRT
Some microprocessors or microcontrollers such as the MC68HC11 have bidirectional reset lines. In order to avoid signal contention, a resistor of 4.7 k should be connected between the ADM709 RESET output and the microcontroller RESET line. This arrangement is shown in Figure 6.
+5V BUFFERED RESET
VCC
VCC
ADM709
tRS
RESET
P
RESET
RESET
GND
GND
Figure 3. Power Off/On RESET Timing
Figure 6. Interfacing to Microprocessors with Bidirectional RESET
VCC
RESET
400ms/DIV
Figure 4. RESET Output vs. VCC
REV. 0
-3-
ADM709
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Plastic DIP (N-8)
C2022-18-4/95
0.195 (4.95) 0.115 (2.93)
8 PIN 1 1
5 0.280 (7.11) 0.240 (6.10) 4
0.430 (10.92) 0.348 (8.84) 0.210 (5.33) MAX 0.160 (4.06) 0.115 (2.93) 0.060 (1.52) 0.015 (0.38)
0.325 (8.25) 0.300 (7.62)
0.130 (3.30) MIN SEATING PLANE
0.015 (0.381) 0.008 (0.204)
0.022 (0.558) 0.014 (0.356)
0.100 (2.54) BSC
0.070 (1.77) 0.045 (1.15)
8-Lead SOIC (SO-8)
8
5 0.1574 (4.00) 0.1497 (3.80)
PIN 1 1 4
0.2440 (6.20) 0.2284 (5.80)
0.1968 (5.00) 0.1890 (4.80) 0.0098 (0.25) 0.0040 (0.10) 0.0500 (1.27) BSC 0.0688 (1.75) 0.0532 (1.35) 0.0192 (0.49) 0.0138 (0.35) 8 0
0.0196 (0.50) x 45 0.0099 (0.25)
0.0098 (0.25) 0.0075 (0.19)
0.0500 (1.27) 0.0160 (0.41)
-4-
REV. 0
PRINTED IN U.S.A.

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