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FM809 Precision Reset Generator Circuit
August 2000
FM809 Precision Reset Generator Circuit
General Description
The FM809 features comprehensive reset generation for microcontroller/microprocessor based systems. If the system VCC voltage level is determined to be in an out-of-tolerance state, the device automatically generates a low-going reset signal. The reset signal is held in the active state (low) for a specified duration (minimum 140 ms) after the VCC returns to an in-tolerance state. The FM809 is fabricated using CMOS technology. The FM809 is available in the SOT-23 package.
Features
I Automatic reset generation on power-up I Minimum 140 ms reset pulse -- compatible with other similar 809 class devices I Other reset pulse choices available: 32 - 256 ms I Choice of commercial and extended temperature ranges I Choice of Reset Thresholds: 4.63V, 4.38V, 4.00V, 3.08V, 2.93V, 2.63V I Package available: SOT-23
Block Diagram
VCC
VCC Tolerance Detect & Reset Monitor
Output Stage
Reset_out (active low)
Temp. Compensated Reference
Connection Diagram
1
1 = GND 2 = RESET' 3 = VCC 2
FM809
3
(c) 2000 Fairchild Semiconductor International FM809 Rev. A.1
1
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FM809 Precision Reset Generator Circuit
Each FM809 device has the following Identifier (FM809yz) (Top Mark on devices will be 09yz) Reset Characteristics RESET THRESHOLD (V)
4.63 4.38 4.00 3.08 2.93 2.63
Identifier(y)
L M J T S R
Fairchild Part Number
FM809Lz FM809Mz FM809Jz FM809Tz FM809Sz FM809Rz
RESET PULSE DURATION (mS)
32 64 128 256
Identifier(z)
E F H Blank
Fairchild Part Number
FM809yE* FM809yF* FM809yH* FM809y
Note*: These choices are available upon special request only. Please work with Fairchild Marketing to determine availability.
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FM809 Rev. A.1
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FM809 Precision Reset Generator Circuit
Product Specifications Absolute Maximum Ratings
Ambient Storage Temperature All Input or Output Voltages with Respect to Ground Lead Temperature (Soldering, 10 seconds) ESD Rating -65C to +150C -0.3V to 6.5V +300C 2000V min.
Operating Conditions
Ambient Operating Temperature Commercial Industrial 0C to +70C -40C to +85C
Electrical Characteristics Parameter
VCC Range IND Supply Current ICC Com
Symbol
Temp
Com
Conditions
Min
1.0 1.2
Typ
Max
5.5V 5.5 50 100
Units
V V A A V V V V V V V V V V V V V V
Reset Threshold
VTH
Com Ind Com Ind Com Ind Com Ind Com Ind Com Ind
`L' Identifier
4.50 4.40
4.63 4.63 4.38 4.38 4.00 4.00 3.08 3.08 2.93 2.93 2.63 2.63
4.75 4.85 4.50 4.56 4.10 4.20 3.15 3.23 3.00 3.08 2.70 2.75
`M' Identifier
4.25 4.16
`J' Identifier
3.89 3.80
`T' Identifier
3.00 2.92
`S' Identifier
2.85 2.78
`R' Identifier
2.55 2.50
nRESET Output Voltage High nRESET Output Voltage Low Reset Timeout Period
VOH VOL TRST
All All All
Isource = 150 mA Isink = 1.2mA
0.8VCC 0.4 175 240 375
ms
Note: Production testing done at TA = +25C, over temperature limits guaranteed by design only.
General Description
The FM809 features a highly accurate voltage reference against which the Vcc is compared. Once the Vcc is below the specified threshold, it will drive the RESET line and continue to hold it low until the VCC returns above the threshold and the time for the RESET pulse duration has expired. The FM809 is immune to short negative going transients on the VCC line. The placement of a 0.1F bypass capacitor as close as possible to the VCC pin provides additional transient immunity. For a VCC value below 1.0V-1.3V, the FM809 does not sink current on the RESET pin. This is not a problem in most systems since most common devices are not functional in this range. If it is desired for the FM809 reset to be functional below the range above, it is suggested to use a 100K pull-down resistor between RESET and VSS.
Interfacing to Bidirectional reset pins
FM809 can be used with microprocessors with bidirectional reset pins. In order to allow the microprocessor to drive the reset line, the output of the FM809 must be connected to the microprocessor through a 4.7k resistor. This will ensure that the RESET line has correct level at both the FM809 as well as the device end.
3
FM809 Rev. A.1
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FM809 Precision Reset Generator Circuit
Typical Operating Characteristics
Supply Current Vs. Temperature (FM809R/S/T)
8 7 6
Icc (uA)
5 4 3 2 1 0 -60 -40 -20 0
V
V
20
40
60
80
100
Temperature (C)
Power up Reset Timeout Vs. Temperature FM809(R/S/T)
300 280 260 240 220 200 -60
-40
-20
0
20
40
60
80
100
Temperature (C)
Normalized Reset Threshold Vs. Temperature FM809(R/S/T)
1.050 1.025 1.000 0.975 0.950 -60 -40 -20 0 20 40 60 80 100 Temperature (C)
4
FM809 Rev. A.1
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FM809 Precision Reset Generator Circuit
Physical Dimensions inches (millimeters) unless otherwise noted
0.45~0.60 0.20 MIN 2.40 0.10
0.40 0.03
1.30 0.10
0.03~0.10 0.38 REF
0.40 0.03 0.96~1.14 2.90 0.10
0.12 -0.023
+0.05
Dimensions in millimeters
0.97REF
0.95 0.03 0.95 0.03 1.90 0.03 0.508REF
SOT-23 Package Dimensions FS Pkg Code AU
Life Support Policy
Fairchild's products are not authorized for use as critical components in life support devices or systems without the express written approval of the President of Fairchild Semiconductor Corporation. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
Fairchild Semiconductor Americas Customer Response Center Tel. 1-888-522-5372 Fairchild Semiconductor Europe Fax: +44 (0) 1793-856858 Deutsch Tel: +49 (0) 8141-6102-0 English Tel: +44 (0) 1793-856856 Francais Tel: +33 (0) 1-6930-3696 Italiano Tel: +39 (0) 2-249111-1
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
Fairchild Semiconductor Hong Kong 8/F, Room 808, Empire Centre 68 Mody Road, Tsimshatsui East Kowloon. Hong Kong Tel; +852-2722-8338 Fax: +852-2722-8383
Fairchild Semiconductor Japan Ltd. 4F, Natsume Bldg. 2-18-6, Yushima, Bunkyo-ku Tokyo, 113-0034 Japan Tel: 81-3-3818-8840 Fax: 81-3-3818-8841
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and Fairchild reserves the right at any time without notice to change said circuitry and specifications.
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FM809 Rev. A.1
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