FM1233B 3-Pin µC Supervisor Circuit General Description Features The FM1233B is a supervisor circuit that monitors a microprocessor power supply or other system voltage and issues a reset pulse when a fault condition exists. Several different threshold voltages are offered to accommodate 5V systems with different tolerances. ■ Precision monitoring of 5V and lower voltage microprocessor systems ■ VTH values of 4.62V, 4.38V and 4.12V ■ Automatic restart of microprocessor after power failure ■ 140ms (min) power-on RESET delay (typ.: 256ms) The device features a precision temperature-compensated voltage reference and comparator. When VCC falls to the threshold voltage, a RESET pulse is issued, holding the output in the active state. When power rises above VTH, the reset remains for approximately 250 ms to allow the system clock and other circuits to stabilize. The reset output of FM1233B is of open-drain active low type. ■ ■ ■ ■ ■ ■ Internal 5kΩ pull-up resistor Other reset choices available: 32 to 128ms Operating Temperature -40°C to +105°C Monitors external pushbutton override Internal switch debounce circuitry SOT23-3 package The FM1233B also can monitor a switch closure on its output, enabling it to recognize an external reset from a pushbutton switch or a µP. In the case of a switch, the closure will be debounced by circuitry internal to the FM1233B. Typical Operating Circuit VCC 3 Controller FM1233B 1 2 RESET GND Connection Diagram GND 1 FM1233B RESET 3 VCC 2 SOT23-3 Package ©2002 Fairchild Semiconductor Corporation FM1233B Rev. D 1 www.fairchildsemi.com FM1233B 3-Pin µC Supervisor Circuit February 2003 Votage on any pin relative to GND VCC RESET Input Current Output Current (RESET) ESD Rating: Human body model >2kV Machine Model >200 V Continuous Power Dissipation (TA = 70°C) SOT23 (derate 4mW above 70°C) 300mW 20mA Operating Temperature Range -40°C to +105°C Storage Temperature Range -65°C to +150°C Lead Temperature (soldering, 10s) +300°C These are stress ratings only, and functional operation is not implied for these levels or beyond. Exposure to Absolute Maximum Rating conditions for extended periods may affect device reliability. -0.3V to +6.0V -0.3V to (VCC + 0.3V) 20mA Electrical Characteristics (VCC = 5V; TA = -40°C to +105°C unless otherwise noted) (Note 1) Parameter Symbol Conditions Operating Voltage VCC Supply Current ICC VCC < 5V Min Typ 1.2 3 Max Units 5.5 V 6 µA Reset Threshold VTH FM1233BF 4.40 4.62 4.86 V Reset Threshold VTH FM1233BD 4.16 4.38 4.55 V Reset Threshold VTH FM1233BE 3.91 4.12 4.32 V Reset Output Voltage VOL FM1233B 0.4 V Reset Timeout Period tRST FM1233B 256 560 ms Pushbutton Detect PBVDET FM1233B VCC = 5V 2.0 V Pushbutton Release PBVREL FM1233B Note 2 0.3 1.5 V Isink = 5mA VCC = VTH(min) 140 0.8 Note 1: Testing at production is done at 25°C only. Limits over temperature are guaranteed by design. Note 2: C = 100pF, VCC = 5V. It is recommended to connect 100pF capacitor between the Reset pin and Ground pin if pushbutton reset is implemented. 2 FM1233B Rev. D www.fairchildsemi.com FM1233B 3-Pin µC Supervisor Circuit Absolute Maximum Ratings FM1233B 3-Pin µC Supervisor Circuit Pin Descriptions Pin Number Name 1 GND 2 RESET 3 VCC Function GROUND RESET remains LOW while VCC is below VTH, and for at least 140ms after VCC rises above VTH. Circuit Timing VCC 3.3V VTH 1V GND RESET 3.3V VTH 1V GND 140ms (min) When VCC begins to rise, RESET follows it until 1.0V or so is reached, whereupon the device regains control, RESET is pulled to ground, etc. When VCC rises above VTH, RESET comes out of RESET 140 ms later. When operating properly with 5V VCC (for example), RESET will also be about 5V. When VCC starts to fall, RESET will follow it down as shown. When VCC drops below VTH, RESET drops to ground (“issues a RESET”) and stays there unless VCC also falls below its minimum operating voltage, approx. 1V. At this point, the supervisor loses control, and its output may rise, only to again follow VCC down to the ground. If it is required that a lower value than GND + 1.0V is needed on RESET signal during VCC ≤ 1V, a 100K resistor may be used on the device output to GND. 3 FM1233B Rev. D www.fairchildsemi.com Connecting an External Reset to the FM1233B VCC The FM1233B features a highly accurate voltage reference to which VCC is compared. Once VCC is below the specified threshold, it will drive the RESET line and continue to hold it low until VCC returns above the threshold and the time for the RESET pulse duration has expired. The FM1233B is immune to short negative going transients on the VCC line. The placement of a 0.1µF bypass capacitor as close as possible to the VCC pin provides additional transient immunity. 3 FM1233 1 Controller 2 RESET For a VCC value below 1.0V, the FM1233B does not sink very much current on the RESET pin. This is not a problem in most systems since common devices are not functional in this range. If it is desired for the FM1233B reset to be functional below this range, use a 100KΩ pull-down resistor between RESET and VSS. GND 100pF PUSH BUTTON Bi-Directional Reset The FM1233B permits an external pushbutton to initiate a reset. Such a connection to pin 2 will be debounced, RESET will go low and recover in typically 250ms. For proper operation, the external switch should be paralleled by an external capacitor of 100pF to 0.01µF. 4 FM1233B Rev. D www.fairchildsemi.com FM1233B 3-Pin µC Supervisor Circuit General Description Part Number Top Marking RESET Threshold (V) Output Type Package Type Packing Method FM1233BFS3X 3BF 4.62 Open-Drain, active LOW 3-Pin, SOT23 3000 units in T&R FM1233BDS3X 3BD 4.38 Open-Drain, active LOW 3-Pin, SOT23 3000 units in T&R FM1233BES3X 3BE 4.12 Open-Drain, active LOW 3-Pin, SOT23 3000 units in T&R Note 3: Devices listed above feature 250ms typical reset pulse width. Consult Fairchild Sales for other reset pulse width options. 5 FM1233B Rev. D www.fairchildsemi.com FM1233B 3-Pin µC Supervisor Circuit Ordering Information FM1233B 3-Pin µC Supervisor Circuit Physical Dimensions inches (millimeters) unless otherwise noted 0.021 0.015 0.055 0.047 0.098 0.083 0.120 0.105 0.0059 0.0035 0.040 0.031 0.079 0.071 0-8˚ 0.010 0.005 0.004 0.001 0.76 2.29 PKG CL 0.76 0.95 LAND PATTERN RECOMMENDATION 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. 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