FM1233A 3-Pin µC Supervisor Circuit General Description Features The FM1233A 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 3.3V and 3.0V systems with different tolerances. ■ Precision monitoring of 3.3V and lower voltage microprocessor systems ■ VTH values of 3.08V, 2.88V and 2.72V ■ Automatic restart of microprocessor after power failure ■ Reset Timeout Period Choice: – Options AC and AD: 140ms (min)/256ms (typ) – Option ABA: 17ms (min)/32ms (typ) – Available on request: 64ms (typ) and 128ms (typ) ■ Internal 5kΩ pull-up resistor ■ Operating Temperature -40°C to +105°C ■ Monitors external pushbutton override ■ Internal switch debounce circuitry ■ SOT23-3 package FM1233A 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 asserted for a minimum period (tRST) to allow the system clock and other circuits to stabilize. The reset output of FM1233A is of open-drain active low type. The FM1233A 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 FM1233A. Typical Operating Circuit VCC 3 Controller FM1233A 1 2 RESET GND Connection Diagram GND 1 FM1233A 3 VCC RESET 2 SOT23-3 Package ©2004 Fairchild Semiconductor Corporation FM1233A Rev. E 1 www.fairchildsemi.com FM1233A 3-Pin µC Supervisor Circuit September 2004 Voltage on any pin relative to GND VCC RESET Input Current Output Current (RESET) Continuous Power Dissipation (TA = 70°C) SOT23 (derate 4mW above 70°C) Operating Temperature Range Storage Temperature Range Lead Temperature (soldering, 10s) -0.3V to +6.0V -0.3V to (VCC + 0.3V) 20mA 20mA 300mW -40°C to +105°C -65°C to +150°C +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. Electrical Characteristics (VCC = 3.3V; TA = -40°C to +105°C unless otherwise noted) (Note 1) Parameter Symbol Conditions Min Typ Max Units 1.2 3.3 5.5 V 3 6 µA Operating Voltage VCC Supply Current ICC VCC < 3.3V Reset Threshold VTH FM1233AC 2.70 2.88 2.97 V Reset Threshold VTH FM1233AD 2.58 2.72 2.86 V Reset Threshold VTH FM1233ABA 2.97 3.08 3.19 V Reset Output Voltage VOL 0.4 V Reset Timeout Period tRST FM1233AC, FM1233AD 140 256 560 ms Reset Timeout Period tRST FM1233ABA 17 32 64 ms 2.0 V 1.5 V ISINK = 1.2mA VCC = VTH(min) Pushbutton Detect PBVDET VCC = 3.3V Pushbutton Release PBVREL Note 2 0.8 0.3 Note 1: Testing at production is done at 25°C only. Limits over temperature are guaranteed by design. Note 2: C = 100pF, VCC = 3.3V. It is recommended to connect 100pF capacitor between the Reset pin and Ground pin if pushbutton reset is implemented. 2 FM1233A Rev. E www.fairchildsemi.com FM1233A 3-Pin µC Supervisor Circuit Absolute Maximum Ratings FM1233A 3-Pin µC Supervisor Circuit Typical Operating Characteristics Supply Current Vs. Temperature 10 8 8 6 6 ICC (µA) 10 4 4 VCC = 3.3V 2 0 2 -55C +25C +110C 0 Temperature (C) Power up Reset timeout (ms) Power up Reset Timeout Vs. Temperature 600 600 500 500 400 400 300 300 200 200 100 -40C +25C +105C 100 Temperature (C) 3 FM1233A Rev. E www.fairchildsemi.com Pin Number Name 1 GND 2 RESET 3 VCC Function GROUND RESET remains LOW while VCC is below VTH, and for at least the minimum Reset Timeout period after VCC rises above VTH. Circuit Timing (Ex: FM1233A) VCC 3.3V VTH 1V GND RESET 3.3V VTH 1V GND 140ms (min) When operating properly with 3V VCC (for example), RESET will also be about 3V. 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. 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 after the minimum Reset Timeout period. 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. 4 FM1233A Rev. E www.fairchildsemi.com FM1233A 3-Pin µC Supervisor Circuit Pin Descriptions Connecting an External Reset to the FM1233A The FM1233A 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 FM1233A 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. VCC 3 FM1233 1 Controller 2 RESET For a VCC value below 1.0V, the FM1233A 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 FM1233A 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 FM1233A permits a pushbutton (or a signal) to initiate a reset externally. Once this external reset is detected on the reset pin, FM1233 also actively asserts the reset signal to maintain the Reset Timeout period when the external reset is not present . FM1233 internally debounces glitches seen during a typical push button closure. For proper operation, the external switch should be paralleled by an external capacitor of 100pF to 0.01µF. 5 FM1233A Rev. E www.fairchildsemi.com FM1233A 3-Pin µC Supervisor Circuit General Description Part Number Top Marking RESET Threshold (V) Output Type Package Type Packing Method FM1233ACS3X 33AC 2.88 Open-Drain, active LOW 3-Pin, SOT23 3000 units in T&R FM1233ADS3X 33AD 2.72 Open-Drain, active LOW 3-Pin, SOT23 3000 units in T&R FM1233ABAS3X 3ABA 3.08 Open-Drain, active LOW 3-PIN, SOT23 3000 units in T&R Note 3: FM1233AC and FM1233AD feature 256ms (typ) Reset timeout while FM1233ABA features 32ms (typ) Reset Timeout. Consult Fairchild Sales for other reset pulse width options. 6 FM1233A Rev. E www.fairchildsemi.com FM1233A 3-Pin µC Supervisor Circuit Ordering Information FM1233A 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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