SGM706 Low-Cost, Microprocessor Supervisory Circuit

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1 GENERAL DESCRIPTION The microprocessor supervisory circuit reduces the complexity and number of components required to monitor power-supply and monitor microprocessor activity. It significantly improves system reliability and accuracy compared to separate ICs or discrete components. The provides power-supply monitoring circuitry that generates a reset output during power-up, power-down and brownout conditions. The reset output remains operational with as low as 1V. Independent watchdog monitoring circuitry is also provided. This is activated if the watchdog input has not been toggled within 1.6 seconds. In addition, there is a 1.25V threshold detector for power-fail warning, low-battery detection, or monitoring an additional power supply. An active-low manual-reset input () is also included. The is available in Green SOP8 package. It operates over an ambient temperature range of -40 to +85. FEATURES Precision Supply-Voltage Monitor 4.65V for -L 4.40V for -M 4.0V for -J 3.08V for -T 2.93V for -S 2.63V for -R Guaranteed Valid at = 1V 200ms Reset Pulse Width Debounced TTL/CMOS-Compatible Manual-Reset Input Independent Watchdog Timer (1.6sec) Timeout Voltage Monitor for Power-Fail or Low-Battery Warning 40 to +85 Operating Temperature Range Green SOP8 Package APPLICATIONS Computers Controllers Intelligent Instruments Automotive Systems Critical µp Power Monitoring REV. A

2 PACKAGE/ORDERING INFORMATION MODEL THRESHOLD (V) PACKAGE DESCRIPTION ORDERING NUMBER PACKAGE MARKING PACKAGE OPTION 4.65 SOP8 -LYS8G/TR -LYS8 Tape and Reel, SOP8 -MYS8G/TR -MYS8 Tape and Reel, SOP8 -JYS8G/TR -JYS8 Tape and Reel, SOP8 -TYS8G/TR -TYS8 Tape and Reel, SOP8 -SYS8G/TR -SYS8 Tape and Reel, SOP8 -RYS8G/TR -RYS8 Tape and Reel, 2500 NOTE: Order number is defined as the follow: ORDER NUMBER SGM 706- X Y X G / TR Tape and Reel Green product Package Type S8 SOP8 Operating Temperature Range Y -40 to +85 THRESHOLD L: 4.65V M:4.40V J: 4.0V T: 3.08V S: 2.93V R: 2.63V ABSOLUTE MAXIMUM RATINGS (Typical values are at T A = 25, unless otherwise noted.) Terminal Voltage (with respect to ) V to 6.0V All Other Inputs V to ( + 0.3V) Input Current,...20mA... 20mA Output Current, (all outputs)... 20mA Operating Temperature Range to +85 Junction Temperature Storage Temperature to +150 Lead Temperature (soldering, 10sec) ESD Susceptibility HBM V MM...300V CAUTION This integrated circuit can be damaged by ESD if you don t pay attention to ESD protection. SGMICRO recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. NOTE: 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. SGMICRO reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. Please contact SGMICRO sales office to get the last datasheet. 2

3 TYPICAL OPERATION CIRCUIT UNREGULATED DC +5V DC LINEAR REGULATOR MICROPROCESSOR PFI WDI WDO I/O LINE NMI PUSHBUTTON SWITCH INTERRUPT 3

4 PIN CONFIGURATION (TOP VIEW) 1 8 WDO WDI PFI 4 5 SOP8 PIN DESCRIPTION PIN NAME FUNCTION 1 Manual-Reset Input triggers a reset pulse when pulled below 0.8V. This active-low input has an internal 250µA ( = +5V) pull-up current. It can be driven from a TTL or CMOS logic line as well as shorted to ground with a switch. 2 Power Supply Voltage that is monitored. 3 0V Ground Reference for all signals. 4 PFI 5 6 WDI 7 8 WDO Power-Fail Voltage Monitor Input. When PFI is less than 1.25V, goes low. Connect PFI to or when not used. Power-Fail Output goes low and sinks current when PFI is less than 1.25V; otherwise stays high. Watchdog Input. If WDI remains high or low for 1.6sec, the internal watchdog timer runs out and WDO goes low (BLOCK DIAGRAM). Floating WDI or connecting WDI to a high-impedance three-state buffer disables the watchdog feature. The internal watchdog timer clears whenever reset is asserted, WDI is three-stated, or WDI sees a rising or falling edge. Active-Low Reset Output pulses low for 200ms when triggered, and stays low whenever is below the reset threshold (4.65V for -L, 4.4V for -M, 4.0V for -J, 3.08V for -T and 2.93V for -S, 2.63V for -R). It remains low for 200ms after rises above the reset threshold or goes from low to high. A watchdog timeout will not trigger unless WDO is connected to. Watchdog Output pulls low when the internal watchdog timer finishes its 1.6sec count and does not go high again until the watchdog is cleared. WDO also goes low during low-line conditions. Whenever is below the reset threshold, WDO stays low; however, unlike, WDO does not have a minimum pulse width. As soon as rises above the reset threshold, WDO goes high with no delay. 4

5 ELECTRICAL CHARACTERISTICS ( = 4.75V to 5.5V for -L; = 4.5V to 5.5V for -M; = 4.07V to 5.5V for -J; = 3.14V to 5.5V for -T; = 2.95V to 5.5V for -S; = 2.68V to 5.5V for -R; T A = -40 C to +85 C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Voltage Range ( ) V Supply Current (I SUPPLY) µa -L M Reset Threshold (V RT ) -J T V -S R L, -M 40 Reset Threshold Hysteresis -J 34 -T, -S 25 mv -R 22 Reset Pulse Width (t RS ) ms I SOURCE = 800µA -1.5 Output Voltage I sink = 3.2mA 0.4 V = 1V, I sink = 50µA 0.3 Watchdog Timeout Period (t WD ) sec WDI Pulse Width (t WP) V IL = 0.4V, V IH = 70 ns Low = 5V 0.8 WDI Input Threshold High = 5V 3.5 Low V RST(MAX) < < 3.6V 0.8 V High V RST(MAX) < < 3.6V 0.7 VCC WDI Input Current WDI = WDI = 0V µa WDO Output Voltage I SOURCE = 800µA -1.5 I sink = 1.2mA 0.4 V Pull-Up Current = 0V µa Pulse Width (t ) 250 ns Input Threshold Low 0.8 T A = +25 C High 2 V to Reset Out Delay (t MD ) 350 ns PFI Input Threshold = 5V V PFI Input Current 0.2 na Output Voltage I SOURCE = 800µA -1.5 I sink = 3.2mA 0.4 V Specifications subject to changes without notice. 5

6 BLOCK DIAGRAM WDI 6 WATCHDOG TRANSITION DETECTOR WATCHDOG TIMER 8 WDO 1 250µA TIMEBASE FOR AND WATCHDOG 2 + _ GENERATOR 7 PFI V for -L* + _ V * 4.65V for -L 4.40V for -M 4.0V for -J 3.08V for -T 2.93V for -S 2.63V for -R 3 6

7 TYPICAL PERFORMANCE CHARACTERISTICS 2kΩ 330pF 10kΩ 30pF PFI +5V pF +1.25V 1kΩ PFI + +5V 1kΩ V 30pF 7

8 TYPICAL PERFORMANCE CHARACTERISTICS 8

9 APPLICATION NOTES Ensuring a Valid Output Down to = 0V When falls below 1V, the output no longer sinks current it becomes an open circuit. High-impedance CMOS logic inputs can drift to undetermined voltages if left undriven. If a pull-down resistor is added to the pin as shown in Figure 1, any stray charge or leakage currents will be drained to ground, holding low. Resistor value (R1) is not critical. It should be about 100kΩ, large enough not to load and small enough to pull to ground. Figure 1. Valid to Ground Circuit Monitoring Voltages Other Than the Unregulated DC Input Monitor voltages other than the unregulated DC by connecting a voltage divider to PFI and adjusting the ratio appropriately. If required, add hysteresis by connecting a resistor (with a value approximately 10 times the sum of the two resistors in the potential divider network) between PFI and. A capacitor between PFI and will reduce the power-fail circuit s sensitivity to high-frequency noise on the line being monitored. can be asserted on other voltages in addition to the +5V line. Connect to to initiate a pulse when PFI drops below 1.25V. Figure 2 shows the configured to assert when the +5V supply falls below the reset threshold, or when the +12V supply falls below approximately 11V. +12V +5V R1 Monitoring a Negative Voltage The power-fail comparator can also monitor a negative supply rail (Figure 3). When the negative rail is good (a negative voltage of large magnitude), is low, and when the negative rail is degraded (a negative voltage of lesser magnitude), is high. By adding the resistors and transistor as shown, a high triggers reset. As long as remains high, the will keep reset asserted ( = low, = high). Note that this circuit s accuracy depends on the PFI threshold tolerance, the line, and the resistors. +5V R1 R2 V- +5V 0V +5V 0V PFI R1 100kΩ V- V TRIP 0V = V TRIP R2 TO μp V TRIP < 0 100kΩ 2N3904 Figure 3. Monitoring a Negative Voltage Interfacing to µps with Bidirectional Reset Pins µps with bidirectional reset pins, such as the Motorola 68HC11 series, can contend with the output. If, for example, the output is driven high and the Microprocessor wants to pull it low, indeterminate logic levels may result. To correct this, connect a 4.7kΩ resistor between the output and the µp reset I/O, as in Figure 4. Buffer the output to other system components. BUFFRED TO OTHER SYSTEM COMPONENTS 1MΩ 1% 130kΩ 1% PFI TO µp 4.7kΩ Microprocessor Figure 2. Monitoring Both +5V and +12V Figure 4. Interfacing to Microprocessors with Bidirectional Reset I/O 9

10 PACKAGE OUTLINE DIMENSIONS SOP8 D e L E1 E b c A D A1 A2 Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A A A b c D E E e BSC BSC L θ

11 04/2010 REV. A SGMICRO is dedicated to provide high quality and high performance analog IC products to customers. All SGMICRO products meet the highest industry standards with strict and comprehensive test and quality control systems to achieve world-class consistency and reliability. For more information regarding SGMICRO Corporation and its products, please visit 11