LM3708/LM3709 Microprocessor Supervisory Circuits with Low Line Output, Manual Reset and Watchdog Timer General Description The LM3708/LM3709 series of microprocessor supervisory circuits provide the maximum flexibility for monitoring power supplies and battery controlled functions in systems without backup batteries. The LM3708/LM3709 series are available in a 9-bump micro SMD package. Built-in features include the following: Reset: Reset is asserted during power-up, power-down, and brownout conditions. RESET is guaranteed down to VCC of 1.0V. Manual Reset Input: An input that asserts reset when pulled low. Low Line Output: This early power failure warning indicator goes low when the supply voltage drops to a value which is 2% higher than the reset threshold voltage. Watchdog Timer: The WDI (Watchdog Input) monitors one of the µP’s output lines for activity. If no output transition occurs during the watchdog timeout period, reset is activated. Features n Standard Reset Threshold voltage: 3.08V n Custom Reset Threshold voltages: For other voltages between 2.2V and 5.0V in 10mV increments, contact National Semiconductor Corp. n No external components required n Manual-Reset input n RESET (LM3708) or RESET (LM3709) outputs n Precision supply voltage monitor n Factory programmable Reset and Watchdog Timeout Delays n Available in micro SMD package for minimum footprint n ± 0.5% Reset threshold accuracy at room temperature n ± 2% Reset threshold accuracy over temperature extremes n Reset assertion down to 1V VCC (RESET option only) n 28 µA VCC supply current Applications n n n n Embedded Controllers and Processors Intelligent Instruments Automotive Systems Critical µP Power Monitoring Typical Application 20011703 © 2002 National Semiconductor Corporation DS200117 www.national.com LM3708/LM3709 Microprocessor Supervisory Circuits with Low Line Output, Manual Reset and Watchdog Timer June 2002 LM3708/LM3709 Connection Diagram Top View (looking from the coating side) micro SMD 9 Bump Package BPA09 20011701 Pin Descriptions Bump No. Name Function A1 MR Manual-Reset input. When MR is less than VMRT (Manual Reset Threshold) RESET/RESET is engaged. B1 VCC Power Supply input. C1 RESET Reset Logic Output. Pulses low for tRP (Reset Timeout Period) when triggered, and stays low whenever VCC is below the reset threshold or when MR is below VMRT. It remains low for tRP after either VCC rises above the reset threshold, or after MR input rises above VMRT (LM3708 only). RESET Reset Logic Output. RESET is the inverse of RESET (LM3709 only). C3 LLO Low-Line Logic Output. Early Power-Fail warning output. Low when VCC falls below VLLOT (Low-Line Output Threshold). This output can be used to generate an NMI (Non-Maskable Interrupt) to provide an early warning of imminent power-failure. B3 GND Ground reference for all signals. A3 WDI Watchdog Input Transition Monitor: If no transition activity occurs for a period exceeding tWD (Watchdog Timeout Period), reset is engaged. A2, C2 NC No Connect. B2 NC No Connect. Test input used at factory only. Leave floating. www.national.com 2 LM3708/LM3709 Block Diagram 20011705 3 www.national.com LM3708/LM3709 Ordering Information 20011704 *For other voltages between 2.2V and 5.0V, please contact National Semiconductor sales office. LM3708/LM3709 Part Number Output Reset Timeout Period Watchdog Timeout Period Package Marking LM3708XQBP-308 totem-pole 200ms 1600ms %%I8 LM3708XQBPX-308 totem-pole 200ms 1600ms %%I8 LM3709XQBP-308 totem-pole 200ms 1600ms %%I9 LM3709XQBPX-308 totem-pole 200ms 1600ms %%I9 %% is the datecode and will vary with time. Table Of Functions Part Number LM3708 LM3709 Active Low Reset Active High Reset x x Output (X = totem-pole) (Y = open-drain) Reset Timeout Period Manual Reset Low Line Output X, Y* Customized Customized x x X Customized Customized x x * = available upon request. Contact National www.national.com Watchdog Timeout Period 4 (Note 1) Power Dissipation If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (VCC) Operating Ratings (Note 1) −0.3V to 6.0V All Other Inputs (Note 3) −40˚C ≤ TJ ≤ 85˚C Temperature Range −0.3V to VCC + 0.3V ESD Ratings (Note 2) Human Body Model Machine Model 1.5kV 150V LM3708/LM3709 Series Electrical Characteristics Limits in the standard typeface are for TJ = 25˚C and limits in boldface type apply over full operating range. Unless otherwise specified: VCC = +2.2V to 5.5V. Symbol Parameter Conditions Min Typ Max Units POWER SUPPLY VCC ICC Operating Voltage Range: VCC LM3708 1.0 5.5 LM3709 1.2 5.5 VCC Supply Current All inputs = VCC; all outputs floating V 28 50 µA VRST +0.5 +2 % RESET THRESHOLD VRST Reset Threshold VCC falling −0.5 −2 VCC falling: TA = 0˚C to 70˚C VRSTH tRP tRD −1.5 +1.5 0.0032 • VRST Reset Threshold Hysteresis Reset Timeout Period Reset Reset Reset Reset Timeout Timeout Timeout Timeout Period Period Period Period VCC to Reset Delay VCC falling at 1mV/µs = = = = E, J, N, S F, K, P, T G, L, Q, U H, M, R, V 1 20 140 1120 1.4 28 200 1600 mV 2 40 280 2240 20 ms µs RESET (LM3709) VOL VOH ILKG RESET RESET Output Leakage Current VCC > 2.25V, ISINK = 900µA 0.3 VCC > 2.7V, ISINK = 1.2mA 0.3 VCC > 4.5V, ISINK = 3.2mA 0.4 VCC > 1.2V, ISOURCE = 50µA 0.8 VCC VCC > 1.8V, ISOURCE = 150µA 0.8 VCC VCC > 2.25V, ISOURCE = 300µA 0.8 VCC VCC > 2.7V, ISOURCE = 500µA 0.8 VCC VCC > 4.5V, ISOURCE = 800µA VCC − 1.5V V V VRESET = 5.5V 1.0 VCC > 1.0V, ISINK = 50µA 0.3 VCC > 1.2V, ISINK = 100µA 0.3 µA RESET (LM3708) VOL VOH RESET RESET VCC > 2.25V, ISINK = 900µA 0.3 VCC > 2.7V, ISINK = 1.2mA 0.3 VCC > 4.5V, ISINK = 3.2mA 0.4 VCC > 2.25V, ISOURCE = 300µA 0.8 VCC VCC > 2.7V, ISOURCE = 500µA 0.8 VCC VCC > 4.5V, ISOURCE = 800µA VCC − 1.5V 5 V www.national.com LM3708/LM3709 Absolute Maximum Ratings LM3708/LM3709 LM3708/LM3709 Series Electrical Characteristics (Continued) Limits in the standard typeface are for TJ = 25˚C and limits in boldface type apply over full operating range. Unless otherwise specified: VCC = +2.2V to 5.5V. Symbol Parameter Conditions Min Typ Max Units +1 µA WDI WDI Watchdog Input Current WDIT Watchdog Input Threshold tWD Watchdog Timeout Period −1 Watchdog Watchdog Watchdog Watchdog Timeout Timeout Timeout Timeout Period Period Period Period = = = = E, F, G, H J, K, L, M N, P, Q, R S, T, U, V 0.2 • VCC 1.225 0.8 • VCC V 4.3 71 1120 17900 6.2 102 1600 25600 9.3 153 2400 38400 ms MR VMRT VMRTH MR Input Threshold MR Threshold Hysteresis RMR MR Pull-up Resistance tMD MR to Reset Delay tMR MR Pulse Width MR, Low 0.8 MR, High MR falling: VCC = VRST 2.0 MAX 0.0032 • VRST to 5.5V 35 56 V mV 75 12 kΩ µS 25 µS LLO VOL LLO Output Voltage VCC > 2.25V, ISINK = 900µA 0.3 VCC > 2.7V, ISINK = 1.2mA 0.3 VCC > 4.5V, ISINK = 3.2mA 0.4 VCC > 2.25V, ISOURCE = 300µA VOH 0.8 VCC VCC > 2.7V, ISOURCE = 500µA 0.8 VCC VCC > 4.5V, ISOURCE = 800µA VCC − 1.5V V LLO OUTPUT VLLOT LLO Output Threshold (VLLO − VRST, VCC falling) VLLOTH Low-Line Comparator Hysteresis tCD Low-Line Comparator Delay 1.01 • VRST VCC falling at 1mV/µs 1.02 • VRST 1.03 • VRST V 0.0032 • VRST mV 20 µs Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed conditions. Note 2: The Human Body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200pF capacitor discharged directly into each pin. Note 3: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal resistance, θJ-A, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperture is calculated using: Where the value of θJ-A for the micro SMD package is 220˚C/W. www.national.com 6 Supply Current vs Supply Voltage 3.3V Supply Current vs Temperature 20011711 20011715 Normalized Reset Threshold Voltage vs Temperature Reset Timeout Period vs VCC 20011712 20011732 Max. Transient Duration vs Reset Comparator Overdrive (VCC = 3.3V) Reset Timeout Period vs Temperature 20011710 20011716 7 www.national.com LM3708/LM3709 Typical Performance Characteristics LM3708/LM3709 Typical Performance Characteristics (Continued) Watchdog Timeout Period vs Temperature (tWD programmed as 6.2ms) Low-Line Comparator Propagation Delay vs Temperature 20011714 20011713 Low-Line Output (LLO) Circuit Information The low-line output comparator is typically used to provide a non-maskable interrupt to a µP when VCC begins falling. LLO monitors VCC and goes low when VCC falls below VLLOT (typically 1.02 • VRST) with hysteresis of 0.0032 • VRST. Reset Output The Reset input of a µP initializes the device into a known state. The LM3708/LM3709 microprocessor supervisory circuits assert a forced reset output to prevent code execution errors during power-up, power-down, and brownout conditions. RESET is guaranteed valid for VCC > 1V. Once VCC exceeds the reset threshold, an internal timer maintains the output for the reset timeout period. After this interval, reset goes high. The LM3708 offers an active-low RESET; The LM3709 offers an active-high RESET. Any time VCC drops below the reset threshold (such as during a brownout), the reset activates. When VCC again rises above the reset threshold, the internal timer starts. Reset holds until VCC exceeds the reset threshold for longer than the reset timeout period. After this time, reset releases. Watchdog Timer Input (WDI) The watchdog timer input monitors one of the microprocessor’s output lines for activity. Each time a transition occurs on this monitored line, the watchdog counter is reset. However, if no transition occurs and the timeout period is reached, the LM3708/LM3709 assumes that the microprocessor has locked up and the reset output is activated. WDI is a high impedance input. Special Precautions for the micro SMD Package As with most integrated circuits, the LM3708 and LM3709 are sensitive to exposure from visible and infrared (IR) light radiation. Unlike a plastic encapsulated IC, the micro SMD package has very limited shielding from light, and some sensitivity to light reflected from the surface of the PC board or long wavelength IR entering the die from the side may be experienced. This light could have an unpredictable affect on the electrical performance of the IC. Care should be taken to shield the device from direct exposure to bright visible or IR light during operation. The Manual Reset input (MR) will initiate a forced reset also. See the Manual Reset Input section. Reset Threshold The LM3708/LM3709 family is available with a reset voltage of 3.08V. Other reset thresholds in the 2.20V to 5.0V range, in steps of 10 mV, are available; contact National Semiconductor for details. Micro SMD Mounting The micro SMD package requires specific mounting techniques which are detailed in National Semiconductor Application Note AN-1112. Referring to the section Surface Mount Technology (SMT) Assembly Considerations, it should be noted that the pad style which must be used with the 9-pin package is the NSMD (non-solder mask defined) type. For best results during assembly, alignment ordinals on the PC board may be used to facilitate placement of the micro SMD device. Manual Reset Input (MR) Many µP-based products require a manual reset capability, allowing the operator to initiate a reset. The MR input is fully debounced and provides an internal 56 kΩ pull-up. When the MR input is pulled below VMRT (1.225V) for more than 25 µs, reset is asserted after a typical delay of 12 µs. Reset remains active as long as MR is held low, and releases after the reset timeout period expires after MR rises above VMRT. Use MR with digital logic to assert or to daisy chain supervisory circuits. It may be used as another low-line comparator by adding a buffer. www.national.com 8 LM3708/LM3709 Timing Diagrams 20011728 FIGURE 1. LM3708 Reset Time with MR and WDI 20011729 FIGURE 2. LLO Output 9 www.national.com LM3708/LM3709 Typical Application Circuit 20011740 FIGURE 3. Long Delay Timer/Oscillator www.national.com 10 inches (millimeters) NOTES: UNLESS OTHERWISE SPECIFIED 1. EPOXY COATING 2. 63Sn/37Pb EUTECTIC BUMP 3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD. 4. PIN 1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION. REMAINING PINS ARE NUMBERED COUNTER CLOCKWISE. 5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS PACKAGE LENGTH AND X3 IS PACKAGE HEIGHT. 6.NO JEDEC REGISTRATION AS OF AUG.1999. 9 bump micro SMD Package NS Package Number BPA09FFB The dimensions of X1, X2 and X3 are given below X1 = 1.412mm X2 = 1.412mm X3 = 0.850mm LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL 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. National Semiconductor Corporation Americas Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 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. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. LM3708/LM3709 Microprocessor Supervisory Circuits with Low Line Output, Manual Reset and Watchdog Timer Physical Dimensions unless otherwise noted