19-1090; Rev 1; 1/99 68HC11/Bidirectional-Compatible µP Reset Circuit Features The MAX6314 low-power CMOS microprocessor (µP) supervisory circuit is designed to monitor power supplies in µP and digital systems. The MAX6314’s RESET output is bidirectional, allowing it to be directly connected to µPs with bidirectional reset inputs, such as the 68HC11. It provides excellent circuit reliability and low cost by eliminating external components and adjustments. The MAX6314 also provides a debounced manual reset input. ♦ Small SOT143 Package This device performs a single function: it asserts a reset signal whenever the VCC supply voltage falls below a preset threshold or whenever manual reset is asserted. Reset remains asserted for an internally programmed interval (reset timeout period) after VCC has risen above the reset threshold or manual reset is deasserted. The MAX6314 comes with factory-trimmed reset threshold voltages in 100mV increments from 2.5V to 5V. Preset timeout periods of 1ms, 20ms, 140ms, and 1120ms (minimum) are also available. The device comes in a SOT143 package. For a µP supervisor with an open-drain reset pin, see the MAX6315 data sheet. ♦ Four Reset Timeout Periods Available: 1ms, 20ms, 140ms, or 1120ms (minimum) ♦ RESET Output Simplifies Interface to Bidirectional Reset I/Os ♦ Precision Factory-Set VCC Reset Thresholds: 100mV Increments from 2.5V to 5V ♦ ±1.8% Reset Threshold Accuracy at TA = +25°C ♦ ±2.5% Reset Threshold Accuracy Over Temp. ♦ Immune to Short VCC Transients ♦ 5µA Supply Current ♦ Pin-Compatible with MAX811 Ordering and Marking Information appears at end of data sheet. ________________________Applications Computers Controllers Intelligent Instruments Typical Operating Circuit Critical µP and µC Power Monitoring Portable/Battery-Powered Equipment VCC Pin Configuration VCC TOP VIEW GND 1 4 LASERTRIMMED RESISTORS VCC 68HC11** VCC µP MAX6314 4.7k RESET MR RESET 2 3 RESET CIRCUITRY RESET MR MAX6314 GND SOT143 **OR OTHER µC/µP WITH BIDIRECTIONAL RESET I/O PIN. * Patents Pending ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX6314* General Description MAX6314 68HC11/Bidirectional-Compatible µP Reset Circuit ABSOLUTE MAXIMUM RATINGS VCC ........................................................................-0.3V to +6.0V All Other Pins..............................................-0.3V to (VCC + 0.3V) Input Current (VCC) .............................................................20mA Output Current (RESET)......................................................20mA Rate of Rise (VCC) ...........................................................100V/µs Continuous Power Dissipation (TA = +70°C) SOT143 (derate 4mW/°C above +70°C) .......................320mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C 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. ELECTRICAL CHARACTERISTICS (VCC = +2.5V to +5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Operating Voltage Range SYMBOL VCC VCC Supply Current ICC Reset Threshold (Note 1) VTH Reset Threshold Tempco VCC to Reset Delay ∆VTH/°C Reset Timeout Period tRP CONDITIONS TA = 0°C to +70°C VCC = 5.5V, no load VCC = 3.6V, no load TA = +25°C TA = -40°C to +85°C VCC = falling at 1mV/µs MAX6314US_ _D1-T MAX6314US_ _D2-T MAX6314US_ _D3-T MAX6314US_ _D4-T MIN TYP MAX UNITS V 5 4 VTH 5.5 12 10 VTH + 1.8% VTH + 2.5% 1.0 VTH - 1.8% VTH - 2.5% 1 20 140 1120 60 35 1.4 28 200 1570 µA V ppm/°C µs 2 40 280 2240 ms MANUAL RESET INPUT MR Input Threshold VIL VIH VIL VIH 0.8 VTH > 4.0V 2.4 0.3 x VCC VTH < 4.0V 0.7 x VCC MR Minimum Input Pulse 1 µs MR Glitch Rejection 100 MR to Reset Delay 500 MR Pull-Up Resistance RESET Output Voltage RESET INTERNAL PULL-UP Transition Flip-Flop Setup Time (Note 2) Active Pull-Up Enable Threshold RESET Active Pull-Up Current RESET Pull-Up Resistance RESET Output Rise Time (Note 3) 32 VOL 63 ns ns 100 VCC > 4.25V, ISINK = 3.2mA 0.4 VCC > 2.5V, ISINK = 1.2mA 0.3 VCC > 1.2V, ISINK = 0.5mA 0.3 VCC > 1.0V, ISINK = 80µA 0.3 tS 400 VCC = 5V VCC = 5V 0.4 4.2 VCC = 3V tR VCC = 5V V 0.9 20 4.7 CLOAD = 120pF CLOAD = 250pF CLOAD = 200pF CLOAD = 400pF 5.2 333 666 333 666 kΩ V ns V mA kΩ ns V Note 1: The MAX6314 monitors VCC through an internal, factory-trimmed voltage divider that programs the nominal reset threshold. Factory-trimmed reset thresholds are available in 100mV increments from 2.5V to 5V (see Ordering and Marking Information). Note 2: This is the minimum time RESET must be held low by an external pull-down source to set the active pull-up flip-flop. Note 3: Measured from RESET VOL to (0.8 x VCC), RLOAD = ∞. 2 _______________________________________________________________________________________ 68HC11/Bidirectional-Compatible µP Reset Circuit SUPPLY CURRENT vs. TEMPERATURE PULL-UP CHARACTERISTICS MAX6314-01 MAX6314-02 6 +5V 4.7kΩ 74HC05 5 MAX6314 PULL-UP 2V/div +5V 74HC05 VCC RESET 100pF SUPPLY CURRENT (µA) 4.7kΩ PULL-UP 2V/div 100pF MAX6314 INPUT 5V/div GND MR VCC = 5V 4 3 VCC = 3V 2 VCC = 1V 1 0 -50 200ns/div -30 -10 10 30 50 70 90 TEMPERATURE (°C) TA = +25°C 2 TA = -40°C 1 30 VTH = 3.00V 20 10 1 2 3 -50 5 4 1.004 1.002 1.000 0.998 0.996 -10 10 30 50 70 -50 -30 -10 10 30 50 TEMPERATURE (°C) 70 90 0.99 0.98 0.97 -50 -30 -10 10 30 50 TEMPERATURE (°C) MAXIMUM TRANSIENT DURATION vs. RESET COMPARATOR OVERDRIVE RESET PULL-UP TIME vs. TEMPERATURE TA = +25°C RESET OCCURS ABOVE CURVE 80 60 VTH = 4.63V 40 20 70 90 70 90 600 500 CL = 390pF 400 300 200 CL = 100pF 100 VTH = 3.00V 0 0.994 1.00 90 100 MAXIMUM TRANSIENT DURATION (µs) MAX6314-06 1.006 1.01 TEMPERATURE (°C) SUPPLY VOLTAGE (V) NORMALIZED RESET THRESHOLD vs. TEMPERATURE (VCC FALLING) -30 RESET PULL-UP-TIME (ns) 0 1.02 0.96 0 0 NORMALIZED RESET THRESHOLD MAX6314-04 VTH = 4.63V 1.03 MAX6314-08 3 40 1.04 NORMALIZED RESET TIMEOUT PERIOD TA = +85°C VCC FALLING AT 1mV/µs MAX6314-07 SUPPLY CURRENT (µA) 5 50 POWER-DOWN RESET DELAY (µs) MAX6314-03 6 4 NORMALIZED RESET TIMEOUT PERIOD vs. TEMPERATURE (VCC RISING) POWER-DOWN RESET DELAY vs. TEMPERATURE MAX6314-05 SUPPLY CURRENT vs. SUPPLY VOLTAGE 0 10 100 1000 RESET COMP. OVERDRIVE, VTH - VCC (mV) -50 -30 -10 10 30 50 TEMPERATURE (°C) _______________________________________________________________________________________ 3 MAX6314 __________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) MAX6314 68HC11/Bidirectional-Compatible µP Reset Circuit ______________________________________________________________Pin Description PIN NAME FUNCTION 1 GND 2 RESET Active-Low Complementary Output. In addition to the normal N-channel pull-down, RESET has a P-channel pull-up transistor in parallel with a 4.7kΩ resistor to facilitate connection to µPs with bidirectional resets. See the Reset Output section. 3 MR Manual Reset Input. A logic low on MR asserts reset. Reset remains asserted as long as MR is low, and for the reset timeout period (tRP) after the reset conditions are terminated. Connect to VCC if not used. 4 VCC Supply Voltage and Reset Threshold Monitor Input Ground VCC LASERTRIMMED RESISTORS MAX6314 VREF VCC 63k RESET GENERATOR MR VCC 2µs ONE-SHOT TRANSITION FLIP-FLOP R Q 4.7k FF S RESET ACTIVE PULL-UP ENABLE COMPARATOR 0.5V GND Figure 1. Functional Diagram 4 _______________________________________________________________________________________ 68HC11/Bidirectional-Compatible µP Reset Circuit The MAX6314 has a reset output consisting of a 4.7kΩ pull-up resistor in parallel with a P-channel transistor and an N-channel pull down (Figure 1), allowing this IC to directly interface with microprocessors (µPs) that have bidirectional reset pins (see the Reset Output section). Reset Output A µP’s reset input starts the µP in a known state. The MAX6314 asserts reset to prevent code-execution errors during power-up, power-down, or brownout conditions. RESET is guaranteed to be a logic low for VCC > 1V (see the Electrical Characteristics ). Once V CC exceeds the reset threshold, the internal timer keeps reset asserted for the reset timeout period (tRP); after this interval RESET goes high. If a brownout condition occurs (monitored voltage dips below its programmed reset threshold), RESET goes low. Any time VCC dips below the reset threshold, the internal timer resets to zero and RESET goes low. The internal timer starts when VCC returns above the reset threshold, and RESET remains low for the reset timeout period. The MAX6314’s RESET output is designed to interface with µPs that have bidirectional reset pins, such as the Motorola 68HC11. Like an open-drain output, the MAX6314 allows the µP or other devices to pull RESET low and assert a reset condition. However, unlike a standard open-drain output, it includes the commonly specified 4.7kΩ pull-up resistor with a P-channel active pull-up in parallel. This configuration allows the MAX6314 to solve a problem associated with µPs that have bidirectional reset pins in systems where several devices connect to RESET. These µPs can often determine if a reset was asserted by an external device (i.e., the supervisor IC) or by the µP itself (due to a watchdog fault, clock error, or other source), and then jump to a vector appropriate for the source of the reset. However, if the µP does assert reset, it does not retain the information, but must determine the cause after the reset has occurred. The following procedure describes how this is done with the Motorola 68HC11. In all cases of reset, the µP pulls RESET low for about four E-clock cycles. It then releases RESET, waits for two E-clock cycles, then checks RESET’s state. If RESET is still low, the µP concludes that the source of the reset was external and, when RESET eventually reaches the high state, jumps to the normal reset vector. In this case, stored state information is erased and processing begins from scratch. If, on the other hand, RESET is high after the two E-clock cycle delay, the processor knows that it caused the reset itself and can jump to a different vector and use stored state information to determine what caused the reset. The problem occurs with faster µPs; two E-clock cycles is only 500ns at 4MHz. When there are several devices on the reset line, the input capacitance and stray capacitance can prevent RESET from reaching the logic-high state (0.8 x VCC) in the allowed time if only a passive pull-up resistor is used. In this case, all resets will be interpreted as external. The µP is guaranteed to sink only 1.6mA, so the rise time cannot be much reduced by decreasing the recommended 4.7kΩ pull-up resistance. The MAX6314 solves this problem by including a pullup transistor in parallel with the recommended 4.7kΩ resistor (Figure 1). The pull-up resistor holds the output high until RESET is forced low by the µP reset I/O, or by the MAX6314 itself. Once RESET goes below 0.5V, a comparator sets the transition edge flip-flop, indicating that the next transition for RESET will be low to high. As soon as RESET is released, the 4.7kΩ resistor pulls RESET up toward VCC. When RESET rises above 0.5V, the active P-channel pull-up turns on for the 2µs duration of the one-shot. The parallel combination of the 4.7kΩ pull-up and the P-channel transistor onresistance quickly charges stray capacitance on the reset line, allowing RESET to transition low to high within the required two E-clock period, even with several devices on the reset line (Figure 2). Once the one-shot times out, the P-channel transistor turns off. This process occurs regardless of whether the reset was caused by VCC dipping below the reset threshold, MR being asserted, or the µP or other device asserting RESET. Because the MAX6314 includes the standard 4.7kΩ pull-up resistor, no external pull-up resistor is required. To minimize current consumption, the internal pull-up resistor is disconnected whenever the MAX6314 asserts RESET. Manual Reset Input Many µP-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. A logic low on MR asserts reset. Reset remains asserted while MR is low, and for the reset active timeout period after MR returns high. To minimize current consumption, the internal 4.7kΩ pull-up resistor on RESET is disconnected whenever RESET is asserted. _______________________________________________________________________________________ 5 MAX6314 _______________Detailed Description MAX6314 68HC11/Bidirectional-Compatible µP Reset Circuit VCC VCC 68HC11 4.7k MR RESET RESET CIRCUITRY CIN RESET RESET CIRCUITRY CIN CSTRAY MAX6314 RESET CIN OTHER DEVICES Figure 2. MAX6314 Supports Additional Devices on the Reset Bus MR has an internal 63kΩ pull-up resistor, so it can be left open if not used. Connect a normally open momentary switch from MR to GND to create a manual reset function; external debounce circuitry is not required. If MR is driven from long cables or if the device is used in a noisy environment, connecting a 0.1µF capacitor from MR to ground provides additional noise immunity. __________Applications Information Negative-Going VCC Transients In addition to issuing a reset to the µP during power-up, power-down, and brownout conditions, these devices are relatively immune to short-duration negative-going transients (glitches). The Typical Operating Characteristics show the Maximum Transient Duration vs. Reset Threshold Overdrive, for which reset pulses are not generated. The graph was produced using negativegoing pulses, starting at VRST max and ending below the programmed reset threshold by the magnitude indicated (reset threshold overdrive). The graph shows the maximum pulse width that a negative-going V CC transient may typically have without causing a reset pulse to be issued. As the amplitude of the transient increases (i.e., goes farther below the reset threshold), the maximum allowable pulse width decreases. A 0.1µF bypass capacitor mounted close to VCC provides additional transient immunity. Ensuring a Valid RESET Output Down to VCC = 0V When V CC falls below 1V, RESET no longer sinks current—it becomes an open circuit. Therefore, highimpedance CMOS-logic inputs connected to RESET can drift to undetermined voltages. This presents no problem in most applications, since most µP and other circuitry is inoperative with VCC below 1V. However, in applications where RESET must be valid down to VCC = 0V, adding a pull-down resistor to RESET will cause any stray leakage currents to flow to ground, holding RESET low (Figure 3). R1’s value is not critical; 100kΩ is large enough not to load RESET and small enough to pull RESET to ground. VCC MAX6314 RESET R1 GND Figure 3. RESET Valid to VCC = Ground Circuit 6 _______________________________________________________________________________________ 68HC11/Bidirectional-Compatible µP Reset Circuit MAX6314 VCC tRP OR µC RESET DELAY RESET 0.5V tS RESET PULLED LOW BY µC OR RESET GENERATOR 0.8 x VCC tR ACTIVE PULL-UP TURNS ON Figure 4. RESET Timing Diagram __________________________________________Ordering and Marking Information NOMINAL VTH (V) PART† MAX6314US50D1-T MAX6314US49D1-T MAX6314US48D1-T MAX6314US47D1-T MAX6314US46D1-T MAX6314US45D1-T MAX6314US44D1-T††† MAX6314US43D1-T MAX6314US42D1-T MAX6314US41D1-T MAX6314US40D1-T MAX6314US39D1-T MAX6314US38D1-T MAX6314US37D1-T MAX6314US36D1-T MAX6314US35D1-T MAX6314US34D1-T MAX6314US33D1-T MAX6314US32D1-T MAX6314US31D1-T MAX6314US30D1-T MAX6314US29D1-T 5.00 4.90 4.80 4.70 4.63 4.50 4.39 4.30 4.20 4.10 4.00 3.90 3.80 3.70 3.60 3.50 3.40 3.30 3.20 3.08 3.00 2.93 MIN tRP (ms) PKG. TOP MARK†† PART† 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 AA_ _ AB_ _ AC_ _ AD_ _ AE_ _ AF_ _ AG_ _ AH_ _ AI_ _ AJ_ _ AK_ _ AL_ _ CA_ _ CB_ _ CC_ _ CD_ _ CE_ _ CF_ _ CG_ _ CH_ _ CI_ _ CJ_ _ MAX6314US28D1-T MAX6314US27D1-T MAX6314US26D1-T††† MAX6314US25D1-T MAX6314US50D2-T MAX6314US49D2-T MAX6314US48D2-T MAX6314US47D2-T MAX6314US46D2-T MAX6314US45D2-T MAX6314US44D2-T††† MAX6314US43D2-T MAX6314US42D2-T MAX6314US41D2-T MAX6314US40D2-T MAX6314US39D2-T MAX6314US38D2-T MAX6314US37D2-T MAX6314US36D2-T MAX6314US35D2-T MAX6314US34D2-T MAX6314US33D2-T NOMINAL VTH (V) 2.80 2.70 2.63 2.50 5.00 4.90 4.80 4.70 4.63 4.50 4.39 4.30 4.20 4.10 4.00 3.90 3.80 3.70 3.60 3.50 3.40 3.30 MIN tRP (ms) PKG. TOP MARK†† 1 1 1 1 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 CK_ _ CL_ _ CM_ _ CN_ _ CO_ _ CP_ _ CQ_ _ CR_ _ CS_ _ CT_ _ CU_ _ CV_ _ CW_ _ CX_ _ CY_ _ CZ_ _ DA_ _ DB_ _ DC_ _ DD_ _ DE_ _ DJ_ _ †The MAX6314 is available in a SOT143 package, -40°C to +85°C temperature range. ††The first two letters in the package top mark identify the part, while the remaining two letters are the lot tracking code. †††Sample stocks generally held on the bolded products; also, the bolded products have 2,500 piece minimum-order quantities. Non-bolded products have 10,000 piece minimum-order quantities. Contact factory for details. Note: All devices available in tape-and-reel only. Contact factory for availability. _______________________________________________________________________________________ 7 MAX6314 68HC11/Bidirectional-Compatible µP Reset Circuit _____________________________Ordering and Marking Information (continued) PART† NOMINAL VTH (V) MAX6314US32D2-T MAX6314US31D2-T MAX6314US30D2-T MAX6314US29D2-T MAX6314US28D2-T MAX6314US27D2-T MAX6314US26D2-T††† MAX6314US25D2-T MAX6314US50D3-T MAX6314US49D3-T MAX6314US48D3-T MAX6314US47D3-T MAX6314US46D3-T††† MAX6314US45D3-T MAX6314US44D3-T††† MAX6314US43D3-T MAX6314US42D3-T MAX6314US41D3-T MAX6314US40D3-T MAX6314US39D3-T MAX6314US38D3-T MAX6314US37D3-T MAX6314US36D3-T MAX6314US35D3-T MAX6314US34D3-T MAX6314US33D3-T MAX6314US32D3-T MAX6314US31D3-T††† MAX6314US30D3-T MAX6314US29D3-T††† 3.20 3.08 3.00 2.93 2.80 2.70 2.63 2.50 5.00 4.90 4.80 4.70 4.63 4.50 4.39 4.30 4.20 4.10 4.00 3.90 3.80 3.70 3.60 3.50 3.40 3.30 3.20 3.08 3.00 2.93 MIN tRP (ms) PKG. TOP MARK†† PART† 20 20 20 20 20 20 20 20 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 DK_ _ DL_ _ DM_ _ DN_ _ DO_ _ DP_ _ DQ_ _ DR_ _ DS_ _ DT_ _ DU_ _ DV_ _ DW_ _ DX_ _ DY_ _ DZ_ _ EA_ _ EB_ _ EC_ _ EG_ _ EH_ _ EI_ _ EJ_ _ EK_ _ EL_ _ EM_ _ EN_ _ EO_ _ EP_ _ ES_ _ MAX6314US28D3-T MAX6314US27D3-T MAX6314US26D3-T††† MAX6314US25D3-T MAX6314US50D4-T MAX6314US49D4-T MAX6314US48D4-T MAX6314US47D4-T MAX6314US46D4-T MAX6314US45D4-T MAX6314US44D4-T††† MAX6314US43D4-T MAX6314US42D4-T MAX6314US41D4-T MAX6314US40D4-T MAX6314US39D4-T MAX6314US38D4-T MAX6314US37D4-T MAX6314US36D4-T MAX6314US35D4-T MAX6314US34D4-T MAX6314US33D4-T MAX6314US32D4-T MAX6314US31D4-T MAX6314US30D4-T MAX6314US29D4-T MAX6314US28D4-T MAX6314US27D4-T MAX6314US26D4-T††† MAX6314US25D4-T NOMINAL VTH (V) 2.80 2.70 2.63 2.50 5.00 4.90 4.80 4.70 4.63 4.50 4.39 4.30 4.20 4.10 4.00 3.90 3.80 3.70 3.60 3.50 3.40 3.30 3.20 3.08 3.00 2.93 2.80 2.70 2.63 2.50 MIN tRP (ms) PKG. TOP MARK†† 140 140 140 140 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 ET_ _ EU_ _ EV_ _ EW_ _ EX_ _ EY_ _ EZ_ _ FA_ _ FB_ _ FC_ _ FD_ _ FE_ _ FF_ _ FG_ _ FH_ _ FI_ _ FJ_ _ FK_ _ FL_ _ FM_ _ FN_ _ FO_ _ FP_ _ FQ_ _ FR_ _ FS_ _ FT_ _ FU_ _ FV_ _ FW_ _ †The MAX6314 is available in a SOT143 package, -40°C to +85°C temperature range. ††The first two letters in the package top mark identify the part, while the remaining two letters are the lot tracking code. †††Sample stocks generally held on the bolded products; also, the bolded products have 2,500 piece minimum-order quantities. Non-bolded products have 10,000 piece minimum-order quantities. Contact factory for details. Note: All devices available in tape-and-reel only. Contact factory for availability. Chip Information TRANSISTOR COUNT: 519 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.