MIC811/MIC812 Microprocessor Reset Circuits MIC811/MIC812 Microprocessor Reset Circuits Description Pin Configuration The MIC811/MIC812 are inexpensive microprocessor supervisory circuits that monitor power supplies in microprocessor based systems. The function of these devices is to assert a reset if either the power supply drops below a designated reset threshold level or MR is forced low. Several different reset threshold levels are available to accomodate 3V, 3.3V or 5V powered systems. The MIC811 has an active low RESET output, while the MIC812 offers an active high RESET output. The reset output is guaranteed to remain asserted for a minimum of 140ms after VCC has risen above the designated reset threshold level. The MIC811/MIC812 come in a 4pin SOT-143 package. Typical Applications · Portable Equipment · Intelligent Instruments · Critical Microprocessor Power Monitoring · Printers/Computers · Controllers Reset Threshold Voltage (V) 4.63 4.38 4.00 3.08 2.93 2.63 Device Suffix L M J T S R Top View GND 1 4 VCC MIC811 RESET 2 3 MR GND 1 4 VCC MIC812 RESET 2 Features RESET Remains Valid with VCC as Low · as 1.4V Voltage Monitor for 3V, 3.3V · Precision or 5V Power Supplies · Available in 4-Pin SOT-143 Package · <15µA Supply Current · 140ms Minimum Reset Pulse Width · Manual Reset Input Typical Operating Circuit Ordering Information Part MIC811_U MIC812_U Package 4-Lead SOT-143 4-Lead SOT-143 Temp. Range -40°C to +85°C -40°C to +85°C Place the device suffix of desired reset threshold voltage from table above in blank to complete the part number. 3 MR VCC VCC VCC MIC811 µP MR RESET RESET 1 MIC811/MIC812 Microprocessor Reset Circuits Absolute Maximum Ratings Terminal Voltage VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V MR . . . . . . . . . . . . . . . . . . . . . -0.3V to (VCC + 0.3V) Input Current, VCC, MR . . . . . . . . . . . . . . . . . . . . 20mA Output Current, RESET, RESET . . . . . . . . . . . . . .20mA Rate of Rise, VCC . . . . . . . . . . . . . . . . . . . . . . 100V/µs Operating Temperature Range MIC81--U . . . . . . . . . . . . . . . . . . . . . . . . -40°C to 85°C Storage Temperature Range . . . . . . . . . . . . .-65°C to 150°C Lead Temperature (Soldering - 10 sec.) . . . . . . . . . . . 300°C Power Dissipation (TA = +70°C) . . . . . . . . . . . . . . . . 320mW Stresses above those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent device failure. Functionality at or above these limits is not implied. Exposure to absolute maximum ratings for extended periods may affect device reliability. Operating ranges define those limits between which the functionality of the device is guaranteed. Electrical Characteristics VCC = 5V for MIC81-L/M/J, VCC = 3.3V for MIC81-S/T, VCC = 3V for MIC81-R, TA = Operating Temperature Range, unless otherwise noted. Parameter Conditions Operating Voltage Range, VCC TA = 0°C to 70°C TA = -40°C to 85°C Supply Current, ICC MIC811L/M/J, MIC812L/M/J VCC < 3.6V, MIC811R/S/T, MIC812R/S/T Reset Voltage Threshold, VTH MIC811L, MIC812L MIC811M, MIC812M MIC811J, MIC812J MIC811T, MIC812T MIC811S, MIC812S MIC811R, MIC812R Reset Timeout Period RESET Output Voltage, VOH ISource = 800µA, MIC811L/M/J ISource = 500µA, MIC811R/S/T RESET Output Voltage, VOL VCC=VTH Min., ISink=3.2mA, MIC811L/M/J VCC=VTH Min., ISink =1.2mA, MIC811R/S/T VCC>1.4V, ISink =50µA, TA = 0°C to 70°C VCC>1.6V, ISink =50µA, TA = -40°C to 85°C RESET Output Voltage, VOH 1.8V < VCC < VTH Min., ISource = 150µA RESET Output Voltage, VOL ISink=3.2mA, MIC812L/M/J ISink=1.2mA, MIC812R/S/T MR Minimum Pulse Width Min Max Units 5.5 5.5 V 9 6 15 10 µA 4.50 4.25 3.89 3.00 2.85 2.55 4.63 4.38 4.00 3.08 2.93 2.63 4.75 4.50 4.10 3.15 3.00 2.70 V 140 240 560 ms 1.4 1.6 VCC - 1.5V 0.8 X VCC 0.8 X VCC 0.4 0.3 MR Input Threshold, VIL VCC > VTH Max., MIC81_L/M_ MIC81_R/S/T 2 µs 2.3 0.7 X VCC 10 V µs 0.5 VCC > VTH Max., MIC81_L/M/J MIC81_R/S/T V V 10 MR Input Threshold, VIH MR Glitch Immunity V 0.4 0.3 0.3 0.3 MR to Reset Delay MR Pull-Up Resistance Typ V 20 100 0.8 0.25 X VCC V 30 kΩ ns MIC811/MIC812 Microprocessor Reset Circuits Pin Functions Pin No. Pin Name Description MIC811 MIC812 GND 1 1 RESET 2 N/A RESET goes low if VCC falls below the reset threshold and remains asserted for one reset timeout period (140ms min.) after VCC exceeds the reset threshold. RESET N/A 2 RESET goes high if VCC falls below the reset threshold and remains asserted for one reset timeout period (140ms min.) after VCC exceeds the reset threshold. MR 3 3 Manual reset input. A logic low on MR forces a reset. The reset will remain asserted as long as MR is held low and for one reset timeout period (140ms min.) after MR goes high. This input can be shorted to ground via a switch or driven from CMOS or TTL logic. Float if unused. VCC 4 4 Power supply input, 3V, 3.3V or 5V. IC Ground Pin. 3 MIC811/MIC812 Microprocessor Reset Circuits Block Diagram + VCC (4) Reset - RESET Threshold (V) GENERATOR MR (3) GND (1) Figure 1. MIC811/812 Block Diagram 4 RESET (2) RESET (MIC812) MIC811/MIC812 Microprocessor Reset Circuits Circuit Description Microprocessor Reset The RESET pin is asserted whenever VCC falls below the reset threshold voltage or if MR (manual reset) is forced low. The reset pin remains asserted for a period of 240ms after VCC has risen above the reset threshold voltage or MR has returned high. The reset function ensures the microprocessor is properly reset and powers up into a known condition after a power failure. RESET will remain valid with VCC as low as 1.4V. VCC Transients The MIC811/MIC812 are relatively immune to negativegoing VCC glitches below the reset threshold. Typically, a negative-going transient 125mV below the reset threshold with a duration of 50µs (25µs for MIC81_R/S/T) or less will not cause an unwanted reset. VCC Vthr MR t1 t1 RESET Figure 2. Reset Timing Diagram Interfacing to Bidirectional Reset Pins The MIC811/MIC812 can interface with µPs with bidirectional reset pins by connecting a 4.7KΩ resistor in series with the MIC811/MIC812 output and the µP reset pin. VCC VCC VCC MIC811 µP RESET RESET 100K RESET Valid to 0V A resistor can be added from the RESET pin to ground to ensure the RESET output remains low with V CC down to 0V. A 100KΩ resistor connected from RESET to ground is recommended. The size of the resistor should be large enough to not load the RESET output and small enough to pull-down any stray leakage currents. Figure 3. RESET Valid to VCC = 0V. 5 MIC811/MIC812 Microprocessor Reset Circuits Alternate Source Cross Reference Guide Industry P/N 6 MIC Direct Replacement MAX811JEUS-T MIC811JU MAX811LEUS-T MAX811MEUS-T MAX811REUS-T MAX811SEUS-T MAX811TEUS-T MAX812JEUS-T MIC811LU MIC811MU MIC811RU MIC811SU MIC811TU MIC812JU MAX812LEUS-T MAX812MEUS-T MIC812LU MIC812MU MAX812REUS-T MAX812SEUS-T MIC812RU MIC812SU MAX812TEUS-T MIC812TU MIC811/MIC812 Microprocessor Reset Circuits Packaging Information U Package, 4-Pin SOT-143 Small-Outline Transistor Package 0.079 0.071 0.055 0.047 0.098 0.083 0.021 0.037 0.030 0.015 0.120 0.105 0.040 0.031 0.080 0.070 0.0059 0.0035 0.004 0.001 0-8¼ 0.010 0.005 Dimensions are in inches. Device Marking Information Lot Code KJXX KLXX KMXX KRXX KSXX KTXX LJXX LLXX LMXX LRXX LSXX LTXX = = = = = = = = = = = = MIC811J MIC811L MIC811M MIC811R MIC811S MIC811T MIC812J MIC812L MIC812M MIC812R MIC812S MIC812T 7 MIC811/MIC812 Microprocessor Reset Circuits Packaging Information Tape and Reel Information 4.0–0.1 fl1.5–0.1 1.75–0.1 2.0–0.05 3.5–0.05 8.0–0.3 4.0–0.1 2.7–0.1 1.2–0.1 3.1–0.1 Dimensions are in millimeters. 8 fl1.1–0.1