MIC8114 Microprocessor Reset Circuit MIC8114 Microprocessor Reset Circuit Description Pin Configuration The MIC8114 is an inexpensive microprocessor reset circuit that monitor power supplies in microprocessor based systems. The function of this device is to assert a reset if either the power supply drops below a designated reset threshold level or MR is forced low. The MIC8114 has an active low RESET output. The reset output is guaranteed to remain asserted for a minimum of 790ms after VCC has risen above the designated reset threshold level. The MIC8114 comes in a 4-pin SOT-143 package. Top View GND 1 4 VCC MIC81 14 RESET 2 3 MR Features Typical Applications · Portable Equipment · Intelligent Instruments · Critical Microprocessor Power Monitoring · Printers/Computers · Controllers · RESET Remains Valid with VCC as Low as 1.4V Voltage Monitor for 3.3V · Precision Power Supplies · Available in 4-Pin SOT-143 Package · <15µA Supply Current · 790ms Minimum Reset Pulse Width · Manual Reset Input · Specifically tailored to the reset requirements of the AMD Elan SC400/410 Typical Operating Circuit VCC Ordering Information Part MIC8114TU Package 4-Lead SOT-143 Temp. Range -40°C to +85°C Place the device suffix of desired reset threshold voltage from table above in blank to complete the part number. VCC VCC MIC81 14 µP MR RESET RESET 1 MIC8114 Microprocessor Reset Circuit 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 . . . . . . . . . . . . . . 20mA Rate of Rise, VCC . . . . . . . . . . . . . . . . . . . . . . 100V/µs Operating Temperature Range MIC8114TU . . . . . . . . . . . . . . . . . . . . . . . . -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 = 3.3V for MIC8114T, TA = Operating Temperature Range, unless otherwise noted. Parameter Operating Voltage Range, VCC Conditions TA = 0°C to 70°C TA = -40°C to 85°C Min Typ Max Units 5.5 5.5 V 9 15 µA 1.4 1.6 Supply Current, ICC Reset Voltage Threshold, VTH 3.00 3.08 3.15 V Reset Timeout Period 790 1200 1800 ms RESET Output Voltage, VOH ISource = 500µA RESET Output Voltage, VOL VCC=VTH Min., ISink =1.2mA VCC>1.4V, ISink =50µA, TA = 0°C to 70°C VCC>1.6V, ISink =50µA, TA = -40°C to 85°C MR Minimum Pulse Width 0.8 X VCC 0.3 0.3 0.3 MR Glitch Immunity 2 µs 0.5 0.7 X VCC V MR Input Threshold, VIL MR Pull-Up Resistance 10 V V V µs 10 MR to Reset Delay MR Input Threshold, VIH V 20 100 0.25 X VCC V 30 kΩ ns MIC8114 Microprocessor Reset Circuit Pin Functions Pin Name Pin No. Description GND 1 IC Ground Pin. RESET 2 RESET goes low if either VCC falls below the supply reset threshold or if MR is asserted. RESET remains asserted for one reset timeout period (790ms min.) after both VCC exceeds the supply reset threshold and MR is deasserted. MR 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 (790ms) min.) after MR goes high. This input can be shorted to ground via a switch or driven from CMOS or TTl logic. Pulled high internally through a 20kΩ resistor. Float if unused. VCC 4 Power supply input. 3 MIC8114 Microprocessor Reset Circuit Block Diagram VCC MR (3) RESET GENERATOR + VCC (4) Reset - Threshold (V) GND (1) Figure 1. MIC8114 Block Diagram 4 RESET (2) MIC8114 Microprocessor Reset Circuit 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 at least 790ms 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 MIC8114 is relatively immune to negative-going VCC glitches below the reset threshold. Typically, a negative-going transient 125mV below the reset threshold with a duration of 25µs or less will not cause an unwanted reset. VCC VCC VCC MIC81 14 µP RESET RESET 100K VCC Vthr MR t1 t1 RESET Figure 2. Reset Timing Diagram 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 MIC8114 Microprocessor Reset Circuit 6 MIC8114 Microprocessor Reset Circuit 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 NVXX = MIC8114 7 MIC8114 Microprocessor Reset Circuit 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