MIC8114 Micrel MIC8114 Microprocessor Reset Circuit General Description Features The MIC8114 is an inexpensive microprocessor supervisory circuit that monitors the power supply in microprocessor based systems. The function of this device is to assert a reset if 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 MIC1814 comes in a 4-pin SOT-143 package. • • • • • • • Precision voltage monitor for 3.3V power supplies Specifically tailored to the AMD Elan SC400/410 /RESET remains valid with VCC as low as 1V 5µA typical supply current 790ms minimum reset pulse width Manual reset input Available in 4-Pin SOT-143 Package Applications • • • • • Portable equipment Intelligent instruments Critical microprocessor power monitoring Printers/computers Embedded controllers Ordering Information Part Number Marking Operating Temp. Range Package MIC8114TU NV –40°C to +85°C 4-lead SOT-143 No MIC8114TUY NV –40°C to +85°C 4-lead SOT-143 Yes Typical Application Pb-Free VCC VCC VCC MIC81 14 µP MR RESET RESET Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com July 2005 1 MIC8114 MIC8114 Micrel Pin Configuration GND 1 4 VCC MIC81 14 3 MR RESET 2 4-Lead SOT-143 Pin Description Pin Number Pin Name Pin Function 1 GND IC Ground Pin 2 /RESET /RESET goes low if either VCC falls below the supply reset threshold voltage or if /MR is asserted. /RESET remains asserted for one reset timeout period after both VCC exceeds the supply reset threshold voltage and /MR is deasserted. 3 /MR 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 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. 4 VCC Power supply Input. MIC8114 2 July 2005 MIC8114 Micrel Absolute Maximum Ratings(Note 1) Operating Ratings(Note 2) Terminal Voltage (VCC) .........................................................–0.3V to +6.0V (/MR) ..................................................–0.3V (VCC + 0.3V) Input Current (VCC, /MR) ............................................ 20mA Output Current (/RESET) ........................................... 20mA Rate of Rise (VCC) ..................................................100V/µS Lead Temperature (soldering, 10 sec.) ...................... 300°C Storage Temperature (TS) ........................ –65°C to +150°C ESD Rating .................................................................... 3kV Operating Temperature Range MIC8114TU ............................................ –40°C to +85°C Power Dissipation (TA = +70°C) .............................. 320mW Electrical Characteristics For typical values, VCC = 3.3V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted Symbol Parameter Condition VCC Operating Voltage Range TA = –40°C to 85°C VTH Reset Voltage Threshold VOH /RESET Output Voltage ICC Supply Current tRST /RESET Output Voltage, VOL /MR Minimum Pulse Width Typ 1 Reset Timeout Period VOL Min VCC = VTH min, ISINK = 1.2mA VCC = 1V, ISINK = 50µA, TA = –40°C to +85°C Units 5.5 V 5 15 µA 3.00 3.08 3.15 V 790 1200 1800 ms 0.8×VCC ISOURCE = 500µA Max V 0.3 V 0.3 V 10 /MR to Reset Delay µs 0.5 /MR Input Threshold, VIH 0.7×VCC /MR Pull-Up Resistance 10 /MR Input Threshold, VIL /MR Glitch Immunity V 20 100 Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. µs 0.25×VCC 30 kΩ ns Timing Diagram VCC VTH /MR /RESET tRST tRST Reset Timing Diagram July 2005 3 MIC8114 MIC8114 Micrel Functional Diagram VCC MR (3) RESET GENERATOR RESET (2) + VCC (4) Reset Threshold (V) - GND (1) MIC8114 4 July 2005 MIC8114 Micrel Applications Information /RESET Valid at Low Voltage A resistor can be added from the /RESET pin-to-ground to ensure the /RESET output remains low with VCC down to 0V. A 100kΩ resistor connected from /RESET-to-ground is recommended. The resistor should be large enough not to load the /RESET output and small enough to pull-down any stray leakage currents Microprocessor Reset The /RESET pin is asserted whenever VCC falls below the reset threshold voltage. The reset pin remains asserted for a period of 790ms after VCC has risen above the reset threshold voltage. 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 1V. VCC Transients The MIC8114 is relatively immune to the negative-going VCC glitches below the reset threshold. Typically, a negative-going transient 125mV below the reset threshold with a duration of 20µs or less will not cause a reset. VCC VCC VCC MIC81 14 µP RESET RESET 100K /RESET Valid to VCC = 0V July 2005 5 MIC8114 MIC8114 Micrel Package Information 0.950 (0.0374) TYP 1.40 (0.055) 2.50 (0.098) 1.20 (0.047) 2.10 (0.083) CL CL DIMENSIONS: MM (INCH) 1.12 (0.044) 0.81 (0.032) 3.05 (0.120) 2.67 (0.105) 0.800 (0.031) TYP 0.400 (0.016) TYP 3 PLACES 8 0 0.10 (0.004) 0.013 (0.0005) 0.150 (0.0059) 0.089 (0.0035) 0.41 (0.016) 0.13 (0.005) 4-Lead SOT-143 (UT) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com The information furnished by Micrel in this datasheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2005 Micrel, Incorporated. MIC8114 6 July 2005