MIC811/812 Micrel MIC811/812 Microprocessor Reset Circuits General Description Features The MIC811 and MIC812 are inexpensive microprocessor supervisory circuits 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. Several different reset threshold levels are available to accommodate 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 designed reset threshold level. Having a push-pull output stage, the MIC811/812 does not require a pull-up resistor at the output. The MIC811/812 comes in a 4-pin SOT-143 package. If a microprocessor voltage supervisor with an open-drain output stage is needed, see MIC6315. • Precision voltage monitor for 3V, 3.3V or 5V power supplies • /RESET remains valid with VCC as low as 1V • 5µA typical supply current • 140ms minimum reset pulse width available • Manual reset input • Available in 4-pin SOT-143 package Applications • • • • • Typical Application Portable equipment Intelligent instruments Critical microprocessor power monitoring Printers/computers Embedded controllers VCC VCC VCC MIC81 1 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 September 2005 1 MIC811/812 MIC811/812 Micrel Ordering Information Part Number Standard Marking Pb-Free Standard Pb-Free Threshold Voltage Operating Temp. Range Package MIC811LU MIC811LUY KL KL 4.63 –40°C to +85°C 4-lead SOT-143 MIC811MU MIC811MUY KM KM 4.38 –40°C to +85°C 4-lead SOT-143 MIC811JU MIC811JUY KJ KJ 4.00 –40°C to +85°C 4-lead SOT-143 MIC811TU MIC811TUY KT KT 3.08 –40°C to +85°C 4-lead SOT-143 MIC811SU MIC811SUY KS KS 2.93 –40°C to +85°C 4-lead SOT-143 MIC811RU MIC811RUY KR KR 2.63 –40°C to +85°C 4-lead SOT-143 MIC812LU MIC812LUY LL LL 4.63 –40°C to +85°C 4-lead SOT-143 MIC812MU MIC812MUY LM LM 4.38 –40°C to +85°C 4-lead SOT-143 MIC812JU MIC812JUY LJ LJ 4.00 –40°C to +85°C 4-lead SOT-143 MIC812TU MIC812TUY LT LT 3.08 –40°C to +85°C 4-lead SOT-143 MIC812SU MIC812SUY LS LS 2.93 –40°C to +85°C 4-lead SOT-143 MIC812RU MIC812RUY LR LR 2.63 –40°C to +85°C 4-lead SOT-143 MIC811/812 2 September 2005 MIC811/812 Micrel Pin Configuration GND 1 4 VCC MIC811 RESET 2 3 MR GND 1 4 VCC MIC812 RESET 2 3 MR MIC811 4-Lead SOT-143 MIC812 4-Lead SOT-143 Pin Description Pin Number MIC811 Pin Number MIC812 Pin Name Pin Function IC Ground Pin 1 1 GND 2 N/A /RESET /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 N/A 2 RESET 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 3 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 (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. 4 4 VCC Power Supply Input. September 2005 3 MIC811/812 MIC811/812 Micrel Absolute Maximum Ratings(Note 1) Operating Ratings(Note 2) Terminal Voltage (VCC) .................................–0.3V to +6.0V Input Current (VCC, /MR) ............................................ 20mA Output Current (/RESET, RESET) .............................. 20mA Lead Temperature (soldering, 10 sec.) ...................... 300°C Storage Temperature (TS) .......................... –65°C to 150°C Rate of Rise (VCC) .................................................. 100V/µs ESD Rating, Note 3 ....................................................... 3kV Operating Temperature Range MIC811 ..................................................... –40°C to 85°C MIC812 ..................................................... –40°C to 85°C Power Dissipation (TA = +70°C) .............................. 320mW Electrical Characteristics For typical values, VCC = 5V for MIC8_L/M/J, VCC = 3.3V for MIC8_S/T, VCC = 3V for MIC8_R; 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 ICC Supply Current Min Reset Voltage Threshold tRST /RESET Output Voltage VOL /RESET Output Voltage RESET Output Voltage VOL RESET Output Voltage /MR Minimum Pulse Width µA 5 10 µA MIC811R, MIC812R: VCC = 3.0V, no load MIC811L, MIC812L 5 10 µA 4.50 4.63 4.75 V MIC811M, MIC812M 4.25 4.38 4.50 V MIC811J, MIC812J 3.89 4.00 4.10 V MIC811T, MIC812T 3.00 3.08 3.15 V MIC811S, MIC812S 2.85 2.93 3.00 V MIC811R, MIC812R 2.55 2.63 2.70 V 140 240 560 ms ISOURCE = 800µA, MIC811L/M/J ISOURCE = 500µA, MIC811R/S/T VCC = VTH min., ISINK = 3.2mA, MIC811L/M/J VCC > 1V, ISINK = 50µA, TA = –40° to +85°C 1.8V < VCC < VTH min., ISOURCE = 150µA ISINK = 3.2mA, MIC812L/M/J ISINK = 1.2mA, MIC812R/S/T VCC–1.5V V 0.8×VCC V 0.8×VCC 0.4 V 0.3 V 0.3 V V 0.4 0.3 10 /MR to Reset Delay /MR Input Threshold VCC > VTH max., MIC81_L/M/J VIL /MR Input Threshold VCC . VTH max., MIC81-L/M/J MIC81_R/S/T V 0.7×VCC 10 /MR Glitch Immunity V 0.8 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. 4 V µs 2.3 MIC81-R/S/T /MR Pull-Up Resistance V µs 0.5 VIH MIC811/812 V 15 VCC = VTH min., ISINK = 1.2mA, MIC811R/S/T VOH Units 5.5 5 Reset Timeout Period VOH Max MIC811L/M/J, MIC812L/M/J: VCC = 5.0V, no load MIC811S/T, MIC812S/T VCC = 3.3V, no load VTH Typ 1 0.25×VCC 30 V kΩ ns September 2005 MIC811/812 Micrel Timing Diagram VCC VTH /MR tRST tRST /RESET Reset Timing Diagram Functional Diagram + VCC (4) Reset Threshold (V) - RESET GENERATOR RESET (2) RESET (MIC812) MR (3) GND (1) September 2005 5 MIC811/812 MIC811/812 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 the /RESET to ground is recommended. The size of the resistor should be large enough not to load the output excessively and small enough to pull-down any stray leakage currents. Microprocessor Reset The /RESET (or RESET) pin is asserted whenever VCC falls below the reset threshold voltage. The /RESET pin remains asserted for a period of 140ms after VCC has risen above the reset threshold voltage. The reset function ensures that the microprocessor is properly reset and powers up in a known condition after a power failure. /RESET will remain valid with VCC as low as 1V. VCC Transients The MIC811/812 are 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 20µs or less will not cause a reset. Interfacing to Bidirectional Reset Pins The MIC811/812 can interface with µPs with bidirectional reset pins by connecting a 4.7kΩ resistor in series with the MIC811/812 output and the µP reset pin. MIC811/812 VCC VCC VCC MIC81 1 µP RESET RESET 100K Reset Valid to VCC = 0V 6 September 2005 MIC811/812 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 (M3) 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. September 2005 7 MIC811/812