MIC1810 Micrel MIC1810 Microprocessor Reset Circuit General Description Features The MIC1810 is an inexpensive microprocessor supervisory circuit that monitors power supplies in microprocessor based systems. The function of these devices is to assert a reset if the power supply drops below a designated reset threshold level. Several different reset threshold levels are available to accommodate 5%, 10%, or 15% drop in 5V powered systems. The MIC1810 has an active low /RESET output. The reset output is guaranteed to remain asserted for a minimum of 100ms after VCChas risen above the designated reset threshold level. The MIC1810 comes in a 3-pin SOT-23 package. • Precision voltage monitor for 5%, 10%, or 15% drop in 5V power supplies • /RESET remains valid with VCC as low as 1V • 5µA supply current (typical) • 100ms minimum reset pulse width • No external components required • Available in 3-pin SOT-23 package Ordering Information Applications • • • • • Portable equipment Intelligent instruments Critical microprocessor power monitoring Printers/computers Embedded controllers Marking* Threshold Voltage Operating Temp. Range Package Pb-Free MIC1810-5U NA 4.62V –40°C to +85°C SOT-23 No MIC1810-10U NB 4.37V –40°C to +85°C SOT-23 No MIC1810-15U NC 4.12V –40°C to +85°C SOT-23 No MIC1810-5UY NA 4.62V –40°C to +85°C SOT-23 Yes Part Number MIC1810-10UY NB 4.37V –40°C to +85°C SOT-23 Yes MIC1810-15UY NC 4.12V –40°C to +85°C SOT-23 Yes * Underbar symbol may not be to scale Typical Application VCC VCC VCC MIC1810 µP 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 MIC1810 MIC1810 Micrel Pin Configuration RESET 1 MIC1810 3 GND VCC 2 3-Lead SOT-23 Pin Description Pin Number Pin Name 1 /RESET MIC1810 Pin Function /RESET goes low if VCC falls below the reset threshold and remains asserted for one reset timeout period (100ms min) after VCC exceeds the reset threshold. 2 VCC Power supply input. 3 GND IC ground pin 2 July 2005 MIC1810 Micrel Absolute Maximum Ratings(Note 1) Operating Ratings(Note 2) Terminal Voltage (VCC) ....................................–0.3V to +6V Input Current (VCC)..................................................... 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, Note 3 ....................................................... 3kV Operating Temperature Range MIC1810-5U ........................................... –40°C to +85°C MIC1810-10U ......................................... –40°C to +85°C MIC1810-15U ......................................... –40°C to +85°C Power Dissipation (TA = +70°C) .............................. 320mW Electrical Characteristics For typical values VCC = 5V, TA = 25°C; bold values indicate –40°C ≤ TA ≤ +85°C; unless noted Symbol ICC Parameter Condition Operating Voltage Range TA = –40°C to +85°C Supply Current VTH Reset Voltage Threshold tRST /RESET Output Voltage, High VOL Max Units 5.5 V 5 20 µA MIC1810-5 4.50 4.62 4.75 V MIC1810-10 4.25 4.37 4.50 V MIC1810-15 4.00 4.12 4.24 V 100 150 250 ms VCC–1.5 ISOURCE = 800µA /RESET Output Voltage, Low Typ 1 Reset Timeout Period VOH Min VCC = VTH min., ISINK = 10mA VCC ≥ 1V, ISINK = 50µA 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. V 0.4 V 0.3 V Timing Diagram VCC VTH VTH tRST tRST /RESET Reset Timing Diagram July 2005 3 MIC1810 MIC1810 Micrel Functional Diagram + VCC (2) Reset Threshold (VTH) RESET GENERATOR - RESET (1) GND (3) MIC1810 4 July 2005 MIC1810 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. See Figure below. Microprocessor Reset The /RESET pin is asserted whenever VCC falls below the reset threshold voltage. The reset pin remains asserted for a period of tRST 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 MIC1810 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 20µs or less will not cause an unwanted reset. VCC VCC VCC MIC1810 µP RESET RESET 100K /RESET Valid to VCC = 0V July 2005 5 MIC1810 MIC1810 Micrel Package Information 1.40 (0.055) 2.50 (0.098) 1.19 (0.047) 2.10 (0.083) C L 2.36 (0.093) 2.28 (0.090) C L DIMENSIONS : MM (INCH) 1.15 (0.045) 0.76 (0.030) 3.05 (0.120) 2.67 (0.105) 0.445 (0.0175) TYP 3 PLACES 0.15 (0.006) 0.076 (0.0030) 8 0 0.10 (0.004) 0.013 (0.0005) 0.41 (0.016) 0.13 (0.005) 3-Pin SOT-23 Small Outline Transistor 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. MIC1810 6 July 2005