MIC6315 Micrel MIC6315 Open-Drain µP Reset Circuit General Description Features The MIC6315 is an inexpensive reset generator circuit that monitors 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 MIC6315 has an active low, open-drain /RESET output. The reset output is guaranteed to remain asserted for a minimum of either 20ms, 140ms, or 1100ms after VCC has risen above the designed reset threshold level. The MIC6315 comes in a 4-pin SOT-143 package. • Precision voltage monitor for 3V, 3.3V or 5V power supplies • /RESET remains valid with VCC as low as 1.4V • <15µA supply current • 20ms, 40ms, or 1100ms minimum reset pulse widths available • Manual reset input • 4-pin SOT-143 package Applications • • • • • Portable equipment Intelligent instruments Critical microprocessor power monitoring Printers/computers Embedded controllers Typical Application VCC VCC VCC 10k MIC6315 MR µP RESET RESET Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com July, 2004 1 M9999-071504 MIC6315 Micrel Ordering Information(1, 2) Marking Nominal VTH (V) MIC6315-26D2U NY 2.63 MIC6315-29D2U NM 2.93 MIC6315-30D2U N2 3.00 MIC6315-31D2U zz 3.08 MIC6315-44D2U zz 4.38 MIC6315-46D2U zz MIC6315-26D3U MIC6315-29D3U Part Number Min. tRST (ms) Operating Temp. Range 20 Package –40°C to +85°C 4-lead SOT-143 20 –40°C to +85°C 4-lead SOT-143 20 –40°C to +85°C 4-lead SOT-143 20 –40°C to +85°C 4-lead SOT-143 20 –40°C to +85°C 4-lead SOT-143 4.63 20 –40°C to +85°C 4-lead SOT-143 NR 2.63 140 –40°C to +85°C 4-lead SOT-143 NP 2.93 140 –40°C to +85°C 4-lead SOT-143 MIC6315-30D3U N3 3.00 140 –40°C to +85°C 4-lead SOT-143 MIC6315-31D3U NU 3.08 140 –40°C to +85°C 4-lead SOT-143 MIC6315-44D3U zz 4.38 140 –40°C to +85°C 4-lead SOT-143 MIC6315-46D3U NX 4.63 140 –40°C to +85°C 4-lead SOT-143 MIC6315-26D4U NS 2.63 1100 –40°C to +85°C 4-lead SOT-143 MIC6315-29D4U NN 2.93 1100 –40°C to +85°C 4-lead SOT-143 MIC6315-30D4U N4 3.00 1100 –40°C to +85°C 4-lead SOT-143 MIC6315-31D4U zz 3.08 1100 –40°C to +85°C 4-lead SOT-143 MIC6315-44D4U zz 4.38 1100 –40°C to +85°C 4-lead SOT-143 MIC6315-46D4U NZ 4.63 1100 –40°C to +85°C 4-lead SOT-143 Notes 1. All devices available in tape and reel only. 2. Parts not yet assigned an identification code are shown as “zz”. Contact Micrel for details. Minimum order may apply. Pin Configuration GND 1 4 VCC MIC6315 RESET 2 3 MR MIC6315-xxDyU 4-Lead SOT-143 Pin Description Pin Number Pin Name Pin Function 1 GND IC Ground Pin. 2 /RESET 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 be driven by TTL or CMOS logic. Float if unused. 4 VCC Power Supply Input. M9999-071504 /RESET goes low if VCC falls below the reset threshold and remains asserted for one reset timeout period after VCC exceeds the reset threshold. 2 July, 2004 MIC6315 Micrel Absolute Maximum Ratings(1) Operating Ratings(2) Terminal Voltage (VCC, /RESET) ...................................... –0.3V to 6.0V (/MR) ........................................ –0.3V to (VCC + 0.3V) Rate of Rise (VCC) ................................................. 100V/µs Input Current (VCC, /MR) ............................................ 20mA Output Current (/RESET) ........................................... 20mA Lead Temperature (soldering, 10 sec.) ..................... 300°C Storage Temperature (TS) ........................ –65°C to 150°C ESD Rating(3) Operating Temperature Range .................. –40°C to +85°C Input Voltage (/RESET) .................................... GND – 5.5V Power Dissipation (TA = +70°C) .............................. 320mW Electrical Characteristics For typical values, VCC = 2.5V to 5.5V, TA = 25°C; bold values indicate –40°C ≤ TA ≤ +85°C; unless noted Symbol Parameter Condition Min Operating Voltage Range ICC Supply Current VTH Reset Voltage Threshold tRST Reset Timeout Period VOL /RESET Output Voltage /RESET Output Leakage 1.4 VIL /MR Input Threshold Units 5.5 V 9 15 µA VCC = 3.6V, no load 6 10 µA VTH–2.5% VTH VTH+2.5% V 20 28 44 ms 140 200 320 ms 1100 1500 2500 ms VCC > 4.25V, ISINK = 3.2mA 0.4 V VCC > 2.5V, ISINK = 1.2mA 0.3 V VCC > 1.4V, ISINK = 50µA 0.3 V 1 µA Note 4 /RESET deasserted µs 10 /MR to Reset Delay /MR Input Threshold Max VCC = 5.5V, no load /MR Minimum Pulse Width VIH Typ µs 0.5 VTH > 4.0V 2.3 V VTH > 4.0V 0.7× ×VCC V VTH > 4.0V 0.8 V VTH > 4.0V 0.25× ×VCC V 30 kΩ /MR Pull-Up Resistance 10 /MR Glitch Immunity 20 100 ns Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. 4. Various reset thresholds available. See ordering information or contact factory. July, 2004 3 M9999-071504 MIC6315 Micrel Timing Diagram VCC VTH /MR tRST tRST /RESET Reset Timing Diagram Functional Diagram + VCC (4) Reset RESET (2) - RESET Threshold (V) GENERATOR MR (3) GND (1) M9999-071504 4 July, 2004 MIC6315 Micrel Wire OR'ing The /RESET Output Because the RESET output is open-drain, several reset sources can be wire-ORed in parallel to allow resets from multiple sources. VCC Transients The MIC6315 is relatively immune to negative-going VCC glitches below the reset threshold. Typically, a negativegoing transient 125mV below the reset threshold with a duration of 25µs or less will not cause an unwanted reset. If additional transient immunity is needed, a bypass capacitor can be placed a close as possible to the MIC6315. Applications Information 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 the duration of the reset timeout period after VCC has risen above the reset threshold or /MR has returned high. The reset function ensures 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 1.4V. The /RESET output is a simple open-drain N-channel MOSFET structure. A pull-up resistor must be used to pull this output up to some voltage. For most applications, this voltage will be the same power supply that supplies VCC to the MIC6315. It is possible however to tie this resistor to some other voltage. This will allow the MIC6315 to monitor one voltage while level-shifting the /RESET output to some other voltage. The pull-up voltage must be limited to 6.0V or less (absolute maximum) to avoid damage to the MIC6315. The resistor must be small enough to supply current to the inputs and leakage paths that are driven by the /RESET output. /RESET Valid at Low Voltage As VCC drops to 0V, the MIC6315 will no longer be able to pull the /RESET output low. At this point, the pull-up resistor will pull the output high. The value of the pull-up resistor and the voltage it is connected to will affect the point at which this happens. July, 2004 +5.0V +3.3V VCC VCC MIC6315 MR RESET 10k 5V SYSTEM RESET MIC6315 Used in a Multiple Supply System 5 M9999-071504 MIC6315 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) 8° 0° 0.10 (0.004) 0.013 (0.0005) 0.800 (0.031) TYP 0.400 (0.016) TYP 3 PLACES 0.150 (0.0059) 0.089 (0.0035) 0.41 (0.016) 0.13 (0.005) 4-Pin SOT-143 (U) MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB USA 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 designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can 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. © 2004 Micrel, Incorporated. M9999-071504 6 July, 2004