ASM161

April 2008 rev 1.5 ASM161/ASM162 µP Supervisory Circuit General Description The ASM161 and ASM162 are cost effective, low power supervisory circuits that monitor power supplies in microprocessor, microcontroller and digital systems. If the power supply drops below the reset threshold level, a reset is asserted and remains asserted for atleast 800ms after VCC has risen above the reset threshold. An improved manual reset architecture gives the system designer additional flexibility. The debounced manual reset input is negative edge triggered. The reset pulse period generated by a MR transition is a minimum of 800 ms and a maximum of 2 sec duration. In addition, The MR input signal is blocked for an additional 49µS minimum after the reset pulse ends. During the MR disable period, the microcontroller is guaranteed a time period free of additional manual reset signals. During this period DRAM contents can be refreshed or other critical system tasks undertaken. operated Low power consumption 3V makes the ASM161/162 ideal for use in portable and battery equipments. With supplies power consumption is 8µW typically and 30µW maximum. The ASM161 has an open-drain, active-LOW RESET output and requires an external pull-up resistor. The ASM162 has an active HIGH RESET output. The ASM161/162 are offered in compact 4-pin SOT-143 packages. No external components are required to trim threshold voltage for monitoring different supply voltages. With six different factory set, reset, threshold ranges from 2.63V to 4.63V, the ASM161/162 are suitable for monitoring 5V, 3.6V and 3.0V supplies. The ASM161/162 are available in temperature ranges 0°c to 70°c and -40°c to +85°c. Reset Threshold Part Suffix L M J T S R Voltage (V) 4.63 4.38 4.00 3.08 2.93 2.63 Key Features • Edge triggered manual reset input • single pulse output • 49µS minimum MR disable period after reset • CMOS/TTL logic or switch interface • Debounced input • Low supply current extends battery life 6µA / 15µA typ/max at 5.5V 4.5µA / 10µA typ/max at 3.6V • Long reset period • 0.8 sec minimum, 2 sec maximum • Two reset polarity options ASM161: Active LOW, open-drain ASM162: Active HIGH • Pinout matches the ASM811/812 • Small 4-Pin SOT-143 package • Two temperature ranges: 0°c to 70°c and -40°c to +85°c Applications • PDAs • Appliances • Computers and embedded controllers • Wireless communication systems • Battery operated and intelligent instruments • Automotive systems • Safety systems PulseCore Semiconductor Corporation 1715 S. Bascom Ave Suite 200 Campbell, CA 95008 • Tel: 408-879-9077 • Fax: 408-879-9018 www.pulsecoresemi.com Notice: The information in this document is subject to change without notice. April 2008 rev 1.5 Typical Operating Circuit ASM161/ASM162 Block Diagram Pin Configuration RESET is open drain µP Supervisory Circuit Notice: The information in this document is subject to change without notice. 2 of 9 April 2008 rev 1.5 Pin Description Pin # ASM161 1 2 ASM162 1 Pin Name GND RESET Ground. Function ASM161/ASM162 Active-LOW, open-drain reset output. RESET remains LOW while VCC is below the reset threshold and for 800ms minimum after VCC rises above the reset threshold. An external pull-up resistor is needed. Active HIGH reset output. RESET remains HIGH while VCC is below the reset threshold and for 800ms after VCC rises above the reset threshold. Manual reset input. A negative going edge transition on MR asserts reset. Reset remains asserted for one reset time-out period (800 ms min). This - 2 RESET 3 3 MR active-LOW input has an internal pull-up resistor. It can be driven from a TTL or CMOS logic line or shorted to ground with a switch. Leave open if unused. 4 4 VCC Power supply input voltage. Manual Reset The ASM161/162 have a unique manual reset circuit. A negative going edge transition on MR initiates the reset. A manual reset generates a single reset pulse of fixed length. The output-reset pulse remains asserted for the Reset Active Time-Out Period tRP and then clears. Once the reset pulse is completed, the MR input remains disabled for at least 49µS but not more than 122µS. This period is specified as tMRD. During the MR disabled period, the microcontroller is guaranteed a time period free of new manual reset signals. This period can be used to refresh critical DRAM contents or other system tasks. The MR pin must be taken HIGH and LOW again after the tMRD period has been completed to initiate another reset pulse. The manual reset input has an internal 20kΩ pull-up resistor. MR can be left open if not used. Detailed Description The reset function ensures the microprocessor is properly reset and powers up into a known condition after a power failure. Reset Timing A reset is generated whenever the supply voltage is below the threshold level (VCC < VTH). The reset duration is at least 800ms after VCC has risen above the reset threshold and is guaranteed to be no more than 2 seconds. The rest signal remains active as long as the monitored supply voltage is below the internal threshold voltage. The ASM161 has an open-drain, active LOW RESET output (which is guaranteed to be in the correct state for VCC down to 1.1 V). The ASM161 uses an external pullup resistor. Output leakage current is under 1µA. A high resistance value can be used to minimize current drain. The ASM162 generates an active-HIGH RESET output. Part Number ASM161 ASM162 Reset Polarity LOW (use external pull-up resistor) HIGH µP Supervisory Circuit Notice: The information in this document is subject to change without notice. 3 of 9 April 2008 rev 1.5 ASM161/ASM162 Application Information Glitch Resistance The ASM161/162 are relatively immune to short duration negative-going VCC transients/glitches. A VCC transient that goes 100mV below the reset threshold and lasts 20s or less will not typically cause a reset pulse. Valid Reset with VCC under 1.1V To ensure that logic inputs connected to the ASM162 RESET pin are in a known state when VCC is under 1.1V, a 100kΩ pull-down resistor at RESET is needed. The value is not critical. This scheme does not work with the open-drain outputs of ASM161. Absolute Maximum Ratings Parameter Pin Terminal Voltage with Respect to Ground VCC RESET, RESET and MR Input Current at VCC and MR Rate of Rise at VCC Power Dissipation (TA = 70°C) Operating Temperature Range Storage Temperature Range Lead Temperature (soldering, 10 sec) ESD rating HBM MM 2 200 KV V -40 -65 -0.3 -0.3 6.0 VCC + 0.3 20 100 320 85 160 300 V V mA V/µs mW °C °C °C Min Max Unit Note: These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. µP Supervisory Circuit Notice: The information in this document is subject to change without notice. 4 of 9 April 2008 rev 1.5 Electrical Characteristics ASM161/ASM162 Unless otherwise noted, VCC is over the full range and TA = 0°c to 70°c for ASM161/162 X C and TA = -40°c to +85°c for ASM161/162 X E devices. Typical values at TA = 25°c, VCC = 5V for L/M/J devices, VCC = 3.3V for T/S devices and VCC = 3V for R devices Parameter Input Voltage (VCC) Range Supply Current (Unloaded) Symbol VCC ICC L Devices M devices J devices Conditions TA = 0°C to 70°C VCC < 5.5V L/M/J VCC < 3.6V R/S/T TA = 25°C Note 1 TA = 25°C Note 1 TA = 25°C Note 1 TA = 25°C Note 1 TA = 25°C Note 1 TA = 25°C Note 1 Min 1.1 TYP Max 5.5 15 Unit V µA 6 4.5 4.63 4.38 4.00 3.08 2.93 2.63 30 Reset Threshold VTH T devices S devices R devices 4.56 4.50 4.31 4.25 3.93 3.89 3.04 3.00 2.89 2.85 2.59 2.55 10 4.70 4.75 4.45 4.50 4.06 4.10 3.11 3.15 2.96 3.00 2.66 2.70 V Reset Threshold Temp Coefficient VCC to reset delay Reset Pulse Width MR Minimum Pulse Width MR Glitch Immunity MR to RESET Propagation Delay MR Input Threshold TCVTH VCC = VTH to (VTH -100mV) TA = 0°C to 70°C TA = -40°C to 85°C 800 600 10 tRPW tMR 20 1400 ppm/ °C µS 2000 2240 ms µS 100 0.5 VIH VIL VIH VIL tMRD VCC > VTH(MAX), L/M/J devices VCC > VTH(MAX), R/S/T devices TA = 0°C to 70°C TA = -40°C to 85°C 10 VCC=VTH min., ISINK=1.2mA, ASM161 R/S/T VCC=VTH min., ISINK=3.2mA, ASM161L/M/J VCC > 1.1, ISINK = 50µA VCC=VTH max., ISINK=1.2mA, ASM162 R/S/T VCC=VTH max., ISINK=3.2mA, ASM162 L/M/J 1.8