AMS811/812 General Description Features The AMS811 / 812 are low-power microprocessor (µP) supervisory circuits used to monitor power supplies in µP and digital systems. They provide excellent circuit reliability and low cost by eliminating external components and adjustments when used with 5Vpowered or 3V-powered circuits. The AMS811 / 812 also provide a debounced manual reset input. These devices perform a single function: They assert a reset signal whenever the V CC supply voltage falls below a preset threshold, keeping it asserted for at least 140ms after VCC has risen above the reset threshold. The only difference between the two devices is that the AMS811 has an active-low RESET output (which is guaranteed to be in the correct state for VCC down to 1V), while the AMS812 has an active-high RESET output. The reset comparator is designed to ignore fast transients on VCC. Reset thresholds are available for operation with a variety of supply voltages. Low supply current makes the AMS811 / 812 ideal for use in portable equipment. The devices come in a 4-pin SOT143 package. ♦ Precision Monitoring of 3V, 3.3V, and 5V Power-Supply Voltages ________________________Applications Computers ♦ 6µA Supply Current ♦ 140ms Min Power-On Reset Pulse Width; RESET Output (AMS811), RESET Output (AMS812) ♦ Guaranteed Over Temperature ♦ Guaranteed RESET Valid to VCC = 1V (AMS811) ♦ Power-Supply Transient Immunity ♦ No External Components ♦ 4-Pin SOT143 Package _______________Ordering Information PART* AMS811_EUS-T AMS812_EUS-T TEMP RANGE PIN-PACKAGE -40°C to +85°C -40°C to +85°C 4 SOT143 4 SOT143 *This part offers a choice of five different reset threshold voltages. Select the letter corresponding to the desired nominal reset threshold voltage, and insert it into the blank to complete the part number. Devices are available in both leaded and lead-free packaging. Specify lead-free by replacing “-T” with “+T” when ordering. Controllers RESET THRESHOLD Intelligent Instruments SUFFIX VOLTAGE (V) Critical µP and µC Power Monitoring Portable/Battery-Powered Equipment ___________Typical Operating Circuit L 4.63 M 4.38 T 3.08 S 2.93 R 2.63 ___________________Pin Configuration TOP VIEW VCC VCC VCC AMS811 AMS812 μP RESET (RESET) MR GND 4 VCC 3 MR AMS811 AMS812 RESET INPUT (RESET) RESET GND 1 2 GND SOT143 PUSHBUTTON SWITCH ( ) ARE FOR AMS812 ( ) ARE FOR AMS812 NOTE: SEE LAST PAGE FOR MARKING INFORMATION. 1 Advanced Monolithic Systems http://www.ams-semitech.com AMS811/812 ABSOLUTE MAXIMUM RATINGS Terminal Voltage (with respect to GND) VCC ......................................................................-0.3V to 6.0V All Other Inputs.......................................-0.3V to (VCC + 0.3V) Input Current, VCC, MR .......................................................20mA Output Current, RESET or RESET .......................................20mA Continuous Power Dissipation (TA = +70°C) SOT143 (derate 4mW/°C above +70°C) .......................320mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL Operating Voltage Range VCC Supply Current ICC CONDITIONS TA = 0°C to +70°C 1.0 TA = -40°C to +85°C 1.2 AMS81_L/M, VCC = 5.5V, IOUT = 0 AMS81_R/S/T, VCC = 3.6V, IOUT = 0 AMS81_L AMS81_M Reset Threshold VTH MIN AMS81_T AMS81_S AMS81_R TA = +25°C 4.54 TA = -40°C to +85°C 4.50 TA = +25°C 4.30 TA = -40°C to +85°C 4.25 TA = +25°C 3.03 TA = -40°C to +85°C 3.00 TA = +25°C 2.88 TA = -40°C to +85°C 2.85 TA = +25°C 2.58 TA = -40°C to +85°C 2.55 Reset Threshold Tempco Reset Active Timeout Period tRP MR Minimum Pulse Width tMR 5.5 6 15 2.7 10 4.63 4.72 4.38 4.46 3.08 3.14 MR to Reset Propagation Delay (Note 2) 3.15 2.93 VIH VIL VIH VIL 2.63 2.98 2.68 µs 560 10 ISOURCE = 150µA, 1.8V < VCC < VTH(MIN) µs 100 ns 0.5 µs 0.8 0.7 x VCC V 0.25 x VCC 20 30 kΩ 0.8 x VCC AMS812R/S/T only, SINK I = 1.2mA, VCC = VTH(MAX) 0.3 AMS812L/M only, SINK I = 3.2mA, VCC = VTH(MAX) 0.4 2 Advanced Monolithic Systems ms 2.3 VCC > VTH(MAX) , AMS81_L/M 10 VOL ppm/°C 140 MR Pull-Up Resistance VOH V 2.70 20 VCC > VTH(MAX) , AMS81_R/S/T µA 3.00 VOD = 125mV, AMS81_R/S/T tMD V 4.50 40 VCC = VTH(MAX) UNITS 4.75 VOD = 125mV, AMS81_L/M MR Glitch Immunity (Note 3) RESET Output Voltage (AMS812) MAX 30 VCC to Reset Delay (Note 2) MR Input Threshold TYP http://www.ams-semitech.com V AMS811/812 ELECTRICAL CHARACTERISTICS (continued) (VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL VOL RESET Output Voltage (AMS811) CONDITIONS MIN MAX 0.3 AMS811L/M only, SINK I = 3.2mA, VCC = VTH(MIN) 0.4 ISINK = 50µA, VCC > 1.0V VOH TYP AMS811R/S/T only, SINK I = 1.2mA, VCC = VTH(MIN) 0.3 AMS811R/S/T only, SOURCE I = 500µA, VCC > VTH(MAX) 0.8 x VCC AMS811L/M only, SOURCE I = 800µA, VCC > VTH(MAX) VCC - 1.5 Note 1: Production testing done at TA = +25°C, over temperature limits guaranteed by design using six sigma design limits. Note 2: RESET output for AMS811, RESET output for AMS812. Note 3: “Glitches” of 100ns or less typically will not generate a reset pulse. 3 Advanced Monolithic Systems http://www.ams-semitech.com UNITS V AMS811/812 Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) 3.0 VCC = 3.3V 2.0 1.5 1.0 VCC = 5.5V 6 4 VCC = 3V 2 0.5 POWER-DOWN RESET DELAY (μs) VCC = 3.6V SUPPLY CURRENT (μA) VCC = 1V -40 -15 10 35 60 85 -40 POWER-DOWN RESET DELAY vs. TEMPERATURE (AMS81_L/M) POWER-UP RESET TIMEOUT vs. TEMPERATURE POWER-UP RESET TIMEOUT (ms) 100 VOD = 125mV VOD = 200mV -40 -15 10 35 60 40 VOD = 125mV 20 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) RESET THRESHOLD DEVIATION vs. TEMPERATURE 1.0005 AMS81_R/S/T VOD = 20mV 0 -15 230 VOD = VTH - VCC 50 60 VOD = 200mV 10 35 TEMPERATURE (°C) 150 VOD = 20mV 80 0 TEMPERATURE (°C) 200 VOD = VTH - VCC VCC = 1V 0 0 NORMALIZED THRESHOLD (V) SUPPLY CURRENT (μA) 100 8 2.5 POWER-DOWN RESET DELAY (μs) POWER-DOWN RESET DELAY vs. TEMPERATURE (AMS81_R/S/T) SUPPLY CURRENT vs. TEMPERATURE (AMS81_L/M) SUPPLY CURRENT vs. TEMPERATURE (AMS81_R/S/T) 220 210 200 AMS81_L/M 190 85 1.0000 0.9995 0.9990 0.9985 0.9980 -40 -15 TEMPERATURE (°C) 10 35 60 85 TEMPERATURE (°C) 4 Advanced Monolithic Systems http://www.ams-semitech.com -40 -15 10 35 TEMPERATURE (°C) 60 85 AMS811/812 Pin Description PIN NAME FUNCTION AMS811 AMS812 1 1 GND 2 — RESET Active-Low Reset Output. RESET remains low while VCC is below the reset threshold or while MR is held low. RESET remains low for the Reset Active Timeout Period (tRP) after the reset conditions are terminated. — 2 RESET Active-High Reset Output. RESET remains high while VCC is below the reset threshold or while MR is held low. RESET remains high for Reset Active Timeout Period (tRP) after the reset conditions are terminated. 3 3 MR Manual Reset Input. A logic low on MR asserts reset. Reset remains asserted as long as MR is low and for 180ms after MR returns high. This active-low input has an internal 20kΩ 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 +5V, +3.3V, or +3V Supply Voltage Ground _______________ Detailed Description Reset Output A microprocessor’s (µP’s) reset input starts the µP in a known state. These µP supervisory circuits assert reset to prevent code execution errors during power-up, power-down, or brownout conditions. RESET is guaranteed to be a logic low for VCC > 1V. Once V CC exceeds the reset threshold, an internal timer keeps RESET low for the reset timeout period; after this interval, RESET goes high. If a brownout condition occurs (VCC dips below the reset threshold), RESET goes low. Any time VCC goes below the reset threshold, the internal timer resets to zero, and RESET goes low. The internal timer starts after VCC returns above the reset threshold, and RESET remains low for the reset timeout period. The manual reset input (MR) can also initiate a reset. See the Manual Reset Input section. The AMS812 has an active-high RESET output that is the inverse of the AMS811’s RESET output. Manual Reset Input Many µP-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. A logic low on MR asserts reset. Reset remains asserted while MR is low, and for the Reset Active Timeout Period (tRP) after MR returns high. This input has an internal 20kΩ pull-up resistor, so it can be left open if it is not used. MR can be driven with TTL or CMOS-logic levels, or with opendrain/collector outputs. Connect a normally open momentary switch from MR to GND to create a manualreset function; external debounce circuitry is not required. If MR is driven from long cables or if the device is used in a noisy environment, connecting a 0.1µF capacitor from MR to ground provides additional noise immunity. Reset Threshold Accuracy The AMS811/AMS812 are ideal for systems using a 5V ±5% or 3V ±5% power supply with ICs specified for 5V ±10% or 3V ±10%, respectively. They are designed to meet worst-case specifications over temperature. The reset is guaranteed to assert after the power supply falls out of regulation, but before power drops below the minimum specified operating voltage range for the system ICs. The thresholds are pre-trimmed and exhibit tight distribution, reducing the range over which an undesirable reset may occur. 5 Advanced Monolithic Systems http://www.ams-semitech.com AMS811/812 MAXIMUM TRANSIENT DURATION (ms) 8 TA = +25°C 7 6 VCC AMS81 _L/M 5 AMS811 4 AMS81 _R/S/T 3 RESET R1 2 GND 1 0 1 10 100 1000 RESET COMPARATOR OVERDRIVE , VTH - VCC (mV) Figure 2. RESET Valid to VCC = Ground Circuit Figure 1. Maximum Transient Duration without Causing a Reset Pulse vs. Comparator Overdrive __________ Applications Information Negative-Going VCC Transients In addition to issuing a reset to the µP during power-up, power-down, and brownout conditions, the AMS811/ AMS812 are relatively immune to short duration negative-going VCC transients (glitches). Figure 1 shows typical transient durations vs. reset comparator overdrive, for which the AMS811/AMS812 do not generate a reset pulse. This graph was generated using a negative-going pulse applied to VCC, starting above the actual reset threshold and ending below it by the magnitude indicated (reset comparator overdrive). The graph indicates the typical maximum pulse width a negative-going VCC transient may have without causing a reset pulse to be issued. As the magnitude of the transient increases (goes farther below the reset threshold), the maximum allowable pulse width decreases. Typically, a VCC transient that goes 125mV below the reset threshold and lasts 40µs or less (AMS81_L/M) or 20µs or less (AMS81_T/S/R) will not cause a reset pulse to be issued. A 0.1µF capacitor mounted as close as possible to VCC provides additional transient immunity. Ensuring a Valid RESET Output Down to VCC = 0V When VCC falls below 1V, the AMS811 RESET output no longer sinks current—it becomes an open circuit. Therefore, high-impedance CMOS-logic inputs connected to the RESET output can drift to undetermined voltages. This presents no problem in most applications, since most µP and other circuitry is inoperative with VCC below 1V. However, in applications where the RESET output must be valid down to 0V, adding a pulldown resistor to the RESET pin will cause any stray leakage currents to flow to ground, holding RESET low (Figure 2). R1’s value is not critical; 100kΩ is large enough not to load RESET and small enough to pull RESET to ground. A 100kΩ pull-up resistor to VCC is also recommended for the AMS812 if RESET is required to remain valid for VCC < 1V. 6 Advanced Monolithic Systems http://www.ams-semitech.com AMS811/812 Interfacing to µPs with Bidirectional Reset Pins µPs with bidirectional reset pins (such as the Motorola 68HC11 series) can contend with the AMS811/AMS812 reset outputs. If, for example, the AMS811 RESET output is asserted high and the µP wants to pull it low, indeterminate logic levels may result. To correct such cases, connect a 4.7kΩ resistor between the AMS811 RESET (or AMS812 RESET) output and the µP reset I/O (Figure 3). Buffer the reset output to other system components. BUFFER BUFFERED RESET TO OTHER SYSTEM COMPONENTS VCC VCC AMS811 μP 4.7k RESET GND RESET GND Figure 3. Interfacing to µPs with Bidirectional Reset I/O 7 Advanced Monolithic Systems http://www.ams-semitech.com AMS811/812 Package Information 4.0 ±0.1 2.0 ±0.05 ø1.5 ±0.1 1.75 ±0.1 8.0 ±0.2 4.0 ±0.1 ø1.1 ±0.1 3.5 ±0.05 NOTE: DIMENSIONS ARE IN MM. AND FOLLOW EIA481-1 STANDARD. MARKING INFORMATION † LOT SPECIFIC CODE XX XX AMAA or KABB = AMS811L ANAA or KABC = AMS811M APAA or KABD = AMS811T AQAA or KABE = AMS811S ARAA or KABF = AMS811R ASAA or KABG = AMS812L ATAA or KABH = AMS812M AVAA or KABI = AMS812T AWAA or KABJ = AMS812S AXAA or KABK = AMS812R SOT-23 5L .EPS † ICs MAY ALSO BE MARKED WITH FULL PART NAME: 811L, 811M_… 8 Advanced Monolithic Systems http://www.ams-semitech.com