MCP809/MCP810 3-Pin Microprocessor Reset Circuits General Description Features The MCP809/810 microprocessor supervisory circuits can be used to monitor the power supplies in microprocessor and digital systems. They provide a reset to the microprocessor during power-up, power-down and brown-out conditions. The function of the MCP809/810 is to monitor the VCC supply voltage, and assert a reset signal whenever this voltage declines below the factory-programmed reset threshold. The reset signal remains asserted for 240ms after VCC rises above the threshold. The MCP809 has an active-low RESET output, while the MCP810 has an active-high RESET output. Seven standard reset voltage options are available, suitable for monitoring 5V, 3.3V, and 3V supply voltages. With a low supply current of only 15µA, the MCP809/810 are ideal for use in portable equipment. The MCP809/MCP810 are available in the 3-pin SOT23 package. n Precise monitoring of 3V, 3.3V, and 5V supply voltages n Fully specified over temperature n 140ms min. Power-On Reset pulse width, 240ms typical Active-low RESET Output (MCP809) Active-high RESET Output (MCP810) n Guaranteed RESET Output valid for VCC≥1V n Low Supply Current, 15µA typ. n Power supply transient immunity Typical Application Circuit Connection Diagram Applications n n n n n n Microprocessor Systems Computers Controllers Intelligent Instruments Portable/Battery-Powered Equipment Automotive 20022302 ( ) are for MCP810 20022301 © 2001 National Semiconductor Corporation DS200223 www.national.com MCP809/MCP810 3-Pin Microprocessor Reset Circuits June 2001 MCP809/MCP810 Ordering Information Reset Threshold (V) MCP809 Supplied as 1000 units, tape & reel MCP809 Supplied as 3000 units, tape & reel Package Top Mark 4.63 MCP809M3-4.63 MCP809M3X-4.63 SVB 4.38 MCP809M3-4.38 MCP809M3X-4.38 SUB 4.00 MCP809M3-4.00 MCP809M3X-4.00 STB 3.08 MCP809M3-3.08 MCP809M3X-3.08 SSB 2.93 MCP809M3-2.93 MCP809M3X-2.93 SRB 2.63 MCP809M3-2.63 MCP809M3X-2.63 SPB Reset Threshold (V) MCP810 Supplied as 1000 units, tape & reel MCP810 Supplied as 3000 units, tape & reel Package Top Mark 4.63 MCP810M3-4.63 MCP810M3X-4.63 SNB 4.38 MCP810M3-4.38 MCP810M3X-4.38 SLB 4.00 MCP810M3-4.00 MCP810M3X-4.00 SKB 3.08 MCP810M3-3.08 MCP810M3X-3.08 SJB 2.93 MCP810M3-2.93 MCP810M3X-2.93 SHB 2.63 MCP810M3-2.63 MCP810M3X-2.63 SGB Package Type NSC Package SOT23-3 MF03A Package Type NSC Package SOT23-3 MF03A Custom voltages and improved accuracies are available, subject to minimum orders. Contact your local National Semiconductor Sales Office for information. Pin Description PIN NAME 3 GND www.national.com Ground reference RESET (MCP809) Active-low output. RESET remains low while VCC is below the reset threshold, and for 240ms after VCC rises above the reset threshold. RESET (MCP810) Active-high output. RESET remains high while VCC is below the reset threshold, and for 240ms after VCC rises above the reset threshold. 1 2 FUNCTION VCC Supply Voltage (+5V, +3.3V, or +3.0V) 2 (Note 1) ESD Rating (Note 2) 2kV If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Continuous Power Dissipation (TA = +70˚C) VCC Maximum Junction Temperature SOT-23 (Note 3) −0.3V to 6.0V RESET, RESET −0.3V to (VCC+ 0.3V) Input Current, VCC Pin 20mA Output Current, RESET, RESET Pin 20mA Rate of Rise, VCC 320mW Ambient Temperature Range −40˚C to +105˚C 125˚C Storage Temperature Range −65˚C to +160˚C Lead Temperature (soldering, 10sec) +300˚C 100V/µs Electrical Characteristics VCC = full range, TA = −40˚C to +105˚C, unless otherwise noted. Typical values are at TA = +25˚C, VCC = 5V for 4.63/4.38/4.00 versions, VCC = 3.3V for 3.08/2.93 versions, and VCC = 3V for 2.63 version. (Note 4) Symbol Parameter VCC Range Conditions Supply Current TA = −40˚C to +105˚C 1.2 5.5 TA = +85˚C to +105˚C MCP8_ _ -4.38 MCP8_ _ -4.00 Reset Threshold (Note 5) MCP8_ _ -3.08 MCP8_ _ -2.93 MCP8_ _ -2.63 VCC < 5.5V, MCP8_ _ -4.63/4.38/4.00 18 60 VCC < 3.6V, MCP8_ _ -3.08/2.93/2.63 15 50 VCC < 5.5V, MCP8_ _ -4.63/4.38/4.00 100 VCC < 3.6V, MCP8_ _ -3.08/2.93/2.63 100 TA = +25˚C 4.56 TA = −40˚C to +85˚C 4.50 4.75 TA = +85˚C to +105˚C 4.40 4.86 Reset Active Timeout Period 4.63 4.31 TA = −40˚C to +85˚C 4.25 TA = +85˚C to +105˚C 4.16 TA = +25˚C 3.93 TA = −40˚C to +85˚C 3.89 TA = +85˚C to +105˚C 3.80 TA = +25˚C 3.04 TA = −40˚C to +85˚C 3.00 TA = +85˚C to +105˚C 2.92 TA = +25˚C 2.89 TA = −40˚C to +85˚C 2.85 TA = +85˚C to +105˚C 2.78 TA = +25˚C 2.59 TA = −40˚C to +85˚C 2.55 2.70 TA = +85˚C to +105˚C 2.50 2.76 VCC = VTH to (VTH − 100mV) TA = −40˚C to +85˚C 140 TA = +85˚C to +105˚C 3 100 4.38 Units V µA 4.70 TA = +25˚C Reset Threshold Temperature Coefficient VCC to Reset Delay (Note 5) Max 5.5 MCP8_ _ -4.63 VTH Typ 1.0 TA = −40˚C to +85˚C ICC Min TA = 0˚C to +70˚C 4.45 4.50 4.56 4.00 4.06 4.10 4.20 3.08 3.11 V 3.15 3.23 2.93 2.96 3.00 3.08 2.63 2.66 30 ppm/˚C 20 µs 240 560 840 ms www.national.com MCP809/MCP810 Absolute Maximum Ratings MCP809/MCP810 Electrical Characteristics (Continued) VCC = full range, TA = −40˚C to +105˚C, unless otherwise noted. Typical values are at TA = +25˚C, VCC = 5V for 4.63/4.38/4.00 versions, VCC = 3.3V for 3.08/2.93 versions, and VCC = 3V for 2.63 version. (Note 4) Symbol VOL Parameter RESET Output Voltage Low (MCP809) Conditions Min RESET Output Voltage High (MCP809) VOL RESET Output Voltage Low (MCP810) VOH RESET Output Voltage High (MCP810) Max 0.3 VCC = VTH min, ISINK = 3.2mA, MCP809-4.63/4.38/4.00 0.4 VCC > 1.0V, ISINK = 50µA VOH Typ VCC = VTH min, ISINK = 1.2mA, MCP809-2.63/2.93/3.08 V 0.3 VCC > VTH max, ISOURCE = 500µA, MCP809-2.63/2.93/3.08 0.8VCC VCC > VTH max, ISOURCE = 800µA, MCP809-4.63/4.38/4.00 VCC−1.5 V VCC = VTH max, ISINK = 1.2mA, MCP810-2.63/2.93/3.08 0.3 VCC = VTH max, ISINK = 3.2mA, MCP810-4.63/4.38/4.00 0.4 1.8V < VCC < VTH min, ISOURCE = 150µA Units 0.8VCC V V Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which the device operates correctly. Operating ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics. Note 2: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. Note 3: Production testing done at TA = +25˚C, over temperature limits guaranteed by design only. Note 4: At elevated temperatures, devices must be derated based on package thermal resistance. The device in the SOT23-3 package must be derated at 4mW/˚C at ambient temperatures above 70˚C. The device has internal thermal protection. Note 5: RESET Output for MCP809, RESET output for MCP810. www.national.com 4 Supply Current vs Temperature (No Load, MCP8_ _-2.63/2.93/3.08) Supply Current vs Temperature (No Load, MCP8_ _-4.63/4.38) 20022303 Power-Down Reset Delay vs Temperature (MCP8_ _-4.63/4.38) 20022304 Power-Up Reset Timeout vs Temperature 20022306 Power-Down Reset Delay vs Temp (MCP8_ _-2.63/2.93/3.08) 20022305 Normalized Reset Threshold vs Temperature 20022308 20022307 5 www.national.com MCP809/MCP810 Typical Performance Characteristics MCP809/MCP810 can have without causing a reset pulse. In general, as the magnitude of the transient increases, going further below the threshold, the maximum allowable pulse width decreases. Typically, for the 4.63V and 4.38V version of the MCP809/810, a VCC transient that goes 100mV below the reset threshold and lasts 20µs or less will not cause a reset pulse. A 0.1 µF bypass capacitor mounted as close as possible to the VCC pin will provide additional transient rejection. Applications Information Benefits of Precision Reset Thresholds A microprocessor supply supervisor must provide a reset output within a predictable range of the supply voltage. A common threshold range is between 5% and 10% below the nominal supply voltage. The 4.63V and 3.08V options of the MCP809/810 use highly accurate circuitry to ensure that the reset threshold occurs only within this range (for 5V and 3.3V supplies). The other voltage options have the same tight tolerance to ensure a reset signal for other narrow monitor ranges. See Table 1 for examples of how the standard reset thresholds apply to 3V, 3.3V, and 5V nominal supply voltages. TABLE 1. Reset Thresholds Related to Common Supply Voltages Reset Threshold 3.0V 3.3V 5.0V 4.63 ± 3% 90 - 95% ± ± ± ± ± 85 - 90% 4.38 4.00 3.08 2.93 2.63 3% 3% 78 - 82% 3% 90 - 95% 3% 86 - 90% 3% 85 - 90% 20022309 FIGURE 2. Maximum Transient Duration without Causing a Reset Pulse vs. Reset Comparator Overdrive 77 - 81% Ensuring a Valid Reset Output Down to VCC = 0V When VCC falls below 1V, the MCP809 RESET output no longer sinks current. A high-impedance CMOS logic input connected to RESET can therefore drift to undetermined voltages. To prevent this situation, a 100kΩ resistor should be connected from the RESET output to ground, as shown in Figure 1. A 100kΩ pull-up resistor to VCC is also recommended for the MCP810, if RESET is required to remain valid for VCC < 1V. Interfacing to µPs with Bidirectional Reset Pins Microprocessors with bidirectional reset pins, such as the Motorola 68HC11 series, can be connected to the MCP809 RESET output. To ensure a correct output on the MCP809 even when the microprocessor reset pin is in the opposite state, connect a 4.7kΩ resistor between the MCP809 RESET output and the µP reset pin, as shown in Figure 3. Buffer the MCP809 RESET output to other system components. 20022310 FIGURE 1. RESET Valid to VCC = Ground Circuit Negative-Going VCC Transients The MCP809/810 are relatively immune to short negative-going transients or glitches on VCC. Figure 2 shows the maximum pulse width a negative-going VCC transient www.national.com 20022311 FIGURE 3. Interfacing to Microprocessors with Bidirectional Reset I/O 6 MCP809/MCP810 3-Pin Microprocessor Reset Circuits Physical Dimensions inches (millimeters) unless otherwise noted 3-Lead SOT23-3 For Ordering, refer to Ordering Information table NS Package Number MF03A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. 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