DS1233A 3.3V EconoReset www.maxim-ic.com FEATURES PIN ASSIGNMENT Automatically restarts microprocessor after power failure Monitors pushbutton for external override Internal circuitry debounces pushbutton switch Maintains reset for 350ms after VCC returns to an in-tolerance condition or pushbutton released Accurate 10% or 15% microprocessor 3.3V power supply monitoring Reduces need for discrete components Precision temperature-compensated voltage reference and voltage sensor Low-cost TO-92 package or surface mount SOT-223 package Internal 5kpull-up resistor Operating temperature of -40C to +85C DALLAS DS1233A Econo Reset 1 1 2 3 1 2 3 BOTTOM VIEW TO-92 PACKAGE 2 4 3 TOP VIEW SOT-223 PACKAGE PIN DESCRIPTION PIN 1 PIN 2 PIN 3 PIN 4 GROUND RESET VCC GROUND (SOT-223 ONLY) DESCRIPTION The DS1233A EconoReset monitors two vital conditions for a microprocessor: power supply and external override. A precision temperature-compensated reference and comparator circuit are used to monitor the status of the power supply (VCC). When an out-of-tolerance condition is detected, an internal power fail signal is generated which forces reset to the active state. When VCC returns to an in-tolerance condition, the reset signal is kept in the active state for approximately 350ms to allow the power supply and processor to stabilize. The second function of the DS1233A is pushbutton reset control. The DS1233A debounces a pushbutton closure and will generate a 350ms reset pulse upon release. OPERATION — POWER MONITOR The DS1233A provides the functions of detecting out-of-tolerance power supply conditions and warning a processor-based system of impending power failure. When VCC is detected as out-of-tolerance as defined by the tolerance of the part selected, the RST signal is asserted. On power-up, RST is kept active for approximately 350ms after the power supply has reached the selected tolerance. This allows the power supply and microprocessor to stabilize before RST is released. 1 of 5 122001 DS1233A OPERATION — PUSHBUTTON RESET The DS1233A provides for a pushbutton switch to be connected to the RST output pin. When the DS1233A is not in a reset cycle, it continuously monitors the RST signal for a low-going edge. If an edge is detected, the DS1233A will debounce the switch by pulling the RST line low. After the internal timer has expired, the DS1233A will continue to monitor the RST line. If the line is still low, the DS1233A will continue to monitor the line looking for a rising edge. Upon detecting a release, the DS1233A will force the RST line low and hold it low for 350ms. NOTE: For proper operation with an external pushbutton, a capacitor between 100pF and 0.01F must be connected between RST and ground. In applications where additional reset current is required, a minimum capacitance of 500 pF should be used, along with a parallel external pull-up resistor of 1k minimum. BLOCK DIAGRAM Figure 1 APPLICATION EXAMPLE Figure 2 2 of 5 DS1233A PUSHBUTTON RESET Figure 3 POWER-UP Figure 4 POWER-DOWN Figure 5 3 of 5 DS1233A ABSOLUTE MAXIMUM RATINGS* Voltage on VCC Pin Relative to Ground Voltage on I/O Relative to Ground Operating Temperature Range Storage Temperature Range Soldering Temperature * -0.5V to +7.0V -0.5V to VCC +0.5V -40°C to +85°C -55°C to +125°C 260°C for 10 seconds This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. RECOMMENDED DC OPERATING CONDITIONS (-40C to +85C) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Supply Voltage VCC 1.2 3.3 5.5 V 1 DC ELECTRICAL CHARACTERISTICS PARAMETER SYMBOL Low Level @ RST VOL Output Current @ 0.4V IOL Operating Current ICC (-40C to +85C; VDD = 3.3V 10%) MIN TYP MAX UNITS NOTES 0.4 V 1 +8 mA 50 A VCC Trip Point 10% VCCTP1 2.80 2.88 2.97 V 1 VCC Trip Point 15% VCCTP2 2.64 2.72 2.80 V 1 Output Capacitance COUT 10 pF Pushbutton Detect PBDV 2.0 V 1 Pushbutton Release PBRD 0.3 0.8 V 1, 2 5 6.25 k Internal Pull-Up Resistor RP AC ELECTRICAL CHARACTERISTICS PARAMETER 0.8 3.75 (-40C to +85C; VCC = 3.3V 10%) SYMBOL MIN TYP MAX UNITS Reset Active Time tRST 250 350 450 ms VCC Detect to RST tRPD 100 ns VCC Slew Rate (2.85V - 2.3V) tF 300 s VCC Slew Rate (2.3V - 2.85V) tR 0 ns Pushbutton Debounce PBDB 250 350 450 ms VCC Detect to RST tRPU 250 350 450 ms NOTES: 1) All voltages are referenced to ground. 2) With a 100pF to 0.01F capacitor connected from RST to ground. 4 of 5 NOTES DS1233A ECONORESET SELECTION GUIDE VCC TRIP POINT 5V 3.3V PUSHBUTTON DETECT MIN TYP MAX MIN TYP MAX DS1233-15 4.0 4.125 4.24 1.8 - 3.3 DS1233-10 4.25 4.375 4.49 1.8 - 3.3 DS1233-5 4.5 4.625 4.75 1.8 - 3.3 DS1233D-15 4.0 4.125 4.24 N/A N/A DS1233D-10 4.25 4.375 4.49 N/A N/A DS1233D-5 4.5 4.625 4.75 N/A N/A DS1833-15 4.0 4.125 4.24 N/A N/A DS1833-10 4.25 4.375 4.49 N/A N/A DS1833-5 4.5 4.625 4.75 N/A N/A DS1233A-15 2.64 2.72 2.80 0.8 - 2.0 DS1233A-10 2.8 2.88 2.97 0.8 - 2.0 PACKAGE INFORMATION For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. TO 92 Q3+1 21-0248 TO 92 Q3+4 21-0250 SOT 223 K3+1 21-0264 5 of 5