§ Automatically restarts microprocessor afterpower failure
§ Monitors pushbutton for external override§ Internal circuitry debounces pushbuttonswitch
§ Maintains reset for 350ms after VCC returns toan in-tolerance condition or pushbuttonreleased
§ Accurate 5%, 10%, or 15% microprocessor5V power supply monitoring
§ Reduces need for discrete components
§ Precision temperature-compensated voltagereference and voltage sensor
§ Low-cost TO-92 package or surface-mountSOT-223 package
§ Internal 5kW pull-up resistor
§ Operating temperature of -40°C to +85°C
FEATURESPIN ASSIGNMENT
DALLASDS1233EconoReset11 2 31 2 3BOTTOM VIEWTO-92 PACKAGE
See Mech.Drawings Sectionon Website
243TOP VIEWSOT-223 PACKAGE
See Mech.Drawings Sectionon Website
PIN DESCRIPTION
PIN 1PIN 2PIN 3PIN 4
GROUND
RESET
VCC
GROUND (SOT-223 ONLY)
DESCRIPTION
The DS1233 EconoReset monitors two vital conditions for a microprocessor: power supply and externaloverride. A precision temperature-compensated reference and comparator circuit are used to monitor thestatus of the power supply (VCC). When an out-of-tolerance condition is detected, an internal power-failsignal 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 andprocessor to stabilize. The second function of the DS1233 is pushbutton reset control. The DS1233debounces a pushbutton closure and will generate a 350ms reset pulse upon release.
OPERATION — POWER MONITOR
The DS1233 provides the functions of detecting out-of-tolerance power supply conditions and warning aprocessor-based system of impending power failure. When VCC is detected as out-of-tolerance, asdefined by the tolerance of the part selected, the RST signal is asserted. On power-up, RST is kept activefor approximately 350ms after the power supply has reached the selected tolerance. This allows the powersupply and microprocessor to stabilize before RST is released.
122001
DS1233
OPERATION — PUSHBUTTON RESET
The DS1233 provides for a pushbutton switch to be connected to the RST output pin. When the DS1233is not in a reset cycle, it continuously monitors the RST signal for a low going edge. If an edge isdetected, the DS1233 will debounce the switch by pulling the RST line low. After the internal timer hasexpired, the DS1233 will continue to monitor the RST line. If the line is still low, the DS1233 willcontinue to monitor the line looking for a rising edge. Upon detecting a release, the DS1233 will force theRST line low and hold it low for 350ms.
NOTE:
For proper operation with an external pushbutton, a capacitor between 100pF and 0.01mF must beconnected between RST and ground. In applications where additional reset current is required, aminimum capacitance of 500pF should be used, along with a parallel external pull-up resistor of1kW minimum.
BLOCK DIAGRAM Figure 1
APPLICATION EXAMPLE Figure 2
DS1233
PUSHBUTTON RESET Figure 3
POWER UP Figure 4
POWER DOWN Figure 5
DS1233
ABSOLUTE MAXIMUM RATINGS*
Voltage on VCC Pin Relative to Ground Voltage on I/O Relative to Ground Operating Temperature RangeStorage Temperature RangeSoldering Temperature *
-0.5V to +7.0V-0.5V to VCC +0.5V-40°C to +85°C-55°C to +125°C260°C for 10 seconds
This is a stress rating only and functional operation of the device at these or any other conditionsabove those indicated in the operation sections of this specification is not implied. Exposure toabsolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
PARAMETERSupply Voltage
SYMBOLVCC
MIN1.2
TYP5.0
MAX5.5
(-40°C to +85°C)
UNITSV
NOTES1
DC ELECTRICAL CHARACTERISTICS PARAMETERLow Level @ RSTOutput Current @ 0.4VOperating CurrentVCC Trip Point 5%VCC Trip Point 10%VCC Trip Point 15%Output CapacitancePushbutton DetectPushbutton ReleaseInternal Pull-Up ResistorSYMBOLVOLIOLICCVCCTP0VCCTP1VCCTP2COUTPBDVPBRDRP (-40°C to +85°C; VDD = 5V ± 10%)MIN+8504.504.254.01.80.33.7554.6254.3754.1254.754.494.24103.30.86.25TYPMAX0.4UNITSVmAmAVVVpFVVkW11, 2111NOTES1AC ELECTRICAL CHARACTERISTICS PARAMETERRESET Active TimeVCC Detect to RSTVCC Slew Rate (4.75V - 4.00V)VCC Slew Rate (4.00V - 4.75V)Pushbutton DebounceVCC Detect to RSTSYMBOLtRSTtRPDtFtRPBDBtRPU (-40°C to +85°C; VCC = 5V ± 10%)MIN2503000250250350350450450TYP350MAX450100UNITSmsnsmsnsmsmsNOTESNOTES:
1)All voltages are referenced to ground.
2)With a 100pF to 0.01mF capacitor connected from RST to ground.
DS1233
ECONORESET SELECTION GUIDE
MEMORY存储芯片DS1233Z-10+T中文规格书 - 图文
