ltc1235 Linear Technology Corporation, ltc1235 Datasheet
ltc1235
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ltc1235 Summary of contents
Page 1
... ADJ +3V 51k 10k THE LTC1235 EXTENDS BATTERY LIFE BY PROVIDING BATTERY POWER ONLY WHEN REQUIRED TO BACK UP RAM DATA. IT SAVES THE BATTERY WHEN NO DATA BACKUP IS NEEDED. THE μP REQUESTS BACKUP WITH THE BACKUP PIN. DESCRIPTION ® The LTC 1235 provides complete power supply monitoring ...
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... X LTC699 8 X LTC1232 Output Current ................... Short Circuit Protected OUT Power Dissipation ...............................................500mW Operating Temperature Range LTC1235C ................................................ 0°C to 70°C + 0.3V) CC Storage Temperature Range ................... –65°C to 150°C Lead Temperature (Soldering, 10 sec.) ................. 300°C RESET 16 RESET 15 WDO OUT ...
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... 10μ SINK 1.6mA 4.25V SINK 1μ SOURCE 1.6mA SINK 1μ 4.25V SOURCE CC LTC1235 = 2.8V, Backup = No Connection, BATT MIN TYP MAX UNITS 4.75 5.50 2.00 4.25 V – 0.05 V – 0.005 – 0.1 V – 0.005 – 0.5 V – 0. ...
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... Note 4: The input pins of PB RST, BACKUP and CE IN, have weak internal pullups which pull to the supply when the input pins are fl oating. Note 5: The LTC1235 can be programmed either to provide or not to provide battery backup power to the V pin during power failure. ...
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... PFI PFO 1.3V – 1.315V V = 20mV STEP PFI 1.295V 0 60 120 140 100 TIME (μs) LTC1235 Power Failure Input Threshold vs Temperature 1.308 1.306 ° C 1.304 1.302 1.300 1.298 1.296 1.294 500 –50 – TEMPERATURE ( 1235 G02 Reset Voltage Threshold vs Temperature 4 ...
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... Memory Logic keeps M2 off even after V is lower than V , falls below V CC BATT be pulled high by an internal pullup and the LTC1235 will provide battery backup when V through BATT PFI (Pin 9): Power Failure Input. PFI is the noninverting input to the Power Fail Comparator, C3. The inverting input ...
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... WDI pin, or LOW LINE goes low. The watchdog timer can be disabled by fl oating WDI (see Figure 11). RESET (Pin 15): Logic output for μP reset control. The LTC1235 provides three ways to generate μP reset. First, whenever V falls below either the reset voltage threshold CC , RESET goes active low ...
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... V rises above the reset voltage threshold. CC Push-Button Reset The LTC1235 provides an logic input pin for direct con- nection to a push-button. The push-button reset input, PB RST, requires an active low signal. Internally, this input signal is debounced and timed for a minimum of 40ms. When this condition is satisfi ed, the reset pulse generator forces the reset outputs to active states ...
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... BATT GND +3V Figure 3. Using BATT ON to Drive External PNP Transistor The LTC1235 is protected for safe area operation with short circuit limit. Output current is limited to approximately 200mA. If the device is overloaded for a long period of time, thermal shutdown turns the power switch off until the device cools down. The threshold temperature for thermal shutdown is approximately 155° ...
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... Although battery standby current is only a tiny leakage current, it can still charge up the stray capacitance on the follows: When V the LTC1235 switches to battery backup or battery sav- ing mode. In either case, the battery supply current pulls V low and the device goes back to normal operation. ...
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... CE IN Chip Enable Input is ignored. CE OUT Logic high. The open circuit output voltage is equal to V Memory Protection The LTC1235 includes memory protection circuitry which ensures the integrity of the data in memory by preventing is at invalid level. Two pins, CE write operations when V CC BACKUP = V ...
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... LTC1235 APPLICATIONS INFORMATION Power Fail Warning The LTC1235 generates a Power Failure Output (PFO) for early warning of failure in the microprocessor’s power sup- ply. This is accomplished by comparing the Power Failure Input (PFI) with an internal 1.3V reference. PFO goes low when the voltage at PFI pin is less than 1.3V. Typically ...
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... Watchdog Input (WDI) within the time-out period, the reset outputs are forced to active states for a minimum of 140ms. The watchdog time-out period is fi xed at 1.0 second minimum on the LTC1235. This time-out period provides adequate time for many systems to service the watchdog timer immediately after a reset ...
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... CE OUT 20ns V BATT PROPAGATION CE IN BACKUP DELAY LOW LINE GND 0.1μ 0.1μF C μP SYSTEM OPTIONAL CONNECTION FOR ADDITIONAL RAMs 0.1μF 1235 TA3 V CC 62512 RAM 62128 RAM 62128 RAM LTC1235 TA4 1235fa ...
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... NOTE 4 .093 – .104 × 45° (2.362 – 2.642) 0° – 8° TYP .050 (1.270) BSC .014 – .019 .016 – .050 (0.356 – 0.482) (0.406 – 1.270) TYP LTC1235 .770* (19.558) MAX .045 – .065 (1.143 – ...
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... LTC1235 RELATED PARTS PART NUMBER DESCRIPTION LTC690 Single Channel Supervisor LTC691 Single Channel Supervisor LTC692 Single Channel Supervisor LTC693 Single Channel Supervisor LTC694 Single Channel Supervisor LTC695 Single Channel Supervisor LTC699 Single Channel Supervisor Linear Technology Corporation 16 1630 McCarthy Blvd., Milpitas, CA 95035-7417 ...