DS1238A-5+ Maxim Integrated Products, DS1238A-5+ Datasheet
DS1238A-5+
Specifications of DS1238A-5+
Related parts for DS1238A-5+
DS1238A-5+ Summary of contents
Page 1
... When an out-of-tolerance condition occurs, the microprocessor reset and power-fail outputs are forced active, and static RAM control unconditionally write protects external memory. The DS1238A also provides early warning detection of a user-defined threshold by driving a non-maskable interrupt. External reset control is provided by a pushbutton reset ...
Page 2
... The V RST so that the , RST and RVT RST The V for the 5% operation option (DS1238A-5) is set for 4.75 volts (4.62 typical). The RST and CCTP signals are excellent for microprocessor reset control, as processing is stopped at the last possible RST moment of in-tolerance power-up, CC ...
Page 3
... DS1238A FUNCTIONAL BLOCK DIAGRAM Figure 1 WATCHDOG TIMER The DS1238A provides a watchdog timer function which forces the active state when the strobe input ( is described below in NO TAG. The watchdog timeout period begins as soon as RST and inactive high-to-low transition occurs at the and begins to timeout again. The watchdog timer does not timeout, a high-to-low transition on timeout of the watchdog as described in the AC Electrical Characteristics ...
Page 4
... RST or NMI When the supply being monitored decays to the voltage sense point, the DS1238A will force the output to an active state. Noise is removed from the time domain hysteresis. That is, the monitored supply is sampled periodically at a rate determined by an internal ring oscillator running at approximately 30 kHz (33 s/cycle) ...
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... POWER MONITOR, WATCHDOG TIMER, AND PUSHBUTTON RESET Figure 3 PUSHBUTTON RESET TIMING Figure 4 Watchdog Timeout Period (typ) First Period Other Timeout Following a Reset 20480 Clks 5120 Clocks 2.2 sec 550 ms X Cpf 2.7 sec 170 ms 2.7 sec 2.7 sec is below DS1238A Reset Active Duration 641 Clks Cpf X Cpf BAT ...
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... Example 1: 5-Volt Supply 10k Ohms 4.8 Volts SENSE R1 10k 4 1. 27.8k Ohm 10k FROM IN INPUT Figure 6 NMI x 5.0 = VMAX Example 2: 12-Volt Supply 10k Ohms 9.0 Volts SENSE R1 9 MAX 10k x 1. 60.9k Ohm 10k 9.00 x 5.0 = 35.4 Volts 1.27 DS1238A ...
Page 7
... MEMORY BACKUP The DS1238A provides all of the necessary functions required to battery back a static RAM. First, an internal switch is provided to supply SRAM power from the primary 5-volt supply (V external battery (V ), whichever is greater. Second, the same power-fail detection described in the BAT power monitor section is used to hold the chip enable output ( ...
Page 8
... POWER SWITCHING Figure 8 Note: If freshness on the DS1238A is not used, and V for system use. BAT01 TIMING DIAGRAMS This section provides a description of the timing diagrams shown in Figure 9 and Figure 10. Figure 9 illustrates the relationship for power down the processor is notified of an impending power failure via an active to save critical data in nonvolatile SRAM ...
Page 9
... POWER-DOWN TIMING Figure DS1238A ...
Page 10
... POWER-UP TIMING Figure DS1238A ...
Page 11
... MAX UNITS NOTES 5.0 5.5 V 5 MAX UNITS NOTES 4 mA 200 nA 100 -0.8 V 0.4 V -0.1V V -0.8 V +1.0 A +1 4.37 4.50 V 4.62 4.75 V +1.0 A 1.27 1.35 V DS1238A 10 ...
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... FPU t 40 100 RPU t 10 FB1 t 0.1 REC 1.7 2.7 TD 110 170 t 20480 TD 5120 t PPF f 0 OSC SYMBOL MIN TYP OUT DS1238A = 5V 10%) CC MAX UNITS NOTES 175 s 175 s 150 144 11 s 100 ns 150 clocks clocks 2 s 250 kHz (t = MAX UNITS NOTES ...
Page 13
... DS1238A can supply at V CCO1 during normal 5-volt operation the maximum average load which the DS1238A can supply through the V CCO2 retention battery supply operation, with a maximum drop of 0.8 volts for commercial, 1.0V for industrial. ...