dp8572a National Semiconductor Corporation, dp8572a Datasheet
dp8572a
Available stocks
Related parts for dp8572a
dp8572a Summary of contents
Page 1
... DP8572A DP8572AM Real Time Clock (RTC) General Description The DP8572A (8572AM militarized version) is intended for use in microprocessor based systems where information is required for multi-tasking data logging or general time of day date information This device is implemented in low voltage silicon gate microCMOS technology to provide low standby power in battery back-up environments The cir- cuit’ ...
Page 2
Absolute Maximum Ratings Specifications for the 883 version of this product are listed separately b Supply Voltage ( Input Voltage ( Output Voltage ( ...
Page 3
AC Electrical Characteristics e e PFAIL 10 Symbol READ TIMING t Address Valid Prior to Read Strobe AR t Read Strobe Width (Note Chip Select to Data ...
Page 4
Military Version Absolute Maximum Ratings The 883 specifications are written to reflect the current (at the time of printing) Rel Electrical Test Specifica- tions (RETS) established by National Semiconductor for this product For a copy of the latest version ...
Page 5
Military Version AC Electrical Characteristics e e PFAIL and Symbol READ TIMING t Address Valid Prior to Read Strobe AR t Read Strobe Width (Note ...
Page 6
Timing Waveforms Read Timing Diagram Write Timing Diagram 9980 – 9980 – 4 ...
Page 7
... General Description (Continued) The DP8572A’s interrupt structure provides three basic types of interrupts Periodic Alarm Compare and Power Fail Interrupt mask and status registers enable the masking and easy determination of each interrupt Pin Description (Inputs) These pins interface to mP control ...
Page 8
... Functional Description The DP8572A contains a fast access real time clock inter- rupt control logic power fail detect logic and CMOS RAM All functions of the RTC are controlled by a set of seven registers A simplified block diagram that shows the major functional blocks is given in Figure 1 ...
Page 9
... Real Time Mode Register If the DP8572A is configured for single supply mode an extra 50 mA may be consumed until the crystal select bits are programmed The user should also ensure ...
Page 10
Functional Description (Continued) The oscillator is programmed via the Real Time Mode Reg- ister to operate at various frequencies The crystal oscillator is designed to offer optimum performance at each frequen- cy Thus at 32 768 kHz the oscillator is ...
Page 11
... POWER FAILURE CIRCUITRY FUNCTIONAL DESCRIPTION Since the clock must be operated from a battery when the main system supply has been turned off the DP8572A pro- vides circuitry to simplify design in battery backed systems This switches over to the back up supply and isolates itself from the host system Figure 6 shows a simplified block ...
Page 12
Functional Description (Continued) 12 ...
Page 13
... If a lock-out delay is enabled the DP8572A will remain active for 480 ms after power fail is detected This will enable the mP to perform last minute bookkeeping before total system collapse ...
Page 14
... PFAIL pin) Thus writing a one to the Time Save bit enables both a software write or power fail write SINGLE POWER SUPPLY APPLICATIONS The DP8572A can be used in a single power supply applica- tion To achieve this the V pin must be connected to BB ...
Page 15
... D6 the oscillator reference is enabled thus the oscillator is referenced to V This allows operation in standard battery BB standby applications At initial power on if the DP8572A is going to be pro- grammed for battery backed mode the V connected to a potential in the range For single supply mode operation the V ...
Page 16
Functional Description (Continued) D5 The Delay Enable bit is used when a power fail occurs If this bit is set a 480 ms delay is generated internally before the mP interface is locked out This will enable the mP to ...
Page 17
... D4 of the Real Time Mode Register D7 The MSB of this register is the enable bit for the Power Fail Interrupt When this bit is set to a one an interrupt will be generated to the mP when V backed mode is selected and the DP8572A is in standby ...
Page 18
Control and Status Register Address Bit Map Main Status Register ADDRESS Page Register RAM Select Select e e Periodic Flag Register ...
Page 19
... Application Hints Suggested Initialization Procedure for DP8572A in Battery Backed Applications that use the V Pin BB 1 Enter the test mode by writing bit D7 in the Period- ic Flag Register 2 Write zero to the RAM TEST mode Register located in page 0 address HEX 1F 3 Leave the test mode by writing bit D7 in the Peri- ...
Page 20
Typical Performance Characteristics Operating Current vs Supply Voltage (Single Supply Mode 768 kHz) OSC Standby Current vs Power Supply Voltage 768 kHz) OSC Operating Current vs Supply Voltage (Battery Backed Mode ...
Page 21
... Physical Dimensions inches (millimeters) 24-Lead Hermetically Sealed Dual-In-Line Package (D) Order Number DP8572AMD 883 NS Package Number D24C Molded Dual-In-Line Package (N) Order Number DP8572AN NS Package Number N24C 21 ...
Page 22
... National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications Plastic Chip Carrier Package (V) Order Number DP8572AV NS Package Number V28A 2 A critical component is any component of a life ...