View DS1221_153577.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

DS1221 Nonvolatile Controller x 4 Chip
www.dalsemi.com NOT RECOMMENDED FOR NEW DESIGNS, SEE DS1321 DATASHEET INSTEAD.
FEATURES
Converts CMOS RAMs into nonvolatile memories Data is automatically protected during power loss 2-to-4 decoder provides for up to 4 CMOS RAMs Provides for redundant batteries Test battery condition on power-up Full 10% operating range Unauthorized access can be prevented with optional security feature 16-pin 0.3-inch DIP saves PC board space Optional 16-pin SOIC surface mount package Optional industrial temperature range of -40C to +85C available
PIN ASSIGNMENT
VCCO VBAT1 *RST A B *RD *WE GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VCCI VBAT2 CE CE0 CE1 CE2 CE3 *D/Q
DS1221 16-Pin DIP (300-mil) See Mech. Drawings Section
VCCO VBAT1 *RST A B *RD *WE GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VCCI VBAT2 CE CE0 CE1 CE2 CE3 *D/Q
PIN DESCRIPTION
A, B
CE CE0 - CE3
VBAT1 VBAT2 * RST VCCI VCCO * RD * WE *D/Q
- Address Inputs - Chip Enable Input - Chip Enable Outputs - + Battery 1 - + Battery 2 - Reset - +5V Supply - RAM Supply - Read Inpu - Write Input - Data Input/Output
DS1221 16-Pin SOIC (300-mil) See Mech. Drawings Section
*Used with optional security circuit only and must be connected to ground in all other cases.
DESCRIPTION
The DS1221 Nonvolatile Controller x 4 Chip is a CMOS circuit which solves the application problem of converting CMOS RAMs into nonvolatile memories. Incoming power is monitored for an out-oftolerance condition. When such a condition is detected, the chip enable outputs are inhibited to accomplish write protection and the battery is switched on to supply RAMs with uninterrupted power. An optional security code prevents unauthorized users from obtaining access to the memory space. The nonvolatile controller/decoder circuitry uses a low-leakage CMOS process which affords precise voltage detection at extremely low battery consumption. By combining the DS1221 with up to four CMOS memories and lithium batteries, nonvolatile operation can be achieved. 1 of 8 111899
DS1221
CONTROLLER /DECODER OPERATION
The DS1221 nonvolatile controller performs six circuit functions required to decode and battery-backup a bank of up to four CMOS RAMs. First, a 2-to-4 decoder provides selection of one of four RAMs (see Figure 1). Second, a switch is provided to direct power from the battery or VCCI supply, depending on which is greater, to the VCCO pin. This switch has a voltage drop of less than 0.2V. The third function which the nonvolatile controller provides is power-fail detection. The DS1221 constantly monitors the VCCI supply. When VCCI falls below 4.5 volts, a precision comparator detects the condition and inhibits the RAM chip enables ( CE0 through CE3 ). The fourth function of write protection is accomplished by holding all chip enable outputs ( CE0 through CE3 ) to within 0.2 volts of VCCI or battery supply. If the Chip Enable Input ( CE ) is low at the time power-fail detection occurs, the chip enable outputs are kept in their present state until CE is driven high. The delay of write protection until the current memory cycle is completed prevents the corruption of data. Power failure detection occurs in the range of 4.5 to 4.25 volts. During nominal supply conditions the chip enable outputs follow the logic of a 2-to-4 decoder. The fifth function the DS1221 performs is to check battery status to warn of potential data loss. Each time that VCCI power is restored the battery voltage is checked with a precision comparator. If the connected battery voltage is less than 2 volts, the second memory cycle is inhibited. Battery status can, therefore, be determined by performing a read cycle after power-up to any location in memory, verifying that memory location content. A subsequent write cycle can then be executed to the same memory location, altering the data. If the next read cycle fails to verify the written data, the contents of the memories are questionable. The sixth function of the nonvolatile controller provides for battery redundancy. In many applications, data integrity is paramount. In these applications it is often desirable to use two batteries to ensure reliability. The DS1221 provides an internal isolation switch which provides for connection of two batteries. During battery back-up operation the battery with the highest voltage is selected for use. If one battery should fail, the other will automatically take over. The switch between batteries is transparent to the user. A battery status warning will occur if both batteries are less than 2.0 volts. If only one battery is used, the second battery input must be grounded. Figure 2 illustrates the connections required for the DS1221 in a typical application.
NONVOLATILE CONTROLLER/DECODER Figure 1
VCCI >=4.5 <4.25 >=4.5 >=4.5 >=4.5 >=4.5 H = High Level L = Low Level X = Irrelevant
CE
H X L L L L
INPUTS B X X L L H H
OUTPUTS A X X L H L H
CE0 CE1 CE2 CE3
H H L H H H
H H H L H H
H H H H L H
H H H H H L
2 of 8
DS1221
TYPICAL APPLICATION Figure 2
SECURITY SEQUENCE Figure 3
OUTPUT LOAD Figure 4
3 of 8
DS1221
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature Short Circuit Output Current * -0.3V to +7.0V 0C to 70C -55C to +125C 260C for 10 seconds 20 mA
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
PARAMETER Supply Voltage Logic 1 Input Logic 0 Input Battery Input SYMBOL VCCI VIH VIL VBAT1, VBAT2 MIN 4.5 2.2 -0.3 2.0 TYP 5.0 MAX 5.5 VCC+0.3 +0.8 4.0
(0C to 70C)
UNITS V V V V NOTES 1 1 1 1, 2
DC ELECTRICAL CHARACTERISTICS
PARAMETER Supply Current Supply Voltage Supply Current Input Leakage Output Leakage CE0 - CE3 , DQ Output @ 2.4V CE0 - CE3 , DQ Output @ 0.4V VCC Trip Point SYMBOL ICCI VCCO ICCO1 IIL ILO IOH IOL VCCTP 4.25 MIN VCC-0.2 -1.0 -1.0 -1.0
(0C to 70C; VCC = 4.5 to 5.5V)
TYP MAX 5 80 +1.0 +1.0 UNITS mA V mA A A mA mA V NOTES 3 1 4, 10
5 5 1
4.0 4.37 4.50
(0C to 70C; VCC < 4.25V)
PARAMETER CE0 - CE3 Output VBAT1 or VBAT2 Battery Current Battery Backup Current @ VCCO = VBAT - 0.5V SYMBOL VOHL IBAT ICCO2 MIN
VCC-0.2 VBAT-0.2
TYP
MAX 0.1 100
UNITS V A A
NOTES 3 6, 7, 10
4 of 8
DS1221
CAPACITANCE
PARAMETER Input Capacitance Output Capacitance SYMBOL CIN COUT MIN TYP MAX 5 7
(tA = 25C)
UNITS pF pF NOTES
AC ELECTRICAL CHARACTERISTICS
PARAMETER CE Propagation Delay CE High to Power-Fail Address Setup SYMBOL tPD tPF tAS MIN 5 20
(0C to 70C; VCC = 4.5 to 5.5V)
TYP 15 MAX 25 0 UNITS ns ns ns NOTES 5 9
(0C to 70C; VCC < 4.5V)
PARAMETER Recovery at Power-Up VCC Slew Rate 4.5 - 4.25V VCC Slew Rate 4.25 - 3V VCC Slew Rate 4.25 - 4.5V CE Pulse Width SYMBOL tREC tF tFB tR tCE MIN 2 300 10 0 TYP 5 MAX 10 UNITS ms s s s s NOTES
1.5
7, 8
NOTES:
1. All voltages are referenced to ground. 2. Only one battery input is required. 3. Measured with VCCO and CE0 - CE3 open. 4. ICCO1 is the maximum average load which the DS1221 can supply to the memories. 5. Measured with a load as shown in Figure 4. 6. ICCO2 is the maximum average load current which the DS1221 can supply to the memories in the battery back-up mode. 7. Chip enable outputs CE0 - CE3 can only sustain leakage current in the battery back-up mode. 8. tCE max. must be met to ensure data integrity on power loss. 9. tAS is only required to keep the decoder outputs glitch-free. While CE is low, the outputs ( CE0 - CE3 ) will be defined by inputs A and B with a propagation delay of tPD from an A or B input change. 10. For applications where higher currents are required, please see the DS1259 Battery Manager Chip data sheet.
5 of 8
DS1221
SECURITY OPTION
When activated by Dallas Semiconductor, the security option prevents unauthorized access. A sequence of events must occur to gain access to the memories (Figure 3). First, a dummy read cycle or a 200 ns active low reset pulse is executed to initialize the sequence. Second, a 64-bit access code must be consecutively written to the DS1221 using the write enable signal ( WE ), the chip enable signal ( CE ), and the data input/output signal (DQ). The code is written to the DS1221 without regard to the address. Actual RAM locations are not written, as the security option is intercepting the data path until access is granted. Instead, a special 64-bit write only register is written. Following the 64 write cycles, the register is compared to a 64-bit pattern uniquely defined by the user and programmed into the DS1221 by Dallas Semiconductor at the time of manufacture. This pattern can only be interrogated by an intelligent controller within the DS1221 and cannot be read by the user. If a read cycle occurs before 64 write cycles are completed, the security sequence is aborted. When a correct match for 64 bits is received, the third part of the security sequence begins by reading a 64-bit read only register. This register consists of 64 bits also defined by the user and programmed into the DS1221 by Dallas Semiconductor at the time of manufacture. For each of the 64 read cycles, 1 bit of the user-defined read only register is driven onto the DQ line. This phase also requires that the 64 read cycles be consecutive. The data being read from the read only register can be used by software to determine if the DS1221 will be permitted to be used with that particular system. After the 64th read cycle has been executed the DS1221 is unlocked and all subsequent memory cycles will be passed through and will become actual memory accesses based upon address inputs. If VCC falls below 4.5 volts or the reset line is driven low, the entire security sequence must be executed again in order to access memory locations.
NOTE:
Contact Dallas Semiconductor sales office for code assignments.
SECURITY OPTION AC ELECTRICAL CHARACTERISTICS
PARAMETER Read Cycle Time CE Access Time RD Access Time CE to Output Low Z RD to Output Low Z CE to Output High Z RD to Output High Z Read Recovery Write Cycle Write Pulse Width Write Recovery Data Setup Data Hold Time CE Pulse Width Reset Pulse Width SYMBOL tRC tCO tOE tCOE tOEE tOD tODO tRR tWC tWP tWR tDS tDH tCW tRST MIN 250
(0C to 70C; VCC = 5V 10%)
TYP MAX 200 100 10 10 100 100 UNITS ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns NOTES
50 250 170 50 100 0 170 200
6 of 8
DS1221
POWER-DOWN Figure 5
POWER-UP Figure 6
7 of 8
DS1221
READ CYCLE TO SECURITY OPTION Figure 7
WRITE CYCLE TO SECURITY OPTION Figure 8
NOTES:
1. tDH and tDS are functions of the first occurring edge of WE or CE . 2. tWR is a function of the latter occurring edge of WE or CE .
RESET FOR SECURITY OPTION Figure 9
8 of 8

▲Up To Search▲

Price & Availability of DS1221

	To Download DS1221 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .