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SN74BCT2414 MEMORY DECODER WITH ON-CHIP SUPPLY VOLTAGE MONITOR
SCBS059B - MARCH 1989 - REVISED NOVEMBER 1993
* * * * * * *
BiCMOS Design Substantially Reduces Standby Current Two Independent 2-Line to 4-Line Decoders or One 3-Line to 8-Line Decoder Separate Enable Inputs for Easy Cascading Two Supply Voltage Terminals (VCC and Vbat ) Built-In Supply-Voltage Monitor for VCC Automatic Cut Off of Outputs During VCC Fail Package Options Include Plastic Small-Outline (DW) Packages and Standard Plastic 300-mil DIPs (N)
DW OR N PACKAGE (TOP VIEW)
VS SD 1A 2A 1B 2B 1G 2G G GND
1 2 3 4 5 6 7 8 9 10
20 19 18 17 16 15 14 13 12 11
VCC Vbat 1Y0 1Y1 1Y2 1Y3 2Y0 2Y1 2Y2 2Y3
description
The SN74BCT2414 is a decoder specially designed to be used in memory systems with battery backup during power failure. The two independent 2-line to 4-line decoders with separate and common control inputs may be externally cascaded to implement a 3-line to 8-line decoder. The circuit has two supply voltage inputs: the voltage monitor (bandgap) is powered via the VCC terminal; the internal logic of the circuit is powered via the Vbat terminal. In case VCC drops below 3.65 V (nominal), the voltage monitor forces the voltage-control (VS) and decoder outputs (Y) to the high level. VS may be used to disconnect the supply voltage of the memories (Vbat) from the system supply. This output is switched off when the on-chip supply voltage monitor detects a power failure. The SN74BCT2414 is characterized for operation from 0C to 70C.
PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.
Copyright (c) 1993, Texas Instruments Incorporated
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* DALLAS, TEXAS 75265
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SN74BCT2414 MEMORY DECODER WITH ON-CHIP SUPPLY VOLTAGE MONITOR
SCBS059B - MARCH 1989 - REVISED NOVEMBER 1993
logic symbol
20 VCOMP X > 3.65 V 1 VS
VCC
SD G
2 9
& EN
X/Y 1A 1B 1G 3 5 7 1
0 1
18 17 16 15 14 13 12 11
1Y0 1Y1 1Y2 1Y3 2Y0 2Y1 2Y2 2Y3
2 2 EN 3 X/Y 1 1 2 2 EN 3 0
2A 2B 2G
4 6 8
This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
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POST OFFICE BOX 655303
* DALLAS, TEXAS 75265
SN74BCT2414 MEMORY DECODER WITH ON-CHIP SUPPLY VOLTAGE MONITOR
SCBS059B - MARCH 1989 - REVISED NOVEMBER 1993
logic diagram (positive logic)
VCC 20 VCOMP 1
VS
Vbat
19
SD
2
18
1Y0
1A
3 17 1Y1
16
1Y2
1B
5
15
1Y3
1G
7
2G
8
G
9 14
2Y0
2A
4
13
2Y1
2B
6
12
2Y2
11 2Y3
POST OFFICE BOX 655303
* DALLAS, TEXAS 75265
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SN74BCT2414 MEMORY DECODER WITH ON-CHIP SUPPLY VOLTAGE MONITOR
SCBS059B - MARCH 1989 - REVISED NOVEMBER 1993
FUNCTION TABLES INPUTS CONTROL G H X X L L L L 1G X H X L L L L SD X X L H H H H SELECT 1B X X X L L H H 1A X X X L H L H 1Y0 H H H L H H H OUTPUTS 1Y1 H H H H L H H 1Y2 H H H H H L H 1Y3 H H H H H H L
INPUTS CONTROL G H X X L L L L 2G X H X H H H H SD X X L H H H H SELECT 2B X X X L L H H 2A X X X L H L H 2Y0 H H H L H H H
OUTPUTS 2Y1 H H H H L H H 2Y2 H H H H H L H 2Y3 H H H H H H L
NOTE: For a 3-line to 8-line decoder, the following pins must be shorted: 1G to 2G, 1A to 2A and 1B to 2B.
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage range, Vbat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 0.5 V to 7 V Supply voltage range, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 0.5 V to 7 V Supply voltage VCC with respect to Vbat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 1.5 V Input voltage range, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 0.5 V to VCC + 0.5 V Off-state output voltage range at VS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 0.5 V to 7 V Voltage range applied to any Y output in the power-off state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 0.5 V to 7 V Voltage applied to any Y output in the power-off state with respect to Vbat . . . . . . . . . . . . . . . . . . . . . . . . 0.5 V Operating free-air temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0C to 70C Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 65C to 150C
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability
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SN74BCT2414 MEMORY DECODER WITH ON-CHIP SUPPLY VOLTAGE MONITOR
SCBS059B - MARCH 1989 - REVISED NOVEMBER 1993
recommended operating conditions
MIN VCC Vbat VIH VIL IIK IOH IOL tt TA Supply voltage Supply voltage High-level input voltage Low-level input voltage Input clamp current High-level output current Low-level Low level output current Input transition time Operating free-air temperature Y outputs VS outputs 0 0 4.5 4.5 2 0.8 -18 - 400 8 20 10 70 NOM 5 5 MAX 5.5 5.5 UNIT V V V V mA A mA ns / V C
electrical characteristics over recommended operating free-air temperature range (unless otherwise noted)
PARAMETER VIK VOH VCC = 4.5 V, Vb t = VCC = 4 5 V 4.5 bat Vbat = 2 V, VCC = 0, VOL VT II IIH IIL IOH IO ICC VS All except VS VS Vb t = VCC = 4 5 V 4.5 bat Vbat = VCC = 4.5 V, Vbat = VCC = 5.5 V, Vbat = VCC = 5.5 V, Vbat = VCC = 5.5 V, Vbat = 4.5 V, Vbat = VCC = 5.5 V, Vb t = VCC = 5 5 V 5.5 bat Vbat = 2.5 V, Ibat Ci Co Any Y VS Vb t = VCC = 5 5 V 5.5 bat Vbat = VCC = 5 V, Vb t = VCC = 0 bat TEST CONDITIONS II = -18 mA IOH = - 20 A IOH = - 400 A IOH = - 50 A IOL = 4 mA IOL = 8 mA IOL = 20 mA 3.65 VI = 5.5 V VI = 2.7 V VI = 0.5 V VCC = 0 VO = 2.25 V Outputs high Outputs low VCC = 0 Outputs high Outputs low VI = 0 or 3 V 4 6.5 5 1 - 30 100 20 20 1 - 200 3 3 10 20 3 MIN 4.4 3.5 1.8 0.4 0.5 1 V A A A A mA mA A mA pF pF V V TYP MAX -1.2 UNIT V
All typical values are at VCC = 5 V, TA = 25C. This value represents the VCC monitor threshold voltage. Typical range is from 3.5 V to 3.8 V. This output condition has been chosen to produce a current that closely approximates one half of the short-circuit output current, IOS. Not more than one output should be tested at a time, and the duration of the test should not exceed one second.
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SN74BCT2414 MEMORY DECODER WITH ON-CHIP SUPPLY VOLTAGE MONITOR
SCBS059B - MARCH 1989 - REVISED NOVEMBER 1993
switching characteristics (see Note 1)
VCC = 5 V, CL = 50 pF, R1 = 500 , R2 = 500 , TA = 25C MIN tPLH tPHL tPLH tPHL tPLH tPHL A or B Any Y Any Y Any Y 1 2 1 2 2 2 TYP 5 5.8 4.5 5.5 6.5 6.5 MAX 10 10 9 9 11 11 VCC = 4.5 V to 5.5 V, CL = 50 pF, R1 = 500 , R2 = 500 , TA = MIN to MAX MIN 1 2 1 2 2 2 MAX 12 12 10 11 12 12 ns ns ns
PARAMETER
FROM (INPUT)
TO (OUTPUT)
UNIT
Any G SD
switching characteristics (see Note 1)
VCC = 5 V, CL = 50 pF, R1 = 500 , R2 = 500 , TA = 25C MIN tPLH tPHL tPLH tPHL VCC VCC Any Y VS 10 15 10 20 TYP 25 45 28 50 MAX 50 100 50 100 VCC = 4.5 V to 5.5 V, CL = 50 pF, R1 = 500 , R2 = 500 , TA = MIN to MAX MIN 10 15 10 20 MAX 250 250 250 250 ns ns
PARAMETER
FROM (INPUT)
TO (OUTPUT)
UNIT
For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions. NOTE 1: Load circuits and voltage waveforms are shown in Section 1.
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SN74BCT2414 MEMORY DECODER WITH ON-CHIP SUPPLY VOLTAGE MONITOR
SCBS059B - MARCH 1989 - REVISED NOVEMBER 1993
APPLICATION INFORMATION
A typical application circuit for a battery-buffered memory in a microcomputer system is shown in Figure 1 which uses the SN74BCT2414. When power fails, the supply-voltage supervisor (TL7705) resets the microcomputer and disables the memory by switching the shutdown input SD of the memory decoder to a logic zero. All memory decoder outputs are forced to a logic one. Abnormal write commands from the microprocessor, which may be issued during further voltage breakdown, no longer affect the contents of the memory. When the system supply voltage becomes lower than approximately 3.65 V, the voltage monitor inside the SN74BCT2414 memory decoder disconnects the input buffers of this circuit from the decoding logic internally and keeps all outputs at a logic one. The VS output is also switched off, disconnecting the system supply voltage from the memory circuits. During this low-voltage condition, the memory decoder and the memory circuits are supplied by the battery.
Microprocessor D0 - D7 A0 - A15 8 VCC D3 R3
16 DBIN WE RESET
R1 Q1 R2 1 k D1 1N4148
SN74BCT2414 VS A15 5V A14 10 k 1G 2G 1B TL7705A VCC SENSE RESIN VREF Ct GND 0.1 F A0 - A12 OE WR 8- x 8K-Byte CMOS RAM For further information on this device, please contact factory. RES A13 2B 1A 2A SD G VCC Vbat 1Y0 1Y1 1Y2 1Y3 2Y0 2Y1 2Y2 2Y3 CE VCC
0.1 F
Figure 1. Memory System With Battery Backup
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SN74BCT2414 MEMORY DECODER WITH ON-CHIP SUPPLY VOLTAGE MONITOR
SCBS059B - MARCH 1989 - REVISED NOVEMBER 1993
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POST OFFICE BOX 655303
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IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE ("CRITICAL APPLICATIONS"). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, AUTHORIZED, OR WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT DEVICES OR SYSTEMS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF TI PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER'S RISK. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI's publication of information regarding any third party's products or services does not constitute TI's approval, warranty or endorsement thereof.
Copyright (c) 1998, Texas Instruments Incorporated

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