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74F845 8-Bit Transparent Latch
April 1988 Revised August 1999
74F845 8-Bit Transparent Latch
General Description
The 74F845 bus interface latch is designed to eliminate the extra packages required to buffer existing latches and provide extra data width for wider address/data paths or buses carrying parity. The 74F845 is functionally- and pin-compatible with AMD's Am29845.
Features
s 3-STATE outputs s Direct replacement for AMD's Am29845
Ordering Code:
Order Number 74F845SC 74F845SPC Package Number M24B N24C Package Description 24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide 24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-100, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter "X" to the ordering code.
Logic Symbols
Connection Diagram
IEEE/IEC
(c) 1999 Fairchild Semiconductor Corporation
DS009601
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74F845
Unit Loading/Fan Out
Pin Names D0-D7 O0-O7 OE1-OE3 LE CLR PRE Description Data Inputs Data Outputs Output Enables Latch Enable Clear Preset U.L. HIGH/LOW 1.0/1.0 150/40 1.0/1.0 1.0/1.0 1.0/1.0 1.0/1.0 Input IIH/IIL Output IOH/IOL 20 A/-0.6 mA -3.0 A/24 mA 20 A/-0.6 mA 20 A/-0.6 mA 20 A/-0.6 mA 20 A/-0.6 mA
Functional Description
The 74F845 consists of eight D-type latches with 3-STATE outputs. The flip-flops appear transparent to the data when Latch Enable (LE) is HIGH. This allows asynchronous operation as the output transition follows the data in transition. On the LE HIGH-to-LOW transition, the data that meets the setup times is latched. Data appears on the bus when the output Enable (OE) is LOW. When OE is HIGH, the bus output is in the high impedance state.
Function Table
Inputs CLR PRE OE H H H H H H H H L L L H H H H H H H H L H L H L H H H H L L L L L L H H LE X H H L H H L X X X L L D X L H X L H X X X X X X Internal Output Function Q X L H NC L H NC H L H L H O Z Z Z Z L H NC H L H Z Z High Z High Z High Z Latched Transparent Transparent Latched Preset Clear Preset Latched Latched
H = HIGH Voltage Level L = LOW Voltage Level X = Immaterial
Z = High Impedance NC = No Change
Logic Diagram
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
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74F845
Absolute Maximum Ratings(Note 1)
Storage Temperature Ambient Temperature under Bias Junction Temperature under Bias VCC Pin Potential to Ground Pin Input Voltage (Note 2) Input Current (Note 2) Voltage Applied to Output in HIGH State (with VCC = 0V) Standard Output 3-STATE Output Current Applied to Output in LOW State (Max) twice the rated IOL (mA) -0.5V to VCC -0.5V to +5.5V -65C to +150C -55C to +125C -55C to +150C -0.5V to +7.0V -0.5V to +7.0V -30 mA to +5.0 mA
Recommended Operating Conditions
Free Air Ambient Temperature Supply Voltage 0C to +70C +4.5V to +5.5V
Note 1: Absolute maximum ratings are values beyond which the device may be damaged or have its useful life impaired. Functional operation under these conditions is not implied. Note 2: Either voltage limit or current limit is sufficient to protect inputs.
DC Electrical Characteristics
Symbol VIH VIL VCD VOH Parameter Input HIGH Voltage Input LOW Voltage Input Clamp Diode Voltage Output HIGH Voltage 10% VCC 10% VCC 5% VCC 5% VCC VOL IIH IBVI ICEX VID IOD IIL IOZH IOZL IOS IZZ ICCZ Output LOW Voltage Input HIGH Current Input HIGH Current Breakdown Test Output HIGH Leakage Current Input Leakage Test Output Leakage Circuit Current Input LOW Current Output Leakage Current Output Leakage Current Output Short-Circuit Current Bus Drainage Test Power Supply Current 63 -60 4.75 3.75 -0.6 50 -50 -150 500 85 10% VCC 2.5 2.4 2.7 2.7 0.5 5.0 7.0 50 V A A A V A mA A A mA A mA Min Max Max Max 0.0 0.0 Max Max Max Max 0.0V Max V Min Min 2.0 0.8 -1.2 Typ Max Units V V V Min VCC Conditions Recognized as a HIGH Signal Recognized as a LOW Signal IIN = -18 mA IOH = -1 mA IOH = -3 mA IOH = -1 mA IOH = -3 mA IOL = 24 mA VIN = 2.7V VIN = 7.0V VOUT = VCC IID = 1.9 A All Other Pins Grounded VIOD = 150 mV All Other Pins Grounded VIN = 0.5V VOUT = 2.7V VOUT = 0.5V VOUT = 0V VOUT = 5.25V VO = HIGH Z
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74F845
AC Electrical Characteristics
TA = +25C Symbol Parameter Min tPLH tPHL tPLH tPHL tPLH tPHL tPZH tPZL tPHZ tPLZ Propagation Delay Dn to On Propagation Delay LE to On Propagation Delay PRE to On Propagation Delay CLR to On Output Enable Time OE to On Output Disable Time OE to On 2.5 1.5 5.0 2.0 3.0 VCC = +5.0V CL = 50 pF Typ 4.8 3.6 8.1 4.4 5.9 Max 8.0 6.5 12.0 7.5 10.0 TA= 0C to +70C VCC = +5.0V CL = 50 pF Min 2.0 1.5 4.5 2.0 2.5 Max 9.0 7.0 13.5 8.0 11.0 ns ns ns Units
3.0 2.5 2.5 1.0 1.0
6.5 5.8 7.6 3.1 2.8
10.0 9.5 12.0 7.5 6.5
2.5 2.0 2.0 1.0 1.0
11.0 10.5 13.0 8.5 7.5
ns
ns
ns
AC Operating Requirements
TA = +25C Symbol Parameter VCC = +5.0V Min tS(H) tS(L) tH(H) tH(L) tW(H) tW(L) tW(L) tREC tREC Setup Time, HIGH or LOW Dn to LE Hold Time, HIGH or LOW Dn to LE LE Pulse Width, HIGH PRE Pulse Width, LOW CLR Pulse Width, LOW PRE Recovery Time CLR Recovery Time 2.0 2.0 2.5 3.0 4.0 5.0 5.0 10.0 12.0 Max TA= 0C to +70C VCC = +5.0V Min 2.5 2.5 3.0 3.5 4.0 5.0 5.0 10.0 13.0 Max ns ns ns ns ns ns ns Units
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74F845
Physical Dimensions inches (millimeters) unless otherwise noted
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide Package Number M24B
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74F845 8-Bit Transparent Latch
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-100, 0.300 Wide Package Number N24C
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and Fairchild reserves the right at any time without notice to change said circuitry and specifications. LIFE SUPPORT POLICY FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. www.fairchildsemi.com 6 2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com

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