SN74F1056 8-BIT SCHOTTKY BARRIER DIODE BUS-TERMINATION ARRAY SDFS085A – AUGUST 1992 – REVISED JULY 1997 D D D SC PACKAGE (TOP VIEW) Designed to Reduce Reflection Noise Repetitive Peak Forward Current 300 mA 8-Bit Array Structure Suited for Bus-Oriented Systems D01 D02 D03 D04 GND GND D05 D06 D07 D08 description This Schottky barrier diode bus-termination array is designed to reduce reflection noise on memory bus lines. This device consists of an 8-bit high-speed Schottky diode array suitable for a clamp to GND. The SN74F1056 is characterized for operation from 0°C to 70°C. 1 2 3 4 5 6 7 8 9 10 D PACKAGE (TOP VIEW) D01 D02 D03 D04 D05 D06 D07 D08 1 16 2 15 3 14 4 13 5 12 6 11 7 10 8 9 NC GND GND GND GND GND GND NC schematic diagrams SC Package D Package 1 1 D01 D02 D01 2 D02 2 15 D03 GND 3 3 D03 14 6 GND 4 D04 GND 4 D04 13 7 D05 D05 5 GND D06 D07 GND 5 8 12 GND 6 D06 9 11 GND 7 D07 10 10 8 D08 GND D08 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Copyright 1997, Texas Instruments Incorporated 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. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 SN74F1056 8-BIT SCHOTTKY BARRIER DIODE BUS-TERMINATION ARRAY SDFS085A – AUGUST 1992 – REVISED JULY 1997 absolute maximum ratings over operating free-air temperature range (unless otherwise noted)† Steady-state reverse voltage, VR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V Continuous forward current, IF: Any D terminal from GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 mA Total through all GND terminals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 mA Repetitive peak forward current, IFRM (see Note 1): Any D terminal from GND . . . . . . . . . . . . . . . . . . 300 mA Total through all GND terminals . . . . . . . . . . . . . . . 1.2 A Continuous total power dissipation at (or below) 25°C free-air temperature . . . . . . . . . . . . . . . . . . . . . 500 mW Operating free-air temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C † 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. NOTE 1: These values apply for tw ≤ 100 µs, duty cycle ≤ 20%. electrical characteristics over recommended operating free-air temperature range (unless otherwise noted) single-diode operation (see Note 2) PARAMETER IR Static reverse current VF Static forward voltage VFM Peak forward voltage Ct Total capacitance TEST CONDITIONS MIN VR = 7 V IF = 18 mA TYP‡ MAX 2 IF = 50 mA IF = 200 mA 0.8 1 1 1.2 1.23 VR = 0, VR = 2 V, UNIT µA V V f = 1 MHz 3 3.75 f = 1 MHz 2.5 3 pF ‡ All typical values are at TA = 25°C. NOTE 2: Test conditions and limits apply separately to each of the diodes. The diodes not under test are open-circuited during the measurement of these characteristics. multiple-diode operation PARAMETER TEST CONDITIONS MIN Ix Internal crosstalk current Total GND current = 1.2 A, See Note 3 ‡ All typical values are at TA = 25°C. NOTE 3: Ix is measured under the following conditions with one diode static, all others switching: Switching diodes: tw = 100 µs, duty cycle = 20% Static diode: VR = 5 V The static diode input current is the internal crosstalk current Ix. TYP‡ MAX 10 50 TYP MAX 5 7 TYP MAX 0.6 0.7 UNIT µA switching characteristics, TA = 25°C PARAMETER trr Reverse recovery time TEST CONDITIONS IF = 10 mA, IRM(REC) = 10 mA, IR(REC) = 1 mA, MIN RL = 100 Ω UNIT ns undershoot characteristics PARAMETER VUS 2 Undershoot voltage TEST CONDITIONS tf = 2 ns, tw = 50 ns, VIH = 5 V, VIL = 0, ZS = 25 Ω, ZO = 50 Ω, L = 36-inch coax POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 MIN UNIT V SN74F1056 8-BIT SCHOTTKY BARRIER DIODE BUS-TERMINATION ARRAY SDFS085A – AUGUST 1992 – REVISED JULY 1997 APPLICATION INFORMATION Large negative transients occurring at the inputs of memory devices (DRAMs, SRAMs, EPROMs, etc.) or on the CLOCK lines of many clocked devices can result in improper operation of the devices. The SN74F1056 diode termination array helps suppress negative transients caused by transmission-line reflections, crosstalk, and switching noise. Diode terminations have several advantages when compared to resistor termination schemes. Split resistor or Thevenin equivalent termination can cause a substantial increase in power consumption. The use of a single resistor to ground to terminate a line usually results in degradation of the output high level, resulting in reduced noise immunity. Series damping resistors placed on the outputs of the driver reduce negative transients, but they also can increase propagation delays down the line, as a series resistor reduces the output drive capability of the driving device. Diode terminations have none of these drawbacks. The operation of the diode arrays in reducing negative transients is explained in the following figures. The diode conducts current when the voltage reaches a negative value large enough for the diode to turn on. Suppression of negative transients is tracked by the current-voltage characteristic curve for that diode. A typical current versus voltage plot for the SN74F1056 is shown in Figure 1. To illustrate how the diode arrays act to reduce negative transients at the end of a transmission line, the test setup in Figure 2(a) was evaluated. The resulting waveforms with and without the diode are shown in Figure 2(b). The maximum effectiveness of the diode arrays in suppressing negative transients occurs when the diode arrays are placed at the end of a line and/or the end of a long stub branching off a main transmission line. The diodes also can be used to reduce the negative transients that occur due to discontinuities in the middle of a line. An example of this is a slot in a backplane that is provided for an add-on card. DIODE FORWARD CURRENT vs DIODE FORWARD VOLTAGE –100 TA = 25°C –90 I I – Forward Current – mA –80 Variable 1: VIN –Ch 1 Linear Sweep: Start 0.000 V Stop –2.000 V Step –0.010 V –70 –60 –50 Constants: VHI –Vs1 VLO –Vs2 –40 –30 3.5000 V 0.0000 V –20 –10 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 VF – Forward Voltage – V Figure 1. Current Versus Voltage for the SN74F1056 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 SN74F1056 8-BIT SCHOTTKY BARRIER DIODE BUS-TERMINATION ARRAY SDFS085A – AUGUST 1992 – REVISED JULY 1997 APPLICATION INFORMATION ZO = 50 Ω Length = 36 in. S1 ZS = 25Ω (a) UNDERSHOOT TEST SETUP 1.03610 µs 1.06110 µs 1.08610 µs S1 Open S1 Closed Vmarker 1 –2.6 V Vmarker 2 Ch 1 Timebase Vmarker 1 Vmarker 2 Offset = 2.340 V Delay = 1.06110 µs Delta V = –600.0 mV = 2.000 V/div = 5.00 ns/div = 0.0000 V = –600.00 mV (b) OSCILLOSCOPE DISPLAY Figure 2. Undershoot Test Setup and Oscilloscope Display 4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 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. 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