? 2002 fairchild semiconductor corporation ds500791 www.fairchildsemi.com november 2002 revised november 2002 fstu32x800 20-bit bus switch with precharged outputs fstu32x800 20-bit bus switch with precharged outputs and ? 2v undershoot protection general description the fairchild switch fstu32x800 provides 20-bits of high-speed cmos ttl-compatible bus switching. the low on resistance of the switch allows inputs to be connected to outputs without adding propagation delay or generating additional ground bounce noise. the a and b ports are protected against undershoot to support an extended range to 2.0v below ground. fairchild?s integrated under- shoot hardened circuit (uhc ? ) senses undershoot at the i/o and responds by preventing voltage differentials from developing and turning the switch on. the device also pre- charges the b port to a selectable bias voltage (biasv) to minimize live insertion noise. the device is organized as two 10-bit switches with a bus enable (oe n ) signal. when oe n is low, the switch is on and port a is connected to port b. when oe n is high, the switch is open and the b port is precharged to biasv through an equivalent 10-k ? resistor. features 4 ? switch connection between two ports undershoot hardened to -2.0v soft enable turn-on to minimize bus-to-bus charge sharing during enable low l cc zero bounce in flow-through mode output precharge to minimize live insertion noise control inputs compatible with ttl level see applications note an-5008 for details ordering code: devices also available in tape and reel. specify by appending the suffix letter ? x ? to the ordering code. uhc ? is a trademark of fairchild semiconductor corporation. order number package number package description fstu32x800qsp mqa48a 48-lead quarter size very small outline package (qvsop), jedec mo-154, 0.150" wide
www.fairchildsemi.com 2 fstu32x800 logic diagrams pin descriptions connection diagram truth table pin name description oe n bus switch enable abus a bbus b biasv n bus b voltage bias oe n b 0 ?b 19 function la 0 ? a 19 connect h biasv precharge
3 www.fairchildsemi.com fstu32x800 absolute maximum ratings (note 1) recommended operating conditions (note 3) note 1: the absolute maximum ratings are those values beyond which the safety of the device cannot be guaranteed. the device should not be operated at these limits. the parametric values defined in the electrical characteristics tables are not guaranteed at the absolute maximum ratings. the recommended operating conditions tables will define the conditions for actual device operation. note 2: the input and output negative voltage ratings may be exceeded if the input and output diode current ratings are observed. note 3: unused control inputs must be held high or low. they may not float. dc electrical characteristics note 4: typical values are at v cc = 5.0v and t a = + 25 c note 5: measured by the voltage drop between a and b pins at the indicated current through the switch. on resistance is determined by t he lower of the voltages on the two (a or b) pins. note 6: per v cc pin. note 7: per ttl driven inputs, control pins only. supply voltage (v cc ) ? 0.5v to + 7.0v dc switch voltage (v s ) ? 2.0v to + 7.0v bias v voltage range ? 0.5v to + 7.0v dc input voltage (v in ) (note 2) ? 0.5v to + 7.0v dc input diode current (l ik ) v in < 0v ? 50 ma dc output (i out ) sink current 128 ma dc v cc /gnd current (i cc /i gnd ) + / ? 100 ma storage temperature range (t stg ) ? 65 c to + 150 c power supply operating (v cc ) 4.0v to 5.5v precharge supply (biasv) 1.5v to v cc input voltage (v in ) 0v to 5.5v output voltage (v out ) 0v to 5.5v input rise and fall time (t r , t f ) switch control input 0 ns/v to 5 ns/v switch i/o 0 ns/v to dc free air operating temperature (t a ) ? 40 c to + 85 c symbol parameter v cc (v) t a = ? 40 c to + 85 c units conditions min typ (note 4) max v ik clamp diode voltage 4.5 ? 1.2 v i in = ? 18 ma v ih high level input voltage 4.0 - 5.5 2.0 v v il low level input voltage 4.0 - 5.5 0.8 v i i input leakage current 5.5 1.0 a0 v in 5.5v i o output current 4.5 0.25 ma biasv = 2.4v, b = 0 i oz off-state leakage current 5.5 1.0 a0 a v cc , v in = v ih r on switch on resistance 4.5 4.0 7.0 ? v s = 0v, i in = 64 ma (note 5) 4.5 4.0 7.0 ? v s = 0v, i in = 30 ma 4.5 8.0 15.0 ? v s = 2.4v, i in = 15 ma 4.0 11.0 20.0 ? v s = 2.4v, i in = 15 ma i cc quiescent supply current (note 6) 5.5 3.0 av s = v cc or gnd, i out = 0 ? i cc increase in i cc per input 5.5 2.5 ma oe input at 3.4v (note 7) other inputs at v cc or gnd i bias bias pin leakage current 5.5 1.0 aoe = 0v, b = 0v, biasv = 5.5v i ozu switch undershoot current 5.5 100.0 ai in = ? 20 ma, oe = 5.5v, v out v ih v iku voltage undershoot 5.5 ? 2.0 v 0.0 ma i in ? 50 ma, oe = 5.5v
www.fairchildsemi.com 4 fstu32x800 ac electrical characteristics note 8: this parameter is guaranteed by design but is not tested. the bus switch contributes no propagation delay other than the rc del ay of the typical on resistance of the switch and the 50 pf load capacitance, when driven by an ideal voltage the source (zero output impedance). capacitance (note 9) note 9: t a = + 25 c, f = 1 mhz, capacitance is characterized but not tested. ac loading and waveforms note: input driven by 50 ? source terminated in 50 ? , ru = rd = 500 ? note: c l includes load and stray capacitance, c l = 50 pf note: input prr = 1.0 mhz, t w = 500 ns figure 1. ac test circuit figure 2. ac waveforms symbol parameter t a = ? 40 c to + 85 c, units conditions figure number c l = 50 pf, ru = rd = 500 ? v cc = 4.5 ? 5.5v v cc = 4.0v min max min max t phl , propagation delay bus to bus 0.25 0.25 ns v i = open figures 1, 2 t plh (note 8) t pzh output enable time 7.0 30.0 35.0 ns v i = open figures 1, 2 oe 1 , oe 2 , to a n , b n biasv = gnd t pzl 7.0 30.0 35.0 ns v i = 7v biasv = 3v t phz output disable time 1.0 6.1 6.5 ns v i = open figures 1, 2 oe 1 , oe 2 , to a n , b n biasv = gnd t plz 1.0 7.3 6.8 ns v i = 7v biasv = 3v symbol parameter typ max units conditions c in control pin input capacitance 3.0 pf v cc = 5.0v c i/o input/output capacitance 5.0 pf v cc , oe = 5.0v
5 www.fairchildsemi.com fstu32x800 20-bit bus switch with precharged outputs physical dimensions inches (millimeters) unless otherwise noted 48-lead quarter size very small outline package (qvsop), jedec mo-154, 0.150" wide package number mqa48a technology description the fairchild switch family derives from and embodies fairchild ? s proven switch technology used for several years in its 74lvx3l384 (fst3384) bus switch product. 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 rea- sonably expected to result in a significant injury to the user. 2. a critical component in any component of a life support device or system whose failure to perform can be rea- sonably 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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