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TC74HC4538AFT Dataheets PDF



Part Number TC74HC4538AFT
Manufacturers Toshiba Semiconductor
Logo Toshiba Semiconductor
Description Dual Retriggerable Monostable Multivibrator
Datasheet TC74HC4538AFT DatasheetTC74HC4538AFT Datasheet (PDF)

TC74HC4538AP/AF/AFT TOSHIBA CMOS Digital Integrated Circuit Silicon Monolithic TC74HC4538AP, TC74HC4538AF, TC74HC4538AFT Dual Retriggerable Monostable Multivibrator The TC74HC4538A is a high speed CMOS MONOSTABLE MULTIVIBRATOR fabricated with silicon gate C2MOS technology. It achieves the high speed operation similar to equivalent LSTTL while maintaining the CMOS low power dissipation. There are two trigger inputs, A input (positive edge input), and B input (negative edge input). These inputs a.

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TC74HC4538AP/AF/AFT TOSHIBA CMOS Digital Integrated Circuit Silicon Monolithic TC74HC4538AP, TC74HC4538AF, TC74HC4538AFT Dual Retriggerable Monostable Multivibrator The TC74HC4538A is a high speed CMOS MONOSTABLE MULTIVIBRATOR fabricated with silicon gate C2MOS technology. It achieves the high speed operation similar to equivalent LSTTL while maintaining the CMOS low power dissipation. There are two trigger inputs, A input (positive edge input), and B input (negative edge input). These inputs are valid for a slow rise/fall time signal (tr = tf = 1 s) as they are schmitt trigger inputs. After triggering, the output stays in a MONOSTABLE state for the time period determined by the external resistor and capacitor (RX, CX). A low level at CD input breaks this STABLE STATE. In the MONOSTABLE state, if a new trigger is applied, it makes the MONOSTABLE period longer (retrigger mode). Limitations for CX and RX are as follows: External capacitor CX ........... No limitation External resistor RX .............. VCC = 2.0 V more than 5 kΩ VCC ≥ 3.0 V more than 1 kΩ All inputs are equipped with protection circuits against static discharge or transient excess voltage. Features (Note) • High speed: tpd = 25 ns (typ.) at VCC = 5 V • Low power dissipation Stand by state: ICC = 4 μA (max) at Ta = 25°C Active state: ICC = 300 μA (max) at Ta = 25°C • High noise immunity: VNIH = VNIL = 28% VCC (min) • Output drive capability: 10 LSTTL loads • Symmetrical output impedance: |IOH| = IOL = 4 mA (min) • Balanced propagation delays: tpLH −∼ tpHL • Wide operating voltage range: VCC (opr) = 2 V to 6 V • Pin and function compatible with 4538B Note: In the case of using only one circuit, CD should be tied to GND, T1·T2·Q· Q should be tied to OPEN, the other inputs should be tied to VCC or GND. TC74HC4538AP TC74HC4538AF TC74HC4538AFT Weight DIP16-P-300-2.54A SOP16-P-300.1.27A TSSOP16-P-0044-0.65A : 1.00 g (typ.) : 0.18 g (typ.) : 0.06 g (typ.) Start of commercial production 1987-11 1 2016-12-02 Pin Assignment 1T1 1 1T2 2 1CD 3 1A 4 1B 5 1Q 6 1Q 7 GND 8 (top view) 16 VCC 15 2T1 14 2T2 13 2CD 12 2A 11 2B 10 2Q 9 2Q Truth Table Inputs A B CD H H X L H H X H L H X X L X: Don’t care Outputs Q Q L H L H L H Note Output Enable Inhibit Inhibit Output Enable Reset TC74HC4538AP/AF/AFT IEC Logic Symbol 1A (4) 1B (5) 1CD (3) 1T1 (1) 1T2 (2) 2A (12) 2B (11) 2CD (13) 2T1 (15) 2T2 (14) & R CX RX/CX & R CX RX/CX (6) 1Q (7) 1Q (10) 2Q (9) 2Q 2 2016-12-02 Block Diagram (Note) TC74HC4538AP/AF/AFT A4 B5 DX CX RX 12 VCC T1 T2 6Q 7Q 3 CD A 12 B 11 DX CX RX 15 14 VCC T1 T2 10 Q 13 CD 9Q Note: Note: CX, RX, DX are external capacitor, resistor, and diode, respectively. External clamping diode, DX The external capacitor is charged to VCC level in the wait state, i.e. when no trigger is applied. Supply voltage is turned off and CX is discharged mainly through the internal (parasitic) diode. If CX is sufficiently large and VCC drops rapidly, there will be some possibility of damaging the IC by rush current or latch-up. If the capacitance of the supply voltage filter is large enough and VCC drops slowly, the rush current is automatically limited and damage to the IC is avoided. The maximum value of forward current through the parasitic diode is ±20 mA. In the case of a large CX, the limitation of fall time of the supply voltage is determined as follows: tf ≥ (VCC - 0.7) CX/20 mA (tf is the time from the voltage supply turning off to the level of supply voltage reaching 0.4 VCC.) In the care of a system that does not satisfy the above condition, an external clamping diode is needed to protect the IC from rush current. 3 2016-12-02 System Diagram VCC QP VrefL C1 T2 QN T1 VCC DR Q A B CK Q F/F CD Timing Chart A B T2 CD Q Q twOUT twOUT TC74HC4538AP/AF/AFT VrefH C2 trr twOUT + trr Q Q VIH VIL VIH VIL VCC VrefH VrefL GND VIH VIL VOH VOL VOH VOL 4 2016-12-02 TC74HC4538AP/AF/AFT Functional Description (1) Stand-by state The external capacitor is fully charge to VCC in the stand-by state. That means, before triggering, QP and QN transistors which are connected to the T2 node are in the off state. Two comparators that relate to the timing of the output pulse, and two reference voltage supplies stop their operation. The total supply current is only leakage current. (2) Trigger operation Trigger operation is effective in either of the following two cases. One is the condition where the A input is low, and the B input has a falling signal. The other, where the B input is high, and the A input has a rising signal. After trigger becomes effective, comparators C1 and C2 start operating, and QN is turned on. The external capacitor discharges through QN. The voltage level at the T2 node drops. If the T2 voltage level falls to the internal reference voltage VrefL, the output of C1 becomes low. The flip-flop is then reset and QN turns off. At that moment C1 stops.


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