It also has a limit, IOH(max), on how much current it can source in the HIGH state. TTL output has a limit, IOL(max), on how much current it can sink in the LOW state.
#Ttl nor gate with totem pole output series#
Supply voltage and temperature range Voltage levels Maximum voltage ratings Power dissipation Propagation delays Fan-outĮxample 8-2: maximum average power dissipation and maximum average propagation delay.ħ4 Series Schottky TTL, 74S Series: higher speed Low-Power Schottky TTL, 74LS series Advanced Schottky TTL, 74AS Series Advanced Low-Power Schottky TTL, 74ALS Series 74F-Fast TTLĮxample 8-3: Noise margin of 74 and 74LS Example 8-4: TTL series with max number of fan-outįigure 8-13: currents when a TTL output is driving several inputs. TI introduced first line of standard TTL: 54/74 series (1964) Manufacturers’ data sheets (Figure 8-11) Circuit operation: LOW state, current-sinking Circuit operation: HIGH state, currentsourcing. Transistor-transistor logic Figure 8-7: NAND gate. Lower than VIL(max) and higher than VIH(min).ĭIP J-Lead Gull-wing Table 8-2 for a complete list. VNH=VOH(min)-VIH(min) VNL=VIL(max)-VOL(max) Example 8-1.įor proper operation the input voltage levels to a logic must be kept outside the indeterminate range. What happens if noise causes the input voltage to drop below VIH(min) or rise above VIL(max)? The noise immunity of a logic circuit refers to the circuit’s ability to tolerate noise without causing spurious changes in the output voltage. Speed-power product measures the combined effect.
Short propagation delays (high speed) Low power dissipation Average Icc(avg)= (ICCH + ICCL)/2 PD(avg) = Icc(avg) x Vcc Vcc (TTL) VDD(MOS) Power dissipation determined by Icc and Vcc. TpLH: delay time in going from logical 0 to logical 1 state (LOW to HIGH) tpHL: delay time in going from logical 1 to logical 0 state (HIGH to LOW) Measured at 50% points.Įvery IC needs a certain amount of electrical power to operate. Related to the current parameters (both in high and low states.) The maximum number of standard logic inputs that an output can drive reliably. IIL(max): low-level input current IOH(min): high-level output current IOL(max): low-level output current High-level input current, the current that flows into an input when a specified highlevel voltage is applied to that input. VIL(max): low-level input voltage VOH(min): high-level output voltage VOL(max): low-level output voltage VIH(min): high-level input voltage, the minimum voltage level required for a logic 1 at an input.
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