Details, datasheet, quote on part number: 74F5074
CategoryLogic => Flip-Flops
Description74F5074; Synchronizing Dual D-type Flip-flop/clock Driver;; Package: SOT27-1 (DIP14)
CompanyPhilips Semiconductors (Acquired by NXP)
DatasheetDownload 74F5074 datasheet
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Features, Applications


Metastable immune characteristics Output skew guaranteed less than 1.5ns High source current (IOH = 15mA) ideal for clock driver


Pin out compatible with 74F74 74F50728 for synchronizing cascaded D­type flip­flop See 74F50729 for synchronizing dual D­type flip­flop with


ORDER CODE DESCRIPTION COMMERCIAL RANGE VCC 5V ±10%, Tamb +70°C 14­pin plastic DIP 14­pin plastic SOT27-1 SOT108-1

Data inputs Clock inputs (active rising edge) Set inputs (active low) Reset inputs (active low)

Q0, 750/33 Data outputs 15mA/20mA Q1 NOTE: One (1.0) FAST unit load is defined as: 20µA in the high state and 0.6mA in the low state.

When the device­under­test a 74F74 (which was not designed with metastable immune characteristics) the waveform will appear as in Fig. 2. Figure 2 shows clearly that the Q output can vary in time with respect to the Q trigger point. This also implies that the or Q output waveshapes may be distorted. This can be verified on an analog scope with a charge plate CRT. Perhaps of even greater interest are the dots running along the 3.5V volt line in the upper right hand quadrant. These show that the Q output did not change state even though the Q output glitched to at least 1.5 volts, the trigger point of the scope. When the device­under­test is a metastable immune part, such as the 74F5074, the waveform will appear as in Fig. 3. The 74F5074 Q output will appear as in Fig. 3. The 74F5074 Q output will not vary with respect to the Q trigger point even when the a part is driven into a metastable state. Any tendency towards internal metastability is resolved by Philips Semiconductor patented circuitry. If a metastable event occurs within the flop the only outward manifestation of the event will be an increased clock­to­Q/Q propagation delay. This propagation delay is, of course, a function of the metastability characteristics of the part defined by and T0. The metastability characteristics of the 74F5074 and related part types represent state­of­the­art TTL technology. After determining the T0 and t of the flop, calculating the mean time between failures (MTBF) is simple. Suppose a designer wants to use the 74F5074 for synchronizing asynchronous data that is arriving at 10MHz (as measured by a frequency counter), has a clock frequency of 50MHz, and has decided that he would like to sample the output of the 74F5074 10 nanoseconds after the clock edge. He simply plugs his number into the equation below: MTBF = e(t'/t)/ TofCfI In this formula, fC is the frequency of the clock, fI is the average input event frequency, and t' is the time after the clock pulse that the output is sampled (t' h, h being the normal propagation delay). In this situation the fI will be twice the data frequency of 20 MHz because input events consist of both of low and high transitions. Multiplying by fC gives an answer 1015 Hz2. From Fig. it is clear that the MTBF is greater than 1010 seconds. Using the above formula the actual MTBF X 1010 seconds or about 480 years.


The is a dual positive edge­triggered D­type featuring individual data, clock, set and reset inputs; also true and complementary outputs. Set (SDn) and reset (RDn) are asynchronous active low inputs and operate independently of the clock (CPn) input. Data must be stable just one setup time prior to the low­to­high transition of the clock for guaranteed propagation delays. Clock triggering occurs at a voltage level and is not directly related to the transition time of the positive­going pulse. Following the hold time interval, data at the Dn input may be changed without affecting the levels of the output. The 74F5074 is designed so that the outputs can never display a metastable state due to setup and hold time violations. If setup time and hold time are violated the propagation delays may be extended beyond the specifications but the outputs will not glitch or display a metastable state. Typical metastability parameters for the 74F5074 are: 135ps and X 106 sec where represents a function of the rate at which a latch in a metastable state resolves that condition and T0 represents a function of the measurement of the propensity of a latch to enter a metastable state.

Philips Semiconductor uses the term 'metastable immune' to describe characteristics of some of the products in its family. Specifically the 74F50XXX family presently consist of 4 products which will not glitch or display an output anomaly under any circumstances including setup and hold time violations. This claim is easily verified on the 74F5074. By running two independent signal generators (see Fig. 1) at nearly the same frequency (in this case 10MHz clock and 10.02 MHz data) the device­under­test can be often be driven into a metastable state. If the Q output is then used to trigger a digital scope set to infinite persistence the Q output will build a waveform. An experiment was run by continuously operating the devices in the region where metastability will occur.



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