| Part Numbert | Mfg | Packt | D/C | Descriptiont | Qty | Company/Contact | |
| PC74HCT02N | PHL | 08+ | in Stock | 1230 |
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PC74HCT02N Datasheet Both the dark current and noise performance of the array can be improved by cooling. The dark current will be reduced 50% for every 70C reduction in array temperature. The noise floor of the output amplifier is proportional tokTC where k is Boltzmann's constant, T is the array temperature in degrees Kelvin and C is the output node capacitance of approximately .17 pF. Cooling can be achieved via a thermo-electric, Joule- Thomson cooler, or liquid nitrogen dewar. PC74HCT02N Price The storage cells of 64Mb, 128Mb and 256Mb SDRAM need to be refreshed every 64ms to maintain data. An auto refresh cycle accomplishes refresh of a single row of storage cells. The inter- nal counter increments automatically on every auto refresh cycle to refresh all the rows. An auto refresh command is issued by asserting low on CS, RAS and CAS with high on CKE and WE. The auto refresh command can only be asserted with all banks being in idle state and the device is not in power down mode (CKE is high in the previous cycle). The time required to com- plete the auto refresh operation is specified by tRc(min). The min- imum number of clock cycles required can be calculated by driving tRC with clock cycle time and them rounding up to the next higher integer. The auto refresh command must be followed by NOP'S until the auto refresh operation is completed. All banks will be in the idle state at the end of auto refresh operation. The auto refresh is the preferred refresh mode when the SDRAM is being used for normal data transactions. The 64Mb and 128Mb SDRAM's auto refresh cycle can be performed once in 15.6us or a burst of 4096 auto refresh cycles once in 64ms. The 256Mb and 512Mb SDRAM's auto refresh cycle can be performed once in 7.8us or a burst of 8192 auto refresh cycles once in 64ms. PC74HCT02N on stock
Power for the top and bottom MOSFET d rivers and most of the internal controller circuitry is derived from the INTVcc pin. The top MOSFET driver is powered from a floating bootstrap capacitor CB. This capacitor is re- charged from INTVccth rough an externaISchottky diode DB when the top MOSFETis turned off. When the EXTVcc pin is grounded, an internal 5V low dropout regulator supplies the INTVcc power from VIN. If EXTVcc rises above 4.7V, the internal regulator is turned off, and an internal switch connects EXTVcc to INTVcc. This allows a high efficiency source connected to EXTVcc, such as an external 5V supply or a secondary output from the converter, to provide the INTVcc power. Voltages up to 7V can be applied to EXTVcc for additional gate drive. If the input voltage is low and INTVcc drops below 3.5V, undervoltage lockout circuitry prevents the power switches from turning on. |
