Why DDR3 is handling higher bit rates(>600Mhz)!!.Answer of that question is very simple.DDR3 is embedded with an 8-Bit prefetch module. Because of this 8-bit early prefetch Internal modules require lesser frequency to achieve Higher data rate.
Friday 23 March 2012
Why DDR3 handling More Bit rates!!!!
Why DDR3 is handling higher bit rates(>600Mhz)!!.Answer of that question is very simple.DDR3 is embedded with an 8-Bit prefetch module. Because of this 8-bit early prefetch Internal modules require lesser frequency to achieve Higher data rate.
Charging lead acid batteries
The different charging techniques for charging lead acid batteries are :
Constant Voltage Charging: This method is the most commonly used for SLA batteries as the individual cells tend to share the voltage and equalize the charge between them. It is important to limit the initial charging current to prevent damage to the battery. However, with a single fixed voltage, it is impossible to properly balance the requirements of a fast charge cycle against the danger of overcharge.
Constant Current Charging: This method can be used for a single 2 V cell but is not recommended for charging a number of series connected cells, a battery, all at the same time. This is because some cells will reach full charge before others and it is very difficult to determine when the battery has reached a fully charged state. If the charge is continued at the same rate, for any extended period of time, severe overcharge may occur to some cells, resulting in damage to the battery.
Taper Current Charging: This method is not really recommended for charging SLA batteries as it can often shorten battery service life due to poor control of the final fully-charged voltage. However, because of the simplicity of the circuit and subsequent low cost, taper current charging is often used to charge a number of series connected batteries that are subject to cyclic use. When using this method it is recommended that the charging time is either limited or that a charging cut-off circuit is incorporated to prevent overcharge.
Using a combination of the constant current charging and two-stage constant voltage charging techniques and also by monitoring the battery terminal voltage and temperature a multi-stage charge profile can be implemented to reduce stress on the battery while giving the shortest possible charge time.
The first part of the multi-stage charge cycle is constant current mode Bulk Charge which limits current to a maximum of 0.25C Amps (where C = battery capacity, so 0.25C is a quarter of the battery capacity), as required by SLA batteries. For example, if the capacity of the SLA battery being charged is 4 A-hr, then the constant current should be limited to 1 A. During this stage, the battery terminal voltage is monitored until the terminal voltage reaches 14.4 V (2.40 V/cell).
Once the terminal voltage reaches 14.4 V the charge cycle automatically moves on to the second stage High Absorption Charge. output changes from constant current to constant voltage and now monitors the charge current. When the charge current drops to 0.05C A, which is 0.2 A for a 4 A-hr battery, the battery will have recovered approximately 70 - 80% of its charge. At this point the output voltage reduces to 13.65 V (2.275 V/cell) : this is the Low Absorption Charge. The remaining 20 - 30% of the charge is carried out at this lower voltage in order to prevent overcharge.
The final stage of the charge cycle is the Float Charge.
Constant Voltage Charging: This method is the most commonly used for SLA batteries as the individual cells tend to share the voltage and equalize the charge between them. It is important to limit the initial charging current to prevent damage to the battery. However, with a single fixed voltage, it is impossible to properly balance the requirements of a fast charge cycle against the danger of overcharge.
Constant Current Charging: This method can be used for a single 2 V cell but is not recommended for charging a number of series connected cells, a battery, all at the same time. This is because some cells will reach full charge before others and it is very difficult to determine when the battery has reached a fully charged state. If the charge is continued at the same rate, for any extended period of time, severe overcharge may occur to some cells, resulting in damage to the battery.
Taper Current Charging: This method is not really recommended for charging SLA batteries as it can often shorten battery service life due to poor control of the final fully-charged voltage. However, because of the simplicity of the circuit and subsequent low cost, taper current charging is often used to charge a number of series connected batteries that are subject to cyclic use. When using this method it is recommended that the charging time is either limited or that a charging cut-off circuit is incorporated to prevent overcharge.
Using a combination of the constant current charging and two-stage constant voltage charging techniques and also by monitoring the battery terminal voltage and temperature a multi-stage charge profile can be implemented to reduce stress on the battery while giving the shortest possible charge time.
The first part of the multi-stage charge cycle is constant current mode Bulk Charge which limits current to a maximum of 0.25C Amps (where C = battery capacity, so 0.25C is a quarter of the battery capacity), as required by SLA batteries. For example, if the capacity of the SLA battery being charged is 4 A-hr, then the constant current should be limited to 1 A. During this stage, the battery terminal voltage is monitored until the terminal voltage reaches 14.4 V (2.40 V/cell).
Once the terminal voltage reaches 14.4 V the charge cycle automatically moves on to the second stage High Absorption Charge. output changes from constant current to constant voltage and now monitors the charge current. When the charge current drops to 0.05C A, which is 0.2 A for a 4 A-hr battery, the battery will have recovered approximately 70 - 80% of its charge. At this point the output voltage reduces to 13.65 V (2.275 V/cell) : this is the Low Absorption Charge. The remaining 20 - 30% of the charge is carried out at this lower voltage in order to prevent overcharge.
The final stage of the charge cycle is the Float Charge.
Wednesday 14 March 2012
Hysteresis in Digital or Analog Devices or IC's
Hysteresis the word it self explain the meaning!!!Hysteresis means the lagging of an effect behind its cause!!.If you are familiar with the digital design,you would definitely gone through the data sheets of Digital ICs with some Input hysteresis values say 200mV.What it does actually meant for? the answer is simple
Let say you detect a Low to high transition at 1.8V(Vref).A 200 mV Hysteresis would mean that your device will detect the Low to high transition at 1.9V and the High to low transition locked at 1.7V.This voltage lag between activating and deactivating the device is known as the Hysteresis of the system.Hysteresis is ensure to avoid several noise transitions would cause the H-L and L-H transitions of the device.So a 200mV Hysteresis means that noise levels lesser than 200mV wont give any disturbance to the Vref of your system..
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