Electric current of static state of A of 2.5 μ and exceed synchronism of peak value of 42 V of low EMI radiant, 2 A/3 A step-down manostat
[introduction] LT8609, LT8609A, LT8609B and LT8609S are to have 3 V to come 42 V is the synchronism of limits of wide input voltage, odd a type, step-down manostat. Series of this parts of an apparatus needs for those only low EMI, efficient optimize with the application of small size solution, agree with the car of requirement severe exacting, industry, computation and communication application. All manostat in this series all have identical 2 A transient state of successive, 3 A (<1 second) load current ability. Their characteristic collect at the watch 1.
LT8609, LT8609A exceeds electric current of small static state with what LT8609S has 2.5 μA, this are crucial to batteries power supply system. These manostat carried MOSFET of N raceway groove to achieve outstanding light laden efficiency by right of compositive top and bottom. LT8609B works to hop at pulse only mode, although prep above of static electric current is other a few parts of an apparatus, but the output ripple that it produces during light load moves is inferior.
All parts of an apparatus of this series all achieve CISPR 25 5 kind radiation EMI regulation asks, this is the standard of the strictest EMI that is aimed at automobile equipment. In addition, LT8609, LT8609A and LT8609S still have patulous spectrum frequency to run a function, in order to reduce EMI peak value. Range of products is here medium, LT8609S has the most conspicuous EMI property, if later development place is narrated, this is based on its proprietary Silent Switcher®2 technologies.
Graph 1. Exceed LT8609S 12 V of low EMI radiate to fall to 5 V synchronism profiling converter.
5.5V comes 42 V input, low EMI, efficient power source of 5 V, 2 A
Graph 1 show gave a 5.5 V to be inputted to 42 V, 5 V/2 A outputs the solution of power source. This solution used manostat of a 16 LT8609S that cite a base, this manostat has frequency of 2 MHz switch. Form this complete solution to need only a few package, include inductor L1 and a few passive package. If the graph is shown 2 times, this solution can achieve the peak value efficiency of 92.9% .
Sudden mode in order to improve light laden efficiency
To batteries power supply application, move in light load and do not have load stand-by during mode, efficient with small unused electric current it is very main character. LT8609, LT8609A and LT8609S are in sudden mode (the electricity of small static state that 2.5 μA has in Burst Mode®) job. Mix in light load fall without laden circumstance, reduce switch frequency gradually, be in thereby hold output power comsumption decreases greatly while voltage ripple is relatively inferior. Graph 2 show: Light laden efficiency maintains in 85% above, and power comsumption is close to Yu Ling below dinky and laden circumstance.
Graph 2. The 12 VIN that is based on LT8609/LT8609A/LT8609S concerns to the efficiency of 5 VOUT step-down converter and load current curve
Tall switch frequency and the hot performance that exceed low EMI radiate and improvement
In a lot of environment such as car system, EMI compatibility is the problem of a fetching attention. By right of compositive change MOSFET, advanced engineering technology, and be as high as 2.2 MHz working frequency, all parts of an apparatus of this series all can achieve the solution of small size, satisfy the EMI standard of the most severe exacting. Besides LT8609B, other a few parts of an apparatus offerred the patulous spectrum frequency that can reduce EMI peak value to run a function. In addition, LT8609S used technology of Silent Switcher 2. Parts of an apparatus of Silent Switcher 2 has collect to shape capacitor of road of annulus of gentle of hot annulus road, the influence that is counted in order to make EMI function not easy by circuit board layout and circuit ply. Can use the circuit with less number of plies board make cost in order to reduce, and do not sacrifice EMI and hot property.
If the graph is shown 2 times, LT8609S has optimal peak value and full laden efficiency in series of this parts of an apparatus. Graph 3 the function of 4 CISPR 25 EMI when showing the graph shows a solution 1 times to use layer and 4 2 circuit board contrast and heat up function contrast with the graph.
Graph 3. The function of EMI of CISPR 25 radiate when the graph shows circuit 1 times to use layer and 4 2 circuit board is compared
Graph 4. The hot property when the graph shows circuit 1 times to use layer and 4 2 circuit board is compared.
Conclusion
The parts of an apparatus in LT8609 series is the sheet that uses easily simply piece type step-down manostat, have collect to be mixed into power MOSFET inside buy compensates circuit. These parts of an apparatus need limits of wide input voltage and low EMI noise technically in the light of those apply and optimize. The electric current of small static state of 2.5 μA and function of sudden mode job make they make solution of step-down of outstanding batteries power supply converter. 200 KHz makes to the switch frequency limits of 2.2 MHz its suit most low power comsumption and application of small power comsumption. Compositive MOSFET and the utmost of switch frequency ability that are as high as 2.2 MHz reduce understanding definitely plan dimension. Result of CISPR 25 scanning showed this solution accords with the rigiddest EMI standard. The technology of Silent Switcher 2 that LT8609S place uses makes its function won’t be affected with what number of plies changes by circuit board layout, reduced greatly thereby develop and make cost.