Silent Switcher Technology - Product Focus
Figure 4: Ch1: LT8610, Ch2: LT8614 switch node rising edge both at 8.4V in, 3.3Vout at 2.2A
domain measurements in Figures 3 to 5 are done with 500MHz Tektronix P6139A probes with close probe tip shield connection to the PCB GND plane, both on the standard demo boards. Besides their 42V absolute maximum input voltage rating in automotive environments, the dropout behaviour is also very important. Often critical 3.3V logic supplies need to be supported through cold crank situations. The LT8614 Silent Switcher regulator maintains the close to ideal behaviour of the LT861x family in this case. Instead of higher undervoltage lockout voltages and maximum duty cycle clamps of alternative parts, the LT8610/11/14 devices operate down to 3.4V and start skipping off cycles as soon as necessary, as shown in Figure 6. This results in the ideal dropout behaviour, as shown in Figure 7. The LT8614’s low
Figure 5: 3 Ch1: LT8610, Ch2: LT8614, both at 13.2V in, 3.3V 2.2A out
minimum on-time of 30ns enables large step-down ratios even at high switching frequencies. As a result, it can supply logic core voltages with a single step- down from inputs up to 42V.
In conclusion, the
LT8614 Silent Switcher regulator reduces EMI from current state-of- the-art switching regulators by more than 20dB, while increasing conversion efficiencies with no drawbacks. A 10x improvement of EMI in the frequency range above 30MHz is attained without compromising minimum on- and off- times or efficiency in the same board area. This is accomplished with no special components or shielding, representing a significant breakthrough in switching regulator design. This level of performance in a single IC has not been possible until now. This is just the sort of breakthrough product that allows end- system designers to take their products to the next level.
Linear Technology |
www.linear.com
Christian Kueck is Strategic Marketing Manager, Power
Management Products at Linear Technology Corporation
Figure 7: LT8614 dropout behaviour
Figure 6: 3 Ch1: LT8610, Ch2: LT8614 switch node dropout behaviour
www.cieonline.co.uk
Components in Electronics
November 2013 21
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