powerZONE Products for the week of August 22, 2005
Linear Technology Says . . .
LT1976H: 60 V 1.5 A Step-Down Dc/Dc Converter Now
Offers 140° Maximum Junction Temperature
Linear Technology Corporation announced the "H-Grade" version
of the LT1976. The LT1976 is a 60V(MAX), Burst Mode, step-down switching
regulator that maintains quiescent current under 100µA.The "H"
Grade version operates up to a junction temperature of 140°C, compared
to the "E" and "I" Grade versions' 125°C maximum
junction temperature. The "H Grade" parts are both tested and
guaranteed to the maximum junction temperature of 140°C. They are ideal
for automotive and industrial applications which are subjected to high ambient
temperatures.
The LT1976 operates within a VIN range of 3.3V to 60V, making ideal for
load dump or cold-crank conditions found in automotive applications. Its
1.5A internal switch can deliver up to 1.25A of continuous output current
at voltages as low as 1.25V. Its 100µA of quiescent current is ideal
for "always on" applications such as automotive security systems
which require a very long battery life.
analogZONE Says...
The LT1976 is already a successful product released in September 2003. The expanded higher temperature rating to 140°C opens the door for the part in a lot more areas of application, specifically in the automotive and heavy industrial markets, particularly with the load dump protection that is offered up to 60 V.
Peak switch current of the fixed 200 kHz switch frequency LT1976 is 1.5 A minimum with a burst mode quiescent of 100 µA, while shutdown current is less than 1 µA. The input capacitor is typically a 0.47 µF ceramic while the output can be a 100 µF tantalum. A 500 kHz version of the LT1976 (without the expanded temperature range, at this time) is available as the LT1977.
A standard external resistive voltage divider to the feedback pin is required to set the output voltage where the feedback is compared against the IC's 1.25 V reference. The only difference in the specifications of the "H" version of the part compared to the lower temperature range "E" and "I" versions that I could see was that the typical switch current limit of 2.4 A is no longer guaranteed over the full temperature range. The part still offers soft start, a power-good flag, can be externally synchronized and has an input voltage range extending from 3.3 V to 60 V.
Linear is asking for a 25 cent premium for the "H" version of the LT1976. It will get it.
The LT1976HFE is in production in a termally-enhanced TSSOP-16 and is priced at $4.85 in 1000-piece lots.