lowpowerZONE Products for the week of July 26, 2010
Semtech Corporation Says…
SC120/1/2: Boost Converter Platform Offers Smallest Low-Vin Devices
Ultra-thin plastic package and step up inputs from as low as 0.7V to a regulated output settable from 1.8V to 5.0V
Semtech Corp., a leading supplier of analog and mixed-signal semiconductors, announced a new boost converter platform offering the world’s smallest step-up regulators for low-voltage applications. The SC120, SC121 and SC122 boost inputs from as low as 0.7V to a regulated output settable from 1.8V to 5.0V and are available in tiny 1.5x2mm ultra-thin (0.6mm max.) plastic packages. With many advanced features, these devices are ideally suited for portable applications powered by alkaline, NiMH, or 1-cell Li-ion batteries, or as point-of-load regulators in non-portable applications where a low voltage needs to be boosted to a higher voltage rail for localized use.
“The new SC120 platform sets the benchmark for its sophisticated features, performance, and ease of use within a tiny, thin, reliable, and green footprint.” said Scott Brown, Semtech Vice President of Marketing for Power Management Products.
EN-Genius Says…
At first blush I would say that Semtech’s claim that the SC12* parts are the smallest synchronous boost dc-dc converters out there is correct. With a footprint of just 3mm2 they beat what I believe is the next smallest in the MAX1760, which has 9.6mm2 as its smallest footprint but has 800 mA as its current limit.
That Maxim part does, however, seem to have been the model on which Semtech based its new parts with the significant feature being that if the feedback pin is grounded the output of the boost converter goes to 3.3 V. If you want to set any other voltage (except in the SC122) then a conventional resistive divider from the rail to the feedback pin does just that.
The SC120, SC121, and SC122 differ slightly in that the SC120 offers a PSAVE (power-save) function at low loads for improved efficiency. The SC121 offers forced PWM operation at all loads (for low noise applications), and the SC122 forces PSAVE at all loads – ideal for keep-alive applications in place of a separate LDO. The SC120 and SC121 also offer active discharge to ground while the SC122 eliminates this in favor of allowing the output voltage to float high during shutdown (which takes about 100 nA of current – with body diode reversal).
The input voltage for the three parts has a minimum of 0.7 V (0.865 V start-up voltage) and a maximum of 4.5 V for the SC120 and SC121 (1.6 V for the SC122). The variable output range for the SC120 and SC121 is from 1.8 V to 5.0 V. Output current depends on the input voltage and ranges from, for example, 80 mA with 1.0 V input (3.3 V output) and 190 mA with 1.8 V input. The reference feedback voltage accuracy is ±1.5%.
Synchronous PWM operation is at a nominal 1.2 MHz which, with the internal low resistance switches (600 mΩ p-channel and 500 mΩ n-channel on-resistances at 3.3 V output), offers efficiencies from 60% to 90% depending on the difference between input and output rails, and the load.
The parts use internal loop compensation and soft start to minimize external components which, for 3.3 V outputs, amount to input and output capacitors (that can be ceramic) and the switching inductor. Current limit and thermal protection are provided as is anti-ringing circuitry.
These three parts are ideal for single-cell operation in portable devices, which could include a myriad of products. These applications have real estate as a critically important factor and the SC12*s cannot fail to please in this respect, especially with the low pin count and low external component count. I personally believe, however, that the pricing is far too low. Volumes will be impressive.
The SC120, SC121, and SC122 are all in production in halogen and Pb-free MLPD-UT-6 packaging (1.5mm x 2mm x 0.6mm) with pricing at $0.80 in 3-k piece lots. The SC120 is also available in SOT-23-6 priced at $0.71, also in 3-k piece lots. Evaluation kits are available.
Data Sheet SC120
Data Sheet SC121
Data Sheet SC122
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