PowerManagement ICs
been suited to its one-wire interface system.Microchip Technology (Chandler, Ariz.) also released its PS501 in the same timeframe, with a claimed accuracy of one percent. Intersil's (Milpitas, Calif.) "high-accuracy" ISL6295 also appeared shortly thereafter (battery capacity accuracy spec not specifically stated).
A sampling of new arrivals include TI's master gateway battery
controller, the bq78PL116, which is part of a complete monitoring and cell-balancing solution designed for three to 16 Li-ion cells. A similar system comes from Atmel (San Jose, Calif.), although specifications are incomplete.
TI also has a device in the monitor class suited to electric and
hybrid vehicle applications; its bq76PL536 is a 3-to-6 cell Li-ion battery monitor and secondary protection IC. The company has also introduced its bq78412 for 12-volt lead-acid batteries (a fairly uncommon product these days), which includes a state- of-charge indicator with run-time display.
Step by step
Beyond monitoring a supply, a PMIC's most critical job includes starting them up and shutting them down. Over the past decade, systems have become much more complicated; there are multiple DC power supply lines and mixed (positive/negative) voltages, where the user needs to bring the various buses up and down in just the right way to avoid system lockup or, in the worst case, damage to system components such as microprocessors or digital signal processor (DSP) chips.
The power-management chips cover three general
applications. The ideal supervisor IC can ramp multiple supply lines up and down in a controlled order (sequencing); bring up each line simultaneously while allowing the user to select the voltage offset for each line or each line voltage as a set percentage of the others (tracking); and allow the user to set upper and/or lower limits of a given bus voltage (margining), which allows the controller to be used in automated testing of circuit boards and the like, or just to keep a microprocessor at its sweet-spot during low-power operation.
Supervisor ICs thus usually have to be accurate to at least
within millivolts and milliseconds. A typical IC might be available as a dedicated device suited to largely sequencing, but ideally can perform all three of the aforementioned functions.
Notable new arrivals include the ADM1168/1169
SANYOSemiconductor's LC709201F battery fuel gauge IC,which detects the remaining power level of 1-cell lithium-ion batteries used inmobile devices, claims the industry's best accuracy of +/-3 percent for battery fuel gauge ICswith no sense resistor
Several other new
entries for basic single/dual cell applications offer some parts-cutting alternatives. These parts have performance better than traditional battery monitors and approach that of one percent gas-gauges. These include the LC709201F from Sanyo Semiconductor USA (Saddle Brook, N.J.) for 1-cell lithium-ion batteries. Sanyo claims +/-3 percent accuracy of remaining battery-operating time and the industry's highest accuracy device for chips without a sense resistor. Quiescent operating current (no input) is 15 microamps.
Maxim's newest arrivals include itsMAX17040/43 (one-cell)
andMAX17041/44 (two-cell) compact fuel-gauges. The company'sModelGauge algorithm eliminates the usual current- sense resistor and reportedly the coulomb counter as well to cut costs by 30 to 50 percent compared to traditional solutions. It can accurately determine voltage to +/-12.5 mV up to 5 volts (its ability to determine remaining battery run time is not directly specified). Its quiescent current is 50 microamps (typical).
24 | April 2011
Maxim'sMAX17040/43 (one-cell) andMAX17041/44 (two-cell) compact fuel gauges leverage the company'sModelGauge algorithmto eliminate the current-sense resistor, alongwith eliminating the coulomb counter and several other discrete components, cutting costs by 30 to 50 percent.
Super Sequencer chips from Analog Devices (Norwood,Mass.). The ADM1168 provides up to eight programmable inputs for monitoring under- voltage and over-voltage for up to eight supplies. The configurable device uses a sequencing engine that provides up to 63 different states. A block of nonvolatile RAMis available that can be used to store user-defined information. It can also store a fault sequence that is written by the sequencing engine when it detects a particular failure. The ADM1169 also integrates a 12-bit A/D converter and four 8-bit voltage output DACs to implement a closed-loop margining system.
More and more chips store a variety of start-up
sequences, tracking, and/or margining states. Also extending to yet another class of power-with-power management IC, the devices include supervisory circuitry as part of a single DC/DC regulator or multi-regulator system with advanced power management capabilities. One example is a digital power management system (e.g., sequencing, margining, tracking) with multi-output DC/DC regulators, such as the just released LTC3880 by Linear Technology (Milpitas, Calif.).
DC/DC systems
Somewhat complementary to supervisor ICs, so-called hot-swap controllers come more fully into focus as we move from portable devices to larger stand-alone systems. Hot-swap controllers
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