Processor and memory power supplies must follow precise start-up sequences otherwise they can be seriously damaged. Therefore it is critical that the voltages are switched on and off in the correct order. Compared to a discrete solution consisting of a collection of standalone DC-DCs, LDOs and chargers, this task has become very easy with AS3607. With its software programmable start-up sequences, the AS3607 is bringing flexibility to the market that is new for midrange PMICs. Other competitors offer PMICs with fixed start-up sequences that are selected with external resistors.
The output voltage and the timing of all regulators of the AS3607 are programmed via software. With the software and demo board, the OTP memory of the AS3607 can easily be programmed enabling fast prototype runs for quick market introduction. The slope of the ramp can be set for the step-down converters. The user can program the start-up sequence with timing steps of 1 ms or 4 ms, insuring that all ARM-based processors can easily be covered. In order to control other parts of the system, the general purpose I/O pins can be programmed to a specific timing.
“Last minute changes, slight modifications or even new features are no problem for the AS3607, because it is easy to modify the start-up sequence, timing and configuration of regulators. There is no need to redesign the power management portion or to re-approve a new PMIC, which saves time and money,” says Manfred Kogler, marketing manager consumer and communications at austriamicrosystems. “Even if the designer decides to switch to another processor, the PMIC can stay the same. All the software and layout can be completely reused and the AS3607 can be easily programmed to the processor’s requirements. So austriamicrosystems’ AS3607 covers several generations of a product line.”
In portable systems, maximizing battery lifetime and minimizing PC board space are critical. The PMIC together with the application processor manage and optimize the power rails within the system to maximize battery charge. The AS3607 PMIC has a significant space benefit over a discrete solution, since it integrates all the regulators, charger, backlight driver and monitoring functions in a 6x6 mm QFN package.
The AS3607 fully programmable power management unit includes: three DC-DC step-down converters and five low-noise LDO regulators suitable for RF applications, an LED backlight driver, two programmable current sinks and a powerful Li-Ion battery charger. The three step-down converters deliver 700 mA each with an efficiency of up to 95%, extending battery life significantly. The fixed 2 MHz switching frequency minimizes PCB footprint by allowing the use of tiny, low-profile inductors.
The AS3607 contains a Li-Ion battery charger with constant current and constant voltage with a maximum charging current of 1 A, enabling fast charging of large batteries. An integrated battery switch separates the battery when charging or whenever an external power supply is present. This enables operation of mobile devices with deeply discharged batteries or even with no battery. In order to be compliant to the USB standard the maximum current can be programmed.
The integrated DC-DC step-up converter is capable of generating voltages up to 30 V to supply OLED displays or LEDs for backlighting LCD displays. In the case of LEDs two strings of up to 8 LEDs can be powered, whereas the current is programmable via registers in 150 µA steps, enabling smooth dimming. In addition an external PWM signal can be used to dynamically control the brightness of the two LED strings. The GPIO pins can be used to get information about charger status, low battery, power good and power-up key.