Power system design in the age of mobile devices, and especially wearable devices, is more challenging than it has ever been. The end users of these devices want them to get smaller and lighter, while at the same time having longer battery life. These opposing goals, and the need to cost reduce and size reduce the circuit boards, are just a few of the challenges facing the power system designer. Shown below are more of the challenges facing the designer of a power system for mobile devices.
To overcome these challenges, Renesas has developed the concept of "Flexible Power Islands" (FPIs). Using FPIs, designers can divide their complex power system into some number of local power regions (or islands), each of which includes the power control, power sequencing and power regulation needed to support loads in the immediate vicinity. This technique results in higher performance and a more efficient solution that can be flexibly tailored to the requirements of each individual system.
In some cases, using an FPI can be very useful to augment the functions included in a power management IC (PMIC). In this use case, the FPI can support local point-of-load regulation, sequencing and power monitoring. This can result in a simpler layout, as well as improved energy and thermal efficiency.
For smaller and simpler systems (which have up to six power rails), the FPI concept can provide most or all of the power system functions needed. In this case, the FPI can serve as a “µPMIC”, but with the added benefit of greater levels of flexibility and customization, with no requirements for NRE.
With the SLG46580, it is possible to capture many of the necessary power system functions including power monitoring, sequencing, reset, and power switching - all in a tiny 2.0mm x 3.0mm 20-pin fully encapsulated plastic package. Using Renesas' easy-to-use GUI-based GreenPAK Designer™ and GreenPAK development hardware, designers can quickly and easily implement their unique configuration of the device, thereby customizing the functions to match their unique power requirements.
The SLG46580 has four LDOs, each with a maximum output current of 150mAs. Each of the LDOs has a programmable output voltage level that can be set to one of 32 different values from 0.9V to 4.35V, and also have programmable options for slew-rate selection and fault detection.
The FPI concept is broadly applicable across a range of end markets, shown below.
- Handheld devices
- Wearable electronics
- Computing and storage
- Consumer electronics
- Smart home
- Networking and communications
- Medical and industrial
Benefits of GreenPAK with LDOs
- Includes many components typically found in power systems
- Power control
- Power sequencing
- Power monitoring
- Power regulation
- 2.0 x 3.0 STQFN packaging for small board area
Tri-Mode 150mA LDO Regulators
- Mode 0: 150mA output with quiescent current at ~60μA
- Mode 1: 100μA output with quiescent current at ~6μA
- Bypass Mode: Acts like a load switch
Flexibility of GreenPAK Configurable Macro-cells
- Analog comparators
- Combination function macro-cells
- Asynchronous state machine (ASM)
- I2C slave protocol interface
Using Asynchronous State Machine for Power Sequencing
The asynchronous state machine (ASM) macro-cell is perfect for driving a flexible power-sequencing architecture. The graphic user interface (GUI) based development tools allow the user to quickly define the operating states, the allowed transitions between states, and link to the signals that drive each state transition. Using other GreenPAK macro-cells allows the user to easily time-based state transitions (using delay macro-cells) and logic functions (using look-up tables). The example state machine shown below is the one used in the demo project to drive both the power sequencing signals for six power rails, as well as the signals to turn on the four LDOs in sequence.
Controlling LDOs with GreenPAK Resources
The LDOs included in these devices allow the user to control many aspects of the output dynamically during operation:
Controlling Output Voltage: Each LDO can support two output voltages, which are user-selectable. There is an internal signal coming from the Connection Matrix that can switch the output voltage during operation.
Controlling Power Consumption: Each LDO regulator can operate in MODE0 (standard active mode supporting full 150mA output), as well as MODE1 (low power mode with maximum 100μA output with reduced quiescent current consumption.
Load Switch Mode: Each LDO has a user-selectable option where the regulator ceases to regulate and the power MOSFET is turned on as a power switch, passing the voltage applied to VIN directly to VOUT.
Changing LDO Behavior Via I2C: All of the control features listed above can also be changed via I2C commands.