S.A.B.Re ICs take new approach to power management
By Mauro Stefanone
Stefanone: S.A.B.Re can replace several components with a single chip, reducing the overall BOM cost of up to 20 percent.
STMicroelectronics has introduced S.A.B.Re ICs to offer a solution with a number of features that can be configured and customized for various applications such as motor drivers, regulators, high-precision ADCs, operational amplifiers, and other digital or analog circuits.
The S.A.B.Re IC has been primarily developed for motion and power-supply management in printer applications. However, due to its flexibility, S.A.B.Re can address any high-power, high-voltage analog and motor application across the industrial segment.
A key advantage over existing motor drivers and switching regulators is that the S.A.B.Re IC manages the whole power section of the application with specific programmable power-up routines. The device can be configured by programming the IC via the serial interface. The regulator start-up sequence is defined by configuring the GPIO inputs and a deeper customization can be obtained through metal layers in order to set different functions.
Internal power management
The device features integrated power-up sequencing, a supervisory function with fault signaling and reset management and very low and optimized power dissipation.
It also has an internal on/off button handler that is able to turn on the IC itself from its sleep mode, that is, the system regulator turns on the whole application. Since the device can be put into sleep mode (power off) by the SoC, every circuit of the system is off except the function to be activated by a wake-up signal (on button pushed). This function allows effective power consumption management without the need for any external circuitry.
If used as a system power supply manager, S.A.B.Re can turn off all the power supplies, reducing the system power consumption down to a very small value (around 35mW). This allows the system to meet the requirements of energy efficiency programs such as Energy Star in the United States.
Power-up routines define the IC operating modes (between four possible settings: basic, single, master and slave), the number of regulators of the application architecture, their type (system regulator or not) and their switch-on sequence.
Basic mode has just one pre-defined start-up sequence, while the other 3 modes provide up to 6 predefined regulator start-up sequences on top of the programmable user selection. Master and slave mode have to be selected when two or more ICs are used on the same application board.
S.A.B.Re block diagram (Click to view full image)
The main components of the S.A.B.Re IC are four configurable bridges that can act as four DC motor drivers, or two DC motor drivers and one stepper motor driver, but that can also function as switching regulators or battery charger.
Additional components are a variable-voltage buck switching regulator, a switching regulator controller, a linear regulator, a multi-channel configurable 9-bit ADC, two operational amplifiers, a bidirectional serial interface and several general-purpose I/Os.
Each of the four H bridges is composed of two independent half bridges, and is protected against: over-current, over-temperature and short circuit to ground, to supply and across the load.
The stepper mode is configured with bridges 3 and 4, and has an internal sequencer with up to 6 operating modes, from full-step to micro-stepping functionality, programmable mixed decay and sinusoidal DACs.
Each H bridge can drive a DC motor with an internal and dedicated PWM programmable signal. S.A.B.Re provides up to 7 PWM signals (3 of them can be externally available through the GPIOs). A digital encoder input can be managed by the GPIOs and internal blocks (9bit ADC, digital comparators and interrupt controller).
Besides the motor-driver function, the bridges can be configured by user settings for several additional modes. H bridges 1 and 2 have the same design architecture and can be paralleled to act as a "Super DC" (DC driver with output resistance divided by half, enhancing its current capabilities). They can also work as half bridges (up to 4 or in parallel) and as switches (single or in parallel).
H bridges 3 and 4, on top of the configurations offered by bridges 1 and 2 that are always available, offer the possibility to act as two buck regulators (or one super buck with bridges in parallel), or as a switching regulator I-V controller for battery charger applications (only bridge 4).
Other configurable S.A.B.Re components are: one variable buck regulator (in addition to the one that can be implemented with one of the bridges, described above), one switching regulator controller (able to drive an external FET), and one linear regulator. All these regulators can be programmed by internal register settings or with an external DAC, and are protected against over-currents.
In addition, the logic portion can be rerouted to obtain specific digital functions (such as interfaces, or to implement an auxiliary switching regulator control loop, or to access a specific internal signal, as well as many others implementations). The number of available gates depends on the already existing functions that remain unused in the customized product.
All existing analog functions can be configured and interconnected, including with digital functions, allowing customers to obtain complex IPs, or just a specific behavior or performance of an existing function.
With the number of configurable blocks of the S.A.B.Re, a user can easily set many chip architectures.
The architecture of an inkjet printer with mid-range features, typically used at home, could have three DC motors: one to feed the paper (bridge 2), one to move the carriage (bridge 1), and one to have some auxiliary function (bridge 4) such as an ink pump or paper tray selection.
The needs in terms of regulated voltages is about 5 values, 5V (half of bridge 3) for a USB host or card reader, the core voltage (half of bridge 3) for the digital SoC, typically 1.8V, the pen voltage, typically 16V, he 2.5V DDR voltage and 3.3V I/O voltage.
Mid-end inkjet printer: motor and power management S.A.B.Re solution
In a low-cost multi-function inkjet printer application, the S.A.B.Re motor section is composed of the stepper motor driver (bridge 3 and 4) for the scanner and two DC motors, one to move the paper (bridge 2) and one to move the carriage (bridge 1).
A low-cost printer also requires a minimum set of power supplies, the core voltage for the SoC supply, a 3.3 V voltage for SoC I/Os and the pen voltage, all managed by the voltage-regulator section.
Low-end multi-function inkjet printer: motor and power management S.A.B.Re solution
For multi-function inkjet printers, the motors usually require more current, and "Super DC" drivers (made by paralleling two H bridges) are needed. An additional stepper motor might also be necessary for maintenance service of the head. With two S.A.B.Re ICs on the same board, one is set as master and the other as slave.
High-end multi-function inkjet printer: motor and power management S.A.B.Re solution
In addition to its technical features, S.A.B.Re introduces a new marketing concept. This is to provide the user with a multi-purpose mixed signal device able to shorten and simplify the supply chain once mass production is achieved.
With its high flexibility, the device can be used in several applications and platforms with just different firmware settings and external components and connections. This possibility reduces time and effort in managing effective bill-of-material procedures, reducing stock effects.
SABRe development kit board
S.A.B.Re can also replace several components with a single chip, reducing the overall BOM cost of up to 20 percent. Engineers with experience of its flexibility and configurability to different application requirements can quickly adapt it to new projects, optimizing time-to-market product development.
The device is supported by a dedicated development kit, including application board, PC interface, software and the related user manual. The kit helps evaluate the functionalities of S.A.B.Re for different device configurations and allows the user to simulate power and reset management, the measurement system, power dissipation, and power-up sequences.
Mauro Stefanone is a product marketing manager at STMicroelectronics. He works on mixed-signal devices and customizable SoC, mainly for printer applications.
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