PMICs Manage Automobile Power Budgets

Power Management Integrated Circuits (PMICs) contain several switching and linear regulators in one package. Having several regulators in one IC serves increasing system demands for multiple voltage rails to supply downstream devices. Having all regulators for the system in one package provides efficient use of space within one part reducing cost and footprint.

Locating multiple regulators in one IC has the advantage of powering an entire embedded system including microprocessors, memory, displays, sensors, and unseen monitor circuits. This article discusses PMICs with respect to their use in automobiles and smart cars. Automobiles continue to add features with embedded systems requiring power. All source their power from the car’s battery. Batteries have limits so use of power within the system must be managed.

Power management is needed in automotive applications to ensure the battery’s limited resource can manage the load. Infotainment options and fancier displays including video and other features draw power. Navigational and communication devices such as sensors and radar need power. PMICs help manage the power budget by providing the needed regulators and controls to optimize sequencing for both smooth transitions and interactive power needs.

With increasing use of power comes increased need for thermal management. Automobile dashboards have increasingly more electronics and this means more heat. PMICs are designed to efficiently use the power they source to avoid losses to heat. Transients also cause both heat and signal loss and PMICs allow synchronization with the system clock to avoid creating additional noise. Many include internal design sequencing to spread out spurs within the spectrum to mitigate heat and noise.

Parameters to Consider When Selecting PMICs

Choosing a PMIC requires careful study of the power supply and overall system analyzing each block’s power needs. Every automobile is unique and the possibilities for adding design and innovation numerous. A good place to start is with the car’s battery as this will define your overall power budget.

Access power intelligently with PMICs

Typical voltage rails for supplied devices in automotive dashboards are 5V, 3.3V, 2.5V, 1.8V, and 1.2V each with its respective load demand. Many PMICs are able to provide these budgets and many provide programmable ranges. Each regulator has a feedback pin with opportunity to add resistor dividers for selectable outputs. There are also pins available for both syncing to the system clock and for setting up slave PMICs to accommodate additional devices. This helps with noise abatement and helps with overall management of power needs.

ECU: Engine Control Unit. A type of electronic control unit or embedded system within automobiles that controls a series of actuators on an internal combustion engine to ensure optimal engine performance.

LDO: Low Dropout. A low-dropout or LDO regulator is a DC linear voltage regulator that can regulate the output voltage even when the supply voltage is very close to the output voltage.

OTP: One-time Programmable. A semiconductor device that is programmable one time only (as opposed to erasable semiconductors that may be reprogrammed).

PMIC: Power Management Integrated Circuit.

POL: Point of Load. A term that describes voltage regulators suitable for insertion within a design between power source and downstream power delivery, used to downregulate within a specific power budget.

Radio Head Unit: An automotive head unit, sometimes referred to as a deck, is a component of an automotive infotainment, which provides a unified hardware interface (mainly, the screen and buttons) for the entire system. Antiquated names for head unit are receiver, in-dash stereo or dash stereo.

The PMICs we consider below are all suitable for sourcing from automotive batteries. Automotive batteries are unique for power sourcing with weakness towards dropping as much as half during cold startup. They also spike considerably from 12V up to 42V when system devices become inactive. It is a fairly hostile power environment requiring robust PMICs immune to hard-working batteries.

Radio head unit in car’s dashboard requires power management

We take a look at several automotive PMICs from several IC vendors. They are described below.

Maxim Integrated MAX16930 Dual Buck with Preboost, 2MHz, 36V

Maxim Integrated offers several PMICs for use in automotive. Their latest and greatest are the MAX16933 and the MAX16930/31 parts. Maxim has considered the increasingly demanding automotive dashboard, also called the radio head unit, that contains all the controls for various displays, audio for music and voice-activated commands, sensor, and radar electronics. All in all the radio head unit is growing to include eight to ten major embedded subsystems.

Maxim Integrated has assessed challenges that a car’s battery produces when used for source energy by the PMICs. This includes drop out and spiking that affect downstream devices and their regulators. Their PMICs include a variety of configurations as well, some offering more switch regulators and some offering preboost for hold up when the car’s battery drops out.

MAX16930 power startup sequence under full load, found on page 6 in MAX16930/MAX16931 datasheet

We highlight the MAX16930 which contains two switch-mode regulators with programmable output ranges of 1V to 10V, and one preboost controller to maintain operation when the car’s battery drops out. Voltage ramp up is designed to follow battery startup ensuring stable source power before subsequent buck ramp ups.

The MAX16930/MAX16931 offer two high-voltage, synchronous step-down controllers, and a step-up preboost controller. They operate with an input voltage supply from 2V to 42V with preboost active and can operate in drop-out condition by running at 95% duty cycle. The devices are intended for applications with mid- to high-power requirements that operate at a wide input voltage range such as during automotive cold-crank or engine stop-start conditions.

The MAX16930/MAX16931 are offered with an asynchronous step-up controller. This preboost circuitry turns on during low input voltage conditions. It is designed to provide power to step-down controller channels with input voltages as low as 2V.

The devices are available in 40-pin TQFN-EP and side-wettable QFND-EP packages and are specified for operation over the -40℃ to +125℃ automotive temperature range.

These PMICs are qualified for use in the automobile industry for POL power applications, for distributed DC power systems, and for navigation and radio head units. Maxim Integrated offers an evaluation board, the MAX16930EVKIT and you will find it on our website along with sourcing and pricing information.

Texas Instruments LP87332D-Q1 Dual High-Current Buck Converter and Dual Linear Regulator

Texas Instruments has designed the LP87332D-Q1 for compatibility with SoC and infotainment application processors in their automotive line of ICs. The LP87332D-Q1 integrates two buck regulators to provide 1.06V for core domains and two LDOs to provide 1.8V for processor and other domains. The bucks are configurable to several voltages: 1.06V, 1.2V, 1.8V, 1.35V, and 1.5V, while the LDOs are configurable to 1.8V, 2.5V, and 3.3V. This makes them adaptable for companion ICs within many systems.

This is found on page 3 in LP8733-Q1 and LP8732-Q1 User's Guide to Power DRA71x, DRA79x, and TDA2E-17

The LP87332D-Q1 PMIC is available in VQFN package and is suitable for use in the automotive head unit and cluster, with automotive camera modules, to power surround view system ECU, to power radar system ECU, and/or to power an automotive display. The PMICs come with an evaluation kit offered by Texas Instruments. Information regards sourcing and pricing is available on our website for the evaluation kit, the LP87332Q1EVM.

ST Microelectronics L5963Q Dual Monolithic Switching Regulator with a Standby Low-Dropout Linear Regulator

St Microelectronics offers a line of automotive ICs including PMICs to complement operation of their full suite of automotive devices. Today we review the L5963Q PMIC. It offers two step-down synchronous switch voltage regulators with the ability to program the outputs with an external resistor divider. Frequency management is available with a frequency divider and the part may be used in either asynchronous or synchronous mode. A copy of ST Microelectronics block diagram for the part is shown below.

L5963Q is a dual step-down switching regulator with internal power switches, high side driver and a low drop-out linear regulator that can operate as standby regulator or normal LDO. All the regulators can be connected directly to the vehicle battery. In addition to an adjustable voltage detector, voltage supervisors are available. The two DC-DC converters can work in free-run condition or synchronize themselves to an external clock. DC/DCs’ PWM outputs have a 180° phase shift. The high operating frequency allowed by the synchronization input helps to reduce AM and FM interferences and grants the use of small and low-cost inductors and capacitors.

This IC finds application in the automotive segment, where load dump protection and wide input voltage range are mandatory.

*ST Microelectronics L5963Q functional block diagram. This is found on Page 7 in L5963Q Dual monolithic switching regulator with LDO and HSD datasheet *

The L5963Q is rated for use in automotive applications. ST Microelectronics offers an evaluation board for development needs. Our site shows sourcing and pricing information, at EVAL-L5963Q.

PMICs are integral devices within any automotive EDA, navigational, operational, or infotainment applications. PMICs allow designers options for managing the automotive battery power budget amongst competing needs of the car. Our site lists many PMICs, a few of which we discussed in this article. Each has links to technical documents and ordering information.

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