Highly integrated PMIC simplifies design: power management solutions for smartphones

In recent years, the market for portable devices such as mobile phones has continued to develop rapidly. It is estimated that the shipment of mobile phones will increase from 1.4 billion in 2011 to 1.8 billion in 2014; the smart phone market is the most dazzling one. Driven by the launch of a large number of low-cost Android phones, the shipment of smart phones will increase from 400 million to 680 million during the same period, and the semiconductor content of smart phones is much higher than that of functional or entry-level phones. At the same time, leading manufacturers pay more attention to user experience, and one of their measures is to select products and solutions that can better meet the application requirements and technology trends of portable devices such as smart phones in product design.

As the world's leading silicon solution provider for energy-efficient electronic products, ON Semiconductor provides a wide range of solutions for portable applications. This article will focus on how ON Semiconductor's high-performance, energy-efficient solutions meet the requirements and technology trends of portable applications such as smartphones, helping design engineers choose suitable component solutions.

Highly integrated PMIC simplifies design and speeds up time to market

As we all know, portable devices are integrating more and more functions, ranging from taking photos to playing audio and video, games and even location services. With the preparation of 3G and even 4G network infrastructure, users are becoming more and more accustomed to wirelessly accessing rich data and multimedia content through portable devices such as smartphones, which requires portable devices to embed more and more powerful radio frequency (RF) modules. The corresponding cost is that power consumption is getting higher and higher, while the progress in battery capacity and technology is still slow. Portable device designers must adapt to this trend of high integration that combines many functions, provide sufficiently long battery life, and meet consumers' demand for slim form factors.

To meet these challenges, a viable strategy for portable device designers is to select a main chipset that integrates multiple functions while selecting a highly integrated power management integrated circuit (PMIC) to help simplify the design, minimize the resources required to control the power supply, and keep the form factor within a controllable range.

Figure 1: Functional diagram of the mini-PMIC provided by ON Semiconductor.

ON Semiconductor provides a series of mini power management ICs (mini-PMICs), the functional diagram of which is shown in Figure 1. These mini power management ICs integrate multiple DC-DC switching converters or low-dropout (LDO) linear converters, and may also integrate a variety of other control or protection functions, such as bus control, sequencer, power good (PG) monitoring, enable, bandgap reference, oscillator, undervoltage lockout and thermal shutdown protection functions or dynamic voltage scaling (DVS), etc. ON Semiconductor's mini-PMICs currently include NCP6922, NCP6914, NCP6924 and NCP69xy (increasing power and functions). Taking NCP6922 as an example, this mini-PMIC provides 4 voltage rails (2 DC-DC plus 2 LDO) with output from 0.6 V to 3.3 V, and integrates multiple functions such as core, power-on sequencer, thermal protection and clock (see Figure 2 for details). It adopts 2.05 mm x 2.05 mm CSP package, which not only reduces the solution size, but also provides design flexibility through I2C control. It is suitable for battery-powered portable devices that require multiple regulated outputs and use digital signal processors (DSPs) and/or microprocessors. This device supports an input voltage range of 2.3 V to 5.5 V, with the latest battery technology; it also supports a DC-DC operating frequency of up to 3 MHz, which can reduce the size of output inductors and capacitors; the static current consumption is as low as 64μA, which helps to extend the battery life; it also supports dynamic voltage regulation (DVS) to improve system energy efficiency.

Figure 2: ON Semiconductor’s NCP6922 mini-PMIC integrates two DC-DCs, two LDOs, and other functions.

It is worth mentioning that this series of mini-PMICs from ON Semiconductor can provide customized power-on sequencing functions to meet the application requirements of different platforms. The LDO integrated in this series of ICs can be powered by DC-DC output to further improve energy efficiency. Other advantages include design flexibility with I2C control, support for voltages as low as 2.3 V to match new battery technology, and QFN and CSP packaging with a pitch as low as 0.4 mm. ON Semiconductor also provides a rich intellectual property (IP) library and modular approach to help customers cope with the trend of high integration and accelerate the process of listing products.

Buck or boost DC-DC switching regulator to power application processor or HDMI port

Although the application of highly integrated PMIC is increasing, not all power domains in portable products need to use highly integrated PMIC. As the functions of portable products continue to increase, the demand for relatively low-integration power conversion ICs has also increased to match the addition of new functions.

For example, for portable products, designers may need to use a DC-DC switching regulator to power a high-power application processor. ON Semiconductor has launched a series of relatively low-integration DC-DC switching buck converter ICs, such as NCP6334B/C, NCP6338, and NCP636x modules. These ICs accept 2.3 V to 5.5 V input voltages to match the latest battery technology. Taking NCP6334B/C as an example, this is a 2 A, 3 MHz DC-DC buck converter that integrates power good (PG) and operating mode selection (PWM mode or PFM/PWM automatic mode). It is a cost-saving and space-saving solution that is very suitable for powering new microprocessors that require high power at low voltage. The NCP6338 has similar functions to the NCP6334, but can provide up to 6 A output current to meet the needs of the latest processors. The NCP636x module is a 0.8 A, 6 MHz DC-DC step-down converter module. The switching frequency of up to 6 MHz facilitates the use of smaller external components, making the total solution size less than 5 mm2 (maximum height 1 mm), which is especially suitable for portable applications with extremely limited tolerances.

Figure 3: The CAT3200HU2 low-noise power IC is suitable for powering HDMI ports.

It is worth mentioning that many smartphones are now equipped with HDMI interfaces, which are convenient for users to transmit video data. These HDMI interfaces are powered by +5 V, which is higher than the supply voltage of lithium-ion batteries commonly used in portable products. At this time, a DC-DC boost converter is needed. Fortunately, ON Semiconductor has launched a low-noise charge pump DC-DC boost converter CAT3200HU2 for HDMI port power supply applications. This device accepts 2.7 V to 4.5 V input and provides 5 V/100 mA (and adjustable output). It uses a UDFN-8 package and is suitable for 3 V to 5 V boost conversion (also suitable for 2.5 V to 3.3 V boost conversion). Typical applications include HDMI and DisplayPort port power supply. Figure 3 shows a typical application circuit.

Low-current, low-noise LDOs extend battery life and reduce size

As mentioned earlier, despite the increasing use of highly integrated PMICs in portable products such as smartphones, there is still ample room for independent DC-DC switching regulators or LDOs, such as the need for LDOs to maximize battery life and minimize size in portable devices, especially those RF and noise-sensitive functions that still require the use of low-noise LDOs. Taking mobile phones as an example, typical applications of LDOs include audio jacks, camera modules, display modules, GPS modules, interfaces, LCD/touch screen controls, microphones, GSM/WCDMA RF sub-circuit boards, Bluetooth modules, and USB ports.

ON Semiconductor offers a wide range of LDOs suitable for portable applications, including the NCP45xx and NCP46xx series, such as NCP4586 (100 mA), NCP4587/89 (150/300 mA), NCP4588 (200 mA), NCP4681/4 (150 mA), NCP4682/5 (150 mA), NCP4680 (100 mA) and NCP4683 (300 mA). In addition, a number of LDOs in the CAT62xx series are also very suitable for portable applications, including the CAT6219 that guarantees 500 mA output current, the CAT6221 that provides two 300 mA peak output currents, the CAT6220 with a typical no-load ground current of only 10μA, the CAT6243 that provides 1 A peak current, and the CAT6289 with ultra-low operating current.

Figure 4: CAT6289 ultra-low operating current NanoPower LDO block diagram and typical application circuit diagram. Take CAT6289 as an example, this is an ultra-low operating current (typical value 400 nA) NanoPower LDO, the input voltage range is 1.8 V to 5.5 V, and it provides 8 standard voltage outputs, including 1.00, 1.20, 1.25, 1.50, 1.80, 2.50, 3.00 and 3.30 V, the typical voltage drop at 10 mA current is 380 mV, and the typical power supply rejection ratio (PSRR) at 1 kHz is -60 dB. This device uses a small 1.5 mm x 1.5 mm TDFN-6 package, which can help portable devices extend battery life and match small form factor design.

OVP and OCP protection solutions for different charging applications of portable devices

Portable devices powered by lithium-ion batteries, such as smartphones, may face risks such as positive/negative overvoltage and overcurrent in daily charging/powering applications, so safe protection solutions are needed. ON Semiconductor's portable device OVP protection solutions mainly include 30 V/up to 3 A series products for wall adapter/USB charging (including NCP347/348, NCP349, NCP367, NCP370, NCP372 and NCP391, etc.), and 20 V/500 mA series products for USB charging (including NCP360, NCP361, NCP362 and NCP373, etc.); OCP protection solutions include NCP380, NCP381 and NCP382, etc.

Take NCP367 as an example. This is a protection IC that provides +30 V overvoltage protection and up to 3 A overcurrent protection with battery voltage detection function (see Figure 5). This device protects portable device batteries from input overvoltage (which disconnects the system from Vbus or AC-DC adapter under fault conditions), charging overcurrent and charging overvoltage. NCP367 provides a low on-resistance of 100 mΩ maximum, helping to reduce solution costs and board space. The ability to support up to 3 A current helps achieve fast charging. The extremely low current consumption of 50 μA typical is compatible with USB 500 μA idle mode. This device can be used for two charging current levels of 1.5 A or 500 mA, which is very suitable for applications such as mobile phones.

Figure 5: Typical application circuit diagram of NCP367.

The NCP382 is a power distribution switch designed for applications that are likely to encounter large capacitive loads or short circuits. In fact, more and more portable electronic devices are powered by USB, but the local USB power supply needs to be protected from external Vbus faults. The NCP382 can provide overcurrent protection by switching to constant current mode when the output load exceeds the current limit threshold or a short circuit occurs, limiting the output current to the desired level (0.5 A, 1 A or 1.5 A). The NCP381 receives a single input of 2.5 V to 5.5 V and provides two outputs. Figure 6 is a typical application circuit diagram of the NCP382.

Figure 6: Typical application circuit diagram of NCP382.

Highly Integrated Switching Battery Charger Helps Speed ​​Up Battery Charging in Portable Devices

Consumers may use a wall AC adapter or a USB input to charge their portable devices. Generally speaking, the wall AC adapter has a higher charging current (such as up to 1.5 A) and requires a shorter charging time; while the USB charging current is relatively small (such as 500 mA) and takes longer. But even if charging is done with a USB input, consumers expect to be able to charge faster. ON Semiconductor's NCP1851 switching battery charger is a highly integrated IC that meets consumers' expectations in this regard. This device accepts a wide input voltage range of 3.6 V to 16 V, provides a positive overvoltage lockout that can be selected between 7 V and 16 V, and provides positive +30 V/negative -30 V input overvoltage protection. This device integrates a DC-DC boost circuit for 5 V USB OTG applications (current 250 mA) and provides 5 V USB transceiver protection. The NCP1851 also integrates a battery FET driver to support "dead battery" operation. The device has a charging current of up to 1.5 A and also integrates a battery temperature monitoring function to protect battery safety during charging, making it very suitable for fast battery charging applications in portable devices.

Figure 7: NCP1851 switching battery charger functional diagram.