Stable current supply is an essential element of high-quality electronic products. For consumer electronics, power management is a key requirement for the success of products. This article will introduce the high performance and high reliability CMOS ULDO for consumer electronics to understand the development trend of ULDO.
Low dropout provides better power conversion efficiency
Power management is also an important requirement for consumer electronics products to have stable power transmission, achieve low power consumption and noise under various load conditions, expect to use less space and have higher reliability. Therefore, a variety of power management IC, such as linear regulator, DC-DC converter, power controller and PMIC are developed and applied to meet the specific requirements of various application fields.
The common linear regulators in power management IC may be divided into standard linear regulators, low dropout regulators (LDO) and ultra-low dropout regulators (ULDO). The key difference among them is the dropout voltage characteristic required to maintain a steady output voltage. The dropout voltage is defined as the minimum output differential voltage to maintain a steady output voltage. From the point of view as power output, a linear regulator can also be regarded as a variable resistor.
When the output current changes, the internal control circuit of the linear regulator adjusts the on-resistance through the components. The adjustable on-resistance range defines the maximum operating current range (the operating output impedance range). For the standard linear regulator, the pass element is Darlington NPN or PNP output stage, with the differential pressure of up to 2V. The linear regulator cannot be applied to any application requiring low dropout, for example, generating a 3.3V voltage from a 3.6V battery supply. Most LDO/ULDO use NMOSFET or PMOSFET with appropriate size as the pass element for lower dropout voltage characteristics.
The important reason for a power circuit to pay attention to voltage drop is the power conversion efficiency. The low dropout performance of LDO can reduce the input voltage and achieve the desired power output. Due to lower power dissipation, higher power conversion efficiency and lower heating can be achieved. The above-mentioned three linear regulators require different minimum input voltages to achieve the same required output power. LDO/ULDO have low dropout and better power conversion efficiency, thus reducing the power consumption. Another advantage of low power consumption is low heat occurrence, which enables smaller package applications.