Ultra-low power linear regulator

The linear voltage regulators of new portable electronic products often use lower working voltage, such as 3.0~3.3V, and must meet the requirements of small size, low voltage difference, high output voltage accuracy, small output voltage temperature coefficient and power off function, etc., in order to reduce the size of the power supply and extend the working life of the battery. The following introduces two linear voltage regulators BAF033 and BAL029/030.

1. BAF033 linear regulator

BAF033 is an ultra-low power linear regulator integrated circuit. The regulator composed of this device has the following main features:

① Ultra-low quiescent current, the typical value is 1.1μA;

② Low voltage difference. When the output current Io=30mA, the voltage difference is less than 0.6V;

③High output accuracy, the maximum tolerance is ±2.5%;

④The output voltage temperature parameter is low, the typical value is ±1×10-4 (℃)-1;

⑤Good linear regulation rate, typical value is 0.001V-1;

⑥Small size, SOT-23 package.

The output voltage of BAF033 is 3.3V, the maximum output current is 50mA, and the maximum input voltage is 10V. The voltage-stabilized power supply composed of this device is mainly used in portable electronic products with large working current, such as mobile communication devices, cameras, etc.

The internal structure of BAF033 is shown in Figure 1. It consists of a voltage reference source, an error amplifier, a P-channel MOSFET, and voltage divider resistors R1 and R2 that determine the output voltage.

The typical application circuit of BAF033 is shown in Figure 2. C1 is the input capacitor, which is 1μF. C2 is the output capacitor, which can be 1 to 4.7μF according to the output current (the larger the output current, the larger the C2 value). It can usually be powered by 3 alkaline batteries or AA rechargeable nickel-cadmium or nickel-metal hydride batteries.

Figure 1 Internal structure of BAF033 Figure 2 Typical application circuit of BAF033

2. BAL029/030 linear voltage regulator controller

The BAL series is a low-power linear voltage regulator controller. It has no internal adjustment tube, so when it is used to form a voltage-regulated power supply, an external PNP power transistor must be used as an adjustment tube. Its characteristics are flexible use, and it can be selected and adjusted according to the load current, so that the output current can be changed from tens of mA to 1A.

The BAL series has two models, BAL029 and BAL030, with fixed output voltages of 2.9V and 3.0V. The features of these two devices are:

Low quiescent operating current, typically 50μA (BAL030):

There is a chip select terminal, and the power consumption is about 0.2μA in each state;

Low voltage drop, when the load current is 100mA, the typical value is 100mV (related to the performance of the external power transistor);

The output voltage has high accuracy, with the maximum allowable difference being ±2.5%;

· Low temperature coefficient, typical value is ±1×10-4 (℃)-1;

·Good linear regulation rate, typical value is 0.001V-1;

Small size, SOT-23 package.

(1) Internal structure and pin function

The internal structure of the BAL series is shown in Figure 3. It consists of a reference voltage source, an error amplifier, a chip select control circuit, and a voltage divider resistor that determines the output voltage. The EXT terminal is the base of an external PNP power transistor, and the error amplifier controls the internal resistance of the external transistor to keep the output voltage stable. The CE pin is the chip select terminal. When this terminal is connected to a low level (grounded), the power is turned on; when this terminal is connected to a high level (connected to UIN), the power is turned off (in each use mode). UOUT is connected to the collector of the external PNP power transistor, VDD is connected to the input voltage, and GND is the ground terminal.

The BAL series is a SOT-23-5 package, and its pin functions are as follows: pin 1 is ground (GND), pin 2 is input (VDD), pin 3 is output (UOUT), pin 4 is the external transistor base (EXT), and pin 5 is the chip select terminal (CE).

(2) Application circuit

The application circuit of BAL series is shown in Figure 4. VT is an external PNP power transistor; Pin ⑤ (CE) is grounded, and the power supply works normally; C1 is the input capacitor, which is generally 1μF; C2 is the output capacitor, which can be selected between 100 and 200μF according to the load current; the input voltage UDD is not greater than 10V.

Figure 3 Internal structure of BAL series Figure 4 Application circuit of BAL series