Positive voltage regulator with low step-down and low noise output

포스트 날짜: 2023-03-10, Exar Corporation

The SPX3819 is a positive voltage regulator with low step-down and low noise output. The device is offered in 8-pin NSOIC, 8-pin DFN and 5-pin SOT-23 packages. In addition, the device provides a very low 800μA ground current at 100mA output.

Pin assignment

The SPX3819 has a maximum initial tolerance of less than 1% and logically-compatible ON/OFF switch input. When disabled, power consumption drops to almost zero. Other key features include reverse battery protection, current limiting and hot shutdown, and a reference bypass pin is also included for optimal low noise output performance.

Due to its very low output temperature coefficient, the device also makes for a superior low-power voltage reference. The SPX3819 is an excellent choice for battery powered applications such as cordless phones, radio control systems and portable computers. It has several fixed output voltage options or adjustable output voltage.

Typical application circuit

Applicable to fixed voltage option only. A 10nF capacitor on the BYP pin will significantly reduce the output noise, but may not be connected if the output noise is not a major problem. The startup speed of the SPX3819 is inversely proportional to the size of the BYP capacitance.

Applications that require a slow increase in output voltage should use a larger CBYP. However, the BYP capacitor can be omitted if a fast connection is required. The internal reference for the SPX3819 is available via the BYP pin. The following figure shows the SPX3819 standard application circuit. EN(Enable) pin pull higher (> 2.0V) Enable the regulator. Off regulator, EN < 0.4 v.

The SPX3819 in the figure below illustrates a typical adjustable output voltage configuration. Two resistors (R1 and R2) set the output voltage. The output voltage can be calculated as follows :VOUT = 1.235V x [1 + R1/R2] R2 must be > 10 kω, R2 should be between 22 kω and 47 kω for best results.