XCM519 datasheet(19/49 Pages) TOREX

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XCM519

Series

■OPERATIONAL EXPLANATION (Continued)

●Voltage Regulator BLOCK

The voltage divided by resistors R1 & R2 is compared with the internal reference voltage by the error amplifier. The N-channel

MOSFET which is connected to the VROUT pin is then driven by the subsequent output signal. The output voltage at the VROUT pin

is controlled & stabilized by a system of negative feedback.

VBIAS pin is power supply pin for output voltage control circuit, protection circuit and CE circuit. When output current increase,

the VBIAS pin supplies output current also. VIN2 pin is connected to a driver transistor and provides output current.

In order to obtain high efficient output current through low on-resistance, please take enough Vgs (=VBIAS – VROUT (T)) of the driver

transistor. Output current triggers operation of constant current limiter and fold-back circuit, heat generation triggers operation of

thermal shutdown circuit, the driver transistor circuit is forced OFF when VBIAS or VIN2 voltage goes lower than UVLO voltage.

Further, the IC's internal circuitry can be shutdown via the EN2 pin's signal.

Figure 1: XC6601B Series

With the XCM519 series, a stable output voltage is achievable even if used with low ESR capacitors, as a phase compensation

circuit is built-in. The output capacitor (CL2) should be connected as close to VROUT pin and VSS pin to obtain stable phase

compensation. Values required for the phase compensation are as the table below.

For a stable power input, please connect an bias capacitor (CBIAS ) of 1.0μF between the VBIAS pin and the VSS pin. Also, please

connect an input capacitor (CIN2) of 1.0μF between the VIN2 pin and the VSS pin. In order to ensure the stable phase

compensation while avoiding run-out of values, please use the capacitor (CBIAS, CIN2, CL2 ) which does not depend on bias or

temperature too much. The table below shows recommended values of CBIAS, CIN, CL.

Recommended Values of CBIAS, CIN2, CL2

BIAS CAPACITOR

INPUT CAPACITOR

OUTPUT CAPACITOR

NOMINAL

VOLTAGE

CBIAS

CIN2

CL2

0.7V～1.8V

CBIAS=1.0μF

CIN2=1.0μF

CL2=4.7μF

XCM519 Datasheet(PDF) 19 Page - Torex Semiconductor