UC3500L-XX-AF5-R datasheet(7/11 Pages) UTC

7 / 11 page

UC3500

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

7 of 11

www.unisonic.com.tw

QW-R502-072.E

PRINCIPLE OF OPERATION

The UTC UC3500 consists of a Band-Gap reference voltage source, error amplifier, VFM control logic core,

oscillator, VLX limiter amplifier, N-channel MOSFET switching transistor and output voltage divider network.

The device compares the Band-Gap reference voltage with the feedback voltage from the output through divider

network. In TON phase, the energy is transferred from the battery to the inductor. The switch is turned off after a

maximum on time set to 2.5µs. In TOFF phase, the energy stored in the inductor is transferred to the load. This

process is continuously performed to ensure stable output voltage. Until the output voltage reaches the expected

value.

Therefore, in case of light load, the device works in PFM mode. In heavy load condition, the device works in

continuous mode, the frequency range up to a maximum 150 KHz set by the built in oscillator. In over current

conditions, the Ton time is shorted; the switching frequency will be higher than 150 KHz.

TYPICAL APPLICATION CIRCUIT

RECONMMENDED COMPONENTS

CIN

COUT

：

47μH (Sunida CD54 Fosc＝500kHz)

：

MA737, or MBRM110L

：

10V 4.7μF (Tantalum)

：

16V 47μF (Tantalum)

UC3500L-XX-AF5-R Datasheet(PDF) 7 Page - Unisonic Technologies