Product Specification

IXD3220/IXD3221

PS034101-0515

PRELIMINARY

4

PIN CONFIGURATION

PIN ASSIGNMENT

PIN NUMBER

PIN NAME

FUNCTIONS

SOT-25

USP-6C

1

6

Chip Enable/Soft Start (Logic High

– IC operating, Logic Low – IC in Off State)

2

5

Ground

3

4

FB

Output Voltage Sense

4

3

EXT

External Transistor Drive

-

2

NC

No Connection

5

1

Power Supply

BLOCK DIAGRAMS

IXD3220/221 A and C versions

IXD3220/221 B and D versions

BASIC OPERATION

The IXD3220/221 series ICs contain a reference voltage source, ramp wave circuit, error amplifier, PWM

comparator, phase compensation circuit, protection circuits, UVLO circuit, and others. IC

’s error amplifier compares

Phase compensated signal from error amplifier

’s output applies to the inverting PWM comparator’s input, which

non-inverting input is connected to the output of the ramp wave circuit. Resulting PWM modulated signal from

comparator determines turn-on time. It applies to the buffer, which drives gate of the external MOSFET. This

process performs continuously to ensure stable output voltage by changing duty cycle of PWM pulses in respect to

error signal.

Reference Voltage Source

The reference voltage source provides the reference voltage to ensure stable output voltage of the DC/DC

converter.

Oscillator

The oscillator determines fixed switching frequency, which can be selected from 300 kHz, 500 kHz, and 1.0 MHz

Clock pulses generated in this circuit are used to produce ramp waveforms needed for PWM operation, and to

synchronize all internal circuits.

The dissipation pad for the USP-6C package

should be solder-plated in recommended

mount pattern and metal masking to enhance

mounting strength and heat release. If the pad

needs to be connected to other pins, it should

be connected to the pin No.1.