BIT3267S datasheet(4/9 Pages) BITEK

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BIT3267S

Pin description:

Functional Description:

Current mode control and slope compensation

For the Boost converter operation, peak current mode controls

power switch according inductor current. It detects the rising

inductorcurrent and turns off power switch when the inductor

current reaches the control level. In addition, BIT3267S built-in

slope compensation is used to avoid sub-harmonic oscillation

when the duty cycle is larger than 50% for the peak current

operation. Some advantages of current mode control is fast

response on line and load regulation, it is also easily been

compensated for stability requirement.

UVLO

hysteresis

Control point

Frequency selection

In the initial state, BIT3267S frequency can be selectable by

an external resistor connected in OCP pin. Please refer R1 as

following figure and selection table for frequency selection.

Frequency

≤ 1KQ

110KHz

22K

220KHz

Pin No.

Symbol

Descriptions

OUT

Output pin

GND

Ground pin

OCP

Over Current Protection and Frequency Selection

OVP

Over Voltage Protection

INN

The inverting input of the error amplifier

CMP

Output of the error amplifier

EN_DIM

Enable and PWM Dimming input

VDD

Power supply

Under Voltage Locked Out, UVLO:

To avoid the abnormal condition happened when the input

voltage drops to low voltage, it is needed to set a low voltage

operation point. Please refer following figure, when the input

voltage is below the low voltage operation point, the under

voltage lockout (UVLO) function will turn-off its output and

most of its internal functions. The recovery hysteresis voltage

is about 1V.

Leading edge blanking and current limit

For the turn on of power switch, please refer following figure,

the current spike will be happened in the rising edge. The

leading edge blanking (LEB) time was built-in the pin of OCP

to prevent the false-trigger from the current spike. In addition,

BIT3267S limits the maximum current flowing through the

external MOSFET.

EN_DIM

CMP

INN

VDD

OUT

OCP

Switch control signal

GND

Rosc1

ROSC1

Switch current

OVP

BIT3267S

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