IR1150STR datasheet(9/16 Pages) IRF

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IR1150(S)/IR1150I(S)(PbF)

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Operating States

UVLO Mode

The IC remains in the UVLO condition until the voltage on

the VCC pin exceeds the VCC turn on threshold voltage,

VCC ON.

During the time the IC remains in the UVLO state, the gate

drive circuit is inactive and the IC draws a

quiescent current of ICC START. The UVLO mode is

accessible from any other state of operation whenever the

IC supply voltage condition of VCC < VCC UVLO occurs.

Standby Mode

The IC is in this state if the supply voltage has exceeded

VCC ON and the VFB pin voltage is less than 20% of VREF .

The oscillator is running and all internal circuitry is biased

in this state but the gate is inactive. This state is

accessible from any other state of operation except OVP.

The IC enters this state whenever the VFB pin voltage has

decreased to 50% of VREF when operating in normal

mode or during a peak current limit fault condition, or 20%

VREF when operating in soft start mode.

Soft Start Mode

This state is activated once the VCC voltage has

exceeded VCCON and the VFB pin voltage has exceeded

20% of VREF.

The soft start time, which is defined as the time required

for the duty cycle to linearly increase from zero to

maximum, is dependent upon the values selected for

compensation of the voltage loop pin COMP to pin COM.

Throughout the soft start cycle, the output of the voltage

error

amplifier

(pin

COMP)

charges

through

the

compensation network. This forces a linear rise of the

voltage at this node which in turn forces a linear increase

in the gate drive duty cycle from 0. This controlled duty

cycle reduces system component stress during start up

conditions as the input current amplitude is increasing

linearly.

Normal Mode

The IC enters normal operating mode once the soft start

transition has been completed. At this point the gate drive

is switching and the IC draws a maximum of ICC from the

supply voltage source. The device will initiate another soft

start sequence in the event of a shutdown due to a fault,

which activates the protection circuitry, or if the supply

voltage drops below the UVLO turn off threshold of VCC

UVLO.

Fault Protection Mode

The fault mode will be activated when any of the protection

circuits are activated. The IC protection circuits include

Supply Voltage Under Voltage Lockout (UVLO), Output

Over Voltage Protection (OVP), Open Loop Protection

(OLP), Output Undervoltage Protection (OUV), and Peak

Current Limit Protection (IPK LIMIT).

Sleep Mode

The sleep mode is initiated by pulling the OVP pin below

0.62V (typ). In this mode the IC draws a very low

quiescent supply current.

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