LD5532 datasheet(12/18 Pages) LEADTREND

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LD5532

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD5532-DS-00 July 2014

VCC

GND

LD5532

R-C filter is required upon negative spike

exceed -0.3V or the total spike width is over

250nS LEB period.

OUT

Line

Fig. 21

Internal Slope Compensation

In the conventional applications, the problem of the stability

is a critical issue for current mode controlling, when it

operates over 50% duty-cycle. As UC384X, It takes slope

compensation from injecting the ramp signal of the RT/CT

pin through a coupling capacitor. It therefore requires no

extra design for the LD5532 since it has integrated it

already.

On/Off Control

The LD5532 can be turned off by pulling COMP pin below

1.5V.

The gate output pin of the LD5532 will be disabled

immediately under such condition. The off-mode can be

released when the pull-low signal is removed.

Over Load Protection (OLP) - Auto Recovery

To protect the circuit from damage due to over-load

condition, short or open-loop condition, the LD5532 is

implemented with smart OLP function. It also features auto

recovery function; see Fig. 22 for the waveform. In case of

fault condition, the feedback system will force the voltage

loop toward the saturation and then pull the voltage high on

COMP pin (VCOMP).

When the VCOMP ramps up to the

OLP threshold of 4.5V and continues over OLP delay time,

the protection will be activated and then turn off the gate

output to stop the switching of power circuit.

With the protection mechanism, the average input power will

be minimized to remain the component temperature and

stress within the safe operating area.

VCC

UVLO(on)

UVLO(off)

COMP

OLP

4.5V

OUT

OLP delay time

Switching

Non-Switching

OLP trip Level

UVLO(off)

OLP Reset

Fig. 22

OVP (Over Voltage Protection) on Vcc - Auto

Recovery

The maximum VGS ratings of the power MOSFETs are

mostly for 30V. To prevent the VGS from fault condition,

LD5532 is implemented with OVP function on Vcc.

If Vcc

voltage is higher than the OVP threshold, the output gate

drive circuit will be shut off simultaneously and the switching

of the power MOSFET is disabled until the next UVLO(on).

The Vcc OVP functions of LD5532 are auto-recoverable.

Open-loop of feedback will usually activate the OVP. Before

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