THV6520 Datasheet, PDF(7/11 Page) THine Electronics, Inc. – THV6520 is a controller IC power supply system with

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

THV6520 Datasheet, PDF (7/11 Pages) THine Electronics, Inc. – THV6520 is a controller IC power supply system with

◁

THV6520_Rev.1.00_E

determined by the output capacitor total capacitance,

COUT, and the output

VLSrip ï½ D ï´ IOUT ï« I peak ï´ ESR

FOSC ï´ COUT

I peak ï½ I IN ï« ïI rip

The first ripple component can be reduced by increasing

COUT. Changing COUT may require adjustment of

compensation R and C in order to provide adequate

phase margin and loop bandwidth.

The second ripple component can be reduced by

selecting low-ESR ceramic capacitors and using several

smaller capacitors in parallel instead of just one large

capacitor.

[Inductor selection]

To prevent magnetic saturation of the inductor core the

inductor has to be rated for a maximum current larger

than IPK in a given application. Since the chip provides

current limit protection of 2A, it is generally

recommended that the inductor be rated at least for 2A.

Selection of the inductor requires trade-off between the

physical size (footprint x height) and its electrical

properties (current rating, inductance, resistance). Within

a given footprint and height, an inductor with larger

inductance typically comes with lower current rating and

often larger series resistance. Larger inductance typically

requires more turns on the winding, a smaller core gap or

a core material with a larger relative permeability. An

inductor with a larger physical size has better electrical

properties than a smaller inductor.

It is desirable to reduce the ripple current ÎIrip in order to

reduce voltage noise on the input and output capacitors.

In practice, the inductor is often much larger than the

capacitors and it is easier and cheaper to increase the size

of the capacitors. The ripple current ÎIrip is then chosen

the largest possible while at the same time not degrading

the maximum input and output current that the converter

can operate with before reaching the current limit of the

chip or the rated current of the inductor.

ïI rip

I peak ï½ I IN ï«

ï£ I MAX

For example, ÎIrip could be set to 20% of IMAX

Voltage detector circuit

Voltage detector circuit senses the voltage on VDIN pin

and turns on a pull-down FET that drives DOUT low if

VDIN voltage falls below the applicable threshold level

VDIN. When VDIN is rising, initially DOUT is pulled

low. As soon as VDIN exceeds (VDIN +ïVDIN), the reset

timer is started. Once VDIN has remained above (VDIN

+ïVDIN) for at least TD, the pull down FET opens and

DOUT is driven high by an external pull-up resistor.

During shut down, when VDIN falls below VDIN the

pull down FET turns on and drives DOUT pin low. To

the external voltage Vext, the rising and falling detection

thresholds VDET,High and VDET,Low, respectively are set by

the external voltage divider R3, R4.

VDet,High ï½ R4 ï« R3 (VDin ï« ïVDin )

VDet , Low

ï½

R4 ï« R3

VDin

VIN

DIN

Fig. 2 Detector setup

THine Electronics, Inc.

7/12

▷