RT6310CSLASHCH datasheet(43/54 Pages) RICHTEK

43 / 54 page

RT6310

is a registered trademark of Richtek Technology Corporation.

DS6310-04

August 2023

www.richtek.com

phase boost by adding CFF in the RT6310, the system's

original bandwidth has to be located at maximum phase

boost frequency.

ph_max

(4)



For putting zero at the correct frequency to implement

maximum phase boost, the first thing is to determine

system's

bandwidth.

simple

way to

measure

bandwidth of the RT6310 is load transient analysis. By

using a converter without feedforward network to

observe the voltage deviation frequency during load

step, the bandwidth of converter is obtained since the

crossover frequency is related to voltage deviation

frequency approximately, as shown in Figure 19.

VOUT

IOUT

Figure 19. A Simple Way to Get the Bandwidth

Following the above concept, the equation of bandwidth

with feedforward CFF is derived, as expressed in

equation (5).

BW =

(5)

R1 C













For optimizing transient response, the CFF is obtained

from equation (5), as shown in equation (6).

(6)











After defining the CFF, please also check the load

regulation, because feedforward capacitor might inject

an offset voltage into VOUT to cause VOUT inaccuracy.

If the output voltage is over-spec caused by calculated

CFF, please decrease the value of feedforward

capacitor CFF.

Thermal Considerations

The junction temperature should never exceed the

absolute maximum junction temperature TJ(MAX), listed

under Absolute Maximum Ratings, to avoid permanent

damage to the device. The maximum allowable power

dissipation depends on the thermal resistance of the IC

package, the PCB layout, the rate of surrounding airflow,

and the difference between the junction and ambient

temperatures. The maximum power dissipation can be

calculated using the following formula:

PD(MAX) = (TJ(MAX) − TA) / θJA

where TJ(MAX) is the maximum junction temperature, TA

is the ambient temperature, and

θJA is the junction-to-

ambient thermal resistance.

For continuous operation, the maximum operating

junction temperature indicated under Recommended

Operating Conditions is 125°C. The junction-to-ambient

thermal

resistance,

θJA(EVB), is highly package

dependent. For a UQFN-23L 3x3 (FC) package, the

thermal resistance,

θJA(EVB), 30.1°C/W is measured in

the natural convection at TA = 25°C on a four-layer

Richtek

evaluation

board.

The

maximum

power

dissipation at TA = 25°C can be calculated as below:

PD(MAX) = (125°C − 25°C) / (30.1°C/W) = 3.32W for a

UQFN-23L 3x3 (FC) package

The maximum power dissipation depends on the

operating ambient temperature for the fixed TJ(MAX) and

the thermal resistance,

θJA(EVB). The de-rating curves

in Figure 20 allows the designer to see the effect of

rising ambient temperature on the maximum power

dissipation.

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