RT6310ASLASHAH datasheet(39/54 Pages) RICHTEK

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RT6310

is a registered trademark of Richtek Technology Corporation.

DS6310-04

August 2023

www.richtek.com

Application Information

Richtek’s component specification does not include the following information in the Application Information section.

Thereby no warranty is given regarding its validity and accuracy. Customers should take responsibility to verify their

own designs and reserve suitable design margin to ensure the functional suitability of their components and systems.

A general RT6310 application circuit is shown in Typical

Application

Circuit

section.

External

component

selection is largely driven by the load requirement. In

this section, the key external components such as the

inductor L, the input capacitor CIN, the output capacitor

COUT, the internal regulator capacitor CVCC, and the

bootstrap capacitor CBOOT are introduced.

Output Voltage Adjust

The RT6310C/CH is internally built with feedback

resistors for setting VOUT voltage to 5.1V. The FF pin is

located between feedback R1 resistor (80k

) and

feedback R2 resistor (40k

). In application, if slightly

decreasing output voltage is needed, the additional

resistor (R3) added between VOUT pin and FF pin

decreases the output voltage. If the output voltage

needs to increase slightly, the additional resistor (R4)

added between FF pin and GND increases the output

voltage. Please refer to the following equation and

Figure 13.

OUT _Valley

REF

REFF

R1//R3

= 1 +

R2//R4

where R1 = 80k , R2 = 40k , V

= 1.7V









VOUT

RT6310C/CH

VOUT

AGND

80k

40k

Figure 13. RT6310C/CH Slightly Adjusts VOUT with FF

Inductor Selection

The inductor selection makes trade-offs among size,

cost, efficiency, and transient response requirements.

Generally, three key inductor parameters are specified

for operation with the device: inductance value (L),

inductor saturation current (ISAT), and DC resistance

(DCR).

A good compromise between size and loss is a 30%

peak-to-

peak ripple current ΔIL to the IC rated current.

The switching frequency, input voltage, output voltage,

and selected inductor ripple current determines the

inductor value as follows :

(

)

OUT

L =

−



 

Larger inductance values result in lower output ripple

voltage and higher efficiency, but a slightly degraded

transient response. Lower inductance values allow for

smaller case size, but the larger ripple current increases

the AC losses in the inductor. To enhance the efficiency,

choose a low-loss inductor having the lowest possible

DC resistance that fits in the allotted dimensions. The

inductor value determines not only the ripple current but

also the load current of boundary between DEM and

CCM.

In the applications, the RT6310 may encounter the

events of power on inrush current (capacitive load or

heavy load) and output overloading. The RT6310

provides the peak and valley current-limit protections to

prevent the device from damages. Moreover, to make

the current-limit protection effective, a saturation current

rating of the inductor must be greater than the valley

current limit of the RT6310.

Input Capacitor Selection

Input capacitance (CIN) is needed to filter the pulsating

current at the drain of the high-side MOSFET. The large

ripple voltage on VIN pin must be minimized by CIN. The

peak-to-peak voltage ripple on input capacitor is

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