VCTA25201B-R33MS6 datasheet(20/50 Pages) RICHTEK

20 / 50 page

RTQ2134-QA

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DSQ2134-QA-02

May

2022

Application Information

The RTQ2134 is a power management IC that

integrates four high efficiency Buck converters, and is

capable of multiphase or single-phase operation. The

RTQ2134 supports 2 + 1 + 1 and 2 + 2 configuration.

Inductor Selection

The inductor selection are 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 to the IC rated current, but

it still depends on size consideration. The inductor used

in the Typical Application Circuit of this datasheet is

recommended. The switching frequency, input voltage,

output voltage, and selected inductor ripple current

determine the inductor value as follows :

OUT

)

L =

−





To enhance the efficiency, choose a low-loss inductor

having the lowest possible DCR that fits in the allotted

dimensions. The selected inductor should have a

saturation current rating greater than the peak current

limit of the device. The core must be large enough not

to saturate at the peak inductor current (IL_PEAK) :

OUT

L_PEAK

OUT_MAX

)

I =

= I

−







The current flowing through the inductor is the inductor

ripple current plus the output current. During power-up,

faults, or transient load conditions, the inductor current

can increase the peak inductor current level calculated

above. In transient conditions, the inductor current can

increase up to the switch current limit of the device. For

this reason, the most conservative approach is to

specify an inductor with a saturation current rating

equal to or greater than the switch current limit rather

than the peak inductor current.

Input Capacitor Selection

Input capacitance, CIN, is needed to filter the pulsating

current at the drain of the HSFET. The CIN should be

sized to do this without causing a large variation in

input

voltage.

Several

capacitors

may

also

paralleled

meet

size,

height

and

thermal

requirements in the design. For low input voltage

applications,

sufficient

bulk

input

capacitance

needed to minimize transient effects during output load

changes.

The input capacitor should be placed as close as

possible to each VIN pin with a low inductance

connection to the PGND of the IC. It is recommended

to connect capacitors between the VIN pin and the

PGND pin as shown in the Typical Application Circuit.

The larger input capacitance is required when a lower

switching frequency is used. The X7R capacitors are

recommended

for

best

performance

across

temperature and input voltage variations.

Output Capacitor Selection

The selection of COUT is determined by considering to

satisfy the voltage ripple and the transient loads. The

peak-to-peak output ripple,

VOUT, is determined by :

OUT

= I

ESR +

8 C



 





where the

IL is the peak-to-peak inductor ripple

current. The highest output ripple is at maximum input

voltage since

IL increases with input voltage. Multiple

capacitors placed in parallel may be needed to meet

the ESR and RMS current handling requirements.

Ceramic capacitors have very low equivalent series

resistance

(ESR)

and

provide

the

best

ripple

performance.

The

X7R

dielectric

capacitor

recommended

for

the

best

performance

across

temperature and input voltage variations. The variation

of the capacitance value with temperature, DC bias

voltage and switching frequency needs to be taken into

consideration. For example, the capacitance value of a

capacitor decreases as the DC bias across the

capacitor increases. Be careful to consider the voltage

coefficient of ceramic capacitors when choosing the

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