RT5508 datasheet(55/57 Pages) RICHTEK

55 / 57 page

RT5508

is a registered trademark of Richtek Technology Corporation

DS5508-01

March

2017

www.richtek.com

The output ripple can be determined as following

equation :

OUT

C_esr

OUT

Boost

D I

D T

ΔV

+ (

)

η C

1-D

2 L



 





For the application of the RT5508 to boost VBAT to

5.3V, a 10

F for input capacitor, an 22F for boost

capacitor and a 100nF for DVDD decoupling capacitor

are recommended.

RL ()

Value (

F)

Manufacturer

Part Number

Description

Size/Height (mm)

10 (2pcs)

Murata

GRM188R61E106M

X5R/15%/25V

0603/0.8

Murata

GRM219R61C226ME15

X5R/15%/16V

0805/0.85

10 (2pcs)

Murata

GRM188R61E106M

X5R/15%/25V

0603/0.8

Murata

GRM219R61C226ME15

X5R/15%/16V

0805/0.85

Filter Free Operation and Ferrite Bead Filters

A ferrite bead filter can often be used if the design is

failing radiated emissions without an LC filter and the

frequency sensitive circuit is greater than 1MHz. This

filter functions well for circuits that just have to pass

FCC and CE because FCC and CE only test radiated

emissions greater than 30MHz. When choosing a

ferrite bead, choose one with high impedance at high

frequencies, and low impedance at low frequencies.

Typically, impedance rises over 150

 before 30MHz to

provide at least

20dB decade is minimum requirement

(such as TDK : MPZ1608S221A). In addition, select a

ferrite bead with adequate current rating to prevent

distortion of the output signal.

Figure 24

Ferrite Chip Bead

OUTP

OUTN

1nF

Ferrite Chip Bead

1nF

Figure 25

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) / JA

where TJ(MAX) is the maximum junction temperature,

TA is the ambient temperature, and JA is the

junction-to-ambient thermal resistance.

For continuous operation, the maximum operating

junction temperature indicated under Recommended

Operating

Conditions

125

C. The junction-to-

ambient thermal resistance,

JA, is highly package

dependent.

For

WL-CSP-29B

2.87x2.07

(BSC)

package, the thermal resistance,

JA, is 33.3C/W on a

standard

JEDEC

51-7

high

effective-thermal-

conductivity four-layer test board. The maximum power

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

RT5508 Datasheet(PDF) 55 Page - Richtek Technology Corporation

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