SC183C

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16

OSC

DROOP

LOAD

OUT

f

V

I

C

⋅

∆

⋅

= 3

(4)

The output capacitor RMS current ripple may be calcu-

lated from Equation 5.

(

)













⋅

⋅

−

⋅

=

IN

OSC

OUT

MAX

IN

OUT

RMS

COUT

V

f

L

V

V

V

I

)

(

)

(

3

2

1

(5)

Table 3 lists the manufacturers of recommended output

capacitor options.

C

The SC183C source input current is a DC supply current

with a triangular ripple imposed on it. To prevent large

input voltage ripple, a low ESR ceramic capacitor is

required. A minimum value of 4.7μF should be used. It is

important to consider the DC voltage coefficient charac-

teristics when determining the actual required value. It

with 5V DC applied may exhibit a capacitance as low as

the

acceptable input ripple voltage and calculate the

minimum value required for C

OSC

OUT

IN

OUT

IN

OUT

IN

f

ESR

I

V

V

V

V

V

C

⋅













−

∆













−

=

1

(6)

The input capacitor RMS ripple current varies with the

input and output voltage. The maximum input capacitor

RMS current is found from Equation 7.













−

=

IN

OUT

IN

OUT

RMS

CIN

V

V

V

V

I

1

)

(

(7)

The input voltage ripple and RMS current ripple are at a

maximum when the input voltage is twice the output

voltage or 50% duty cycle.

The input capacitor provides a low impedance loop for

the edges of pulsed current drawn by the PMOS switch.

Low ESR/ESL X5R ceramic capacitors are recommended

for this function. To minimise stray inductance, the capaci-

Applications Information (continued)

tor should be placed as closely as possible to the PVIN and

PGND pins of the SC183C.

Manufacturer

Part Nunber

Value

(μF)

Type

Rated

Voltage

(VDC)

Value

at

3.3V

(μF)

Dimensions

LxWxH

(mm)

Murata

GRM21BR60J106K

10±10%

X5R

6.3

4.74

2.0x1.25x1.25

(EIA:0805)

Murata

GRM219R60J106K

10±10%

X5R

6.3

4.05

2.0x1.25x0.85

(EIA:0805)

Murata

GRM21BR60J226M

22±20%

X5R

6.3

6.57

2.0x1.25x1.25

(EIA:0805)

Murata

GRM31CR60J476M

47±20%

X5R

6.3

20.3

3.2x1.6x1.6

(EIA:1206)

Table 3 – Recommended Capacitors