Datasheet

PM6644 Application information
Doc ID 023203 Rev 1 23/35
K is a constant (< 0.1) that defines the ratio between the controller bandwidth and the
switching frequency.
The output capacitor must store the inductor energy generating an output ripple within the
output voltage ripple requirements.
If an output tantalum capacitor is used, in CCM the voltage ripple V
RIPPLEout
is given by:
Equation 14
A low ESR capacitor is required to reduce the output voltage ripple.
If an output ceramic capacitor is used, in CCM the voltage ripple V
RIPPLEout
is given by:
Equation 15
Finally the output capacitor choice heavily impacts the load transient response.
Tabl e 12 shows a list of some capacitor part numbers.
3.1.4 Maximum RMS output current
Both high-side and low-side embedded power MOSFETs of the switching regulator can
withstand a maximum RMS current of 300 mA.
The maximum sustainable RMS output current I
LOADRMS
of the switching regulator depends
on the application specifications of:
● input voltage V
IN
●
output voltage V
OUT
●
inductor current ripple ∆I
L
(that depends on the switching frequency F
SW
and on the
inductor value L, according to Equation 7 ).
The maximum RMS currents of high-side (I
RMS,HS
) and low-side (I
RMS,LS
) MOSFETs are
given by:
Equation 16
Table 12. Output capacitor part number
Manufacturer Part number
Capacitor value
(µF)
Rated voltage (V) ESR max. (MΩ)
TAYIO YUDEN JMK212BJ226MG-T 22 6.3 70
SANYO POSCAP 6TPC33M 33 6.3 7 to 15
V
RIPPLEout
R
out
∆I
L
⋅=
V
RIPPLEout
T
sw
∆I
L
⋅
8C
OUT
⋅
-------------------------=
I
RMS HS,
DI
LRMS
DI
LOAD
()
2
∆I
L
()
2
12
----------------+⋅ 300mA==⋅=