PM6670ASTR STMicroelectronics, PM6670ASTR Datasheet - Page 41

• Manufacturer Part Number: PM6670ASTR
• Description: IC CTLR DDR2/3 MEM PS 24VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6670ASTR

• Applications: Memory, DDR2/DDR3 Regulator
• Current - Supply: 800µA
• Voltage - Supply: 4.5 V ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-VFQFN, 24-VFQFPN
• For Use With: 497-8412 - BOARD EVAL PM6670AS DDR2/3497-8411 - BOARD EVAL PM6670S DDR2/3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6305-2; PM6670ATR

PM6670AS
8.1.2
The saturation current of the inductor should be greater than I
saturation core inductors. Using soft-ferrite cores it is possible (but not advisable) to push
the inductor working near its saturation current.
In
Table 13.
In pulse-skip mode, low inductance values produce a better efficiency versus load curve,
while higher values result in higher full-load efficiency because of the smaller current ripple.
Input capacitor selection
In a buck topology converter the current that flows through the input capacitor is pulsed and
with zero average value. The RMS input current can be calculated as follows:
Equation 33
Neglecting the second term, the equation 10 is reduced to:
Equation 34
The losses due to the input capacitor are thus maximized when the duty-cycle is 0.5:
Equation 35
The input capacitor should be selected with a RMS rated current higher than I
Tantalum capacitors are good in terms of low ESR and small size, but they occasionally can
burn out if subjected to very high current during operation. Multi-layers-ceramic-capacitors
(MLCC) have usually a higher RMS current rating with smaller size and they remain the best
choice. The drawback is their quite high cost.
COILTRONICS
Manufacturer
Table 13
COILCRAFT
COILCRAFT
COILCRAFT
WURTH
some inductors are listed.
Evaluated inductors (@fsw = 400 kHz)
P
loss
MVR1261C-112
MLC1538-102
MLC1240-901
7443552100
=
HC8-1R2
Series
ESR
I
Cin
RMS
Cin
Doc ID 14436 Rev 2
⋅
I
=
CinRMS
I
Cin
I
RMS
LOAD
Inductance (µH)
(max)
=
2
⋅
I
0.9
1.1
1.2
LOAD
D
1
1
2
⋅
1 (
=
−
ESR
D
D
⋅
)
1 (
+
Cin
−
12
1
) D
⋅
0 (
D
+40 °C rms
current (A)
5 .
⋅
(
Δ
13.4
12.4
16.0
L,PEAK
⋅
20
16
I
I
LOAD
L
)
2
Application information
(max))
not only in case of hard
2
-30% saturation
current (A)
CINRMS
21.0
24.5
25.4
20
20
(max).
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