參數(shù)資料
型號(hào): PM6680ATR
廠商: STMICROELECTRONICS
元件分類: 穩(wěn)壓器
英文描述: 0.4 A DUAL SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, QCC32
封裝: 5 X 5 MM, LEAD FREE, VFQFPN-32
文件頁數(shù): 24/48頁
文件大?。?/td> 1932K
代理商: PM6680ATR
Design guidelines
PM6680A
30/48
9
Design guidelines
The design of a switching section starts from two parameters:
Input voltage range: in notebook applications it varies from the minimum battery
voltage, VINmin to the AC adapter voltage, VINmax.
Maximum load current: it is the maximum required output current, ILOAD(max).
9.1
Switching frequency
It's possible to set 3 different working frequency ranges for the two sections with FSEL pin
Switching frequency mainly influences two parameters:
Inductor size: for a given saturation current and RMS current, greater frequency allows
to use lower inductor values, which means smaller size.
Efficiency: switching losses are proportional to frequency. High frequency generally
involves low efficiency.
9.2
Inductor selection
Once that switching frequency is defined, inductor selection depends on the desired
inductor ripple current and load transient performance.
Low inductance means great ripple current and could generate great output noise. On the
other hand, low inductor values involve fast load transient response.
A good compromise between the transient response time, the efficiency, the cost and the
size is to choose the inductor value in order to maintain the inductor ripple current
I
L
between 20 % and 50 % of the maximum output current ILOAD(max). The maximum IL
occurs at the maximum input voltage. With this considerations, the inductor value can be
calculated with the following relationship:
Equation 12
where fsw is the switching frequency, VIN is the input voltage, VOUT is the output voltage and
I
L is the selected inductor ripple current.
In order to prevent overtemperature working conditions, inductor must be able to provide an
RMS current greater than the maximum RMS inductor current ILRMS:
Equation 13
Where
I
L(max) is the maximum ripple current:
IN
OUT
L
sw
OUT
IN
V
I
f
V
L
×
×
=
12
(max))
I
(
(max))
I
(
I
2
L
2
LOAD
LRMS
+
=
相關(guān)PDF資料
PDF描述
PM6680A 0.4 A DUAL SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, QCC32
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PM6685TR DUAL SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, QCC32
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