參數(shù)資料
型號(hào)： AP1623S
英文描述： PWM Control Step-Down Switching Regulator-Converter
中文描述： PWM控制降壓型開(kāi)關(guān)穩(wěn)壓器，轉(zhuǎn)換器
文件頁(yè)數(shù)： 5/6頁(yè)
文件大小： 182K
代理商： AP1623S
AP1623
PWM Control Step-Down Switching Regulator-Controllers
Function Description
PWM Control (AP1623 Series)
The AP1623 consists of DC/DC converters that
employ a pulse-width modulation (PWM) system.
In converters of the AP1623, the pulse width varies
in a range from 0 to 100, according to the load
current, and yet ripple voltage produced by the
switching can easily be removed through a filter
because the switching frequency remains constant.
Therefore, these converters provide a low-ripple
power over broad ranges of input voltage and load
current.
External adjustment of output voltage
The AP1623 allows the user to select 3 types of the
output voltage, when external resistances R
A
, R
B
,
and capacitor C
C
are added, as illustrated in Typical
Application Circuit. Moreover, a temperature
gradient
can
be
obtained
by
inserting
thermal-resistor or other element in series with R
A
and R
B
.
Therefore, the output voltage (OUT) is determined
by the output voltage value VOUT of the AP1623,
and the ratio of the parallel resistance value of
external resistance R
B
and internal resistance R
1
+
R
2
of the IC, to external resistance R
A
. The output
voltage is expressed by the following equation:
OUT = V
OUT
+ V
OUT
× R
A
÷ (R
B
// (R
1
+ R
2
))
(Note:// denotes a combined resistance in parallel.)
The voltage accuracy of the output OUT set by
resistances R
A
and R
B
is not only affected by the
IC’s output voltage accuracy (V
OUT
± 2.4%), but also
by the absolute precision of external resistances R
A
and R
B
in use and the absolute value deviations of
internal resistances R
1
and R
2
in the IC.
Let us designate the maximum deviations of the
absolute value of external resistances R
A
and R
B
by
R
A
max and R
B
max, respectively, the minimum
deviations by R
A
min and R
B
min, respectively, and
the maximum and minimum deviations of the
absolute value of internal resistances R
1
and R
2
in
the IC by (R
1
+ R
2
)max and (R
1
+ R
2
)min,
respectively. Then, the minimum deviation value
OUTmin and the maximum deviation value
OUTmax of the output voltage OUT are expressed
by the following equations:
OUTmin = V
OUT
× 0.976 + V
OUT
× 0.976 × R
A
min ÷
(R
B
max// (R
1
+ R
2
)max)
OUTmax = V
OUT
× 1.024 + V
OUT
× 1.024 × R
A
max ÷
(R
B
min// (R
1
+ R
2
)min)
The voltage accuracy of the output OUT cannot be
made higher than the output voltage accuracy (V
OUT
± 2.4%) of the IC itself, without adjusting the
external resistances R
A
and R
B
involved. The closer
Anachip Corp.
www.anachip.com.tw Rev. 0.1 Feb 10, 2004
5/6
a
the voltage value of the output OUT and the output
voltage value (V
OUT
) of the IC are brought to one
other, the more the output voltage remains immune
to deviations in the absolute accuracy of externally
connected resistances R
A
and R
B
and the absolute
value of internal resistances R
1
and R
2
in the IC.
In particular, to suppress the influence of deviations
in internal resistances R
1
and R
2
in the IC, a major
contributor to deviations in the output OUT, the
external resistances R
A
and R
B
must be limited to a
much smaller value than that of internal resistances
R
1
and R
2
in the IC.
On the other hand, a reactive current flows through
external resistances R
A
and R
B
. This reactive
current must be reduced to a negligible value with
respect to the load current in the actual use of the
IC so that the efficiency characteristics will not be
degraded. This requires that the value of external
resistance R
A
and R
B
be made sufficiently large.
However, too large a value (more than 1 M
) for
the external resistances R
A
and R
B
would make the
IC vulnerable to external noise. Check the influence
of this value on actual equipment.
There is a tradeoff between the voltage accuracy of
the output OUT and the reactive current. This
should be taken into consideration based on the
requirements of the intended application.
Deviations in the absolute value of internal
resistances R1 and R2 in the IC vary with the
output voltage of the AP1623, and are broadly
classified as follows:
. Output voltage 2.5V
→
4.44M
to 27.0M
. Output voltage 3.3V
→
3.60M
to 23.3M
. Output voltage 5.0V
→
2.45M
to 2.45M
When a value of R
1
+R
2
given by the equation
indicated below is taken in calculating the voltage
value of the output OUT, a median voltage deviation
will be obtained for the output OUT.
R
1
+ R
2
= 2 ÷ ( 1 ÷ maximum deviation in absolute
value of internal resistances R
1
and R
2
in IC + 1 ÷
minimum deviation in absolute value of internal
resistances R
1
and R
2
of IC)
Moreover, add a capacitor C
C
in parallel to the
external resistance R
A
in order to avoid output
oscillations and other types of instability.
Make sure that C
C
is larger than the value given by
the following equation:
C
C
(F)
×
×
2
(
÷
1
π
≥
R
A
(
If a large C
C
-value is selected, a longer soft-start
time than the one set up in the IC will be set.
)
5
×
)
kHz
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AP1623SA 制造商:ANACHIP 制造商全稱(chēng):Anachip Corp 功能描述:PWM Control Step-Down Switching Regulator-Converter
AP1623SL 制造商:ANACHIP 制造商全稱(chēng):Anachip Corp 功能描述:PWM Control Step-Down Switching Regulator-Converter
AP1623SLA 制造商:ANACHIP 制造商全稱(chēng):Anachip Corp 功能描述:PWM Control Step-Down Switching Regulator-Converter
AP1624 制造商:DIODES 制造商全稱(chēng):Diodes Incorporated 功能描述:PWM/PFM DUAL MODE STEP-UP DC/DC CONTROLLER
AP1624WA 制造商:ANACHIP 制造商全稱(chēng):Anachip Corp 功能描述:PWM/PFM Dual Mode Step-up DC/DC Controller
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