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參數(shù)資料
| 型號(hào)： | ADP1110AR-5 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類(lèi)： | 穩(wěn)壓器 |
| 英文描述： | Circular Connector Cable Assembly; Connector Type A:Circular Receptacle; Connector Type B:Stripped End Leads; Cable Length:10ft RoHS Compliant: Yes |
| 中文描述： | 1.5 A SWITCHING REGULATOR, 90 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁(yè)數(shù)： | 14/16頁(yè) |
| 文件大小： | 418K |
| 代理商： | ADP1110AR-5 |
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ADP1110
–7–
REV. 0
CALCULATING THE INDUCTOR VALUE
Selecting the proper inductor value is a simple three-step
process:
1. Define the operating parameters: minimum input voltage,
maximum input voltage, output voltage and output current.
2. Select the appropriate conversion topology (step-up, step-
down, or inverting).
3. Calculate the inductor value, using the equations in the
following sections.
INDUCTOR SELECTION–STEP-UP CONVERTER
In a step-up or boost converter (Figure 19), the inductor must
store enough power to make up the difference between the input
voltage and the output voltage. The power that must be stored
is calculated from the equation:
P L = VOUT +VD V IN MIN
()
() I
OUT
()
(Equation 1)
where VD is the diode forward voltage (
≈ 0.5 V for a 1N5818
Schottky). Because energy is only stored in the inductor while
the ADP1110 switch is ON, the energy stored in the inductor
on each switching cycle must be must be equal to or greater
than:
P
f
L
OSC
(Equation 2)
in order for the ADP1110 to regulate the output voltage.
When the internal power switch turns ON, current flow in the
inductor increases at the rate of:
IL (t) =
V IN
R'
1
e
–R't
L
(Equation 3)
where L is in Henrys and R' is the sum of the switch equivalent
resistance (typically 0.8
at +25°C) and the dc resistance of
the inductor. If the voltage drop across the switch is small
compared to VIN, a simpler equation can be used:
IL (t) =
V IN
L
t
(Equation 4)
Replacing ‘t’ in the above equation with the ON time of the
ADP1110 (10
s, typical) will define the peak current for a
given inductor value and input voltage. At this point, the
inductor energy can be calculated as follows:
EL =
1
2
L
I 2PEAK
(Equation 5)
As previously mentioned, EL must be greater than PL/fOSC so
that the ADP1110 can deliver the necessary power to the load.
For best efficiency, peak current should be limited to 1 A or
less. Higher switch currents will reduce efficiency because of
increased saturation voltage in the switch. High peak current also
increases output ripple. As a general rule, keep peak current as low
as possible to minimize losses in the switch, inductor and diode.
In practice, the inductor value is easily selected using the equations
above. For example, consider a supply that will generate 12 V at
120 mA from a 4.5 V to 8 V source. The inductor power required
is from Equation 1:
PL = 12 V + 0.5 V 4.5 V
()120 mA = 960 mW
On each switching cycle, the inductor must supply:
PL
f OSC
=
960 mW
70 kHz
=13.7J
Assuming a peak current of 1 A as a starting point, (Equation 4)
can be rearranged to recommend an inductor value:
L
=
V IN
IL(MAX )
t
=
4.5V
1 A
10
s = 45 H
Substituting a standard inductor value of 47
H with 0.2 dc
resistance will produce a peak switch current of:
IPEAK =
4.5V
1.0
1
e
–1.0
10 s
47
H
= 862 mA
Once the peak current is known, the inductor energy can be
calculated from Equation 5:
EL =
1
2
47
H
() 862mA
()2 =17.5J
Since the inductor energy of 17.5
J is greater than the P
L/fOSC
requirement of 13.7
J, the 47 H inductor will work in this
application. By substituting other inductor values into the same
equations, the optimum inductor value can be determined.
When selecting an inductor, the peak current must not exceed
the maximum switch current of 1.5 A.
The peak current must be evaluated for both minimum and
maximum values of input voltage. If the switch current is high
when VIN is at its minimum, the 1.5 A limit may be exceeded at the
maximum value of VIN. In this case, the ADP1110’s current limit
feature can be used to limit switch current. Simply select a resistor
(using Figure 7) that will limit the maximum switch current to the
IPEAK value calculated for the minimum value of VIN. This will
improve efficiency by producing a constant IPEAK as VIN increases.
See the “Limiting the Switch Current” section of this data sheet for
more information.
Note that the switch current limit feature does not protect the
circuit if the output is shorted to ground. In this case, current is
only limited by the dc resistance of the inductor and the forward
voltage of the diode.
INDUCTOR SELECTION–STEP-DOWN CONVERTER
The step-down mode of operation is shown in Figure 20.
Unlike the step-up mode, the ADP1110’s power switch does not
saturate when operating in the step-down mode; therefore,
switch current should be limited to 800 mA in this mode. If the
input voltage will vary over a wide range, the ILIM pin can be
used to limit the maximum switch current. Higher switch
current is possible by adding an external switching transistor as
shown in Figure 22.
The first step in selecting the step-down inductor is to calculate
the peak switch current as follows:
IPEAK =
2 IOUT
DC
V OUT +VD
V IN –V SW +VD
(Equation 6)
where: DC = duty cycle (0.69 for the ADP1110)
VSW = voltage drop across the switch
VD = diode drop (0.5 V for a 1N5818)
IOUT = output current
VOUT = the output voltage
VIN = the minimum input voltage
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADP1110AR-REEL7 | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel |
| ADP1111 | 功能描述:板上安裝壓力/力傳感器 14.7kPa 0.15kgf/cm Pressure Sensor RoHS:否 制造商:Honeywell 工作壓力:0 bar to 4 bar 壓力類(lèi)型:Gage 準(zhǔn)確性:+ / - 0.25 % 輸出類(lèi)型:Digital 安裝風(fēng)格:Through Hole 工作電源電壓:5 V 封裝 / 箱體:SIP 端口類(lèi)型:Dual Radial Barbed, Same sides |
| ADP1111_09 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Micropower, Step-Up/Step-Down SW Regulator; Adjustable and Fixed 3.3 V, 5 V, 12 V |
| ADP1111AN | 制造商:Analog Devices 功能描述:Conv DC-DC Single Non-Inv/Inv/Step Up/Step Down 2V to 30V 8-Pin PDIP 制造商:Rochester Electronics LLC 功能描述:MICROPOWER STEP-UP/DOWN SWITCHING REG. - Bulk 制造商:Analog Devices 功能描述:IC SWITCHING REGULATOR |
| ADP1111AN-12 | 制造商:Analog Devices 功能描述:Conv DC-DC Single Non-Inv/Inv/Step Up/Step Down 2V to 30V 8-Pin PDIP N 制造商:Rochester Electronics LLC 功能描述:MICROPOWER STEP-UP/DOWN SWITCHING REG. - Bulk |
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