参数资料
型号: ADP1111ANZ-5
厂商: Analog Devices Inc
文件页数: 11/15页
文件大小: 0K
描述: IC REG BUCK BST INV 5V 0.2A 8DIP
标准包装: 50
类型: 降压(降压),升压(升压),反相
输出类型: 固定
输出数: 1
输出电压: 5V
输入电压: 2 V ~ 30 V
频率 - 开关: 72kHz
电流 - 输出: 200mA
同步整流器:
工作温度: -40°C ~ 85°C
安装类型: 通孔
封装/外壳: 8-DIP(0.300",7.62mm)
包装: 管件
供应商设备封装: 8-PDIP
ADP1111
Table I. Component Selection for Typical Converters
Input
Output
Output
Circuit
Inductor
Inductor
Capacitor
Voltage
2 to 3.1
2 to 3.1
2 to 3.1
2 to 3.1
5
5
6.5 to 11
12 to 20
20 to 30
5
12
Voltage
5
5
12
12
12
12
5
5
5
–5
–5
Current (mA)
90 mA
10 mA
30 mA
10 mA
90 MA
30 mA
50 mA
300 mA
300 mA
7 mA
250 mA
Figure
4
4
4
4
4
4
5
5
5
6
6
Value
15 μ H
47 μ H
15 μ H
47 μ H
33 μ H
47 μ H
15 μ H
56 μ H
120 μ H
56 μ H
120 μ H
Part No.
CD75-150K
CTX50-1
CD75-150K
CTX50-1
CD75-330K
CTX50-1
CTX50-4
CTX100-4
CTX50-4
CTX100-4
Value
33 μ F
10 μ F
22 μ F
10 μ F
22 μ F
15 μ F
47 μ F
47 μ F
47 μ F
47 μ F
100 μ F
Notes
*
**
**
**
**
NOTES
CD = Sumida.
CTX = Coiltronics.
* *Add 47 Ω from I LIM to V IN .
**Add 220 Ω from I LIM to V IN .
POSITIVE-TO-NEGATIVE CONVERSION
The ADP1111 can convert a positive input voltage to a negative
output voltage as shown in Figure 22. This circuit is essentially
identical to the step-down application of Figure 19, except that
also reduces the circuit’s output voltage sensitivity to tempera-
ture, which otherwise would be dominated by the –2 mV V BE
contribution of Q1. The output voltage for this circuit is
determined by the formula:
the “output” side of the inductor is connected to power ground.
When the ADP1111’s internal power switch turns off, current
V OUT = 1.25 V ?
R 2
R 1
flowing in the inductor forces the output (–V OUT ) to a negative
potential. The ADP1111 will continue to turn the switch on
until its FB pin is 1.25 V above its GND pin, so the output
voltage is determined by the formula:
Unlike the positive step-up converter, the negative-to-positive
converter’s output voltage can be either higher or lower than the
input voltage.
V OUT = 1.25 V ? ? 1 +
INPUT
+
C INPUT
R LIM
?
?
R 2 ?
R 1 ? ?
+
C2
R LIM
1
I LIM
2
V IN
L1
SW1 3
D1
1N5818
R2
Q1
MJE210
+
D2
2N3906
C L
POSITIVE
OUTPUT
1 2 3
I LIM V IN SW1
ADP1111
SW2 4
L1
R2
OUTPUT
ADP1111
FB 8
AO SET GND SW2
6 7 5 4
R1
10k Ω
FB 8
AO SET GND
6 7 5
D1
1N5818
R1
+
C L
NEGATIVE
INPUT
NC
NC
NC
NC
NEGATIVE
OUTPUT
Figure 23. ADP1111 Negative-to-Positive Converter
Figure 22. Positive-to-Negative Converter
The design criteria for the step-down application also apply to
the positive-to-negative converter. The output voltage should be
limited to |6.2 V| unless a diode is inserted in series with the
SW2 pin (see Figure 20.) Also, D1 must again be a Schottky
diode to prevent excessive power dissipation in the ADP1111.
NEGATIVE-TO-POSITIVE CONVERSION
The circuit of Figure 23 converts a negative input voltage to a
positive output voltage. Operation of this circuit configuration is
similar to the step-up topology of Figure 18, except the current
through feedback resistor R2 is level-shifted below ground by a
PNP transistor. The voltage across R2 is V OUT –V BEQ1 . How-
ever, diode D2 level-shifts the base of Q1 about 0.6 V below
ground thereby cancelling the V BE of Q1. The addition of D2
0
REV. A
LIMITING THE SWITCH CURRENT
The ADP1111’s R LIM pin permits the switch current to be
limited with a single resistor. This current limiting action occurs
on a pulse by pulse basis. This feature allows the input voltage
to vary over a wide range without saturating the inductor or
exceeding the maximum switch rating. For example, a particular
design may require peak switch current of 800 mA with a 2.0 V
input. If V IN rises to 4 V, however, the switch current will
exceed 1.6 A. The ADP1111 limits switch current to 1.5 A and
thereby protects the switch, but the output ripple will increase.
Selecting the proper resistor will limit the switch current to
800 mA, even if V IN increases. The relationship between R LIM
and maximum switch current is shown in Figure 6.
The I LIM feature is also valuable for controlling inductor current
when the ADP1111 goes into continuous-conduction mode.
–11 –
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