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參數(shù)資料
| 型號(hào)： | ADP1111AR |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Micropower, Step-Up/Step-Down SW Regulator; Adjustable and Fixed 3.3 V, 5 V, 12 V |
| 中文描述： | 1.5 A SWITCHING REGULATOR, 88 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁(yè)數(shù)： | 12/16頁(yè) |
| 文件大?。?/td> | 406K |
| 代理商： | ADP1111AR |
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ADP1111
–12–
REV. 0
This occurs in the step-up mode when the following condition is
met:
V
OUT
+
V
DIODE
V
IN
V
SW
<
1
1
DC
where DC is the ADP1111’s duty cycle. When this relationship
exists, the inductor current does not go all the way to zero
during the time that the switch is OFF. When the switch turns
on for the next cycle, the inductor current begins to ramp up
from the residual level. If the switch ON time remains constant,
the inductor current will increase to a high level (see Figure 24).
This increases output ripple and can require a larger inductor
and capacitor. By controlling switch current with the I
LIM
resistor, output ripple current can be maintained at the design
values. Figure 25 illustrates the action of the I
LIM
circuit.
Figure 24.
Figure 25.
The internal structure of the I
LIM
circuit is shown in Figure 26.
Q1 is the ADP1111’s internal power switch that is paralleled by
sense transistor Q2. The relative sizes of Q1 and Q2 are scaled
so that I
Q2
is 0.5% of I
Q1
. Current flows to Q2 through an
internal 80
resistor and through the R
LIM
resistor. These two
resistors parallel the base-emitter junction of the oscillator-
disable transistor, Q3. When the voltage across R1 and R
LIM
exceeds 0.6 V, Q3 turns on and terminates the output pulse. If
only the 80
internal resistor is used (i.e. the I
LIM
pin is
connected directly to V
IN
), the maximum switch current will be
1.5 A. Figure 6 gives R
LIM
values for lower current-limit values.
72kHz
OSC
V
IN
POWER
SWITCH
SW2
SW1
R
LIM
DRIVER
80
(INTERNAL)
I
LIM
I
Q1
200
V
IN
(EXTERNAL)
Q2
ADP1111
Q1
Q3
R1
Figure 26. ADP1111 Current Limit Operation
The delay through the current limiting circuit is approximately
1
μ
s. If the switch ON time is reduced to less than 3
μ
s, accuracy
of the current trip-point is reduced. Attempting to program a
switch ON time of 1
μ
s or less will produce spurious responses
in the switch ON time; however, the ADP1111 will still provide
a properly regulated output voltage.
PROGRAMMING THE GAIN BLOCK
The gain block of the ADP1111 can be used as a low-battery
detector, error amplifier or linear post regulator. The gain block
consists of an op amp with PNP inputs and an open-collector
NPN output. The inverting input is internally connected to the
ADP1111’s 1.25 V reference, while the noninverting input is
available at the SET pin. The NPN output transistor will sink
about 300
μ
A.
Figure 27a shows the gain block configured as a low-battery
monitor. Resistors R1 and R2 should be set to high values to
reduce quiescent current, but not so high that bias current in
the SET input causes large errors. A value of 33 k
for R2 is a
good compromise. The value for R1 is then calculated from the
formula:
R
1
=
V
LOBATT
1.25
V
1.25
V
R
2
where
V
LOBATT
is the desired low battery trip point. Since the
gain block output is an open-collector NPN, a pull-up resistor
should be connected to the positive logic power supply.
ADP1111
1.25V
REF
SET
GND
AO
5V
R
L
47k
TO
PROCESSOR
R1
R2
V
BAT
V
IN
33k
R1= V
V
LB
= BATTERY TRIP POINT
LB
–1.25V
Figure 27a. Setting the Low Battery Detector Trip Point
200mA/div
200mA/div
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ADP1111AN-3.3 | Micropower Step-Up/Step-Down SW Regulator. Adjustable and Fixed 3.3 V 5 V 12 V(406.88 k) |
| ADP1111AR-3.3 | Micropower Step-Up/Step-Down SW Regulator. Adjustable and Fixed 3.3 V 5 V 12 V(406.88 k) |
| ADP1111AN-12 | Micropower, Step-Up/Step-Down SW Regulator; Adjustable and Fixed 3.3 V, 5 V, 12 V |
| ADP1111AN-33 | Micropower, Step-Up/Step-Down SW Regulator; Adjustable and Fixed 3.3 V, 5 V, 12 V |
| ADP1111AN-5 | Micropower, Step-Up/Step-Down SW Regulator; Adjustable and Fixed 3.3 V, 5 V, 12 V |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADP1111AR-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 SOIC N 制造商:Rochester Electronics LLC 功能描述:MICROPOWER STEP-UP/DOWN SWITCHING REG. - Bulk |
| ADP1111AR-12-REEL | 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 SOIC N T/R |
| ADP1111AR-3.3 | 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 SOIC N 制造商:Rochester Electronics LLC 功能描述:MICROPOWER STEP-UP/DOWN SWITCHING REG. - Bulk |
| ADP1111AR-3.3-REEL | 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 SOIC N T/R 制造商:Analog Devices 功能描述:CONV DC-DC SGL-OUT NON-INV/INV/STEP UP/STEP DOWN 8SOIC N - Tape and Reel |
| ADP1111AR-33 | 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 |
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