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參數資料
| 型號： | ADP3000AR-12 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 穩壓器 |
| 英文描述： | Top Entry Connector Hood; Enclosure Material:Aluminum Alloy; For Use With:C146 Rectangular Circular Connectors; Connecting Termination:Screw; Gender:Male; No. of Contacts:48; Operating Voltage:400V; Series:C-146 RoHS Compliant: Yes |
| 中文描述： | SWITCHING REGULATOR, 400 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | MS-012-AA, SOIC-8 |
| 文件頁數： | 7/12頁 |
| 文件大小： | 342K |
| 代理商： | ADP3000AR-12 |
ADP3000
–7–
REV. 0
Table II. Recommended Capacitors
Vendor
Series
Type
Phone Numbers
AVX
Sanyo
Sprague
Panasonic
TPS
OS-CON
595D
HFQ
Surface Mount
Through-Hole
Surface Mount
Through-Hole
(803) 448-9411
(619) 661-6835
(603) 224-1961
(201) 348-5200
DIODE SELECTION
The ADP3000’s high switching speed demands the use of
Schottky diodes. Suitable choices include the 1N5817, 1N5818,
1N5819, MBRS120LT3 and MBR0520LT1. Do not use fast
recovery diodes because their high forward drop lowers effi-
ciency. Neither general-purpose diodes nor small signal diodes
should be used.
PROGRAMMING THE SWITCHING CURRENT LIMIT
OF THE POWER SWITCH
The ADP3000’s R
LIM
pin permits the cycle by cycle switch
current limit to be programmed with a single external resistor.
This feature offers major advantages which ultimately decrease
the component cost and P.C.B. real estate. First, it allows the
ADP3000 to use low value, low saturation current and physi-
cally small inductors. Additionally, it allows the ADP3000 to
use a physically small surface mount tantalum capacitor with a
typical ESR of 0.1
to achieve an output ripple as low as 40
mV to 80 mV, as well as low input ripple.
As a rule of thumb, the current limit is usually set to approximately
3 to 5 times the full load current for boost applications and
about 1.5–3 times of the full load current in buck applications.
The internal structure of the I
LIM
circuit is shown in Figure 17.
Q1 is the ADP3000’s internal power switch, which is paralleled
by sense transistor Q2. The relative sizes of Q1 and Q2 are
scaled so that IQ2 is 0.5% of IQ1. Current flows to Q2 through
both an internal 80
resistor and the R
LIM
resistor. The voltage
on these two resistors biases 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 8a gives values for lower current-limit values.
V
IN
POWER
SWITCH
SW2
SW1
R
DRIVER
80
(INTERNAL)
I
LIM
I
Q1
200
V
IN
(EXTERNAL)
Q2
ADP3000
Q1
400kHz
OSC
Q3
R1
Figure 17. ADP3000 Current Limit Operation
The delay through the current limiting circuit is approximately
0.3
μ
s. If the switch ON time is reduced to less than 1.7
μ
s,
accuracy of the current trip-point is reduced. Attempting to
program a switch ON time of 0.3
μ
s or less will produce
spurious responses in the switch ON time. However, the
ADP3000 will still provide a properly regulated output voltage.
PROGRAMMING THE GAIN BLOCK
The gain block of the ADP3000 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
ADP3000’s 1.245 V reference, while the noninverting input is
available at the SET pin. The NPN output transistor will sink in
excess of 300
μ
A.
Figure 18 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
–1.245
V
1.245
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.
ADP3000
1.245V
GND
AO
5V
R
L
47k
TO
R1
V
BATT
V
IN
SET
R
HYS
R2
33k
1.6M
V
LB
= BATTERY TRIP POINT
R1 =
V
LB
– 1.245V
37.7μA
Figure 18. Setting the Low Battery Detector Trip Point
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相關代理商/技術參數 |
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|---|---|
| ADP3000AR-12-REEL | 制造商:Analog Devices 功能描述: |
| ADP3000AR-3.3 | 制造商:Rochester Electronics LLC 功能描述:MCROPWR STPUP/DWN H. FRQ. SWT. REG. 3.3V - Bulk |
| ADP3000AR-3.3-REEL | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel |
| ADP3000AR-33 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Micropower Step-Up/Step-Down Fixed 3.3 V, 5 V, 12 V and Adjustable High Frequency Switching Regulator |
| ADP3000AR-5 | 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 |
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