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ADP1173AN PDF 데이터시트 : 부품 기능 및 핀배열

부품번호 ADP1173AN
기능 Micropower DC-DC Converter
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ADP1173AN 데이터시트, 핀배열, 회로
a
FEATURES
Operates From 2.0 V to 30 V Input Voltages
Only 110 A Supply Current (Typical)
Step-Up or Step-Down Mode Operation
Very Few External Components Required
Low Battery Detector On-Chip
User-Adjustable Current Limit
Internal 1 A Power Switch
Fixed or Adjustable Output Voltage Versions
8-Pin DIP or SO-8 Package
APPLICATIONS
Notebook and Palmtop Computers
Cellular Telephones
Flash Memory Vpp Generators
3 V to 5 V, 5 V to 12 V Converters
9 V to 5 V, 12 V to 5 V Converters
Portable Instruments
LCD Bias Generators
GENERAL DESCRIPTION
The ADP1173 is part of a family of step-up/step-down switching
regulators that operates from an input supply voltage of as little as
2 V to 12 V in step-up mode and to 30 V in step-down mode.
The ADP1173 consumes as little as 110 µA in standby mode,
making it ideal for applications that need low quiescent current.
An auxiliary gain amplifier can serve as a low battery detector,
linear regulator (under voltage lockout) or error amplifier.
The ADP1173 can deliver 80 mA at 5 V from a 3 V input in
step-up configuration or 100 mA at 5 V from a 12 V input in
step-down configuration. For input voltages of less than 2 V use
the ADP1073.
Micropower
DC-DC Converter
ADP1173
FUNCTIONAL BLOCK DIAGRAMS
SET
VIN
1.245V
REFERENCE
A2
GAIN BLOCK/
ERROR AMP
ADP1173
A1 OSCILLATOR
COMPARATOR
DRIVER
AO
ILIM
SW1
GND
FB
SW2
SET
VIN
1.245V
REFERENCE
ADP1173-3.3
ADP1173-5
ADP1173-12
A2
GAIN BLOCK/
ERROR AMP
A1 OSCILLATOR
AO
ILIM
SW1
R1
GND
COMPARATOR
DRIVER
R2
753k
ADP1173-3.3: R1 = 456k
ADP1173-5: R1 = 250k
ADP1173-12: R1 = 87.4k
SENSE
SW2
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 1997




ADP1173AN pdf, 반도체, 판매, 대치품
ADP1173–Typical Performance Characteristics
1.2
1.0 VIN = 3V
VIN = 2V
0.8
0.6
VIN = 5V
0.4
0.2
0
0.2
0.4 0.6 0.8 1.0
SWITCH CURRENT – A
1.2
Figure 2. Saturation Voltage vs.
Switch Current in Step-Up Mode
1.6
1.4
VCE(SAT)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.05 0.15 0.25 0.35 0.45 0.55 0.65 0.75
SWITCH CURRENT – A
Figure 3. Switch ON Voltage vs.
Switch Current in Step-Down Mode
1100
1000
900
800
700
600
500
400
300
200
100
10
2V < VIN < 5V
100
RLIM
1000
Figure 4. Maximum Switch Current
vs. RLIM in Step-Up Mode
1000
900
VIN =24V WITH L = 500µH @ VOUT = 5V
800
700
600
500
400
300
200 VIN =12V WITH L = 250µH @ VOUT = 5V
100
0
100 1000
RLIM
Figure 5. Maximum Switch Current
vs. RLIM in Step-Down Mode
100
90
80
70
60
50
40 VIN = 5V
30
20
VIN = 2V
10
0
0 100 200 300 400 500 600 700 800 900
SWITCH CURRENT – mA
Figure 6. Supply Current vs.
Switch Current
120
110
100
90
80
70
60
50
40
–40
QUIESCENT CURRENT
0 25 70
TEMPERATURE – °C
85
Figure 7. Quiescent Current vs.
Temperature
25.5
25
24.5
24
23.5
23
22.5
22
21.5
3
OSCILLATOR FREQUENCY
5 10 15 20 25
INPUT VOLTAGE – Volts
30
Figure 8. Oscillator Frequency vs.
Input Voltage
80
70
60
50
40
30
20
10
–40
VIN = 3V
0 25 70
TEMPERATURE – °C
85
Figure 9. Set Pin Bias Current vs.
Temperature
450
400
350
300
250
200
150
100
50
0
–40
VIN = 3V
0 25 70
TEMPERATURE – °C
85
Figure 10. Feedback Pin Bias Current
vs. Temperature
–4– REV. 0

4페이지










ADP1173AN 전자부품, 판매, 대치품
ADP1173
For example, assume that +5 V at 300 mA is required from a
12 V to +24 V input. Deriving the peak current from Equation 6
yields:
I PEAK
=
2
×
300 mA
0.55
12
5 + 0.5
– 1.5 + 0.5
= 545 mA
The peak current can then be inserted into Equation 7 to calcu-
late the inductor value:
L
=
12 –1.5 – 5
545 mA
×
23
µs
=
232
µH
Since 232 µH is not a standard value, the next lower standard
value of 220 µH would be specified.
To avoid exceeding the maximum switch current when the
input voltage is at +24 V, an RLIM resistor should be specified.
Using the step-down curve of Figure 5, a value of 180 will
limit the switch current to 600 mA.
Inductor Selection—Positive-to-Negative Converter
The configuration for a positive-to-negative converter using the
ADP1173 is shown in Figure 17. As with the step-up converter,
all of the output power for the inverting circuit must be supplied
by the inductor. The required inductor power is derived from
the formula:
( ) ( )PL = |VOUT|+V D × IOUT
(8)
The ADP1173 power switch does not saturate in positive-to-
negative mode. The voltage drop across the switch can be
modeled as a 0.75 V base-emitter diode in series with a 0.65
resistor. When the switch turns on, inductor current will rise at
a rate determined by:
IL
(t)
=
VL
R'
1–
_ R't
eL

(9)
where R' = 0.65 + RL(DC)
where VL = VIN – 0.75 V
For example, assume that a –5 V output at 50 mA is to be
generated from a +4.5 V to +5.5 V source. The power in the
inductor is calculated from Equation 8:
( )PL = |5V|+ 0.5V × (50 mA) = 275 mW
During each switching cycle, the inductor must supply the
following energy:
PL
f OSC
=
275 mW
24 kHz
=11.5 µJ
Using a standard inductor value of 220 µH, with 0.2 dc
resistance, will produce a peak switch current of:
I PEAK
=
4.5V – 0.75V
0.65 Ω + 0.2
1–
e
–0.85
220
× 23
µH
µs

= 375 mA
Once the peak current is known, the inductor energy can be
calculated from Equation 5:
EL
=
1
(220
2
µH
)
×
(375
mA)2
= 15.5
µJ
The inductor energy of 15.5 µJ is greater than the PL/fOSC
requirement of 11.5 µJ, so the 220 µH inductor will work in
this application.
The input voltage only varies between 4.5 V and 5.5 V in this
example. Therefore, the peak current will not change enough to
require an RLIM resistor and the ILIM pin can be connected
directly to VIN. Care should be taken to ensure that the peak
current does not exceed 650 mA.
CAPACITOR SELECTION
For optimum performance, the ADP1173’s output capacitor
must be carefully selected. Choosing an inappropriate capacitor
can result in low efficiency and/or high output ripple.
Ordinary aluminum electrolytic capacitors are inexpensive, but
often have poor Equivalent Series Resistance (ESR) and
Equivalent Series Inductance (ESL). Low ESR aluminum ca-
pacitors, specifically designed for switch mode converter appli-
cations, are also available, and these are a better choice than
general purpose devices. Even better performance can be
achieved with tantalum capacitors, although their cost is higher.
Very low values of ESR can be achieved by using OS-CON*
capacitors (Sanyo Corporation, San Diego, CA). These devices
are fairly small, available with tape-and-reel packaging, and have
very low ESR.
The effects of capacitor selection on output ripple are demon-
strated in Figures 11, 12, and 13. These figures show the output
of the same ADP1173 converter, which was evaluated with
three different output capacitors. In each case, the peak switch
current is 500 mA and the capacitor value is 100 µF. Figure 11
shows a Panasonic HF-series* radial aluminum electrolytic.
When the switch turns off, the output voltage jumps by about
90 mV and then decays as the inductor discharges into the
capacitor. The rise in voltage indicates an ESR of about
0.18 . In Figure 12, the aluminum electrolytic has been
replaced by a Sprague 593D-series* tantalum device. In this
case the output jumps about 35 mV, which indicates an ESR of
0.07 . Figure 13 shows an OS-CON SA series capacitor in the
same circuit, and ESR is only 0.02 .
*All trademarks are properties of their respective holders.
REV. 0
–7–

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