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PDF ( 数据手册 , 数据表 ) ADP1173AN-33

零件编号 ADP1173AN-33
描述 Micropower DC-DC Converter
制造商 Analog Devices
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ADP1173AN-33 数据手册, 描述, 功能
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-33 pdf, 数据表
ADP1173
Figure 11. Aluminum Electrolytic
Figure 12. Tantalum Electrolytic
Figure 13. OS-CON Capacitor
If low output ripple is important, the user should consider the
ADP3000. This device switches at 400 kHz, and the higher
switching frequency simplifies the design of the output filter.
Consult the ADP3000 data sheet for additional details.
All potential current paths must be considered when analyzing
very low power applications, and this includes capacitor leakage
current. OS-CON capacitors have leakage in the 5 µA to 10 µA
range, which will reduce efficiency when the load is also in the
microampere range. Tantalum capacitors, with typical leakage
in the 1 µA to 5 µA range, are recommended for very low power
applications.
DIODE SELECTION
In specifying a diode, consideration must be given to speed,
forward voltage drop and reverse leakage current. When the
ADP1173 switch turns off, the diode must turn on rapidly if
high efficiency is to be maintained. Schottky rectifiers, as well as
fast signal diodes such as the 1N4148, are appropriate. The
forward voltage of the diode represents power that is not deliv-
ered to the load, so VF must also be minimized. Again, Schottky
diodes are recommended. Leakage current is especially impor-
tant in low current applications, where the leakage can be a
significant percentage of the total quiescent current.
For most circuits, the 1N5818 is a suitable companion to the
ADP1173. This diode has a VF of 0.5 V at 1 A, 4 µA to 10 µA
leakage, and fast turn-on and turn-off times. A surface mount
version, the MBRS130T3, is also available. For applications
where the ADP1173 is “off” most of the time, such as when the
load is intermittent, a silicon diode may provide higher overall
efficiency due to lower leakage. For example, the 1N4933 has a
1 A capability, but with a leakage current of less than 1 µA. The
higher forward voltage of the 1N4933 reduces efficiency when
the ADP1173 delivers power, but the lower leakage may outweigh
the reduction in efficiency.
For switch currents of 100 mA or less, a Schottky diode such as
the BAT85 provides a VF of 0.8 V at 100 mA and leakage less
than 1 µA. A similar device, the BAT54, is available in a SOT23
package. Even lower leakage, in the 1 nA to 5 nA range, can be
obtained with a 1N4148 signal diode.
General purpose rectifiers, such as the 1N4001, are not suitable
for ADP1173 circuits. These devices, which have turn-on times
of 10 µs or more, are too slow for switching power supply
applications. Using such a diode “just to get started” will result
in wasted time and effort. Even if an ADP1173 circuit appears
to function with a 1N4001, the resulting performance will not
be indicative of the circuit performance when the correct diode
is used.
CIRCUIT OPERATION, STEP-UP (BOOST) MODE
In boost mode, the ADP1173 produces an output voltage that
is higher than the input voltage. For example, +12 V can be
generated from a +5 V logic power supply or +5 V can be
derived from two alkaline cells (+3 V).
Figure 16 shows an ADP1173 configured for step-up operation.
The collector of the internal power switch is connected to the
output side of the inductor, while the emitter is connected to
GND. When the switch turns on, pin SW1 is pulled near ground.
This action forces a voltage across L1 equal to VIN–VCE(SAT),
and current begins to flow through L1. This current reaches a
final value (ignoring second-order effects) of:
I PEAK
V IN
V CE(SAT ) × 23 µs
L
where 23 µs is the ADP1173 switch’s “on” time.
–8– REV. 0







ADP1173AN-33 equivalent, schematic
–16–










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