DataSheet.es    


PDF ADP1173AN Data sheet ( Hoja de datos )

Número de pieza ADP1173AN
Descripción Micropower DC-DC Converter
Fabricantes Analog Devices 
Logotipo Analog Devices Logotipo



Hay una vista previa y un enlace de descarga de ADP1173AN (archivo pdf) en la parte inferior de esta página.


Total 16 Páginas

No Preview Available ! ADP1173AN Hoja de datos, Descripción, Manual

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

1 page




ADP1173AN pdf
ADP1173
APPLICATIONS
Theory of Operation
The ADP1173 is a flexible, low power switch mode power
supply (SMPS) controller. The regulated output voltage can be
greater than the input voltage (boost or step-up mode) or less
than the input (buck or step-down mode). This device uses a
gated-oscillator technique to provide very high performance
with low quiescent current.
A functional block diagram of the ADP1173 is shown on the
front page. The internal 1.245 V reference is connected to one
input of the comparator, while the other input is externally
connected (via the FB pin) to a feedback network connected to
the regulated output. When the voltage at the FB pin falls below
1.245 V, the 24 kHz oscillator turns on. A driver amplifier pro-
vides base drive to the internal power switch, and the switching
action raises the output voltage. When the voltage at the FB pin
exceeds 1.245 V, the oscillator is shut off. While the oscillator is
off, the ADP1173 quiescent current is only 110 µA. The com-
parator includes a small amount of hysteresis, which ensures
loop stability without requiring external components for fre-
quency compensation.
The maximum current in the internal power switch can be set
by connecting a resistor between VIN and the ILIM pin. When the
maximum current is exceeded, the switch is turned OFF. The
current limit circuitry has a time delay of about 2 µs. If an
external resistor is not used, connect ILIM to VIN. Further
information on ILIM is included in the Limiting the Switch
Current section of this data sheet.
The ADP1173 internal oscillator provides 23 µs ON and 19 µs
OFF times, which is ideal for applications where the ratio
between VIN and VOUT is roughly a factor of two (such as
converting +3 V to + 5 V). However, wider range conversions
(such as generating +12 V from a +5 V supply) can easily be
accomplished.
An uncommitted gain block on the ADP1173 can be connected
as a low battery detector. The inverting input of the gain block
is internally connected to the 1.245 V reference. The noninvert-
ing input is available at the SET pin. A resistor divider, con-
nected between VIN and GND with the junction connected to
the SET pin, causes the AO output to go LOW when the low
battery set point is exceeded. The AO output is an open
collector NPN transistor which can sink 100 µA.
The ADP1173 provides external connections for both the
collector and emitter of its internal power switch, which permits
both step-up and step-down modes of operation. For the step-
up mode, the emitter (pin SW2) is connected to GND and the
collector (pin SW1) drives the inductor. For step-down mode,
the emitter drives the inductor while the collector is connected
to VIN.
The output voltage of the ADP1173 is set with two external
resistors. Three fixed-voltage models are also available:
ADP1173-3.3 (+3.3 V), ADP1173-5 (+5 V) and ADP1173-12
(+12 V). The fixed-voltage models are identical to the ADP1173,
except that laser-trimmed voltage-setting resistors are included
on the chip. On the fixed-voltage models of the ADP1173,
simply connect the feedback pin (Pin 8) directly to the output
voltage.
COMPONENT SELECTION
General Notes on Inductor Selection
When the ADP1173 internal power switch turns on, current
begins to flow in the inductor. Energy is stored in the inductor
core while the switch is on, and this stored energy is then
transferred to the load when the switch turns off. Both the
collector and the emitter of the switch transistor are accessible
on the ADP1173, so the output voltage can be higher, lower or
of opposite polarity than the input voltage.
To specify an inductor for the ADP1173, the proper values of
inductance, saturation current and dc resistance must be
determined. This process is not difficult, and specific equations
for each circuit configuration are provided in this data sheet. In
general terms, however, the inductance value must be low
enough to store the required amount of energy (when both
input voltage and switch ON time are at a minimum) but high
enough that the inductor will not saturate when both VIN and
switch ON time are at their maximum values. The inductor
must also store enough energy to supply the load without
saturating. Finally, the dc resistance of the inductor should be
low, so that excessive power will not be wasted by heating the
windings. For most ADP1173 applications, an inductor of
47 µH to 470 µH, with a saturation current rating of 300 mA to
1 A and dc resistance <1 is suitable. Ferrite core inductors
which meet these specifications are available in small, surface-
mount packages.
To minimize Electro-Magnetic Interference (EMI), a toroid or
pot core type inductor is recommended. Rod core inductors are
a lower cost alternative if EMI is not a problem.
CALCULATING THE INDUCTOR VALUE
Selecting the proper inductor value is a simple three-step
process:
1. Define the operating parameters: minimum input voltage,
maximum input voltage, output voltage and output current.
2. Select the appropriate conversion topology (step-up, step-
down, or inverting).
3. Calculate the inductor value, using the equations in the
following sections.
Inductor Selection—Step-Up Converter
In a step-up, or boost, converter (Figure 14), the inductor must
store enough power to make up the difference between the
input voltage and the output voltage. The power that must be
stored is calculated from the equation:
( ) ( )PL = VOUT +V D V IN(MIN) × IOUT
(1)
where VD is the diode forward voltage (0.5 V for a 1N5818
Schottky). Energy is only stored in the inductor while the
ADP1173 switch is ON, so the energy stored in the inductor on
each switching cycle must be must be equal to or greater than:
PL
f OSC
(2)
in order for the ADP1173 to regulate the output voltage.
REV. 0
–5–

5 Page





ADP1173AN arduino
ADP1173
The internal structure of the ILIM circuit is shown in Figure 21.
Q1 is the ADP1173’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 an
internal 80 resistor and through the RLIM resistor. These two
resistors parallel the base-emitter junction of the oscillator-
disable transistor, Q3. When the voltage across R1 and RLIM
exceeds 0.6 V, Q3 turns on and terminates the output pulse. If
only the 80 internal resistor is used (i.e., the ILIM pin is con-
nected directly to VIN), the maximum switch current will be
1.5 A. Figures 4 and 5 gives RLIM values for lower current-limit
values.
ILIM
RLIM
(EXTERNAL)
VIN
80
R1 (INTERNAL)
Q3 SW1
DRIVER
OSCILLATOR
Q2
Q1
SW2
Figure 21. Current Limit Operation
The delay through the current limiting circuit is approximately
2 µs. If the switch ON time is reduced to less than 4 µs, accu-
racy of the current trip-point is reduced. Attempting to program
a switch ON time of 2 µs or less will produce spurious responses
in the switch ON time. However, the ADP1173 will still provide
a properly regulated output voltage.
PROGRAMMING THE GAIN BLOCK
The gain block of the ADP1173 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
ADP1173’s 1.245 V reference, while the noninverting input is
available at the SET pin. The NPN output transistor will sink
about 100 µA.
VBAT
+5V
2
R1 ADP1173
VIN
100k
1.245V
SET REF
7
AO
6
TO
PROCESSOR
GND
R2 5
R1 = VLB –1.245V
12.5µA
VLB = BATTERY TRIP POINT
R2 = 100k
Figure 22. Setting the Low Battery Detector Trip Point
Figure 22 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 100 kfor R2 is a
good compromise. The value for R1 is then calculated from the
formula:
R1
=
V
LOBATT
1.245
1.245
V
V
R2
where VLOBATT 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.
VBAT
5V
2
R1
ADP1173
VIN
47k
1.245mV
SET REF
7
AO
6
TO
PROCESSOR
GND
R2 5
R3
1.6M
Figure 23. Adding Hysteresis to the Low Battery Detector
REV. 0
–11–

11 Page







PáginasTotal 16 Páginas
PDF Descargar[ Datasheet ADP1173AN.PDF ]




Hoja de datos destacado

Número de piezaDescripciónFabricantes
ADP1173ANMicropower DC-DC ConverterAnalog Devices
Analog Devices
ADP1173AN-12Micropower DC-DC ConverterAnalog Devices
Analog Devices
ADP1173AN-33Micropower DC-DC ConverterAnalog Devices
Analog Devices
ADP1173AN-5Micropower DC-DC ConverterAnalog Devices
Analog Devices

Número de piezaDescripciónFabricantes
SLA6805M

High Voltage 3 phase Motor Driver IC.

Sanken
Sanken
SDC1742

12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters.

Analog Devices
Analog Devices


DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares,
permitiéndote verlos en linea o descargarlos en PDF.


DataSheet.es    |   2020   |  Privacy Policy  |  Contacto  |  Buscar