Datenblatt-pdf.com


ADP3051 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADP3051
Beschreibung PWM Step Down DC-DC
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 16 Seiten
ADP3051 Datasheet, Funktion
FEATURES
Current mode control for simple loop compensation
Input voltage range: 2.7 V to 5.5 V
Output voltage range: 0.8 V to 5.5 V
Tri-Mode™ operation for high efficiency
550 kHz PWM operating frequency
High accuracy over line, load, and temperature
Micropower shutdown mode
Space-saving MSOP-8 package
APPLICATIONS
Li-ion powered handhelds
MP3 players
PDAs and palmtops
Consumer electronics
500 mA PWM Step-Down DC-DC with
Synchronous Rectifier
ADP3051
GENERAL DESCRIPTION
The ADP3051 is a low noise, current mode, pulse width modu-
lator (PWM) step-down converter capable of supplying over
500 mA to output voltages as low as 0.8 V. This device integrates
a low resistance power switch and synchronous rectifier, provid-
ing excellent efficiency over the entire output voltage range and
eliminating the need for a large and costly external Schottky
rectifier. Its 550 kHz switching frequency permits the use of
small external components.
Current mode control and external compensation allow the
regulator to be easily optimized for a wide range of operating
conditions. The ADP3051 operates at a constant 550 kHz
frequency at medium to heavy loads; it smoothly transitions
into Tri-Mode operation to save power at light loads. A pin-
controlled micropower shutdown mode is also included.
The ADP3051’s 2.7 V to 5.5 V input operating range makes it
ideal for both battery-powered applications as well as those with
3.3 V or 5 V supply buses. It is available in a space-saving, 8-lead
MSOP package.
VIN 3.3V
10µF
10k
270pF
TYPICAL APPLICATION CIRCUIT
ADP3051
4 IN
SW 3
7 SHDN
10µH
12.5k
6 COMP
FB 5
27pF
PGND
2
GND
8
10k
VOUT 1.8V
10µF
Figure 1.
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 that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
www.DataSheet4U.com
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.






ADP3051 Datasheet, Funktion
ADP3051
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, VOUT = 3.3V, circuit of Figure 20, component values of Table 4, TA = 25°C, unless otherwise specified.
100
90 VIN = 3.6V
80
70
60
VIN = 5.5V
VOUT = 3.3V
L = 22µH
0.5
0.4
0.3
0.2
0.1
0
–0.1
–0.2
VOUT = 2.5V
VIN = 3.6V
50
40
1
10 100
ILOAD (mA)
1000
–0.3
–0.4
–0.5
0
100 200 300 400 500
ILOAD (mA)
Figure 3. Output Efficiency vs. Load Current, VOUT = 3.3 V
100
Figure 6. Output Voltage Error vs. Load Current
600
90 VIN = 2.7V
80
70 VIN = 3.6V
60
VIN = 5.5V
50
VOUT = 2.5V
L = 22µH
COUT = 22µF
580
560
VIN = 5.5V
540
520
500
VIN = 3.6V
VIN = 2.7V
VOUT = 1.2V
ILOAD = 500mA
40
1
10 100
ILOAD (mA)
1000
Figure 4. Output Efficiency vs. Load Current, VOUT = 2.5 V
100
90 VIN = 3.6V
80 VIN = 2.5V
70
VIN = 5.5V
VOUT = 1.2V
L = 10µH
COUT = 22µF
60
50
40
1
10 100
ILOAD (mA)
1000
Figure 5. Output Efficiency vs. Load Current, VOUT = 1.2 V
480
–40
–15 10 35 60
TEMPERATURE (°C)
85
600
550
500
450
400
350
300
250
200
150
100
50
0
0
Figure 7. Oscillator Frequency vs. Temperature
100 200 300 400 500
ILOAD (mA)
Figure 8. Oscillator Frequency vs. Load Current, VIN = 3.6 V, VOUT = 1.2 V
Rev. 0 | Page 6 of 16

6 Page









ADP3051 pdf, datenblatt
ADP3051
Inductor Selection
The ADP3051’s high switching frequency allows the use of a
physically small inductor. The inductor ripple current is deter-
mined by
( )IL
=
VOUT × VIN VOUT
VIN × fSW × L
Where ∆IL is the peak-to-peak inductor ripple current and fSW is
the switching frequency. As a guideline, the inductor peak-to-
peak current ripple is typically set to be one-third the maximum
dc load current. Using this guideline and solving for L,
( )L
=
3×VOUT × VIN VOUT
VIN × fSW × I LOAD(MAX )
Simplifying for the known constants
( )L
=
5
μH ×
VOUT
VIN
×
×
VIN VOUT
I LOAD(MAX)
It is important to ensure that the inductor is capable of handling
the maximum peak inductor current, ILPK, determined by
I LPK
=
I LOAD(MAX
)
+
⎜⎛
I L
2
⎟⎞
Finally, the ADP3051’s internal slope compensation is designed
to ensure stability of the inner current mode control loop when
the inductor is chosen so that the down-slope of the inductor
current is less than 320 mA/µs
L
VOUT
320 mA /μs
OUTPUT CAPACITOR SELECTION
The output capacitor should be chosen to meet output voltage
ripple requirements for the application. Output voltage ripple is
a function of the inductor ripple current and the impedance of
the output capacitor at the switching frequency. The magnitude
of the capacitive impedance is
XCOUT
=
1
2π × COUT
×
f SW
For capacitors with relatively large capacitance or high
equivalent series resistance (ESR), e.g., tantalum or electrolytic
capacitors, the ESR dominates the impedance at the switching
frequency; therefore, the output ripple voltage is mainly a func-
tion of ESR. In this case, the output capacitor should be chosen
based on the ESR by the equation
ESRCOUT
VRIPPLE
I L
Where VRIPPLE is the peak-to-peak output ripple voltage and
ESRCOUT is the output capacitor ESR. For capacitors with rela-
tively small capacitance and/or resistance, the capacitance
dominates the output voltage ripple. In this case, choose the
output capacitor by the capacitance using the equation
( )COUT
VIN
× fSW 2 × L ×VRIPPLE
C OUT
I L
8 f SW VOUT
Multilayer ceramic (MLC), tantalum, OS-CON, or similar low
ESR capacitors are recommended. Table 5 lists some vendors
that make suitable capacitors.
Table 5. Capacitor Suppliers
Manufacturer Capacitor Type
AVX Tantalum
Murata
MLCC
Sanyo
OS-CON
Taiyo-Yuden
MLCC
Contact Info
www.avxcorp.com
www.murata.com
www.sanyovideo.com
www.t-yuden.com
Input Capacitor Selection
The input capacitor reduces input voltage ripple caused by
switch currents. Select an input capacitor capable of withstand-
ing the rms input current
ICIN (RMS) I LOAD(MAX)
( )VOUT VIN VOUT
VIN
Where ICIN(RMS) is the rms ripple rating of the input capacitor. As
with the output capacitor, a low ESR capacitor is recommended
to help to minimize input voltage ripple.
Compensation Design
The ADP3051’s external compensation network allows design-
ers to easily optimize the part’s performance for a particular
application with just a series RC network (RC and C1 of
Figure 21) from COMP to GND typically required to
compensate the regulator.
The dc loop gain is given by the equation
AVDC
=
VFB
× GEA × ROEA × RLOAD
VOUT × RCS
where:
VFB is the feedback voltage regulation threshold, 0.8 V.
GEA is the error amplifier transconductance, 320 µs.
ROEA is the error amplifier output impedance (10 MΩ).
RCS is the 2.9 Ω current sense gain.
RLOAD is the equivalent output resistance, equal to the output
voltage divided by the load current.
Rev. 0 | Page 12 of 16

12 Page





SeitenGesamt 16 Seiten
PDF Download[ ADP3051 Schematic.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
ADP3050200 kHz/ 1 A High-Voltage Step-Down Switching RegulatorAnalog Devices
Analog Devices
ADP3051PWM Step Down DC-DCAnalog Devices
Analog Devices

TeilenummerBeschreibungHersteller
CD40175BC

Hex D-Type Flip-Flop / Quad D-Type Flip-Flop.

Fairchild Semiconductor
Fairchild Semiconductor
KTD1146

EPITAXIAL PLANAR NPN TRANSISTOR.

KEC
KEC


www.Datenblatt-PDF.com       |      2020       |      Kontakt     |      Suche