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ADP2370 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADP2370
Beschreibung (ADP2370 / ADP2371) Low Quiescent Current Buck Regulator
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 32 Seiten
ADP2370 Datasheet, Funktion
Data Sheet
High Voltage, 1.2 MHz/600 kHz, 800 mA,
Low Quiescent Current Buck Regulator
ADP2370/ADP2371
FEATURES
Input voltage range: 3.2 V to 15 V, output current: 800 mA
Quiescent current < 14 µA in power saving mode (PSM)
>90% efficiency
Force PWM pin (SYNC), 600 kHz/1.2 MHz frequency pin
(FSEL)
Fixed outputs: 0.8 V, 1.2 V, 1.5 V, 1.8 V, 2.5 V, 3.0 V, 3.3 V, 5 V,
and adjustable option
100% duty cycle capability
Initial accuracy: ±1%
Low shutdown current: <1.2 µA
Quick output discharge (QOD) option
Synchronizable to an external clock
8-lead, 0.75 mm × 3 mm × 3 mm LFCSP (QFN) package
Supported by ADIsimPower design tool
APPLICATIONS
Portable and battery-powered equipment
Automatic meter readers (WSN)
Point of sales and transaction processing instruments
Medical instruments
Medium format display tablets and pads
GENERAL DESCRIPTION
The ADP2370/ADP2371 are high efficiency, low quiescent current,
800 mA buck (step-down) dc-to-dc converters in small 8-lead,
3 mm × 3 mm LFCSP (QFN) packages. The total solution requires
only three tiny external components.
The buck regulator uses a proprietary high speed current mode,
constant frequency PWM control scheme for excellent stability
and transient response. The need for an external rectifier is elimi-
nated by using a high efficiency synchronous rectifier architecture.
To ensure the longest battery life in portable applications, the
ADP2370/ADP2371 employ a power saving variable frequency
mode that reduces the switching frequency under light load
conditions. The ADP2370/ADP2371 operate from input voltages
of 3.2 V to 15 V allowing the use of multiple alkaline/NiMH,
lithium cells, or other standard power sources.
The ADP2370/ADP2371 offer multiple options for setting the
operational frequency. The ADP2370/ADP2371 can be synchro-
nized to a 600 kHz to 1.2 MHz external clock or it can be forced
to operate at 600 kHz or 1.2 MHz via the FSEL pin. The ADP2370/
ADP2371 can be forced to operate in PWM mode (FPWM)
when noise considerations are more important than efficiency.
VIN = 6V
CIN
10µF
TYPICAL APPLICATION CIRCUIT
VIN
1
ADP2370/
ADP2371
PGND
8
POWER GOOD
1.2MHz
600kHz
FSEL 2
ON
OFF
EN
3
SYNC
4
AGND
(EXPOSED PAD)
7 SW
PG
6
FB
5
VOUT = 3.3V
COUT
10µF
Figure 1.
A power-good output is available to indicate when the output
voltage is below 92% of its nominal value.
The ADP2371 is identical to the ADP2370 except that the
ADP2371 includes the addition of an integrated switched
resistor, quick output discharge function (QOD) that auto-
matically discharges the output when the device is disabled.
Both devices include an internal power switch and a synchronous
rectifier for minimal external part count and high efficiency.
The ADP2370/ADP2371 also include internal soft start and
internal compensation for ease of use.
During a logic controlled shutdown, the input is disconnected
from the output and the regulator draws less than 1.2 μA from
the input source. Other key features include undervoltage lockout
to prevent deep battery discharge and soft start to prevent input
overcurrent at startup. Short-circuit protection and thermal over-
load protection circuits prevent damage under adverse conditions.
The ADP2370/ADP2371 each use one 0805 capacitor, one 1206
capacitor, and one 4 mm × 4 mm inductor. The total solution
size is about 53 mm2 resulting in a very small footprint solution
to meet a variety of portable applications.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor 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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2012 Analog Devices, Inc. All rights reserved.
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ADP2370 Datasheet, Funktion
ADP2370/ADP2371
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter
VIN to PGND and Ground Plane
SW to PGND and Ground Plane
FB to PGND and Ground Plane
EN to PGND and Ground Plane
PG to PGND and Ground Plane
SYNC to PGND and Ground Plane
FSEL to PGND and Ground Plane
Temperature Range
Storage
Operating Ambient
Operating Junction
Soldering Conditions
Rating
−0.3 V to +17 V
−0.7 V to VIN + 0.3 V
−0.3 V to +6 V
−0.3 V to +17 V
−0.3 V to +17 V
−0.3 V to +17 V
−0.3 V to +17 V
−65°C to +150°C
−40°C to +85°C
−40°C to +125°C
JEDEC J-STD-020
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL DATA
Absolute maximum ratings apply individually only, not in com-
bination. Exceeding the junction temperature (TJ) limit can
cause damage to the ADP2370/ADP2371. Monitoring ambient
temperature does not guarantee that TJ is within the specified
temperature limits. The maximum ambient temperature may
require derating in applications with high power dissipation and
poor thermal resistance.
In applications with moderate power dissipation and low
printed circuit board (PCB) thermal resistance, the maximum
ambient temperature can exceed the maximum limit as long
as the junction temperature is within specification limits. The
junction temperature of the device is dependent on the ambient
temperature, the power dissipation of the device, and the junction
to ambient thermal resistance of the package (θJA).
Maximum junction temperature (TJ) is calculated from the
ambient temperature (TA) and power dissipation (PD) using
the formula
TJ = TA + (PD × θJA)
Junction-to-ambient thermal resistance (θJA) of the package is
based on modeling and calculation using a 4-layer board. θJA is
highly dependent on the application and board layout. In applica-
tions where high maximum power dissipation exists, close
Data Sheet
attention to thermal board design is required. The value of θJA can
vary, depending on PCB material, layout, and environmental con-
ditions.
The specified values of θJA are based on a 4-layer, 4 in. × 3 in.
circuit board. See JESD 51-7, High Effective Thermal Conduc-
tivity Test Board for Leaded Surface Mount Packages, for detailed
information on board construction. For more information, see
Application Note AN-772, A Design and Manufacturing Guide for
the Lead Frame Chip Scale Package (LFCSP).
ΨJB is the junction to board thermal characterization parameter
with units of °C/W. The ΨJB of the package is based on modeling
and calculation using a 4-layer board. The JESD51-12, Guidelines
for Reporting and Using Electronic Package Thermal Information,
states that thermal characterization parameters are not the same
as thermal resistances. ΨJB measures the component power flowing
through multiple thermal paths rather than a single path as in
thermal resistance, θJB. Therefore, ΨJB thermal paths include
convection from the top of the package as well as radiation
from the package, factors that make ΨJB more useful in real-
world applications. Maximum junction temperature (TJ) is
calculated from the board temperature (TB) and power
dissipation (PD) using the formula
TJ = TB + (PD × ΨJB)
For more detailed information regarding ΨJB, see JESD51-12
and JESD51-8, Integrated Circuit Thermal Test Method Envi-
ronmental Conditions—Junction-to-Board.
THERMAL RESISTANCE
θJA and ΨJB are specified for the worst-case conditions, that is, a
device soldered in a circuit board for surface-mount packages.
θJC is a parameter for surface-mount packages with top mounted
heat sinks.
Table 4. Thermal Resistance
Package Type
8-Lead 3 mm × 3 mm LFCSP
θJA θJC ΨJB Unit
36.7 23.5 17.2 °C/W
ESD CAUTION
Rev. A | Page 6 of 32
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ADP2370 pdf, datenblatt
ADP2370/ADP2371
90
85
80
600kHz
75
1.2MHz
70
65
60
55
50
45
40
0.01 0.1 1 10 100 1000
LOAD (mA)
Figure 27. Efficiency vs. Load Current, Different Switching Frequency,
VOUT = 1.8 V, VIN = 9 V
VIN
1
INDUCTOR CURRENT
VOUT
2
3
CH1 500mA BW CH2 20.0mV
CH3 1.00V BW
BW M10.0µs A CH3
T 11.00%
4.56V
Figure 28. Line Transient, VOUT = 1.8 V, PSM Mode, 100 mA, VIN1 = 4 V to 5 V,
2 μs Rise Time, CIN = 3.3 μF
VIN
1 INDUCTOR CURRENT
VOUT
CH1 200mA BW CH2 20.0mV
CH3 1.00V BW
BW M10.0µs A CH3
T 11.20%
4.64V
Figure 29. Line Transient, VOUT = 1.8 V, PWM Mode, 800 mA, VIN1 = 4 V to 5 V,
2 μs Rise Time, CIN = 3.3 μF
Data Sheet
VIN
INDUCTOR CURRENT
1
VOUT
23
CH1 500mA BW CH2 20.0mV
CH3 1.00V BW
BW M10.0µs A CH3
T 11.0%
4.56V
Figure 30. Line Transient, VOUT = 1.2 V, PSM Mode, 100 mA, VIN1 = 4 V to 5 V,
2 μs Rise Time, CIN = 3.3 μF
VIN
INDUCTOR CURRENT
1
VOUT
2
3
CH1 500mA BW CH2 10.0mV
CH3 1.00V BW
BW M10.0µs A CH3
T 10.80%
5.44V
Figure 31. Line Transient, VOUT = 1.2 V, PWM Mode, 800 mA, VIN1 = 4 V to 5 V,
2 μs Rise Time, CIN = 3.3 μF
VIN
INDUCTOR CURRENT
1
VOUT
2
3
CH1 200mA Ω BW CH2 20.0mV
CH3 1.00V BW
BW M10.0µs A CH3
T 11.40%
6.78V
Figure 32. Line Transient, VOUT = 3.3 V, PSM Mode, 100 mA, VIN1 = 6 V to 7 V,
2 μs Rise Time, CIN = 3.3 μF
Rev. A | Page 12 of 32
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