ADP2102-EVAL [ADI]
600mA 3MHz Synchronous Step-Down DC-DC Converter; 600毫安的3MHz同步降压型DC- DC转换器
| 型号： | ADP2102-EVAL |
| 厂家： | 
ADI |
| 描述： | 600mA 3MHz Synchronous Step-Down DC-DC Converter |
| 文件： | 总7页 (文件大小：230K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
600mA 3MHz Synchronous
Step-Down DC-DC Converter
ADP2102
Preliminary Technical Data
FEATURES
GENERAL DESCRIPTION
95% peak efficiency
The ADP2102 is a low quiescent current step-down DC-DC
converter optimized to regulate low output voltages in a
compact 3mmx3mm LFCSP package. At high load currents, the
ADP2102 uses a current mode, constant on time, pseudo fixed
frequency, valley current control scheme for excellent stability
and transient response with very few, small external
components. To ensure the longest battery life in portable
applications, the ADP2102 has a power saving mode that
reduces the switching frequency under light load conditions to
significantly reduce the quiescent current.
Optimized for low output voltages
Optimized for extremely small ceramic inductors
Up to 600mA, load current
2.7 V to 5.5 V input voltage range
Operates with a Single Li-Ion battery
Fixed Output Voltage from 0.8V to 1.875V
Adjustable Output Voltage from 0.8V to 1.875V
Low 60μA quiescent current
Internal Synchronous rectifier
3 MHz Operating Frequency
The ADP2102 runs from input voltages from 2.7V to 5.5V
allowing single Li+/Li- polymer cell, multiple Alkaline/Ni-MH
cells and other standard power sources. ADP2102 output
voltage is adjustable from 0.8V to 1.875V, while the suffix part
numbers ADP2102-XX indicate pre-set voltage ranges of 1.875,
1.8, 1.5, 1.375, 1.25, 1.2, 1.0 & 0.8V. All versions include an
internal power switch and a synchronous rectifier for high
efficiency while internal compensation guarantees minimal
number of external components. During logic-controlled
shutdown, the input is disconnected from the output and it
draws less than 0.1μA from the input source. Other key features
include under voltage lockout to prevent deep battery discharge
and soft start to prevent input current overshoot at startup.
0.1μA Shutdown Supply Current
Small 8-Lead 3 x3 LFCSP Package
Enable /shutdown logic input
Under Voltage Lockout
Internal Soft Start
Internal Compensation
APPLICATIONS
Wireless Handsets
Portable Media Players
PDA’s and Palmtop Computers
Digital Cameras
Smart Phones
TYPICAL PERFORMANCE CHARACTERITICS
TYPICAL APPLICATION CIRCUIT
ADP2102_Efficiency
Vout= 1.375V L =2.2uH Cin= Cout = 10uF
100
Vin= 2.7V
90
80
70
60
Vin=3.0V
Vin=3.6V
Vin=4.2V
0
100
200
300
400
500
600
Load Current ( mA)
Figure 1.
Figure 2.
Rev. PrA
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 registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
©2007 Analog Devices, Inc. All rights reserved.
Preliminary Technical Data
ADP2102
SPECIFICATIONS
VIN= 3.6V, Bold values indicate TJ = −40°C to + 85°C, unless otherwise noted.1
Table 1.
Parameters
Conditions
VIN rising
Min
2.7
2.2
Typ
Max
5.5
2.5
Units
V
V
mV
V
%
Input Voltage Range2
Under voltage Lockout Threshold
Under voltage Lockout Hysterisis
Output Voltage Range
Output Voltage Accuracy
Load Regulation
2.4
200
ADP2102_Fixed
0.8
-1
1.875
1
0.5
0.6
816
50
80
1
600
600
400
1
Vout=0.8V -1.875V, Iload= 0-600mA
Iout = 10mA
0.3
0.3
800
1
60
0.1
%
Line Regulation
FB Regulation Voltage
FB Bias current
Operating Current
Shutdown Current
%
784
mV
nA
μA
μA
mA
mΩ
mΩ
μA
ns
ADP2102, VFB= 0.9V
EN=0V
Output Current
LX On Resistance
P-Channel Switch
N-channel Synchronous Rectifier
PVIN=5.5V, VLX= 0V,5.5V
300
250
LX Leakage Current
LX Minimum –Off Time
Forward Current Limit
100
1
P-Channel Switch or N-Channel Synchronous Rectifier
EN=MODE= 0, 5.5V
A
EN,MODE Input High Threshold
EN,MODE Input Low Threshold
EN,MODE Input Leakage Current
Switching Frequency
1.3
-1
V
V
μA
MHz
μs
0.4
1
0.1
3
500
150
15
Soft Start Period
250
800
Thermal Shutdown Threshold
Thermal Shutdown Hysterisis
°C
°C
1 All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC). Typical values are at TA = +25°C, VIN = 3.6 V.
2 This is the VIN input voltage range over which the rest of the specifications are valid. The part operates as expected until VIN goes below the UVLO threshold.
Rev. PrA | Page 2 of 7
Preliminary Technical Data
ADP2102
ABSOLUTE MAXIMUM RATINGS
THERMAL RESISTANCE
Table 2.
Parameter
Rating
Table 3. Thermal Resistance
Package Type
8-Lead LFCSP
AVIN,EN,MODE,FB/OUT to AGND
LX to PGND
PVIN to PGND
PGND to AGND
AVIN to PVIN
Operating Ambient Temperature Range −40°C to +85°C1
Operating Junction Temperature
Storage Temperature Range
Soldering Conditions
−0.3V to +6V
−0.3V to +(VIN + 0.3 V)
−0.3V to +6V
−0.3V to 0.3V
-0.3V to 0.3V
1
θJA
54
1
Unit
°C/W
W
Maximum Power Dissipation
1 Junction-to-ambient thermal resistance (θJA) of the package is based on
modeling and calculation using a 4-layer board. The junction-to-ambient
thermal resistance is application and board-layout dependent. In
applications where high maximum power dissipation exists, attention to
thermal board design is required. The value of θJA can vary depending on
PCB material, layout, and environmental conditions. For more information,
please refer to Application Note AN-772: A Design and Manufacturing Guide
for the Lead Frame Chip Scale Package (LFCSP).
125°C
−65°C to +150°C
JEDEC J-STD-020
1 In applications where high power dissipation and poor thermal resistance
are present, the maximum ambient temperature may have to be de-rated.
Maximum ambient temperature (TA(MAX)) is dependent on the maximum
operating junction temperature (TJ(MAXOP)) = 125°C), the maximum power
dissipation of the device (PD(MAX)), and the junction-to-ambient thermal
resistance of the part/package in the application (θJA), using the following
equation: TA(MAX) = TJ(MAXOP) – (θJA x PD(MAX)).
BOUNDARY CONDITION
Natural convection, 4-layer board, exposed pad soldered to the PCB.
ESD CAUTION
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.
Absolute maximum ratings apply individually only, not in
combination. Unless otherwise specified all other voltages
referenced to GND.
Rev. PrA| Page 3 of 7
Preliminary Technical Data
ADP2102
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 3.Pin Configuration
Table 4. Pin Function Descriptions
Pin
No.
Mnemonic Description
1
MODE
Mode Input. To set the ADP2102 to Forced Continuous Conduction Mode (CCM), drive MODE high. To set the
ADP2102 to Power Saving Mode (PSM), drive MODE low.
2
3
EN
Enable Input. Drive EN high to turn on the ADP2102. Drive EN low to turn it off and reduce the input current to 0.1μA.
This pin cannot be left floating.
Output Sense Input or Feedback Input. For fixed output versions, OUT is the top of the internal resistive voltage
divider. Connect OUT to the Output Voltage. For adjustable (non-suffix) versions, FB is the input to the error amplifier.
Drive FB through a resistive voltage divider to set the output voltage. The FB regulation threshold is 0.8V.
FB/OUT
4
5
6
AGND
PGND
LX
Analog Ground. Connect AGND to PGND at a single point as close as to the ADP2102 as possible.
Power Ground.
Switch Output. LX is the drain of the p-channel MOSFET switch and n-channel Synchronous rectifier. Connect the
output LC filter between LX and output voltage.
7
8
PVIN
AVIN
Power Source Input. Drive PVIN with a 2.7V to 5.5V power source.
Power Source Input. AVIN is the supply for the ADP2102 internal circuitry. For noise reduction, place an external RC
filter between PVIN and AVIN.
Rev. PrA | Page 4 of 7
Preliminary Technical Data
ADP2102
THEORY OF OPERATION
The ADP2102 is a high frequency synchronous step down dc-
dc buck converter optimized for battery powered portable
applications. It is based on a constant-ON time current mode
control architecture with voltage feed forward to null frequency
variation with line voltage thus creating a pseudo fixed
frequency.
load step occurs. When a load step occurs, the constant ON-
time control loop responds by modulating the OFF time up or
down to quickly get back to regulation. This momentary
frequency variation results in a faster load transient response
than a fixed frequency current mode control loop of similar
bandwidth with similar external filter inductor and capacitor.
This is an advantage of constant–ON time control scheme.
This type of control allows generation of very low output
voltages at higher switching frequency and offers a very fast
load and line transient response with minimal external
component count and size. The ADP2102 provides features like
Under Voltage Lock Out, Thermal Shutdown and Short Circuit
Protection.
As described above the frequency of the constant ON-time
control loop remains constant to a first order with line and
output voltage. There are some second order effects that cause
this frequency to increase slightly with load current.
Resistive voltage losses in the High and Low Side Power
Switches, package parasitics, inductor DCR and board parasitic
resistance cause the loop to compensate by reducing the OFF-
time and there fore increasing the switching frequency with
increasing load current.
The ADP2102 uses valley current mode control, which helps to
prevent minimum-ON time limitations at very low output
voltages. This allows high frequency operation resulting in low
filter inductor and capacitor values.
A minimum OFF-time constraint is introduced to allow the
inductor valley current sensing on the synchronous switch.
CONTROL SCHEME
The ADP2102’s High Side Power Switch ON-time is determined
by a one shot timer whose pulse width is directly proportional
to output voltage and inversely proportional to the input or line
voltage. Another one-shot timer sets a minimum OFF time to
allow for inductor valley current sensing,
FORCED CONTINUOUS CONDUCTION MODE
When the MODE pin is HIGH, the ADP2102 operates in
Forced Continuous Conduction Mode. In this mode,
irrespective of the load current, the inductor current stays
continuous and is the preferred mode of operation for low noise
applications. During this mode, the switching frequency stays
close to 3MHz typically. In this mode, the efficiency is lower
compared to the Power Save Mode during light loads but the
output voltage ripple is minimized.
The constant ON-time one-shot timer is triggered at the rising
edge of EN and subsequently when the Low Side Power Switch
current is below the valley current limit threshold and the
minimum OFF-time one-shot timer has timed out.
While the constant ON-time is asserted, the high side power
switch is turned on. This causes the inductor current to ramp
positively. After the constant ON–time has completed the high
side power switch turns off and the low side power switch turns
on. This causes the inductor current to ramp negatively until
the sensed current flowing in this switch has reached valley
current limit. At this point, the low side power switch turns off
and a new cycle begins again with the high side switch turning
on provided the minimum OFF-time one shot has timed out.
POWER SAVE MODE
When the MODE pin is LOW, the ADP2102 operates in Power
Save Mode. In this mode, at light load currents, the part
automatically goes into reduced frequency operation where
some pulses are skipped to increase efficiency while still
remaining in regulation. At light loads, a zero crossing
comparator truncates the low side switch ON-time when the
inductor current becomes negative. In this condition, the part
works in Discontinuous Conduction Mode (DCM). The
threshold between CCM and DCM is approximately
CONSTANT ON-TIME TIMER
The constant ON-time timer sets the High Side Switch on time.
This fast, low jitter, adjustable one shot varies the ON-time in
response to input voltage for a given output voltage. The High
Side Switch ON –time is inversely proportional to the input
voltage and directly proportional to the output voltage.
Iload (skip) = (Vin- Vout) / (2 x L) x Ton
For higher load currents, the inductor current does not cross
zero threshold and the device switches to the Continuous
Conduction Mode and the frequency is fixed to the nominal
value. As a result of this auto –mode control technique, the
losses are minimized at light loads, improving the system
efficiency.
Ton = K. (Vout /Vin) & Fsw = 1/K
Where “K” is an internally set On-time scale factor constant
resulting in a constant switching frequency. As can be seen in
the above equation, the steady state switching frequency is
CURRENT LIMIT
The ADP2102 has protection circuitry to limit the amount of
current flowing through the High Side and the Low Side
switches. When the current flowing in the forward direction
becomes excessive due to a short on the OUT node to ground
theoretically independent of both the input and output voltages
to a first order. Therefore, with line voltage feed forward the
constant ON- time control scheme is pseudo fixed frequency.
This means the loop switches at a constant frequency until a
Rev. PrA | Page 5 of 7
ADP2102
Preliminary Technical Data
or otherwise, the ADP2102 operates in frequency fold back by
increasing the OFF time enough to keep the output current
fixed. Therefore, during this fault condition the ADP2102 acts
as a constant current source at the current limit of 1A typical.
and the entire control circuitry is switched off. For proper
operation, the EN pin must be terminated and must not be left
floating.
UNDER VOLTAGE LOCK OUT
The under voltage lockout circuit prevents the device from
operating incorrectly at low input voltages. It prevents the
converter from turning on the main switch and the
synchronous switch under undefined conditions and therefore
preventing deep discharge of the battery supply
SOFT START
The ADP2102 has in internal soft start function that ramps the
output voltage in a controlled manner upon startup by limiting
the inrush current. This prevents possible input voltage drops
when a battery or a high impedance power source is connected
to the input of the converter.
THERMAL SHUTDOWN
When the Junction Temperature, Tj, exceeds typically 150 °C,
the device goes into Thermal Shutdown. In this mode, the High
Side and Low Side Power Switches are turned off. The device
continues its operation when the junction temperature when
the junction temperature falls below typically 135 °C again.
ENABLE
The device starts operation with soft start when the EN pin is
brought high. Pulling the EN pin low forces the device into
shutdown, with a typical shutdown current of 0.1ꢀa. In this
mode both the High Side and Low Side Power Switches are
turned off, the internal resistor feedback divider is disconnected
Rev. PrA| Page 6 of 7
Preliminary Technical Data
OUTLINE DIMENSIONS
ADP2102
Figure 4. 8 -Lead Lead Frame Chip Scale Package [LFCSP]
3 mm x 3 mm Body, Dimensions shown in millimeters
ORDERING GUIDE
Model
Temperature Range
Package Description
Package Option
Branding
ADP2102
ADP2102-EVAL
–40°C to +85°C
8-Lead Lead Frame Chip Scale Package [LFCSP]
Evaluation Board
©2007 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
PR06631-0-2/07(PrA)
Rev. PrA| Page 7 of 7
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