A7115 [AITSEMI]
DC-DC CONVERTER;
| 型号： | A7115 |
| 厂家： | 
AiT Semiconductor |
| 描述： | DC-DC CONVERTER DC-DC转换器 |
| 文件： | 总12页 (文件大小：384K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
DESCRIPTION
FEATURES
The A7115 is
a
high efficiency monolithic
High Efficiency: Up to 96%
synchronous buck regulator using a constant
frequency, current mode architecture. Supply
current with no load is 300uA and drops to <1uA in
shutdown. The 2.5V to 6.5V input voltage range
makes the A7115 ideally suited for single Li-Ion,
two to four AA battery-powered applications. 100%
duty cycle provides low dropout operation,
extending battery life in portable systems. PWM
pulse skipping mode operation provides very low
output ripple voltage for noise sensitive
applications. Switching frequency is internally set at
1.5MHz, allowing the use of small surface mount
inductors and capacitors. The internal synchronous
switch increases efficiency and eliminates the need
for an external Schottky diode. Low output voltages
are easily supported with the 0.6V feedback
reference voltage.
1.5MHz Constant Switching Frequency
1.5A Output Current at VIN=3V
Integrated Main switch and synchronous
rectifier. No Schottky Diode Required
2.5V to 6.5V Input Voltage Range
Output Voltage as Low as 0.6V
100% Duty Cycle in Dropout
Quiescent Current: 300μA(input < 4.2V)
Slope Compensated Current Mode Control for
Excellent Line and Load Transient Response
Short Circuit Protection
<1uA Shutdown Current
Soft start
Available in SOT-25 Package
APPLICATION
Cellular and Smart Phones
Microprocessors and DSP Core Supplies
Wireless and DSL Modems
PDAs
The A7115 is available in SOT-25 package.
ORDERING INFORMATION
MP3 / MP4 /PMP Player
Digital Still and Video Cameras
Portable Instruments
Package Type
SOT-25
Part Number
A7115E5R
TYPICAL APPLICATION
E5
A7115E5VR
V: Halogen free Package
R: Tape & Reel
Note
AiT provides all RoHS products
Suffix “ V “ means Halogen free Package
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 1 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
PIN DESCRIPTION
Top View
Pin #
1
Symbol
RUN
Function
Regulator Enable control input. Drive RUN above 1.5V to turn on the part. Drive
RUN below 0.6V to turn it off. In shutdown, all functions are disabled drawing
<1μA supply current. Do not leave RUN floating.
2
3
GND
SW
Ground.
Power Switch Output. It is the Switch note connection to Inductor. This pin
connects to the drains of the internal P-CH and N-CH MOSFET switches.
Supply Input Pin. Must be closely decoupled to GND, Pin 2, with a 22μF or
greater ceramic capacitor.
4
VIN
FB
Feedback Input Pin. Connect FB to the center point of the external resistor
divider. The feedback threshold voltage is 0.6V.
5
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 2 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage
RUN, VFB Voltages
-0.3V~+7V
-0.3V~VIN +0.3V
-0.3V~VIN +0.3V
SW Voltages
Package Thermal ResistanceNOTE1
θJA
220°C/W
110°C/W
θJC
Operating Temperature Range
Junction Temperature NOTE2
Storage Temperature Range
Lead Temperature (Soldering, 10s)
-40°C~+85°C
+125°C
-65°C~+150°C
+260°C
Stress beyond above listed “Absolute Maximum Ratings” may lead permanent damage to the device. These are stress ratings only and
operations of the device at these or any other conditions beyond those indicated in the operational sections of the specifications are not
implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
NOTE1: Thermal Resistance is specified with approximately 1 square of 1 oz copper.
NOTE2: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula:
TJ = TA + (PD)x(220°C/W)
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 3 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICSNOTE3
VIN =VRUN= 3.6V, TA = 25°C, unless otherwise noted.
Parameter
Input Voltage Range
Input DC Supply Current
Active Mode
Conditions
Min.
2.5
Typ.
Max.
6.5
Unit
V
VFB=0.5V or VOUT=90%
FB =0V, VIN=4.2V
300
0.1
400
μA
Shutdown Mode
V
0.1
TA = +25°C
0.5880 0.6000 0.6120
0.5865 0.6000 0.6135
0.5820 0.6000 0.6180
±30
V
V
Regulated Feedback Voltage
VFB Input Bias Current
TA =0°C ≤ TA ≤ 85°C
TA =-40°C ≤ TA ≤ 85°C
VFB = 0.65V
V
nA
%/V
%/V
%
Reference Voltage Line Regulation VIN=2.5V to 5.5V, IOUT=10mA
0.5
0.5
0.5
0.60
0.60
Output Voltage Line Regulation
Output Voltage Load Regulation
VIN=2.5V to 5.5V, IOUT=10mA
IOUT=10 to 1500mA
VIN =3V, VFB=0.5V or
Peak Inductor Current
2.5
1.2
3.5
A
VOUT=90% ,Duty Cycle <35%
Oscillator Frequency
VFB =0.6V or VOUT=100%
ISW=300mA
1.5
135
95
1.8
200
150
MHz
mΩ
mΩ
RDS(ON) of P-CH MOSFET
RDS(ON) of N-CH MOSFET
ISW=-300mA
V
RUN=0V, VSW=0V or 5V,
SW Leakage
±0.01
1.3
±1
μA
mS
V
VIN=5V
Soft start
RUN Threshold Low
RUN Threshold High
RUN Leakage Current
Thermal Shutdown
0.6
±1
-40°C ≤ TA ≤ 85°C
1.5
±0.01
165
μA
°C
NOTE3: 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization.
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 4 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
Test Typical Application above unless otherwise specified
1.
η vs. IO(VO=1.2V)
2.
η vs. IO(VO=3.3V)
3.
Ripple(CH1:VIN, CH2:VO, CH3:VSW
)
4.
Ripple(CH1:VIN, CH2:VO, CH3:VSW)
VIN=3.6V,VO=1.8V,IO=0
VIN=3.6V,VO=1.8V,IO=1.5A
5.
Soft Start(CH1:VIN, CH2:VO, CH3:VSW,CH4:ISW
)
6.
Soft Start(CH1:VIN, CH2:VO, CH3:VSW,CH4:ISW
)
VIN=3.6V,VO=1.8V,IO=0
VIN=3.6V,VO=1.8V,RL=1.5Ω
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 5 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
BLOCK DIAGRAM
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 6 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
DETAILED INFORMATION
Operation
A7115 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve
high efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a
fixed switching frequency, and uses the slope compensated current mode architecture. This Step-Down
DC-DC Converter supplies 1500mA output current at VOUT = 1.8V with input voltage range from 2.5V to 6.5V.
Current Mode PWM Control
Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for
excellent load and line responses and protection of the internal main switch (P-Ch MOSFET) and
synchronous rectifier (N-CH MOSFET). During normal operation, the internal P-Ch MOSFET is turned on for
a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when
the peak inductor current is above the error voltage. The current comparator, ICOMP limits the peak inductor
current. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until
either the inductor current starts to reverse, as indicated by the current reversal comparator, IZERO, or the
beginning of the next clock cycle. The OVDET comparator controls output transient overshoots by turning the
main switch off and keeping it off until the fault is no longer present.
Idle Mode Operation
At very light loads, the A7115 automatically enters pulse skipping Mode. In the pulse skipping Mode, the
inductor current may reach zero or reverse on each pulse. The PWM control loop will automatically skip
pulses to maintain output regulation. The bottom MOSFET is turned off by the current reversal comparator,
IZERO and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for the
switching regulator.
Dropout Operation
When the input voltage decreases toward the value of the output voltage, the A7115 allows the main switch to
NOTE4
remain on for more than one switching cycle and increases the duty cycle
until it reaches 100%. The
output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At low
input supply voltage, the RDS(ON) of the P-Channel MOSFET increases, and the efficiency of the converter
decreases. Caution must be exercised to ensure the heat dissipated not to exceed the maximum junction
temperature of the IC.
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 7 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
NOTE4: The duty cycle D of a step-down converter is defined as:
Where TON is the main switch on time and fOSC is the oscillator frequency (1.5MHz).
Maximum Load Current
The A7115 will operate with input supply voltage as low as 2.5V, however, the maximum load current
decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope
compensation signal reduces the peak inductor current as a function of the duty cycle to prevent
sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the duty
cycle decreases.
Layout Guidance
When laying out the PCB board, the following suggestions should be taken to ensure proper operation of the
A7115. These items are also illustrated graphically in Figure 1.
1. The power traces, including the GND trace, the SW trace and the VIN trace should be kept short, direct
and wide.
2. The VFB pin should be connected directly to the feedback resistor. The resistive divider R1/R2 must be
connected between the (+) plate of COUT and ground.
3. Connect the (+) plate of C1 to the VIN pin as closely as possible. This capacitor provides the AC current to
internal power MOSFET.
4. Keep the switching node, SW, away from the sensitive VFB node.
5. Keep the (-) plates of C1 and C3 as close as possible.
Figure1. A7115 Suggested Layout
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 8 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
Application Information
Setting the Output Voltage
Typical application above shows the basic application circuit with A7115. The external resistor sets the output
voltage according to the following equation:
R1=200KΩ for all outputs; R2=200kΩ for VOUT=1.2V, R2=300kΩ for VOUT=1.5V, R2=400kΩ for VOUT=1.8V,
and R2=633.3kΩ for VOUT=2.5V.
Inductor Selection
For most designs, the A7115 operates with inductors of 1μH to 4.7μH. Low inductance values are physically
smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived
from the following equation:
Where ΔIL is inductor Ripple Current. Large value inductors lower ripple current and small value inductors
result in high ripple currents. Choose inductor ripple current approximately 35% of the maximum load current
1500mA, or ΔIL=525mA.
For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor
is 2.2μH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the
50mΩ to 150mΩ range. For higher efficiency at heavy loads (above 500mA), or minimal load regulation (but
some transient overshoot), the resistance should be kept below 100mΩ. The DC current rating of the inductor
should be at least equal to the maximum load current plus half the ripple current to prevent core saturation.
Table 1 lists some typical surface mount inductors that meet target applications for the A7115.
Table 1. Typical Surface Mount Inductors
Part Number
L (μH) Max DC Current (A) DCR (mΩ) Size LxWxH (mm)
2.2
3.3
4.7
2.0
3.3
4.7
3.0
2.6
3.4
3.3
2.6
2.1
28.7
35.6
19
Sumida CDRH5D16
Sumida CDRH8D28
5.8x5.8x1.8
8.3x8.3x3.0
23
Coiltronics SD53
29
5.2x5.2x3.0
39
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 9 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
Input Capacitor Selection
The input capacitor reduces the surge current drawn from the input and switching noise from the device. The
input capacitor impedance at the switching frequency shall be less than input source impedance to prevent
high frequency switching current passing to the input. A low ESR input capacitor sized for maximum RMS
current must be used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of
their low ESR and small temperature coefficients. A 22μF ceramic capacitor for most applications is sufficient.
Output Capacitor Selection
The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability.
The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or
X7R dielectrics are recommended due to their low ESR and high ripple current. The output ripple VOUT is
determined by:
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 10 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
PACKAGE INFORMATION
Dimension in SOT-25 (Unit: mm)
Symbol
Min
Max
1.250
A
A1
A2
b
1.050
0.000
1.050
0.300
0.100
2.820
1.500
2.650
0.100
1.150
0.500
c
0.200
D
3.020
E
1.700
E1
e
2.950
0.950(BSC)
2.000
e1
L
1.800
0.300
0°
0.600
θ
8°
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 11 -
A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
IMPORTANT NOTICE
AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to
discontinue any integrated circuit product or service without notice, and advises its customers to obtain the
latest version of relevant information to verify, before placing orders, that the information being relied on is
current.
AiT Semiconductor Inc.'s integrated circuit products are not designed, intended, authorized, or warranted to
be suitable for use in life support applications, devices or systems or other critical applications. Use of AiT
products in such applications is understood to be fully at the risk of the customer. As used herein may involve
potential risks of death, personal injury, or servere property, or environmental damage. In order to minimize
risks associated with the customer's applications, the customer should provide adequate design and
operating safeguards.
AiT Semiconductor Inc. assumes to no liability to customer product design or application support. AiT
warrants the performance of its products of the specifications applicable at the time of sale.
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 12 -
相关型号：
©2020 ICPDF网 联系我们和版权申明