A7111J6VR-33 [AITSEMI]
SYNCHRONOUS PSM/PWM BUCK (STEP-DOWN) DC-DC CONVERTER;
| 型号： | A7111J6VR-33 |
| 厂家： | 
AiT Semiconductor |
| 描述： | SYNCHRONOUS PSM/PWM BUCK (STEP-DOWN) DC-DC CONVERTER DC-DC转换器 |
| 文件： | 总15页 (文件大小：477K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
DESCRIPTION
FEATURES
The A7111 is a constant frequency, 1.5MHz, slope
compensated current mode PWM stepdown
converter working under an input voltage range of
2.5V to 5.5V. This feature makes the A7111 suitable
for single cell Liion battery-powered applications.
High Efficiency: Up to 96%
1.5MHz Constant Switching Frequency
Current Mode Operation for Excellent Line and
Load Transient Response
No Schottky Diode Required
The internal synchronous rectifier is desired to
increase efficiency without an external Schottky
diode. 100% duty cycle capability extends battery life
in portable devices, while the quiescent current is
200μA at no load, and drops to < 1μA in shutdown.
Pulse Skipping Mode operation increases efficiency
at light loads, further extending battery life.
2.5V to 5.5V Input Voltage Range
1.0V,1.2V,1.5V,1.8V,2.5V and 3.3V
Fixed/Adjustable Output Voltage
100% Duty Cycle in Dropout Mode
Low Quiescent Current: 200μA
Over temperature Protection
Short Circuit Protection
The A7111 is offered in a low profile (1mm) 5-pin,
thin SOT-23 package, and is available in an
adjustable version and fixed output versions of 1.0V,
1.2V, 1.5V , 1.8V, 2.5V and 3.3V.
Shutdown Quiescent Current < 1μA
Available in SOT-25 and DFN6(2x2) package
APPLICATION
The A7111 is available in SOT-25 and DFN6(2x2)
Package.
Cellular and Smart Phones
Wireless Handsets and DSL Modems
Microprocessors and DSP Core Supplies
PDAs
ORDER INFORMATION
Digital Still and Video Cameras
MP3/MP4/MP5 Players
Portable Instruments
GPS Receivers
Package Type
SOT-25
Part Number
A7111E5R-XX
A7111E5VR-XX
A7111J6R-XX
A7111J6VR-XX
E5
J6
DFN6
(2x2)
TYPICAL APPLICATION CIRCUIT
XX: Output Voltage
33=3.3V,ADJ=Adjustable
R: Tape & Reel
Note
V: Halogen free Package
AiT provides all RoHS products
Suffix “V” means Halogen free Package
Figure 1. A7111-ADJ Typical Application Circuit
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 1 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
PIN DESCRIPTION
Top View
Top View
Function
Pin #
Symbol
EN
SOT-23
1
DFN6
Regulator Enable Control Input. Drive EN above 1.5V to
turn on the part. Drive EN below 0.3V to turn it off. In
shutdown, all functions are disabled drawing <1KA
supply current. Do not leave EN floating.
2
2
3
1 , 5
4
GND
SW
Ground
Power Switch Output. It is the Switch note connection to
external 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 2.2µF or greater ceramic capacitor.
VFB (ADJ): Feedback Input Pin. Connect FB to the
center point of the external resistor divider.
The feedback threshold voltage is 0.6V.
4
5
3
6
VIN
VFB/VOUT
VOUT (Fixed): Output Voltage Pin.
An internal resistive divider divides the output voltage
down for comparison to the internal reference voltage.
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 2 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage
-0.3V to +6V
-0.3V to +VIN
-0.3V to (VIN+0.3V)
1.1A
EN, VFB Voltages
SW Voltages
P-Channel Switch Source Current (DC)
N-Channel Switch Sink Current (DC)
Peak SW Sink and Source Current
Operating Temperature Range
Junction Temperature NOTE
Storage Temperature Range
Lead Temperature (Soldering, 10s)
1.1A
1.5A
-40°C to +85°C
+125°C
-65°C to +150°C
+300°C
Stresses above may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at
these or any other conditions beyond those indicated in the Electrical Characteristics is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect device reliability.
NOTE: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula:
TJ = TA + (PD) x (220°C/W)
THERMAL RESISTANCE
Package
SOT-25
DFN6
θJA
θJC
250°C/W
165°C/W
130°C/W
20°C/W
NOTE: Thermal Resistance is specified with approximately 1 square of 1 oz copper
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 3 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
ELECTRICAL CHARACTERISTICS
VIN = VEN = 3.6V, TA = 25°C, unless otherwise specified.
Parameter
Input Voltage Range
Input DC Supply Current
Active Mode
Conditions
MIN
2.5
TYP
-
MAX
5.5
unit
V
-
200
0.1
µA
µA
V
V
FB = 0.5V or VOUT = 90%
FB = 0V, VIN = 4.2V
300
1.0
-
Shutdown Mode
V
TA = +25°C
0.5880
0.5865
0.5850
-
0.6000
0.6000
0.6000
-
0.6120
0.6135
0.6150
±30
Regulated Feedback
Voltage
TA = 0°C ≤ TA ≤ 85°C
TA = -40°C ≤ TA ≤ 85°C
VFB = 0.65V
V
V
VFB Input Bias Current
Reference Voltage Line
Regulation
nA
VIN = 2.5V to 5.5V
-
0.04
0.4
%/V
12V
18V
-40°C ≤ TA ≤ 85°C
-40°C ≤ TA ≤ 85°C
1.164
1.746
20
1.200
1.800
50
1.236
1.854
80
V
V
Regulated Output Voltage
Output Overvoltage Lockout
ΔVOVL=VOVL-VFB, Adjustable Version
ΔVOVL= VOVL– VOUT, Fixed Version
mV
%
2.5
7.8
13
Output Voltage Line
Regulation
VIN= 2.5V to 5.5V
-
-
-
0.04
0.5
0.40
%
%
A
Output Voltage Load
Regulation
-
-
VIN=3V, VFB=0.5V or VOUT=90%
Duty Cycle <35%
Peak Inductor Current
1.3
Oscillator Frequency
RDS(ON) of P-CH MOSFET
RDS(ON) of N-CH MOSFET
SW Leakage
VFB=0.6V or VOUT=100%
ISW = 300mA
1.2
1.5
0.40
0.35
±0.01
1.8
0.50
0.45
±1
MHz
Ω
-
-
-
ISW = -300mA
Ω
VEN = 0V, VSW = 0V or 5V, VIN = 5V
µA
EN Threshold
-40°C ≤ TA ≤ 85°C
0.3
-
1.1
1.30
±1
V
EN Leakage Current
±0.01
µA
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 4 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
1.
3.
5.
Output Voltage vs Load Current
Reference Voltage vs Temperature
Supply Current vs Supply Voltage
2.
4.
6.
Efficiency vs Output Current
Output Voltage vs Input Voltage
Start_up from Shutdown
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 5 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
7.
Load Step
8.
Load Step
9. Load Step
10. Load Step
11. Pulse Skipping Mode
12. Output Short
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 6 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
BLOCK DIAGRAM
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 7 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
DETAILED INFORMATION
Operation
The A7111 uses a constant frequency, current mode step-down architecture. Both the main switch
(P-channel MOSFET) and the synchronous rectifier (N-channel MOSFET) are integrated internally. This
Step-Down DC-DC Converter can supply 600mA output current over a wide input voltage range from 2.5V to
5.5V. The over voltage comparator OVDET guards against transient overshoots >7.8% by turning the main
switch off and keeping it off until the fault is removed.
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. During normal operation, the internal main switch is turned on for a certain
time to ramp the inductor current at each rising edge of the internal oscillator, and turned off when the peak
inductor current reaches the controlled value. 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, IRCMP, or the beginning of the next clock cycle.
Pulse Skipping Mode Operation
At very light loads, the A7111 will automatically enter Pulse Skipping Mode to increase efficiency, further
extending battery life. In this mode, the control loop skips PWM pulses while maintaining output in regulation,
and the switching frequency depends on the load condition. This is a kind of PFM mode operation.
Dropout Operation
When the input voltage decreases toward the value of the output voltage, the A7111 will keep the main switch
NOTE5
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.
NOTE5: 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).
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 8 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
Short Circuit Protection
The A7111 has short circuit protection. When output is shorted to ground, the oscillator frequency is reduced
to prevent the inductor current from increasing beyond the PFET current limit. The PFET current limit is also
reduced to lower the short circuit current. The frequency and current limit will return to the normal values once
the short circuit condition is removed and the feedback voltage reaches 0.6V.
Maximum Load Current
The A7111 will operate with input supply voltage as low as 2.5V, however the maximum load current
decreases at lower input voltage due to large IR drop on the main switch and synchronous rectifier.
Application Information
Figure 2 below shows the basic application circuit with A7111 fixed output versions.
Figure 2. Basic Application Circuit with fixed output versions
Setting the Output Voltage
Figure 1 of page #1 shows the basic application circuit with A7111 adjustable output version. The external
resistor sets the output voltage according to the following equation:
Table 1-Resistor Selection vs Output Voltage Setting
VOUT
R1
R2
1.0V
1.2V
1.5V
1.8V
2.5V
3.3V
180
180
180
180
158
180
120
180
270
360
499
810
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 9 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
Inductor Selection
The output inductor is selected to limit the ripple current to some predetermined value, typically 20%~40% of
the full load current at the maximum input voltage. In continuous mode, the ripple current is determined by:
A reasonable starting point for setting ripple current is ΔIL = 240mA (40% of 600mA). For output voltages
above 2.0V, when efficiency at light load condition is important, the minimum recommended inductor is 2.2µH.
For optimum voltage-positioning load transients, choose an inductor with DC series resistance below 150mΩ.
For higher efficiency at heavy loads (above 200mA), 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. Thus, a 720mA
rated inductor should be enough for most applications (600mA+120mA).
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. In continuous mode, the source current of the main
switch is a square wave of duty cycle VOUT/VIN. To prevent large voltage transients, a low ESR input capacitor
sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by:
This formula has a maximum at VIN = 2VOUT, where IRMS = IOUT/2. This simple worst-case condition is
commonly used for design because even significant deviations do not offer much relief. Ceramic capacitors
with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current.
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 ΔVOUT is
determined by:
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 10 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
Efficiency Considerations
Layout Considerations
When laying out the printed circuit board, the following checklist should be used to ensure proper operation of
the A7111. These items are also illustrated graphically in Figures 5 and 6. Check the following in your layout:
1.
2.
3.
The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short,
direct and wide.
Does the VFB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be
connected between the (+) plate of COUT and ground.
Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to
the internal power MOSFETS.
4.
5.
Keep the switching node, SW, away from the sensitive VFB node.
Keep the (-) plates of CIN and COUT as close as possible.
Figure 3. A7111-ADJ Layout Circuit
Figure 4. A7111-1.8 Layout Circuit
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 11 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
Figure 5. A7111-ADJ Suggested Layout
Figure 6. A7111-XX (Fixed) Suggested Layout
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 12 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
PACKAGE INFORMATION
Dimension in SOT-25 (Unit: mm)
Symbol
Min
Max
A
A1
A2
b
1.050
0.000
1.050
0.300
0.100
2.820
1.500
2.650
1.250
0.100
1.150
0.500
0.200
3.020
1.700
2.950
c
D
E
E1
e
0.950(BSC)
e1
L
1.800
0.300
0°
2.000
0.600
8°
θ
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 13 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC CONVERTER
Dimension in DFN6(2x2) Package (Unit: mm)
Symbol
Min
Max
A
A1
A3
b
0.700
0.000
0.175
0.200
1.950
1.000
1.950
0.500
0.800
0.050
0.250
0.350
2.050
1.450
2.050
0.850
D
D2
E
E2
e
0.650TYP.
L
0.300
0.400
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 14 -
A7111
AiT Semiconductor Inc.
www.ait-ic.com
1.5 MHZ, 1A SYNCHRONOUS PSM/PWM
BUCK (STEP-DOWN) DC-DC 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
In order to
involve potential risks of death, personal injury, or servere property, or environmental damage.
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.
REV1.1
- MAY 2011 RELEASED, FEB 2013 REVISED -
- 15 -
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