BCD AUR9717 Dual 1a, 1.5mhz pwm step-down dc-dc converter with ovp Datasheet

Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
General Description
Features
The AUR9717 is a high efficiency step-down
DC-DC voltage converter. The chip operation is
optimized using constant frequency, peak-current
mode architecture with built-in synchronous power
MOSFET switchers and internal compensators to
reduce external part counts. It is automatically
switching between the normal PWM mode and LDO
mode to offer improved system power efficiency
covering a wide range of loading conditions.
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The oscillator and timing capacitors are all built-in
providing an internal switching frequency of 1.5MHz
that allows the use of small surface mount inductors
and capacitors for portable product implementations.
Additional features including Soft Start (SS), Under
Voltage Lock Out (UVLO), Input Over Voltage
Protection (IOVP) and Thermal Shutdown Detection
(TSD) are integrated to provide reliable product
applications.
AUR9717
Dual Channel High Efficiency Buck Power
Converter
Low Quiescent Current
Output Current: 1A
Adjustable Output Voltage from 1V to 3.3V
Wide Operating Voltage Range: 2.5V to 5.5V
Built-in Power Switchers for Synchronous
Rectification with High Efficiency
Feedback Voltage: 600mV
1.5MHz Constant Frequency Operation
Automatic PWM/LDO Mode Switching Control
Thermal Shutdown Protection
Low Drop-out Operation at 100% Duty Cycle
No Schottky Diode Required
Internal Input Over Voltage Protection
Applications
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The device is available in adjustable output voltage
versions ranging from 1V to 3.3V, and is able to
deliver up to 1A.
Mobile Phone, Digital Camera and MP3 Player
Headset, Radio and Other Hand-held Instruments
Post DC-DC Voltage Regulation
PDA and Notebook Computer
The AUR9717 is available in WDFN-3×3-10
package.
WDFN-3×3-10
Figure 1. Package Type of AUR9717
Oct. 2011
Rev. 1.0
BCD Semiconductor Manufacturing Limited
1
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Pin Configuration
D Package
(WDFN-3×3-10)
Pin 1 Mark
EN1
1
10
LX1
FB1
2
9
GND
VIN2
3
8
VIN1
GND
4
7
FB2
LX2
5
6
EN2
Figure 2. Pin Configuration of AUR9717 (Top View)
Pin Description
Pin Number
Pin Name
1
EN1
Enable signal input of channel 1, active high
2
FB1
Feedback voltage of channel 1
3
VIN2
Power supply input of channel 2
4, 9
GND
5
LX2
Connection from power MOSFET of channel 2 to inductor
6
EN2
Enable signal input of channel 2, active high
7
FB2
Feedback voltage of channel 2
8
VIN1
Power supply input of channel 1
10
LX1
Connection from power MOSFET of channel 1 to inductor
Oct. 2011
Function
This pin is the GND reference for the NMOSFET power stage. It
must be connected to the system ground
Rev. 1.0
BCD Semiconductor Manufacturing Limited
2
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Functional Block Diagram
Figure 3. Functional Block Diagram of AUR9717
Ordering Information
AUR9717
A
Package
D: WDFN-3×3-10
G: Green
Circuit Type
A: Adjustable Output
Package
Temperature
Range
WDFN-3×3-10
-40 to 80°C
Part Number
AUR9717AGD
Marking ID
9717A
Packing Type
Tape & Reel
BCD Semiconductor's Pb-free products, as designated with "G" in the part number, are RoHS compliant and
green.
Oct. 2011
Rev. 1.0
BCD Semiconductor Manufacturing Limited
3
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Absolute Maximum Ratings (Note 1)
Parameter
Symbol
Value
Unit
Supply Input Voltage
VIN1, VIN2
0 to 6.5
V
Enable Input Voltage
VEN1, VEN2
Switch Output Voltage
VLX1, VLX2
-0.3 to
VIN1(VIN2)+0.3
-0.3 to
VIN1(VIN2)+0.3
V
V
VIN1-VIN2 Voltage (Note 2)
VDF
-0.3 to 0.3
V
Power Dissipation (On PCB, TA=25°C)
PD
2.22
W
Thermal Resistance (Junction to Ambient, Simulation)
θJA
45.13
°C/W
Thermal Resistance (Junction to Case, Simulation)
θJC
6.97
°C/W
Operating Junction Temperature
TJ
160
°C
Operating Temperature
TOP
-40 to 85
°C
Storage Temperature
TSTG
-55 to 150
°C
ESD (Human Body Model)
VHBM
2000
V
ESD (Machine Model)
VMM
200
V
Note 1: Stresses greater than those listed under “Absolute Maximum Ratings” 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 under “Recommended Operating Conditions” is not implied. Exposure to “Absolute
Maximum Ratings” for extended periods may affect device reliability.
Note 2: The absolute voltage difference between VIN1 and VIN2 can not exceed 0.3V.
Recommended Operating Conditions
Parameter
Symbol
Min
Max
Unit
Supply Input Voltage
VIN1, VIN2
2.5
5.5
V
Junction Temperature Range
TJ
-20
125
°C
Ambient Temperature Range
TA
-40
80
°C
Oct. 2011
Rev. 1.0
BCD Semiconductor Manufacturing Limited
4
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Electrical Characteristics
VIN=VEN1=VEN2=5V, VFB1=VFB2=0.6V, L1=L2=2.2μH, CIN1=CIN2=4.7μF, COUT1=COUT2=10μF, TA=25°C,
unless otherwise specified.
Parameter
Symbol
Conditions
Min Typ Max Unit
Input Voltage Range
VIN
VIN=VIN1=VIN2
Shutdown Current
Regulated Feedback
Voltage
Regulated
Output
Voltage Accuracy
Peak
Inductor
Current
IOFF
VEN1=VEN2=0V
VFB
For Adjustable Output Voltage
Oscillator Frequency
ΔVOUT1/VOUT1,
ΔVOUT2/VOUT2
IPK
VIN=2.5V to 5.5V,
IOUT1=IOUT2=0 to 1A
2.5
0.585
V
0.1
1
μA
0.6
0.615
V
3
%
-3
VFB1=VFB2=0.5V
fOSC
5.5
1.5
1.2
1.5
A
1.8
MHz
PMOSFET RON
RON(P)
IOUT1=IOUT2=200mA
0.28
Ω
NMOSFET RON
RON(N)
IOUT1=IOUT2=200mA
0.25
Ω
ILX
VEN1=VEN2=0V,
VLX1=VLX2=0V or 5V
0.01
LX Leakage Current
Feedback Current
Input Over Voltage
Protection
EN Leakage Current
EN High-level Input
Voltage
EN Low-level Input
Voltage
Under Voltage Lock
Out
IFB1, IFB2
VIOVP
6
IEN1, IEN2
0.01
VEN_H1, VEN_H2
VIN=2.5V to 5.5V
VEN_L1, VEN_L2
VIN=2.5V to 5.5V
VUVLO
Hysteresis
Thermal Shutdown
Oct. 2011
0.1
μA
30
nA
V
0.1
1.5
μA
V
0.6
V
Rising
1.8
V
Hysteresis
0.1
V
160
°C
TSD
Rev. 1.0
BCD Semiconductor Manufacturing Limited
5
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Typical Performance Characteristics
Figure 4. Efficiency vs. Output Current
Figure 5. Efficiency vs. Load Current
Figure 6. Efficiency vs. Load Current
Oct. 2011
Figure 7. UVLO Threshold vs. Temperature
Rev. 1.0
BCD Semiconductor Manufacturing Limited
6
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Typical Performance Characteristics (Continued)
Figure 9. Output Current Limit vs. Input Voltage
Figure 8. Output Voltage vs. Output Current
Figure 10. Output Voltage vs. Temperature
Oct. 2011
Figure 11. Frequency vs. Input Voltage
Rev. 1.0
BCD Semiconductor Manufacturing Limited
7
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Typical Performance Characteristics (Continued)
Figure 12. Output Current Limit vs. Temperature
Figure 13. Frequency vs. Temperature
VOUT
200mV/div
VLX
2V/div
VEN
2V/div
Time
Figure 14. Temperature vs. Load Current
Oct. 2011
400ns/div
Figure 15. Waveform of VIN=4.5V, VOUT=1.5V, L=2.2μH
Rev. 1.0
BCD Semiconductor Manufacturing Limited
8
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Typical Performance Characteristics (Continued)
VEN
2V/div
VOUT
1V/div
VLX
2V/div
Time
200μs/div
Figure 16. Soft Start
Oct. 2011
Rev. 1.0
BCD Semiconductor Manufacturing Limited
9
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
Application Information
deviations do not much relieve. The selection of COUT
is determined by the Effective Series Resistance
(ESR) that is required to minimize output voltage
ripple and load step transients, as well as the amount
of bulk capacitor that is necessary to ensure that the
control loop is stable. Loop stability can be also
checked by viewing the load step transient response
as described in the following section. The output
ripple, △VOUT, is determined by:
The basic AUR9717 application circuit is shown in
Figure 18.
1. Inductor Selection
For most applications, the value of inductor is chosen
based on the required ripple current with the range of
2.2μH to 4.7μH.
ΔI L =
ΔVOUT ≤ ΔI L [ ESR +
V
1
VOUT (1 − OUT )
f ×L
VIN
3. Load Transient
A switching regulator typically takes several cycles to
respond to the load current step. When a load step
occurs, VOUT immediately shifts by an amount equal
to △ILOAD×ESR, where ESR is the effective series
resistance of output capacitor. △ILOAD also begins to
charge or discharge COUT generating a feedback error
signal used by the regulator to return VOUT to its
steady-state value. During the recovery time, VOUT
can be monitored for overshoot or ringing that would
indicate a stability problem.
VOUT
VOUT
][1 −
]
f × ΔI L ( MAX )
VIN ( MAX )
4. Output Voltage Setting
The DC current rating of the inductor should be at
least equal to the maximum output current plus half
the highest ripple current to prevent inductor core
saturation. For better efficiency, a lower
DC-resistance inductor should be selected.
The output voltage of AUR9717 can be adjusted by a
resistive divider according to the following formula:
VOUT = VFB × (1 +
2. Capacitor Selection
The input capacitance, CIN, is needed to filter the
trapezoidal current at the source of the top MOSFET.
To prevent large ripple voltage, a low ESR input
capacitor sized for the maximum RMS current must
be used. The maximum RMS capacitor current is
given by:
VOUT
R1
FB
[V (V − VOUT )] 2
× OUT IN
VIN
AUR 9717
R2
GND
It indicates a maximum value at VIN=2VOUT, where
IRMS=IOUT/2. This simple worse-case condition is
commonly used for design because even significant
Oct. 2011
R1
R
) = 0.6V × (1 + 1 )
R2
R2
The resistive divider senses the fraction of the output
voltage as shown in Figure 17.
1
I RMS = I OMAX
1
]
8 × f × COUT
The output ripple is the highest at the maximum input
voltage since △IL increases with input voltage.
The largest ripple current occurs at the highest input
voltage. Having a small ripple current reduces the ESR
loss in the output capacitor and improves the efficiency.
The highest efficiency is realized at low operating
frequency with small ripple current. However, larger
value inductors will be required. A reasonable starting
point for ripple current setting is △IL=40%IMAX . For a
maximum ripple current stays below a specified
value, the inductor should be chosen according to the
following equation:
L =[
AUR9717
Figure 17. Setting the Output Voltage
Rev. 1.0
BCD Semiconductor Manufacturing Limited
10
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Application Information (Continued)
NMOSFET RDS(ON)N resistance and the duty cycle
(D):
5. Efficiency Considerations
The efficiency of switching regulator is equal to the
output power divided by the input power times 100%.
It is usually useful to analyze the individual losses to
determine what is limiting efficiency and which
change could produce the largest improvement.
Efficiency can be expressed as:
RSW = RDS (ON )P × D + RDS (ON ) N × (1 − D )
Therefore, to obtain the I2R losses, simply add RSW to
RL and multiply the result by the square of the
average output current.
Efficiency=100%-L1-L2-…..
Other losses including CIN and COUT ESR dissipative
losses and inductor core losses generally account for
less than 2% of total additional loss.
Where L1, L2, etc. are the individual losses as a
percentage of input power.
Although all dissipative elements in the regulator
produce losses, two major sources usually account for
most of the power losses: VIN quiescent current and
I2R losses. The VIN quiescent current loss dominates
the efficiency loss at very light load currents and the
I2R loss dominates the efficiency loss at medium to
heavy load currents.
6. Thermal Characteristics
In most applications, the part does not dissipate much
heat due to its high efficiency. However, in some
conditions when the part is operating in high ambient
temperature with high RDS(ON) resistance and high
duty cycles, such as in LDO mode, the heat
dissipated may exceed the maximum junction
temperature. To avoid the part from exceeding
maximum junction temperature, the user should do
some thermal analysis. The maximum power
dissipation depends on the layout of PCB, the thermal
resistance of IC package, the rate of surrounding
airflow and the temperature difference between
junction and ambient.
5.1 The VIN quiescent current loss comprises two
parts: the DC bias current as given in the electrical
characteristics and the internal MOSFET switch gate
charge currents. The gate charge current results from
switching the gate capacitance of the internal power
MOSFET switches. Each cycle the gate is switched
from high to low, then to high again, and the packet
of charge, dQ moves from VIN to ground. The
resulting dQ/dt is the current out of VIN that is
typically larger than the internal DC bias current. In
continuous mode,
7. PC Board layout considerations
When laying out the printed circuit board, the
following checklist should be used to optimize the
performance of AUR9717.
I GATE = f × (Q P + Q N )
1. The power traces, including the GND trace, the LX
trace and the VIN trace should be kept direct, short and
wide.
Where QP and QN are the gate charge of power
PMOSFET and NMOSFET switches. Both the DC
bias current and gate charge losses are proportional to
the VIN and this effect will be more serious at higher
input voltages.
2. Put the input capacitor as close as possible to the
VIN and GND pins.
3. The FB pin should be connected directly to the
feedback resistor divider.
5.2 I2R losses are calculated from internal switch
resistance, RSW and external inductor resistance RL.
In continuous mode, the average output current
flowing through the inductor is chopped between
power PMOSFET switch and NMOSFET switch.
Then, the series resistance looking into the LX pin is
a function of both PMOSFET RDS(ON)P and
Oct. 2011
4. Keep the switching node LX away from the
sensitive FB pin and the node should be kept small
area.
Rev. 1.0
BCD Semiconductor Manufacturing Limited
11
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Typical Application
COUT 1
10µF
VOUT1
L1 2.2µH
R1
1
R2
2
3
Connected
to VIN
4
5
CIN2
4.7µF
EN1
FB 1
VIN2
GND
LX1
AUR9717
C1
IR2
GND
VIN1
FB2
LX2
EN2
10
C IN1
4.7µF
9
8
VIN = 2.5V to 5.5V
7
R4
6
R3
C2
IR4
VOUT2
L 2 2.2µH
Note 3: VOUT 1 = VFB1 × (1 +
COUT2
10µF
R
R1
) ; VOUT 2 = VFB2 × (1 + 3 )
R2
R4
When R2 or R4=300kΩ to 60kΩ, the IR2 or IR4=2μA to 10μA, and R1×C1 or R3×C2 should be in the range between
3×10-6 and 6×10-6 for component selection.
.
Figure 18. Typical Application Circuit of AUR9717 (Note 3)
Table 1. Component Guide
VOUT1 or VOUT2
(V)
3.3
Oct. 2011
R1 or R3
(kΩ)
453
R2 or R4
(kΩ)
100
C1 or C2
(pF)
13
L1 or L2
(μH)
2.2
2.5
320
100
18
2.2
1.8
200
100
30
2.2
1.2
100
100
56
2.2
1.0
68
100
82
2.2
Rev. 1.0
BCD Semiconductor Manufacturing Limited
12
Data Sheet
Dual 1A, 1.5MHz PWM Step-down DC-DC Converter with OVP
AUR9717
Mechanical Dimensions
WDFN-3×3-10
Oct. 2011
Rev. 1.0
Unit: mm(inch)
BCD Semiconductor Manufacturing Limited
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