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AUR9705
1.5MHZ 1A STEP-DOWN DC-DC CONVERTER
Description
Pin Assignments
(Top View)
The AUR9705 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.
Pin 1 Mark
The oscillator and timing capacitors are all built-in providing an
NC
1
EN
2
VIN
3
internal switching frequency of 1.5MHz that allows the use of small
surface mount inductors and capacitors for portable product
implementations. Additional features included Soft Start (SS), Under
Voltage Lock Out (UVLO) and Thermal Shutdown Detection (TSD) to
provide reliable product applications.
Exposed
Pad
6
FB
5
GND
4
LX
WDFN-2×2-6
(Top View)
The device is available in adjustable output voltage versions ranging
from 1V to 3.3V, and is able to deliver up to 1A.
The AUR9705 is available in WDFN-2×2-6 and TSOT-23-5 packages.
VIN
1
GND
2
EN
3
5
LX
4
FB
Features
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 Switches 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
AUR9705
Document number: DS41991 Rev. 3 - 3
TSOT-23-5
Applications
Mobile Phone, Digital Camera and MP3 Player
Headset, Radio and Other Hand-held Instrument
Post DC-DC Voltage Regulation
PDA and Notebook Computer
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AUR9705
Typical Applications Circuit
1
NC
2
VIN = 2.5V to 5.5V
EN
3
VIN
AUR9705
IR2
R2
FB 6
GND
LX
5
C1
R1
VOUT
4
L 2.2μH
CIN
4.7μF
COUT
10μF
VIN = 2.5V to 5.5V
CIN
4.7μF
1
2
3
VIN
GND
EN
AUR9705
For WDFN-2×2-6
LX
5
L 2.2μH
VOUT
C1
FB
R1
COUT
10μF
4
IR2
R2
For TSOT-23-5
Note 1:
VOUT VFB (1
R1
).
R2
When R2=300kΩ to 60kΩ, the IR2=2μA to 10μA, and R1×C1 should be in the range between 3×10-6 and 6×10-6 for component selection.
VOUT (V)
R1 (kΩ)
R2 (kΩ)
C1 (pF)
L1 (μH)
3.3
453
100
13
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
Table 1. Component Guide
AUR9705
Document number: DS41991 Rev. 3 - 3
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AUR9705
Pin Descriptions
Pin Number
Pin Name
Function
WDFN-2×2-6
TSOT-23-5
1
—
NC
No internal connection (Floating or connected to GND)
2
3
EN
Enable signal input, active high
3
1
VIN
Power supply input
4
5
LX
Connect to inductor
5
2
GND
6
4
FB
This pin is the GND reference for the NMOS power stage. It must be
connected to the system ground
Feedback voltage from the output of the power supply
Functional Block Diagram
EN
VIN
2 (3)
Saw-tooth
Generator
Bias
Generator
Oscillator
Current
Sensing
+
Soft
Start
6 (4)
+
-
FB
Control
Logic
-
+
Error
Amplifier
+
Document number: DS41991 Rev. 3 - 3
LX
-
Over Voltage
Comparator
+
Reverse Inductor
Current Comparator
Thermal
Shutdown
5 (2)
GND
A (B)
A for WDFN-2×2-6
B for TSOT-23-5
AUR9705
4 (5)
Buffer &
Dead Time
Control
Logic
Modulator
Bandgap
Reference
3 (1)
Over Current
Comparator
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AUR9705
Absolute Maximum Ratings (Note 2)
Symbol
Note 2:
Parameter
Value
Unit
VIN
Supply Input Voltage
0 to 6.0
V
VEN
Enable Input Voltage
-0.3 to VIN+0.3
V
VLX
Switch Output Voltage (Note 3)
-0.3 to VIN+0.3
V
PD
Power Dissipation (On PCB, TA=+25°C)
1.89
W
θJA
Thermal Resistance (Junction to Ambient, Simulation)
53
°C/W
θJC
Thermal Resistance (Junction to Case, Simulation)
0.85
°C/W
TJ
Operating Junction Temperature
+160
°C
TOP
Operating Temperature
-40 to +85
°C
TSTG
Storage Temperature
-55 to +150
°C
VHBM
ESD (Human Body Model)
2000
V
VMM
ESD (Machine Model)
200
V
Stresses greater than those listed under “Absolute Maximum Ratings” can 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 can affect device reliability.
3:
If the switching spike duration is less than 100ns, the absolute maximum range of VLX should be -4.5V to 7.5V.
Recommended Operating Conditions
Symbol
Parameter
Min
Max
Unit
VIN
Supply Input Voltage
2.5
5.5
V
TJ
Junction Temperature Range
-20
+125
°C
TA
Ambient Temperature Range
-40
+80
°C
AUR9705
Document number: DS41991 Rev. 3 - 3
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AUR9705
Electrical Characteristics (VIN=VEN=5V, VFB=0.6V, L=2.2μH, CIN= 4.7μF, COUT=10μF, TA=+25°C, unless otherwise specified.)
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
VIN
Input Voltage Range
—
2.5
—
5.5
V
IOFF
Shutdown Current
VEN=0V
—
0.1
1
μA
VFB
Regulated1Feedback Voltage
For Adjustable Output Voltage
0.585
0.6
0.615
V
Regulated Output Voltage
Accuracy
VIN=2.5V to 5.5V,
IOUT=0 to 1A
-3
—
3
%
IPK
Peak Inductor Current
VFB=0.5V
—
1.5
—
A
fOSC
Oscillator Frequency
—
1.2
1.5
1.8
MHz
RON(P)
PMOSFET RON
IOUT =200mA
—
0.25
—
Ω
RON(N)
NMOSFET RON
IOUT =200mA
—
0.27
—
Ω
IQ
Quiescent Current
IOUT=0A, VFB=0.7V
—
100
—
μA
ILX
LX Leakage Current
VEN=0V, VLX=0V or 5V
—
0.01
0.1
μA
IFB
Feedback Current
—
—
—
30
nA
IEN
EN Leakage Current
—
—
0.01
0.1
μA
VEN_H
EN High-Level Input Voltage
VIN=2.5V to 5.5V
1.5
—
—
V
VEN_L
EN Low-Level Input Voltage
VIN=2.5V to 5.5V
—
—
0.6
V
VUVLO
Under Voltage Lock Out
Rising
—
1.8
—
V
Hysteresis
—
—
0.1
—
V
Thermal Shutdown
—
—
+160
—
°C
ΔVOUT/VOUT
—
TSD
AUR9705
Document number: DS41991 Rev. 3 - 3
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AUR9705
Performance Characteristics
Efficiency vs. Output Current (VOUT=2.5V)
100
100
90
90
80
80
70
70
60
Efficiency (%)
Efficiency (%)
Efficiency vs. Output Current (VOUT=1.2V)
60
50
COUT=10F
40
L=2.2H
VIN=2.5V
30
VIN=3.3V
30
20
VIN=4.2V
20
VIN=5V
10
VIN=5.5V
50
COUT=10F
40
L=2.2H
VIN=3.3V
VIN=4.2V
VIN=5V
10
VIN=5.5V
0
0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0.0
0.1
0.2
0.3
Output Current (A)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Output Current (A)
Efficiency vs. Output Current (VOUT=3.3V)
Frequency vs. Input Voltage
100
1.60
90
1.55
80
1.50
Frequency (MHz)
Efficiency (%)
70
60
50
40
COUT=10F
30
L=2.2H
VIN=4.2V
20
VIN=5.0V
10
VIN=5.5V
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.40
1.35
VOUT=1.2V
1.30
L=2.2H
COUT=10F
1.25
0
0.0
1.45
1.0
1.20
2.5
Output Current (A)
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Output Voltage vs. Output Current
(VOUT=1.2±0.03V)
Output Ripple
(VIN=5.0V, VOUT=3.3V, IOUT=1A)
1.25
L=2.2H
COUT=10F
1.24
Output Voltage (V)
1.23
2.5V
3.3V
4.2V
5V
5.5V
1.22
1.21
1.20
1.19
1.18
1.17
1.16
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Output Current (A)
AUR9705
Document number: DS41991 Rev. 3 - 3
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AUR9705
Performance Characteristics (continued)
.
Power Off through VIN
(VIN=VEN=5.0 to 0V, VOUT=3.3V, IOUT=1A)
Soft Start (Power Up through EN)
(VIN=5.0V, VOUT=3.3V, IOUT=1A, VEN=0 to 5.0V)
Load Transient
(VIN=5.0V, VOUT=1.2V, IOUT=0.1 to 1A)
Load Transient
(VIN=5.0V, VOUT=3.3V, IOUT=0.1 to 1A)
Short Circuit
(VIN=5.0V, VOUT=3.3V Short to GND, IOUT=1A)
AUR9705
Document number: DS41991 Rev. 3 - 3
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AUR9705
Application Information
The basic AUR9705 application circuit is shown in Typical Applications Circuit, external components selection is determined by the load current and is
critical with the selection of inductor and capacitor values.
1. Inductor Selection
For most applications, the value of inductor is chosen based on the required ripple current with the range of 2.2H to 4.7H.
I
L
V
1
VOUT (1 OUT )
f L
VIN
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 [
VOUT
VOUT
][1
]
f I L ( MAX )
VIN ( MAX )
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.
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:
1
I RMS
I OMAX
[V (V VOUT )] 2
OUT IN
VIN
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 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:
VOUT I L [ ESR
1
]
8 f COUT
The output ripple is the highest at the maximum input voltage since IL increases with input voltage.
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 V OUT to its steady-state value. During the recovery time, VOUT can be monitored
for overshoot or ringing that would indicate a stability problem.
4. Output Voltage Setting
The output voltage of AUR9705 can be adjusted by a resistive divider according to the following formula:
VOUT VFB (1
R1
R
) 0.6V (1 1 )
R2
R2
The resistive divider senses the fraction of the output voltage as shown in Figure of Setting the Output Voltage.
AUR9705
Document number: DS41991 Rev. 3 - 3
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AUR9705
Application Information (continued)
VOUT
R1
FB
AUR9705
R2
GND
Setting the Output Voltage
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:
Efficiency=100%-L1-L2-…..
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 I 2R loss dominates the
efficiency loss at medium to heavy load current.
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,
I GATE f (QP QN )
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.
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) and NMOSFET
RDS(ON) resistance and the duty cycle (D):
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.
Other losses including CIN and COUT ESR dissipative losses and inductor core losses generally account for less than 2 % of total additional loss.
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.
AUR9705
Document number: DS41991 Rev. 3 - 3
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AUR9705
Ordering Information
AUR9705 XX XX - XX
Product Name
Package
Packing
RoHS/Green
A: Adjustable Output
G1 : RoHS Compliant
and Green
Temperature Range
WDFN-2×2-6
Package
D : WDFN-2x2-6
H : TSOT-23-5
Part Number
Marking ID
Packing
AUR9705AGD
705
Tape & Reel
AUR9705AGH
9705AG
Tape & Reel
-40 to +80°C
TSOT-23-5
Package Outline Dimensions (All dimensions in mm (inch).)
Please see http://www.diodes.com/package-outlines.html for the latest version.
(1)
Package Type: WDFN-2×2-6
BOTTOM VIEW
TOP VIEW
1. 950(0. 077)
2. 050(0. 081)
1. 300(0. 051) REF
N4
N6
1. 350(0. 053)
1. 450(0. 057)
1. 950(0. 077)
2. 050(0. 081)
0. 550(0. 022)
0. 650(0. 026)
PIN #1
IDENTIFICATION
Pin 1 Mark
0. 250(0. 010)
0. 350(0. 014)
N3
0. 250(0. 010)
0. 350(0. 014)
N1
0. 650(0. 026) BSC
SIDE VIEW
0. 203(0. 008) REF
0. 700(0. 028)
0. 800(0. 031)
AUR9705
Document number: DS41991 Rev. 3 - 3
0. 000(0. 000)
0. 050(0. 002)
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AUR9705
Package Outline Dimensions (continued) ( All dimensions in mm(inch).)
Please see http://www.diodes.com/package-outlines.html for the latest version.
(2)
Package Type: TSOT-23-5
2.800(0.110)
3.000(0.118)
5
0°
8°
R0.100(0.004)
MIN
4
0.600(0.024)
REF
2.600(0.102)
3.000(0.118)
1.500(0.059)
1.700(0.067)
0.300(0.012)
0.500(0.020)
2
1
3
0.950(0.037)
TYP
0.100(0.004)
0.250(0.010)
0.300(0.012)
0.510(0.020)
GAUGE PLANE
0.250(0.010)
TYP
1.900(0.075)
TYP
5°
A1
A
4X7
°
A2
A
Symbol
A1
A2
min(mm) max(mm) min(inch) max(inch) min(mm) max(mm) min(inch) max(inch) min(mm) max(mm) min(inch) max(inch)
Option1 0.700 0.900 0.028 0.035 0.700 0.800 0.028 0.031
Option2
-
AUR9705
Document number: DS41991 Rev. 3 - 3
1.000
-
.
0.039 0.840 0.900 0.033 0.035
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0.000 0.100
0.000 0.004
0.010 0.100
0.000 0.004
February 2020
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AUR9705
Suggested Pad Layout
Please see http://www.diodes.com/package-outlines.html for the latest version.
(1)
Package Type: WDFN-2×2-6
E
Y2
Y
X2
Y1
X1
Dimensions
Y
(mm)/(inch)
X1
(mm)/(inch)
Y1
(mm)/(inch)
X2
(mm)/(inch)
Y2
(mm)/(inch)
E
(mm)/(inch)
Value
2.400/0.094
0.400/0.016
0.600/0.024
1.500/0.059
0.700/0.028
0.650/0.026
AUR9705
Document number: DS41991 Rev. 3 - 3
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AUR9705
Suggested Pad Layout (continued)
Please see http://www.diodes.com/package-outlines.html for the latest version.
(2)
Package Type: TSOT-23-5
E
E
Z
Y
X
Dimensions
E
(mm)/(inch)
X
(mm)/(inch)
Y
(mm)/(inch)
Z
(mm)/(inch)
Value
0.950/0.037
0.700/0.028
1.000/0.039
3.199/0.126
AUR9705
Document number: DS41991 Rev. 3 - 3
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IMPORTANT NOTICE
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes
without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the
application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or
trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume
all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated
website, harmless against all damages.
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel.
Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and
hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or
indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.
Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings
noted herein may also be covered by one or more United States, international or foreign trademarks.
This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the
final and determinative format released by Diodes Incorporated.
LIFE SUPPORT
Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the
labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the
failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any
use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related
information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its
representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2020, Diodes Incorporated
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AUR9705
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