Anpec APW7145 3a, 12v, synchronous-rectified buck converter Datasheet

APW7145
3A, 12V, Synchronous-Rectified Buck Converter
Features
General Description
•
Wide Input Voltage from 4.3V to 14V
The APW7145 is a 3A synchronous-rectified Buck con-
•
Output Current up to 3A
•
Adjustable Output Voltage from 0.8V to VIN
verter with integrated 55mΩ power MOSFETs. The
APW7145, designed with a current-mode control scheme,
can convert wide input voltage of 4.3V to 14V to the output
voltage adjustable from 0.8V to VIN to provide excellent
- ±2% System Accuracy
•
55mΩ Integrated Power MOSFETs
•
High Efficiency up to 95%
output voltage regulation.
For high efficiency over all load current range, the
- Automatic Skip/PWM Mode Operation
•
APW7145 is equipped with an automatic Skip/PWM mode
operation. At light load, the IC operates in the Skip mode,
Current-Mode Operation
- Easy Feedback Compensation
which keeps a constant minimum inductor peak current,
to reduce switching losses. At heavy load, the IC works in
- Stable with Low ESR Output Capacitors
- Fast Load/Line Transient Response
PWM mode, which inductor peak current is programmed
by the COMP voltage, to provide high efficiency and excel-
•
Power-On-Reset Monitoring
•
Fixed 500kHz Switching Frequency in PWM Mode
•
Built-In Digital Soft-Start and Soft-Stop
•
Current-Limit Protection with Frequency Foldback
•
123% Over-Voltage Protection
•
Hiccup-Mode 50% Under-Voltage Protection
•
Over-Temperature Protection
•
<3µA Quiescent Current in Shutdown Mode
•
This device, available SOP-8P and DFN4x4-8 packages,
provides a very compact system solution with minimal
SOP-8P and Compact 4mmx4mm DFN-8
external components and PCB area.
lent output voltage regulation.
The APW7145 is also equipped with power-on-reset, softstart, soft-stop, and whole protections (under-voltage,
over-voltage, over-temperature, and current-limit) into a
single package. In shutdown mode, the supply current
drops below 3µA.
(DFN4x4-8) Packages
•
Lead Free and Green Devices Available
100
(RoHS Compliant)
90
80
Applications
70
60
VIN=5V, VOUT=3.3V, L1=2.2µH
•
OLPC, UMPC
50
•
Notebook Computer
40
VIN=12V, VOUT=3.3V, L1=4.7µH
•
Handheld Portable Device
30
VIN=5V, VOUT=1.2V, L1=2.2µH
•
VIN=12V, VOUT=5V, L1=6.8µH
20
Step-Down Converters Requiring High Efficiency
10
and 3A Output Current
0
0.001
VIN=12V, VOUT=2V, L1=3.3µH
0.01
0.1
1
10
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise
customers to obtain the latest version of relevant information to verify before placing orders.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
1
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APW7145
Pin Configuration
APW7145
NC
VIN
AGND
FB
1
2
3
4
APW7145
8
7
6
5
9
LX
PGND
LX
EN
COMP
NC
VIN
AGND
FB
1
2
3
4
SOP-8P
(Top View)
8
7
6
5
PGND
LX
EN
COMP
DFN4x4-8
(Top View)
The Pin 7 must be connected to the Exposed Pad
Ordering and Marking Information
Package Code
KA : SOP-8P
QA: DFN4x4-8
Operating Ambient Temperature Range
I : -40 to 85 oC
Handling Code
TR : Tape & Reel
Assembly Material
G : Halogen and Lead Free Device
APW7145
Assembly Material
Handling Code
Temperature Range
Package Code
APW7145 KA :
APW7145
XXXXX
XXXXX - Date Code
APW7145 QA :
APW7145
XXXXX
XXXXX - Date Code
Note: ANPEC lead-free products contain molding compounds/die attach materials and 100% matte tin plate termination finish; which
are fully compliant with RoHS. ANPEC lead-free products meet or exceed the lead-free requirements of IPC/JEDEC J-STD-020D for
MSL classification at lead-free peak reflow temperature. ANPEC defines “Green” to mean lead-free (RoHS compliant) and halogen
free (Br or Cl does not exceed 900ppm by weight in homogeneous material and total of Br and Cl does not exceed 1500ppm by
weight).
Absolute Maximum Ratings
Symbol
(Note 1)
Parameter
VIN
VIN Supply Voltage (VIN to AGND)
VLX
LX to GND Voltage
PGND to AGND Voltage
EN to AGND Voltage
FB, COMP to AGND Voltage
PD
Power Dissipation
TSDR
Unit
V
> 100ns
-1 ~ VIN+1
< 100ns
- 5 ~ VIN+5
Storage Temperature
Maximum Lead Soldering Temperature, 10 Seconds
V
-0.3 ~ +0.3
V
-0.3 ~ VIN+0.3
V
-0.3 ~ 6
V
Internally Limited
Maximum Junction Temperature
TSTG
Rating
-0.3 ~ 15
W
150
o
-65 ~ 150
o
260
o
C
C
C
Note1: Stresses beyond 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 rating conditions for extended periods may affect device
reliability
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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APW7145
Thermal Characteristics
Symbol
θJA
θJC
Parameter
Typical Value
Junction-to-Ambient Thermal Resistance in Free Air
Unit
(Note 2)
SOP-8P
DFN4x4-8
50
65
o
SOP-8P
DFN4x4-8
20
30
o
C/W
Junction-to-Case Resistance in Free Air (Note 3)
C/W
Note 2: θJA is measured with the component mounted on a high effective thermal conductivity test board in free air.
Note 3: The case temperature is measured at the center of the exposed pad on the underside of the SOP-8P and DFN4x4-8 packages.
Recommended Operating Conditions (Note 4)
Symbol
VIN
Parameter
Range
Unit
VIN Supply Voltage
4.3 ~ 14
V
VOUT
Converter Output Voltage
0.8 ~ VIN
V
IOUT
Converter Output Current
0~3
A
CIN
Converter Input Capacitor (MLCC)
COUT
LOUT
TA
TJ
8 ~ 50
µF
Converter Output Capacitor
20 ~ 1000
µF
Effective Series Resistance
0 ~ 60
mΩ
Converter Output Inductor
1 ~ 22
µH
Resistance of the Feedback Resistor connected from FB to GND
1 ~ 20
kΩ
Ambient Temperature
Junction Temperature
-40 ~ 85
o
-40 ~ 125
o
C
C
Note 4: Refer to the Typical Application Circuits.
Electrical Characteristics
Refer to the “Typical Application Circuits”. These specifications apply over VIN=12V, VOUT=3.3V and TA= -40 ~ 85°C, unless otherwise
specified. Typical values are at TA=25°C.
Symbol
Parameter
APW7145
Test Conditions
Unit
Min.
Typ.
Max.
VFB = VREF +50mV, VEN=3V, LX=NC
-
0.5
1.5
mA
VEN = 0V
-
-
3
µA
3.9
4.1
4.3
V
-
0.5
-
V
-
0.8
-
V
TJ = 25 C, IOUT=10mA, VIN=12V
-1.0
-
+1.0
IOUT=10mA~3A, VIN=4.75~14V
-2.0
-
+2.0
SUPPLY CURRENT
IVIN
IVIN_SD
VIN Supply Current
VIN Shutdown Supply Current
POWER-ON-RESET (POR) VOLTAGE THRESHOLD
VIN POR Voltage Threshold
VIN rising
VIN POR Hysteresis
REFERENCE VOLTAGE
VREF
Reference Voltage
Regulated on FB pin
o
Output Voltage Accuracy
%
Line Regulation
VIN = 4.75V to 14V
-
+0.02
-
%/V
Load Regulation
IOUT = 0.5A ~ 3A
-
-0.04
-
%/A
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
3
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APW7145
Electrical Characteristics (Cont.)
Refer to the “Typical Application Circuits”. These specifications apply over VIN=12V, VOUT=3.3V and TA= -40 ~ 85°C, unless otherwise
specified. Typical values are at TA=25°C.
Symbol
Parameter
APW7145
Test Conditions
Unit
Min.
Typ.
Max.
450
500
550
kHz
-
80
-
kHz
OSCILLATOR AND DUTY CYCLE
FOSC
TON_MIN
Oscillator Frequency
TJ = -40 ~ 125oC, VIN = 4.75 ~ 14V
Foldback Frequency
VOUT = 0V
Maximum Converter’s Duty
-
99
-
%
Minimum Pulse Width of LX
-
150
-
ns
CURRENT-MODE PWM CONVERTER
Gm
Error Amplifier Transconductance
VFB=VREF±50mV
-
200
-
µA/V
Error Amplifier DC Gain
COMP = NC
-
80
-
dB
-
0.1
-
V/A
Between VIN and Exposed Pad,
VIN = 5V, TJ=25°C
-
70
100
Between VIN and Exposed Pad,
VIN = 12V, TJ=25°C
-
55
80
Between GND and Exposed Pad,
VIN = 5V, TJ=25°C
-
55
100
Between GND and Exposed Pad,
VIN = 12V, TJ=25°C
-
45
80
Current-Sense to COMP Voltage
Transresistance
High-Side Switch Resistance
Low-Side Switch Resistance
mΩ
mΩ
PROTECTIONS
High-Side Switch Current-limit
Peak Current
5
6.5
8
A
VTH_UV
FB Under-Voltage Threshold
VFB falling
45
50
55
%
VTH_OV
FB Over-Voltage Threshold
VFB rising
118
123
128
%
ILIM
TOTP
FB Under-Voltage Debounce
-
1
-
µs
Over-Temperature Trip Point
-
150
-
o
Over-Temperature Hysteresis
TD
Dead-Time
VLX = -0.7V
C
-
40
-
o
-
20
-
ns
1.5
2
2.5
ms
0.5
V
C
SOFT-START, SOFT-STOP, ENABLE, AND INPUT CURRENTS
TSS
Soft-Start / Soft-Stop Interval
EN Low Logic Level
VEN falling
-
-
EN High Logic Level
VEN rising
2.1
-
-
V
High-side Switch Leakage Current
VEN = 0V, VLX = 0V
-
-
2
µA
-100
-
+100
nA
-100
-
+100
nA
IFB
FB Pin Input Current
IEN
EN Pin Input Current
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
VEN = 0V ~ VIN
4
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APW7145
Typical Operating Characteristics
(Refer to the application circuit 1 in the section “Typical Application Circuits”, VIN=12V, VOUT=3.3V, L1=4.7µH)
Output Current vs. Output Voltage
3.4
90
3.38
80
3.36
Output Voltage, VOUT (V)
Efficiency (%)
Output Current vs. Efficiency
100
70
60
VIN=5V, VOUT=3.3V, L1=2.2µH
50
VIN=12V, VOUT=5V, L1=6.8µH
40
VIN=12V, VOUT=3.3V, L1=4.7µH
30
VIN=5V, VOUT=1.2V, L1=2.2µH
20
10
VIN=12V, VOUT=2V, L1=3.3µH
0
0.001
3.34
3.32
3.3
3.28
3.26
3.24
3.22
3.2
0.01
0.1
1
10
0
1
Output Current, IOUT (A)
Current Limit Level (Peak Current)
3.4
IOUT=500mA
Output Voltage, VOUT (V)
3.38
Current Limit Level, ILIM (A)
3
Output Voltage vs. Supply Voltage
vs. Junction Temperature
7
2
Output Current, IOUT (A)
7.5
7
6.5
6
3.36
3.34
3.32
3.3
3.28
3.26
3.24
3.22
5.5
3.2
-40
-20
0
20
40
60
80
100 120 140
4
6
Junction Temperature, TJ (oC)
10
12
14
Reference Voltage vs. Junction Temperature
VIN Input Current vs. Supply Voltage
2.0
0.816
Reference Voltage, VREF (V)
VFB=0.85V
VIN Input Current, IVIN (mA)
8
Supply Voltage, VIN (V)
1.5
1.0
0.5
0.812
0.808
0.804
0.800
0.796
0.792
0.788
0.784
-50
0.0
0
2
4
6
8
10
12
14
Supply Voltage, VIN (V)
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
-25
0
25
50
75
100
125
150
o
Junction Temperature, TJ ( C)
5
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APW7145
Typical Operating Characteristics (Cont.)
(Refer to the application circuit 1 in the section “Typical Application Circuits”, VIN=12V, VOUT=3.3V, L1=4.7µH)
Oscillator Frequency vs.
Junction Temperature
Oscillator Frequency, FOSC (kHz)
550
540
530
520
510
500
490
480
470
460
450
-50
-25
0
25
50
75
100
125
150
o
Junction Temperature, TJ ( C)
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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APW7145
Operating Waveforms
(Refer to the application circuit 1 in the section “Typical Application Circuits”, VIN=12V, VOUT=3.3V, L1=4.7µH)
Power On
Power Off
IOUT=3A
IOUT=3A
VIN
VIN
1
1
VOUT
VOUT
2
2
IL1
IL1
3
3
CH1 : VIN , 5V/div
CH2 : VOUT , 2V/div
CH3 : IL1 , 2A/div
Time : 1ms/div
CH1 : VIN , 5V/div
CH2 : VOUT , 2V/div
CH3 : IL1 , 2A/div
Time : 10ms/div
Shutdown
Enable
IOUT=3A
1
IOUT=3A
VEN
VEN
1
VOUT
VOUT
2
2
IL1
IL1
3
3
CH1 : VEN , 5V/div
CH2 : VOUT , 2V/div
CH3 : IL1, 2A/div
Time : 100µs/div
CH1 : VEN , 5V/div
CH2 : VOUT , 2V/div
CH3 : IL1 , 2A/div
Time : 1ms/div
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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APW7145
Operating Waveforms (Cont.)
(Refer to the application circuit 1 in the section “Typical Application Circuits”, VIN=12V, VOUT=3.3V, L1=4.7µH)
Short Current
Short Circuit
IOUT =3~7A
VOUT is shorted to GND by a short wire
VLx
1
VLX
1
VOUT
VOUT
2
2
IL1
IL1
3
3
CH1 : VLX , 10V/div
CH2 : VOUT , 2V/div
CH3 : IL1 , 5A/div
Time : 20µs/div
CH1 : VLX , 5V/div
CH2 : VOUT , 200mV/div
CH3 : IL1 , 5A/div
Time : 5ms/div
Load Transient Response
Load Transient Response
1
IOUT= 50mA-> 3A ->50mA
IOUT rising/falling time=10µs
VOUT
IOUT= 0.5A-> 3A ->0.5A
IOUT rising/falling time=10µs
1
VOUT
IL1
IL1
2
2
CH1 : VOUT , 200mV/div
CH1 : VOUT , 100mV/div
CH2 : IL1 , 2A/div
CH2 : IL1 , 2A/div
Time : 100µs/div
Time : 100µs/div
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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APW7145
Operating Waveforms (Cont.)
(Refer to the application circuit 1 in the section “Typical Application Circuits”, VIN=12V, VOUT=3.3V, L1=4.7µH)
Switching Waveform
Switching Waveform
VLX
IOUT=0.2A
VLX
IOUT=3A
1
1
IL1
IL1
2
2
CH1 : VLX , 5V/div
CH2 : IL1 , 2A/div
Time : 1µs/div
CH1 : VLX , 5V/div
CH2 : IL1 , 2A/div
Time : 1µs/div
Line Transient
VIN= 5~12V
Over-Voltage Protection
VIN
VIN rising/falling time=20µs
VIN
VOUT
1
1
VOUT
2
2
VLX
3
IL1
4
IL1
3
IOUT=-1A
CH1 : VIN , 5V/div
CH2 : VOUT , 50mV/div (Voffset=3.3V)
CH3 : IL1 , 2A/div
Time : 100µs/div
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
CH1 : VIN , 5V/div
CH2 : VOUT , 2V/div
CH3 : VLX , 5V/div
CH4 : IL1 , 5A/div
Time : 20µs/div
9
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APW7145
Pin Description
PIN
FUNCTION
NO.
NAME
1
NC
No Connection.
2
VIN
Power Input. VIN supplies the power (4.3V to 14V) to the control circuitry, gate drivers
and step-down converter switches. Connecting a ceramic bypass capacitor and a
suitably large capacitor between VIN and both of AGND and PGND to eliminate
switching noise and voltage ripple on the input to the IC.
3
AGND
Ground of MOSFET Gate Drivers and Control Circuitry.
4
FB
Output Feedback Input. The APW7145 senses the feedback voltage via FB and
regulates the voltage at 0.8V. Connecting FB with a resistor-divider from the converter’s
output sets the output voltage from 0.8V to VIN.
5
COMP
Output of the error amplifier. Connecting a series RC network from COMP to GND to
compensate the regulation control loop. In some cases, an additional capacitor from
COMP to GND is required.
6
EN
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn
on the regulator, drive it low to turn it off. Connecting this pin to VIN if it is not used.
7
LX
Power Switching Output. LX is the junction of the high-side and low-side power
MOSFETs to supply power to the output LC filter.
8
PGND
Power Ground of the APW7145, which is the source of the N-channel power MOSFET.
Connect this pin to the system ground with lowest impedance.
LX
Power Switching Output. LX is the Drain of the P-channel MOSFET to supply power to
the output. The Exposed Pad provides current with lower impedance than the Pin 7.
Connecting the pad to output LC filter via a top-layer thermal pad on PCBs. The PCB will
be a heat sink of the IC.
9
(Exposed Pad)
Block Diagram
VIN
Current Sense
Amplifier
Power-OnReset
Zero-Crossing
Comparator
POR
OVP
123%VREF
50%VREF
UVP
UG
Soft-Start /
Soft-Stop
and
Fault Logic
Gate
Driver
Soft-Start /
Soft-Stop
FB
Inhibit
LX
Gate
Control
Gm
VREF
VIN
Current
Limit
Error
Amplifier
VIN
LG
Current
Compartor
COMP
Gate
Driver
PGND
Slope
Compensation
EN
Enable/
Shutdown
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
OverTemperature
Protection
FB
10
Oscillator
500kHz
AGND
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APW7145
Typical Application Circuit
1. 4.3~14V Single Power Input Step-down Converter (with a Ceramic Output Capacitor)
VIN
C1
2
VIN
L1
3A
Enable
6
LX
EN
U1
LX
APW7145
Shutdown
PGND
5
VOUT
7
8
C2
COMP
R3
(±
5%)
C3
(±30%)
9
FB
AGND
3
R1
±
1%
4
R2
±1%
C4
(±
30%, Optional)
a. Cost-effective Feedback Compensation (C4 is no connection)
V IN(V)
V OUT(V)
12
5
12
L1(µF)
C2(µF)
C2 ESR(mΩ)
R1(kΩ)
R2(kΩ)
R3(kΩ)
C3(pF)
6.8
22
5
63.0
12
33.0
820
5
6.8
44
3
63.0
12
68.0
820
12
3.3
4.7
22
5
46.9
15
27.0
1000
12
3.3
4.7
44
3
46.9
15
56.0
1000
12
2
3.3
22
5
30.0
20
18.0
1800
12
2
3.3
44
3
30.0
20
33.0
1800
12
1.8
3.3
22
5
18.8
15
15.0
1800
12
1.8
3.3
44
3
18.8
15
30.0
1800
5
3.3
2.2
22
5
46.9
15
27.0
470
5
3.3
2.2
44
3
46.9
15
56.0
470
5
1.8
2.2
22
5
25.0
20
15.0
820
5
1.8
2.2
44
3
25.0
20
30.0
820
5
1.5
2.2
22
5
21.9
25
12.0
1000
5
1.5
2.2
44
3
21.9
25
24.0
1000
5
1.2
2.2
22
5
7.5
15
10.0
1200
5
1.2
2.2
44
3
7.5
15
20.0
1200
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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APW7145
Typical Application Circuit (Cont.)
b. Fast-Transient-Response Feedback Compensation (C4 is connected)
VIN(V)
VOUT(V)
L1(µH)
C2(µF)
C2 ESR(mΩ)
R1(kΩ)
R2(kΩ)
R3(kΩ)
C3(pF)
C4(pF)
12
5
6.8
22
5
63.0
12
43
680.0
27
12
5
6.8
44
3
63.0
12
82
680.0
27
12
3.3
4.7
22
5
46.9
15
27
1000.0
27
12
3.3
4.7
44
3
46.9
15
56
1000.0
27
12
2
3.3
22
5
30.0
20
18
1800.0
27
12
2
3.3
44
3
30.0
20
33
1800.0
27
12
1.8
3.3
22
5
18.8
15
15
1800.0
33
12
1.8
3.3
44
3
18.8
15
30
1800.0
33
5
3.3
2.2
22
5
46.9
15
27
470.0
27
5
3.3
2.2
44
3
46.9
15
56
470.0
27
5
1.8
2.2
22
5
25.0
20
15
820.0
56
5
1.8
2.2
44
3
25.0
20
30
820.0
56
5
1.5
2.2
22
5
22
25
12
1000
56
5
1.5
2.2
44
3
22
25
24
1000
56
5
1.2
2.2
22
5
7.5
15
10
1200
180
5
1.2
2.2
44
3
7.5
15
20
1200
270
2. +12V Single Power Input Step-down Converter (with an Electrolytic Output Capacitor)
C1
2.2µF
2
VIN
C5
470µF
VIN
12V
L1
4.7µH /3A
Enable
6
LX
EN
U1
LX
APW7145
Shutdown
PGND
5
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
8
R1
46.9K
1%
COMP
R3
100K
C3
1000pF
9
7
FB
AGND
3
4
VOUT
3.3V/3A
C2
470µF
(ESR=30mΩ)
R2
15K
1%
12
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APW7145
Function Description
VIN Power-On-Reset (POR)
The under-voltage threshold is 50% of the nominal output voltage. The undervoltage comparator has a built-in
The APW7145 keeps monitoring the voltage on the VIN
2µs noise filter to prevent the chips from wrong UVP shutdown caused by noise. The under-voltage protection
pin to prevent wrong logic operations which may occur
when VIN voltage is not high enough for the internal con-
works in a hiccup mode without latched shutdown. The
IC will initiate a new soft-start process at the end of the
trol circuitry to operate. The VIN POR has a rising threshold of 4.1V (typical) with 0.5V of hysteresis.
preceding delay.
During start-up, the VIN voltage must exceed the enable
voltage threshold. Then, the IC starts a start-up process
Over-Voltage Protection (OVP)
and ramps up the output voltage to the voltage target.
The over-voltage function monitors the output voltage by
FB pin. When the FB voltage increase over 123% of the
reference voltage due to the high-side MOSFET failure,
Digital Soft-Start
The APW7145 has a built-in digital soft-start to control the
rise rate of the output voltage and limit the input current
or for other reasons, the over-voltage protection comparator will force the low-side MOSFET gate driver high. This
surge during start-up. During soft-start, an internal voltage
ramp (VRAMP), connected to one of the positive inputs of
action actively pulls down the output voltage and eventually attempts to blow the internal bonding wires. As soon
the error amplifier, rises up from 0V to 0.95V to replace the
reference voltage (0.8V) until the voltage ramp reaches
as the output voltage is within regulation, the OVP comparator is disengaged. The chip will restore its normal
the reference voltage.
During soft-start without output over-voltage, the APW7145
operation. This OVP scheme only clamps the voltage overshoot and does not invert the output voltage when other-
converter’s sinking capability is disabled until the output
voltage reaches the voltage target.
wise activated with a continuously high output from lowside MOSFET driver - a common problem for OVP
Digital Soft-Stop
schemes with a latch.
At the moment of shutdown controlled by EN signal, un-
Over-Temperature Protection (OTP)
der-voltage event, or over-temperature protection, the
APW7145 initiates a digital soft-stop process to discharge
The over-temperature circuit limits the junction tempera-
the output voltage in the output capacitors. Certainly, the
load current also discharges the output voltage.
ture of the APW7145. When the junction temperature exceeds TJ = +150oC, a thermal sensor turns off the both
power MOSFETs, allowing the devices to cool. The thermal sensor allows the converters to start a start-up pro-
During soft-stop, the internal voltage ramp (VRAMP) falls
down from 0.95V to 0V to replace the reference voltage.
cess and regulate the output voltage again after the junction temperature cools by 40 oC. The OTP is designed
Therefore, the output voltage falls down slowly at light load.
After the soft-stop interval elapses, the soft-stop process
ends and the the IC turns on the low-side power MOSFET.
with a 40 oC hysteresis to lower the average TJ during
continuous thermal overload conditions, increasing life-
Output Under-Voltage Protection (UVP)
time of the APW7145.
In the operational process, if a short-circuit occurs, the
Enable/Shutdown
output voltage will drop quickly. Before the current-limit
circuit responds, the output voltage will fall out of the re-
Driving EN to the ground initiates a soft-stop process
and then places the APW7145 in shutdown. When in
shutdown, after the soft-stop process is completed, the
quired regulation range. The under-voltage continually
monitors the FB voltage after soft-start is completed. If a
internal power MOSFETs turns off, all internal circuitry
shuts down and the quiescent supply current reduces to
load step is strong enough to pull the output voltage lower
than the under-voltage threshold, the IC shuts down
less than 3mA.
converter’s output.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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APW7145
Function Description (Cont.)
Current-Limit Protection
The APW7145 monitors the output current, flowing through
the high-side power MOSFET, and limits the current peak
at current-limit level to prevent loads and the IC from damages during overload or short-circuit conditions.
Frequency Foldback
The foldback frequency is controlled by the FB voltage.
When the output is shortened to the ground, the frequency
of the oscillator will be reduced to 80kHz. This lower frequency allows the inductor current to safely discharge,
thereby preventing current runaway. The oscillator’s frequency will gradually increase to its designed rate when
the feedback voltage on FB again approaches 0.8V.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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APW7145
Application Information
T=1/FOSC
Setting Output Voltage
The regulated output voltage is determined by:
VOUT
VLX
R1
= 0.8 ⋅ (1 +
)
R2
DT
(V)
I
IOUT
IL
Suggested R2 is in the range from 1K to 20kΩ. For
portable applications, a 10K resistor is suggested for R2.
To prevent stray pickup, please locate resistors R1 and R2
IOUT
IQ1
close to APW7145.
I
ICOUT
Input Capacitor Selection
Use small ceramic capacitors for high frequency
VOUT
decoupling and bulk capacitors to supply the surge current needed each time the P-channel power MOSFET (Q1)
VOUT
turns on. Place the small ceramic capacitors physically
close to the VIN and between the VIN and the GND.
Figure 1. Converter Waveforms
The important parameters for the bulk input capacitor are
Output Capacitor Selection
the voltage rating and the RMS current rating. For reliable
operation, select the bulk capacitor with voltage and
An output capacitor is required to filter the output and supply the load transient current. The filtering requirements
are the function of the switching frequency and the ripple
current ratings above the maximum input voltage and largest RMS current required by the circuit. The capacitor volt-
current (∆I). The output ripple is the sum of the voltages,
having phase shift, across the ESR, and the ideal output
age rating should be at least 1.25 times greater than the
maximum input voltage and a voltage rating of 1.5 times is
capacitor. The peak-to-peak voltage of the ESR is calculated as the following equations:
a conservative guideline. The RMS current (IRMS) of the
bulk input capacitor is calculated as the following equation:
IRMS = IOUT ⋅ D ⋅ (1- D)
(A)
where D is the duty cycle of the power MOSFET.
For a through hole design, several electrolytic capacitors
may be needed. For surface mount designs, solid tanta-
D=
VOUT
VIN
........... (1)
∆I =
VOUT ·(1 - D)
FOSC ·L
........... (2)
VESR = ∆I. ⋅ ESR
lum capacitors can be used, but caution must be exercised with regard to the capacitor surge current rating.
........... (3)
The peak-to-peak voltage of the ideal output capacitor is
calculated as the following equation:
∆VCOUT =
VIN
VIN
IQ1
CIN
........... (4)
For the applications using bulk capacitors, the ∆VCOUT is
Q1
IL
LX
Q2
∆I
(V)
8 ⋅ FOSC ⋅ COUT
much smaller than the VESR and can be ignored. Therefore,
the AC peak-to-peak output voltage (∆VOUT ) is shown as
IOUT
VOUT
L
ICOUT
below:
ESR
∆VOUT = ∆ I ⋅ ESR
COUT
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
15
(V)
........... (5)
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APW7145
Application Information (Cont.)
VOUT ·(VIN - VOUT )
≤ 1.2
500000 ·L ·VIN
Output Capacitor Selection (Cont.)
For the applications using ceramic capacitors, the VESR is
much smaller than the ∆V COUT and can be ignored.
L≥
Therefore, the AC peak-to-peak output voltage (∆VOUT ) is
close to ∆VCOUT.
VOUT ·(VIN - VOUT )
600000 ·VIN
........... (6)
(H)
where VIN = VIN(MAX)
The load transient requirements are the function of the
slew rate (di/dt) and disengaged\the magnitude of the
Layout Consideration
transient load current. These requirements are generally
met with a mix of capacitors and careful layout. High fre-
In high power switching regulator, a correct layout is important to ensure proper operation of the regulator. In
quency capacitors initially supply the transient and slow
the current load rate seen by the bulk capacitors. The bulk
general, interconnecting impedance should be minimized
by using short and wide printed circuit traces. Signal and
filter capacitor values are generally determined by the ESR
(Effective Series Resistance) and voltage rating require-
power grounds are to be kept separating and finally combined using ground plane construction or single point
ments rather than actual capacitance requirements.
High frequency decoupling capacitors should be placed
grounding. Figure 2 illustrates the layout, with bold lines
indicating high current paths. Components along the bold
as close to the power pins of the load as physically
possible. Be careful not to add inductance in the circuit
lines should be placed close together. Below is a checklist for your layout:
board wiring that could cancel the usefulness of these
low inductance components. An aluminum electrolytic
1. Firstly, to initial the layout by placing the power
components. Orient the power circuitry to achieve a
clean power flow path. If possible, make all the con-
capacitor’s ESR value is related to the case size with lower
ESR available in larger case sizes. However, the Equiva-
nections on one side of the PCB with wide and copper
filled areas.
lent Series Inductance (ESL) of these capacitors increases
with case size and can reduce the usefulness of the capacitor to high slew-rate transient loading.
+
VIN
-
Inductor Value Calculation
1
2
NC VIN
The operating frequency and inductor selection are inter6
related in that higher operating frequencies permit the
use of a smaller inductor for the same amount of inductor
EN
5
COMP
C3
FB
AGND
3
Accepting larger values of ripple current allows the use of
low inductances, but results in higher output voltage ripple
+
7
C 2 Load
VOUT
PGND
R3
equation (2) shows that the inductance value has a direct
effect on ripple current.
L1
9
U1
APW7145
Compensation
Network
ripple current. However, this is at the expense of efficiency
due to an increase in MOSFET gate charge losses. The
C1
LX
LX
-
8
R1
4
R2
C4(Optional)
Feedback
Divider
Figure 2. Current Path Diagram
and greater core losses. A reasonable starting point for
setting ripple current is ∆I ≤ 0.4 ⋅ IOUT(MAX). Please be no-
2. In Figure 2, the loops with same color bold lines con-
ticed that the maximum ripple current occurs at the maximum input voltage. The minimum inductance of the in-
duct high slew rate current. These interconnecting impedances should be minimized by using wide and short
ductor is calculated by using the following equation:
printed circuit traces.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
16
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APW7145
Application Information (Cont.)
Layout Consideration (Cont.)
3. Keep the sensitive small signal nodes (FB and COMP)
away from switching nodes (LX or others) on the PCB.
Therefore, place the feedback divider and the feedback
compensation network close to the IC to avoid switching noise. Connect the ground of feedback divider directly to the AGND pin of the IC using a dedicated ground
trace.
4. Place the decoupling ceramic capacitor C1 near the
VIN as close as possible. Use a wide power ground
plane to connect the C1 and C2 to provide a low impedance path between the components for large and high
slew rate current.
VIN
VOUT
Ground
C2
C1
1
2
3
4
7
VLX
L1
8
5
6
APW7145
SOP-8P
For dissipating heat
VIN
Ground
VOUT
Ground
C2
C1
1
2
3
4
7
VLX
L1
8
6
5
APW7145
DFN4x4
For dissipating heat
Ground
Figure 3. Recommended Layout Diagram
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
17
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APW7145
Package Information
SOP-8P
-T- SEATING PLANE < 4 mils
D
SEE VIEW A
h X 45o
E
THERMAL
PAD
E1
E2
D1
c
A1
0.25
A2
A
b
e
GAUGE PLANE
SEATING PLANE
θ
L
VIEW A
S
Y
M
B
O
L
A
SOP-8P
INCHES
MILLIMETERS
MAX.
MIN.
MIN.
MAX.
1.60
0.063
0.000
0.15
0.006
A1
0.00
A2
1.25
b
0.31
0.51
0.012
0.020
c
0.17
0.25
0.007
0.010
D
4.80
5.00
0.189
0.197
D1
2.50
3.50
0.098
0.138
0.244
0.049
E
5.80
6.20
0.228
E1
3.80
4.00
0.150
0.157
E2
2.00
3.00
0.079
0.118
e
1.27 BSC
0.050 BSC
h
0.25
0.50
0.010
0.020
L
0.40
1.27
0.016
0.050
0o C
8o C
θ
0oC
8o C
Note : 1. Followed from JEDEC MS-012 BA.
2. Dimension "D" does not include mold flash, protrusions or gate burrs.
Mold flash, protrusion or gate burrs shall not exceed 6 mil per side .
3. Dimension "E" does not include inter-lead flash or protrusions.
Inter-lead flash and protrusions shall not exceed 10 mil per side.
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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APW7145
Package Information
DFN4x4-8
A
Pin 1
b
E
D
D2
A1
A3
L
K
E2
Pin 1 Corner
e
S
Y
M
B
O
L
DFN4x4-8
INCHES
MILLIMETERS
MIN.
MAX.
MIN.
MAX.
A
0.80
1.00
0.031
0.039
A1
0.00
0.05
0.000
0.002
A3
0.20 REF
0.008 REF
b
0.25
0.35
0.010
0.014
D
3.90
4.10
0.154
0.161
D2
3.10
3.30
0.122
0.130
E
3.90
4.10
0.154
0.161
E2
2.40
2.60
0.094
0.102
0.60
0.016
e
0.80 BSC
L
0.40
K
0.20
0.031 BSC
0.024
0.008
Note : 1. Followed from JEDEC MO-229 VGGB.
Copyright  ANPEC Electronics Corp.
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APW7145
Carrier Tape & Reel Dimensions
P0
P2
P1
A
B0
W
F
E1
OD0
K0
A0
A
OD1 B
B
T
SECTION A-A
SECTION B-B
H
A
d
T1
Application
SOP-8P
Application
DFN4x4-8
A
H
T1
C
d
D
W
E1
F
330.0±2.00
50 MIN.
12.4+2.00
-0.00
13.0+0.50
-0.20
1.5 MIN.
20.2 MIN.
12.0±0.30
1.75±0.10
5.5±0.05
P0
P1
P2
D0
D1
T
A0
B0
K0
2.0±0.05
1.5+0.10
-0.00
1.5 MIN.
0.6+0.00
-0.40
6.40±0.20
5.20±0.20
2.10±0.20
4.0±0.10
8.0±0.10
A
H
T1
C
d
D
W
E1
F
330.0±2.00
50 MIN.
12.4+2.00
-0.00
13.0+0.50
-0.20
1.5 MIN.
20.2 MIN.
12.0±0.30
1.75±0.10
5.5±0.05
P0
P1
P2
D0
D1
T
A0
B0
K0
2.0±0.05
1.5+0.10
-0.00
1.5 MIN.
0.6+0.00
-0.40
4.30±0.20
4.30±0.20
1.30±0.20
4.0±0.10
8.0±0.10
(mm)
Devices Per Unit
Package Type
SOP-8P
DFN4x4-8
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
Unit
Tape & Reel
Tape & Reel
Quantity
2500
3000
20
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APW7145
Taping Direction Information
SOP-8P
USER DIRECTION OF FEED
DFN4x4-8
USER DIRECTION OF FEED
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APW7145
Classification Profile
Classification Reflow Profiles
Profile Feature
Sn-Pb Eutectic Assembly
Pb-Free Assembly
100 °C
150 °C
60-120 seconds
150 °C
200 °C
60-120 seconds
3 °C/second max.
3°C/second max.
183 °C
60-150 seconds
217 °C
60-150 seconds
See Classification Temp in table 1
See Classification Temp in table 2
Time (tP)** within 5°C of the specified
classification temperature (Tc)
20** seconds
30** seconds
Average ramp-down rate (Tp to Tsmax)
6 °C/second max.
6 °C/second max.
6 minutes max.
8 minutes max.
Preheat & Soak
Temperature min (Tsmin)
Temperature max (Tsmax)
Time (Tsmin to Tsmax) (ts)
Average ramp-up rate
(Tsmax to TP)
Liquidous temperature (TL)
Time at liquidous (tL)
Peak package body Temperature
(Tp)*
Time 25°C to peak temperature
* Tolerance for peak profile Temperature (Tp) is defined as a supplier minimum and a user maximum.
** Tolerance for time at peak profile temperature (tp) is defined as a supplier minimum and a user maximum.
Copyright  ANPEC Electronics Corp.
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APW7145
Classification Reflow Profiles (Cont.)
Table 1. SnPb Eutectic Process – Classification Temperatures (Tc)
3
Package
Thickness
<2.5 mm
Volume mm
<350
235 °C
Volume mm
≥350
220 °C
≥2.5 mm
220 °C
220 °C
3
Table 2. Pb-free Process – Classification Temperatures (Tc)
Package
Thickness
<1.6 mm
1.6 mm – 2.5 mm
≥2.5 mm
Volume mm
<350
260 °C
260 °C
250 °C
3
Volume mm
350-2000
260 °C
250 °C
245 °C
3
Volume mm
>2000
260 °C
245 °C
245 °C
3
Reliability Test Program
Test item
SOLDERABILITY
HOLT
PCT
TCT
HBM
MM
Latch-Up
Method
JESD-22, B102
JESD-22, A108
JESD-22, A102
JESD-22, A104
MIL-STD-883-3015.7
JESD-22, A115
JESD 78
Description
5 Sec, 245°C
1000 Hrs, Bias @ Tj=125°C
168 Hrs, 100%RH, 2atm, 121°C
500 Cycles, -65°C~150°C
VHBM≧2KV
VMM≧200V
10ms, 1tr≧100mA
Customer Service
Anpec Electronics Corp.
Head Office :
No.6, Dusing 1st Road, SBIP,
Hsin-Chu, Taiwan
Tel : 886-3-5642000
Fax : 886-3-5642050
Taipei Branch :
2F, No. 11, Lane 218, Sec 2 Jhongsing Rd.,
Sindian City, Taipei County 23146, Taiwan
Tel : 886-2-2910-3838
Fax : 886-2-2917-3838
Copyright  ANPEC Electronics Corp.
Rev. A.7 - Mar., 2011
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