Anpec APW7077ZBI-TRL Pwm step-up dc-dc converter Datasheet

APW7077/A
PWM Step-Up DC-DC Converter
Features
•
•
•
•
•
General Description
Low Start-up Voltage 0.9V
The APW7077/A series are multi- function PWM
step-up DC-DC converter with an adaptive voltage mode
controller and higher efficiency application from one to
four cells battery packs. The APW7077/A series are
set PWM operating mode, voltage-mode to follow
portable application. And built-in driver pin, EXT pin,
for connecting to an external transistor or MOSFET
during light load, the device will automatically skip
switching cycles to maintain high efficiency. The
APW7077/A series consists of PW M controller,
reference voltage, phase compensation, oscillator,
soft-start, driver block. It will provide to operate suitable
voltage without external compensation circuit. The
APW7077/A series have fixed voltage and adjustable
voltage version from a wide input voltage ranges 0.7V
to 5.5V for step-up DC-DC converter. The start-up is
guaranteed at 1V and the device is operating down to
0.7V. And providing up to 300mA loading current.
Besides, low quiescent current (switch-off) is
guaranteed.
Fixed 300kHZ Operating Frequency
Built-In Internal Soft Start Circuit
Low Operating Current
3.3V and 5V ( ±2.5%) Fixed (APW7077) or
Adjustable Output Voltage (APW7077A)
•
High Efficiency Up to 88% at 400mA
Output Current
•
•
•
High Output Current Up to 1A
Compact Package: SOT-23-5
Lead Free Available (RoHS Compliant)
Applications
•
•
•
•
•
Cellular and Portable Phones
Portable Audio
Pinouts
Camcorders and Digital Still Camera
Hand-held Instrument
PDAs
EXT
GND
EXT
GND
5
4
5
4
1
2
3
C E V OUT NC
SOT-23-5 (Top View)
APW7077
1
2
3
FB V DD CE
SOT-23-5 (Top View)
APW7077A
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.4 - Sep, 2005
1
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APW7077/A
Ordering and Marking Information
Package Code
B : SOT-23-5
Temp. Range
I : -40 to 85 ° C
Handling Code
TU : Tube
TR : Tape & Reel
Voltage Code
R : 3.3V
Z : 5.0V
Lead Free Code
L : Lead Free Device
Blank : Original Device
APW7077/A
Lead Free Code
Handling Code
Temp. Range
Package Code
Voltage Code
APW7077 B :
77RX
APW7077A B :
XX - Date Code, R : 3.3V
A77X
X - 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 and compatible with both SnPb and lead-free soldiering
operations. ANPEC lead-free products meet or exceed the lead-free requirements of IPC/JEDEC J STD-020C
for MSL classification at lead-free peak reflow temperature.
Block Diagram
VDD
Phase
Compensation
VOUT
V DD
VDD
NC
PWM
Controller
Error Amp.
RAMP
GEN.
Vref=1.0V
Voltage
Reference
GND
EXT
Driver
PWM Comp.
Oscillator
Soft-Start
V DD
CE
APW 7077
VDD
Phase
Compensation
VDD
VDD
VDD
FB
PWM
Controller
Error Amp.
RAMP
GEN.
Voltage
Reference
GND
Driver
EXT
PWM Comp.
Oscillator
Soft-Start
VDD
CE
APW7077A
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
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APW7077/A
Absolute Maximum Ratings
Symbol
Parameter
Value
Unit
VDD
Supply voltage
-0.3 to 7
V
VIO
Input / output pins (CE, FB, EXT)
-0.3 to 7
V
TA
Operating Ambient Temperature Range
-40 to 85
°C
TJ
Junction Temperature Range
-40 to 150
°C
TSTG
Storage Temperature Range
-65 to +150
°C
TS
Soldering Temperature
300, 10 seconds
°C
VESD
Minimum ESD Rating
±2
kV
Pin Descrpition
Pin Number
Pin Name
Function Description
3
CE
Chip enable input. High = operating mode; Low = shutdown mode
5
5
EXT
External MOSFET or transistor drive pin.
4
4
GND
Ground pins of the circuit.
X
2
VDD
Supply voltage.
FB: Internal 1.0V reference voltage. Use a resistor divider to set
X
1
FB
the output voltage from and VOUT =
3
X
NC
No internal connection to the pin.
2
X
VOUT
VOUT Provides bootstrap power to the IC.
APW7077
APW7077A
1

R2 
1 +

R1 

VFB.
Thermal Characteristics
Symbol
R θJA
Parameter
Thermal Resistance − Junction to Ambient
SOT-23-5
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
3
Value
Unit
200
°C/W
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APW7077/A
Electrical Characteristics
(for all values TA = 25°C, VOUT = 3.3V, unless otherwise noted)
Symbol
Parameter
Test Condition
APW7077A
Min
Typ
Max
Unit
Step-Up Section
VIN
VDD
Minimum Operating Input
Voltage
Operating Voltage
Start-up Voltage
fSW
DMAX
Operating Frequency
Oscillator Frequency Line
Regulation
Maximum Duty Cycle
VOUT = VDD
VIN = VDD
0.9
1.9
Io<10mA, VOUT = VDD (<5.5V)
0.9
VOUT = 12V, Io<10mA, VDD = VIN
1.9
2.0
VDD = 3.3V, VFB = 0.5V
270
300
5.5
V
1
V
V
330
±1.2
2.0V<VDD<5.5V
VFB = 0.5V
V
81
88
%
95
±0.5
Maximum Duty Line Regulation 2.0V<VDD<5.5V
KHZ
%
%
Power MOSFET
ISOURCE EXT Output Source Current
Duty≤5%, EXT = VDD-0.4V
-70
-110
-150
mA
Duty≤5%, EXT = 0.4V
80
120
160
mA
Output Voltage Range
External Divider
2.0
Feedback Voltage
ILOAD = 0mA
0.98
Feedback Voltage Line
Regulation
2.0V<VDD<5.5V
±0.1
IFB
Feedback Input Current
VFB = 1.4V
0.03
50
nA
TSS
Soft-start Time
25
40
ms
ISINK
EXT Output Sink Current
Control Section
VFB
Soft-start Threshold Voltage
10
Duty = 50%
Soft-start Hysteresis Voltage
1.02
V
%
1.65
V
150
mV
150
230
µA
VDD = VCE = 3.3V, VFB = 1.1V
100
150
µA
Stand-by Current
VDD = VCE = 3.3V, VFB = 1.3V
17
25
µA
Switch-off Current
VDD = 3.3V, VCE = 0V
1
2
µA
0.7
V
Operating Current
IOFF
Logic LOW (VIL)
Logic HIGH(VIH)
ICE
1
VDD = VCE = 3.3V, VFB = 0.5V
Iq
VCE
V
CE Pin Input Current
1.2
VCE = 0V
VCE = 3.3V
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
4
V
1
2
µA
0.07
50
nA
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APW7077/A
Electrical Characteristics (Cont.)
(for all values TA = 25°C, VOUT = 3.3V, unless otherwise noted)
Symbol
Parameter
Test Condition
APW7077
Min
Typ
Max
Unit
Step-Up Section
VIN
Minimum Operating Input
Voltage
Operating Voltage
0.7
V
1
5.5
V
APW7077_33, Io<10mA
0.9
V
APW7077_33, 10mA<Io<100mA
1.1
V
APW7077_50, Io<10mA
0.9
V
APW7077_50, 10mA<Io<100mA
1.1
V
Hold Voltage
ILOAD = 10mA
0.7
0.8
V
fSW
Operating Frequency
VOUT = 3.3VX96%
270
300
330
KHZ
DMAX
Maximum Duty Cycle
VOUT = 3.3VX96%
81
88
95
%
-70
-110
-150
mA
80
120
160
mA
Start-up Voltage
VHOLD
Power MOSFET
ISOURCE EXT Output Source Current Duty≤5%, EXT = 2.9V
ISINK
EXT Output Sink Current
Duty≤5%, EXT = 0.4V
Control Section
VOUT
TSS
APW7077-33
IIN = 0mA
3.218
3.3
3.383
V
APW7077-50
IIN = 0mA
4.875
5
5.125
V
10
25
40
ms
Soft-start Time
Soft-start Threshold Voltage Duty = 50%
1.65
V
Soft-start Hysteresis Voltage
150
mV
VCE = VOUT, VOUT = 0.96VOUT
200
300
µA
VCE = VOUT, VOUT = 1.04VOUT
160
240
µA
Stand-by Current
VCE = VOUT, VOUT = 1.3VOUT
35
55
µA
Switch-off Current
VCE = 0V
1
2
µA
0.7
V
Iq
Operating Current
IOFF
VCE
Logic LOW (VIL)
Logic HIGH (VIH)
ICE
CE Pin Input Current
1.2
VCE = 0V
VCE = 2.0V
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
5
V
1
2
µA
0.07
50
nA
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APW7077/A
Application Circuit
Application Circuit for APW7077
10uH/1.5A
VIN
SS12
VOUT=3.3V(APW7077-33)
VOUT=5V(APW7077-50)
CE
EXT
100uF
VOUT
APW7077
APM2300A
NC
100uF
10uF
GND
1uF
Application Circuit for APW7077A
10uH/1.5A
VIN
2.5~5.2V
2R2
SS12
9~12V/50mA
V O U T =(1+R2/R1)*1.0V
FB
EXT
4.7uF
VDD
APW7077A
APM2300A
0.1uF
GND
CE
1uF
10uF
R2
820K/620K
R1/75K
C F F /1000pF
Application Circuit for APW7077A
VIN
10uH/1.5A
3~5V
SS12
V O U T =(1+R2/R1)*1.0V
FB
EXT
100uF
VDD
APM2300A
APW7077A
CE
GND
10uF
100uF
1uF
R2/300K
R1/75K
C F F /33pF
*R1 ≦100K Ω is recommended
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
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APW7077/A
Typical Characteristics
Start-up/Hold Voltage vs. Output Current
1.6
1.6
1.4
1.4
1.2
Input Voltage (V)
Input Voltage (V)
Start-up/Hold Voltage vs. Output Current
VSTART-up
1
0.8
Vhold
0.6
1.2
VSTART-up
1
0.8
Vhold
0.6
0.4
0.4
0.2
0.2
VOUT=5.0V
VOUT=3.3V
0
0
0
50
100
150
200
250
0
300
Output Current (mA)
100
150
200
250
300
Output Current (mA)
Efficiency vs. Output Current
Efficiency vs. Output Current
100
100
90
90
80
VDD =3V
80
VDD =5V
Efficiency(%)
Efficiency(%)
50
70
VDD=3.3V
60
50
40
VDD =2V
70
60
50
40
30
30
VOUT=12V
L=10µF
20
1
10
20
100
1
Rev. A.4 - Sep, 2005
10
100
1000
Output Current (mA)
Output Current (mA)
Copyright  ANPEC Electronics Corp.
VOUT=5V
L=10µH
7
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APW7077/A
Typical Characteristics (Cont.)
Output Voltaget vs. Output Current
3.32
5.02
3.315
5. 015
3.31
5.01
Output Voltage (V)
Output Voltage (V)
Output Voltaget vs. Output Current
3.305
VIN=2.5V
3.3
3.295
VIN=1.2V
VIN=2.0V
3.29
5. 005
VIN=3.0V
5
4. 995
4.99
VIN=1.2V
VIN=2.0V
4. 985
3.285
VOUT=5.0V
VOUT=3.3V
4.98
3.28
0
200
400
600
800
0
1 0 00
200
Output Current (mA)
400
600
800
1 0 00
Output Current (mA)
Output Voltage vs. Temperature
Oscillation Frequency vs. Temperature
3.40
3 30
Oscillation Frequency (kHz)
3.38
Output Voltage (V)
3.36
3.34
3.32
3.30
3.28
3.26
3.24
3.22
3.20
3 20
3 10
3 00
2 90
2 80
2 70
-40
-20
0
20
40
60
80
-40
Temperature (°C)
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
8
-20
0
20
40
Temperature (°C)
60
80
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APW7077/A
Typical Characteristics (Cont.)
Load Transient Waveform
Load Transient Waveform
VIN=3.3V, VOUT=5V, IOUT=10mA->300mA->10mA
L=10µH, COUT=22µF+22µF+0.1µF, Cff=33pF
CH1:VOUT, 100mV/DIV, Time=1ms/DIV
CH4:IOUT, 200mA/DIV
VIN=3.3V, VOUT=12V, IOUT=5mA->50mA->5mA
L=10µH, COUT=4.7µF+0.1µF, Cff=560pF
CH1:VOUT, 100mV/DIV, Time=1ms/DIV
CH4:IOUT, 20mA/DIV
EXT Driving Current vs. Supply Voltage
EXT Rds,on vs. Supply Voltage
100
140
Rds,on resistance (Ω)
Sink/Source Current (mA)
160
120
ISINK
(EXT=0.4V)
100
80
ISOURCE
(EXT=VDD-0.4V)
60
40
10
EXT to VDD
EXT to GND
20
1
0
0
1
2
3
4
5
0
6
Supply Voltage (V)
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
1
2
3
4
5
6
Supply Voltage (V)
9
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APW7077/A
Typical Characteristics (Cont.)
Feedback Voltage vs. Supply Voltage
250
2.5
200
2
Feedback Voltage (V)
Supply Current ( µA)
Supply Current vs. Supply Voltage
Switching Mode
150
100
Non Switching Mode
50
1.5
1
0.5
0
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
0
0.5
1
1.5
Supply Voltage (V)
2.5
3
3.5
4
4.5
5
5.5
Maximum Duty vs. Supply Voltage
Oscillation Frequency vs. Supply Voltage
350
100
90
300
Maximum Duty (%)
Oscillation Frequency (kHz)
2
Supply Voltage (V)
250
200
150
100
80
70
60
50
40
30
20
50
10
0
0
0
0.5
1
1. 5
2
2.5
3
3.5
4
4.5
5
5.5
0
Supply Voltage (V)
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
0. 5
1
1. 5
2
2.5
3
3.5
4
4.5
5
5. 5
Supply Voltage (V)
10
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APW7077/A
Typical Characteristics (Cont.)
Feedback Voltage vs. Temperature
1.020
Feedback Voltage (V)
1.015
1.010
1.005
1.000
0.995
0.990
0.985
0.980
-40
-20
0
20
40
Temperature (°C)
60
80
Function Description
Operation
The APW7077/A operation can be best understood by
referring to the block diagram. The error amplifier
monitors the output voltage via the feedback resistor
divider by comparing the feedback voltage with the
reference voltage. When the feedback voltage is lower
than the reference voltage, the error amplifier output
will decrease. The error amplifier output is then
compared with the oscillator ramp voltage at the PWM
controller.
The APW7077/A series are low noise fixed frequency
voltage–mode PWM DC–DC controllers, and consist
of start–up circuit, reference voltage, oscillator, loop
compensation network, PWM control circuit, and low
ON resistance driver.
APW7077 provide on–chip feedback resistor and loop
compensation network, the system designer can get
the regulated fixed output voltage 3.3V and 5.0V with
a small number of external components, it is optimized
for battery powered portable products where large
output current is required. APW7077A provide internal
reference voltage 1.0V and output voltage setting by
external resistance for higher voltage requirement. The
quiescent current is typically 120uA (VOUT = 3.3V,
fsw = 300kHz), and can be further reduced to about
1.0uA when the chip is disabled (VCE < 0.7V).
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
When the feedback voltage is higher than the reference
voltage, the error amplifier output increases and the
duty cycle decreases. When the external power switch
is on, the current ramps up in the inductor, storing
energy in the magnetic field. When the external power
switch is off, the energy stored in the magnetic field is
transferred to the output filter capacitor and the load.
The output filter capacitor stores the charge while the
11
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APW7077/A
Function Description (Cont.)
Operation (Cont.)
ramp up to let output voltage reach to setting voltage
without over shooting issue whenever heavy load or
light load condition. The soft start time 25ms is
setting by internal circuit.
inductor current is higher than the output current, then
sustains the output voltage until the next switching
cycle.
Oscillator
As the load current is decreased, the switch transistor
turns on for a shorter duty cycle. Under the light load
condition, the controller will skip switching cycles to
reduce power consumption, so that high efficiency is
maintained at light loads.
The oscillator frequency is internally set to 300 kHz at
an accuracy of +/-10% and with low temperature
coefficient of 3.3%/°C.
Enable/Disable Operation
Fixed Output Voltage (for APW7077 only)
The APW7077/A series offer IC shutdown mode by chip
enable pin (CE pin) to reduce current consumption.
When voltage at pin CE is greater than 1.2 V, the
chip will be enabled, which means the controller is
in normal operation. When voltage at pin CE is less
than 0.7 V, the chip is disabled, which means IC is
shutdown and quiescent current become 1uA.
The APW7077 VOUT is set by an integrate feedback
resistor network. This is trimmed to a selected voltage
3.3 V or 5.0 V with an accuracy of +/-2.5%.
Setting Output Voltage (for APW7077A only)
For APW7077A, the output voltage is adjustable. The
output voltage is set using the FB pin and a resistor
divider connected to the output as shown in the typical
operating circuit. The internal reference voltage is 1.0V
with 2% variation, so the ratio of the feedback resistors
sets the output voltage according to the following
equation:
R2
V OUT = (1 +
) × 1.0V
R1
To avoid the thermal noise from feedback resistor,
(R1+R2) resistance smaller than 1MΩ and 1% variation
is recommended.
The CE pin pull high to VDD(or VOUT) by internal resistor,
and this resistance is greater than 1MΩ . So this chip
will enable normally when CE pin floating.
Important: DO NOT apply a voltage between 0.7V
to 1.2 V to pin CE as this is the CE pin’s hysteresis
voltage range. Clearly defined output states can
only be obtained by applying voltage out of this
range.
Compensation
The device is designed to operate in continuous
conduction mode. An internal compensation circuit
was designed to guarantee stability over the full
input/output voltage and full output load range.
Soft Start
There is a sof t start function is integration in
APW7077/A series to avoid the over shooting when
power on. When power is applied to the device, the
soft start circuit first pumps up the output voltage to
let VDD(or VOUT) approximately 1.65V at a fixed duty
cycle 50%. This is the voltage level at which the
controller can operate normally. When supply voltage
more than 1.65V the internal reference voltage will be
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
Step–up Converter Operating Mode
The step–up DC–DC controller is designed to operate
in continuous conduction mode (CCM) or discontinuous
conduction mode (DCM).
For a step up converter in a CCM, the duty cycle D is
12
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APW7077/A
Function Description (Cont.)
The inductor peak current can be calculated as
Step–up Converter Operating Mode (Cont.)
given by
Ipk =
V OUT − V IN
D =
V OUT
In higher output voltage or small output current
V

V
2⋅L
⋅ OUT  OUT − 1
TS ⋅ RLOAD VIN  VIN

External components values can be calculated from
these equations, however, the optimized value should
obtained through experimental results.
L≥
APW7077/A series are designed to work well with a
6.8 to 12uH inductors in most applications 10uH is a
sufficiently low value to allow the use of a small
surface mount coil, but large enough to maintain low
ripple. Lower inductance values supply higher output
current, but also increase the ripple and reduce
efficiency. Higher inductor values reduce ripple and
improve efficiency, but also limit output current. The
inductor should have small DCR, usually less than
1mΩ, to minimize loss. It is necessary to choose an
inductor with a saturation current greater than the peak
current which the inductor will encounter in the
application.
2
fsw × IO × Ratio
A system can be designed to operate in continuous
mode for load currents above a certain level usually
20 to 50% (Ratio define as 0.2~0.5) of full load at
minimum input voltage. When IO smaller than (IO*Ratio),
the controller system will into DCM.
∆IL is the ripple current flowing through the inductor,
which affects the output voltage ripple and core losses.
Based on 20%(Ratio=0.2) current ripple, VOUT=5V,
IO=1A and VIN =1.8V system, the inductance value is
calculated as 6.9uH and a 6.8uH inductor is used.
The inductor ripple current is important for a few
reasons. One reason is because the peak switch
current will be the average inductor current (IL) plus
∆IL.
The inductor current ripple has an expression
∆ IL =
As a side note, discontinuous operation occurs when
the inductor current falls to zero during a switching
cycle, or ∆I L is greater than the average inductor
current. Therefore, continuous conduction mode occurs
V IN × D
fsw × L
The maximum DC input current can be calculated as
I L (max) =
V OUT × I O (max)
V IN (min)
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
2
Inductor Selection
The minimum value of inductor to maintain continuous
conduction mode can be determined by the following
VOUT × D(1 − D)
∆ IL
capacitor
Critical Inductance Value
equation.
V IN
+
NOTES:
D – On–time duty cycle
IL – Average inductor current
IPK – Peak inductor current
IO – Desired dc output current
VIN – Nominal operating dc input voltage
VOUT – Desired dc output voltage
ESR – Equivalent series resistance of the output
application, the step–up DC–DC controller operated in
discontinuous conduction mode almost. For a step-up
converter in a DCM, the duty cycle D is given by
D=
V OUT × I O
13
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APW7077/A
Function Description (Cont.)
Inductor Selection (Cont.)
If the regulator will be loaded uniformly, with very little
load changes, and at lower current outputs, the input
capacitor size can often be reduced. The size can also
be reduced if the input of the regulator is very close to
the source output. The size will generally need to be
larger for applications where the regulator is supplying
nearly the maximum rated output or if large load steps
are expected. A minimum value of 10µF should be
used for the less stressful conditions while a 22µF to
47µF capacitor may be required for higher power and
dynamic loads. Small ESR Tantalum or ceramic capacitor should be suitable and the total input ripple
voltage can be calculated
when ∆IL is less than the average inductor current.
Care must be taken to make sure that the switch will
not reach its current limit during normal operation.
The inductor must also be sized accordingly. It should
have a saturation current rating higher than the peak
inductor current expected. The output voltage ripple is
also affected by the total ripple current.
Output Capacitor
The output capacitor is used for sustaining the output
voltage when the external MOSFET or bipolar
transistor is switched on and smoothing the ripple
voltage.
∆ V IN = ∆ I L × ESR
The output capacitance needed is calculated in
Design Example
equations.
It is supposed that a step–up DC–DC controller with
3.3 V output delivering a maximum 1000 mA output
current with 100 mV output ripple voltage powering
from a 2.4 V input is to be designed.
COUT (min) =
IO(max) × D
fsw × ∆VOUT
The ESR is also important because it determines the
peak to peak output voltage ripple according to the
approximate equation:
ESR =
Design parameters:
VIN = 2.4 V
VOUT = 3.3 V
IO = 1.0 A
∆VOUT = 100 mV
fsw= 300 kHZ
Ratio = 0.2 (typical for small output ripple voltage)
? VOUT
? IO
With 1% output voltage ripple, low ESR capacitor
should be used to reduce output ripple voltage. In
general, a 100uF to 220uF low ESR (0.10Ω to 0.30Ω)
Tantalum capacitor should be appropriate. The choice
Assume the diode forward voltage and the transistor
saturation voltage are both 0.3V. Determine the maximum steady state duty cycle at VIN = 2.4 V:
of output capacitors is also somewhat arbitrary and
depends on the design requirements for output voltage
ripple. A minimum value of 10µF is recommended and
may be increased to a larger value.
D=0.273
Input Capacitor
Calculate the maximum inductance value which can
The input capacitor can stabilize the input voltage and
generate the desired current output and the preferred
delta inductor current to average inductor current ratio:
minimize peak current ripple from the source. The size
used is dependant on the application and board layout.
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
L=10uH
14
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APW7077/A
Function Description (Cont.)
Design Example(Cont.)
Determine the output capacitance value for the desired
output ripple voltage:
Determine the average inductor current and peak inductor current:
COUT=33uF
The ESR of the output capacitor is 0.05Ω . Therefore,
IL=1.38A
∆IL=0.218A
Ipk=1.45A
a Tantalum capacitor with value of 33 uF to 47uF and
ESR of 0.05Ω can be used as the output capacitor.
Therefore, a 10 uH inductor with saturation current
larger than 1.73 A can be selected as the initial trial.
However, according to experimental result, 220uF
output capacitor gives better overall operational stability
and smaller ripple voltage.
External Component Selection
Diode Selection
External Switch Transistor
The output diode for a boost regulator must be chosen correctly depending on the output voltage and the
output current. The diode must be rated for a reverse
voltage equal to or greater than the output voltage used.
The average current rating must be greater than the
maximum load current expected, and the peak current rating must be greater than the peak inductor
current. During short circuit testing, or if short circuit
conditions are possible in the application, the diode
current rating must exceed the switch current limit.
The diode is the largest source of loss in DC–DC
converters. The most importance parameters which
affect their efficiency are the forward voltage drop, VF,
and the reverse recovery time, trr. The forward voltage
drop creates a loss just by having a voltage across
the device while a current flowing through it. The reverse recovery time generates a loss when the diode
is reverse biased, and the current appears to actually
flow backwards through the diode due to the minority
carriers being swept from the P–N junction. Using
Schottky diodes with lower forward voltage drop will
decrease power dissipation and increase efficiency.
An enhancement N–channel MOSFET or a bipolar NPN
transistor can be used as the external switch transistor.
Since enhancement MOSFET is a voltage driven
device, it is a more efficient switch than a BJT
transistor. However, the MOSFET requires a higher
voltage to turn on as compared with BJT transistors.
An enhancement N–channel MOSFET can be selected
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
by the following guidelines:
• Low ON–resistance, RDS(on).
• Low gate threshold voltage, VGS(th), typically
<1.5V, it is especially important for the low VOUT
device, like VOUT = 2.4V.
• Rated continuous drain current, ID, should be
larger than the peak inductor current, i.e. ID > IPK.
• Gate capacitance should be 1200 pF or less.
For bipolar NPN transistor, medium power transistor
with continuous collector current typically 1A to 5A
and VCE(sat) < 0.2 V should be employed. The driving capability is determined by the DC current gain,
HFE, of the transistor and the base resistor, Rb; and
15
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APW7077/A
External Component Selection (Cont.)
transistor. Moreover, a speed–up capacitor, Cb, should
be connected in parallel with Rb to reduce switching
loss and improve efficiency. Cb can be calculated by
the equation below:
External Switch Transistor (Cont.)
the controller’s EXT pin must be able to supply the
necessary driving current. Rb can be calculated by
the following equation:
It is due to the variation in the characteristics of the
transistor used. The calculated value should be used
as the initial test value and the optimized value should
be obtained by the experiment.
Since the pulse current flows through the transistor,
the exact Rb value should be finely tuned by the
experiment. Generally, a small Rb value can increase
the output current capability, but the efficiency will
decrease due to more energy is used to drive the
Layout Considerations
Ground Plane
Switching Noise Decoupling Capacitor
One point grounding should be used for the output
power return ground, the input power return ground,
and the device switch ground to reduce noise. The
input ground and output ground traces must be thick
enough for current to flow through and for reducing
ground bounce.
On APW7077 fixed voltage application, a 0.1µF ceramic capacitor should be placed close to the VOUT pin
and GND pin of the chip to filter the switching spikes
in the output voltage monitored by the VOUT pin.
Feedback Network
On APW7077A application, the feedback networks
should be connected directly to a dedicated analog
ground plane and this ground plane must connect to
the GND pin. If no analog ground plane is available
then this ground must tie directly to the GND pin. The
feedback network, resistors R1 and R2, should be kept
Power Signal Traces
Low resistance conducting paths should be used for
the power carrying traces to reduce power loss so as
to improve efficiency (short and thick traces for connecting the inductor L can also reduce stray
inductance). Trace connections made to the inductor
and schottky diode should be minimized to reduce
power dissipation and increase overall efficiency.
into the system.
Output Capacitor
Input Capacitor
The output capacitor should be placed close to the
output terminals to obtain better smoothing effect on
the output ripple.
In APW7077A high output voltage application circuit,
the input voltage(VIN) is tied to chip supply pin(VDD).
The input capacitor CIN in VIN must be placed close to
the IC. This will reduce copper trace resistance which
effects input voltage ripple of the IC. For additional
close to the FB pin, and away from the inductor, to
minimize copper trace connections that can inject noise
The output capacitor, COUT, should also be placed close
to the IC. Any copper trace connections for the COUT
capacitor can increase the series resistance, which
directly effects output voltage ripple and efficiency.
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
input voltage filtering, a 1µF capacitor can be placed
in parallel with CIN, close to the VDD pin, to shunt any
high frequency noise to ground.
16
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APW7077/A
Layout Considerations (Cont.)
MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS
Surface mount board layout is a critical portion of the
total design. The footprint for the semiconductor packages must be the correct size to insure proper solder
connection interface between the board and the
package. With the correct pad geometry, the packages will self align when subjected to a solder reflow
process.
Bottom Layer
1300mil
Demo Board Circuit Layout
1600 mil
Top Layer
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
17
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APW7077/A
Packaging Information
SOT-23-5
e1
5
4
E1
1
E
3
2
e
b
D
A2
A
a
A1
Dim
A
A1
A2
b
D
E
E1
e
e1
L
L1
L2
a
L
Millimeters
Min.
0.95
0.05
0.90
0.35
2.8
2.6
1.5
Inches
Max.
1.45
0.15
1.30
0.55
3.00
3.00
1.70
Min.
0.037
0.002
0.035
0.0138
0.110
0.102
0.059
0.35
0.55
0.014
0.7
10°
0.020
0°
0.20 BSC
0.5
0°
Max.
0.057
0.006
0.051
0.0217
0.118
0.118
0.067
0.037
0.075
0.95
1.90
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
L2
L1
0.022
0.008 BSC
18
0.028
10°
www.anpec.com.tw
APW7077/A
Physical Specifications
Terminal Material
Lead Solderability
Solder-Plated Copper (Solder Material : 90/10 or 63/37 SnPb), 100%Sn
Meets EIA Specification RSI86-91, ANSI/J-STD-002 Category 3.
Reflow Condition
(IR/Convection or VPR Reflow)
tp
TP
Critical Zone
T L to T P
Temperature
Ramp-up
TL
tL
Tsmax
Tsmin
Ramp-down
ts
Preheat
25
t 25 °C to Peak
Time
Classificatin Reflow Profiles
Profile Feature
Average ramp-up rate
(TL to TP)
Preheat
- Temperature Min (Tsmin)
- Temperature Max (Tsmax)
- Time (min to max) (ts)
Time maintained above:
- Temperature (T L)
- Time (tL)
Peak/Classificatioon Temperature (Tp)
Time within 5°C of actual
Peak Temperature (tp)
Ramp-down Rate
Sn-Pb Eutectic Assembly
Pb-Free Assembly
3°C/second max.
3°C/second max.
100°C
150°C
60-120 seconds
150°C
200°C
60-180 seconds
183°C
60-150 seconds
217°C
60-150 seconds
See table 1
See table 2
10-30 seconds
20-40 seconds
6°C/second max.
6°C/second max.
6
minutes
max.
8 minutes max.
Time 25°C to Peak Temperature
Notes: All temperatures refer to topside of the package .Measured on the body surface.
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
19
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APW7077/A
Classificatin Reflow Profiles(Cont.)
Table 1. SnPb Entectic Process – Package Peak Reflow Temperature s
Package Thickness
Volume mm 3
Volume mm 3
<350
≥350
<2.5 mm
240 +0/-5°C
225 +0/-5°C
≥2.5 mm
225 +0/-5°C
225 +0/-5°C
Table 2. Pb-free Process – Package Classification Reflow Temperatures
Package Thickness
Volume mm 3
Volume mm 3
Volume mm 3
<350
350-2000
>2000
<1.6 mm
260 +0°C*
260 +0°C*
260 +0°C*
1.6 mm – 2.5 mm
260 +0°C*
250 +0°C*
245 +0°C*
≥2.5 mm
250 +0°C*
245 +0°C*
245 +0°C*
*Tolerance: The device manufacturer/supplier shall assure process compatibility up to and
including the stated classification temperature (this means Peak reflow temperature +0°C.
For example 260°C+0°C) at the rated MSL level.
Reliability test program
Test item
SOLDERABILITY
HOLT
PCT
TST
ESD
Latch-Up
Method
MIL-STD-883D-2003
MIL-STD-883D-1005.7
JESD-22-B,A102
MIL-STD-883D-1011.9
MIL-STD-883D-3015.7
JESD 78
Description
245°C, 5 SEC
1000 Hrs Bias @125°C
168 Hrs, 100%RH, 121°C
-65°C~150°C, 200 Cycles
VHBM > 2KV, VMM > 200V
10ms, 1tr > 100mA
Carrier Tape & Reel Dimensions
t
E
P
Po
D
P1
Bo
F
W
Ao
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
D1
20
Ko
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APW7077/A
Carrier Tape & Reel Dimensions(Cont.)
T2
J
C
A
B
T1
Application
A
178±1
SOT-23-5
F
B
C
J
72 ± 1.0 13.0 + 0.2 2.5 ± 0.15
D
3.5 ± 0.05 1.5 +0.1
D1
Po
1.5 +0.1
4.0 ± 0.1
T1
T2
W
P
E
8.4 ± 2
1.5± 0.3
8.0±0.3
4 ± 0.1
1.75± 0.1
P1
Ao
Bo
Ko
t
1.4± 0.1
0.2±0.03
2.0 ± 0.1 3.15 ± 0.1 3.2± 0.1
(mm)
Cover Tape Dimensions
Application
SOT-23-5
Carrier Width
8
Cover Tape Width
5.3
Devices Per Reel
3000
Customer Service
Anpec Electronics Corp.
Head Office :
No.6, Dusing 1st Road, SBIP,
Hsin-Chu, Taiwan, R.O.C.
Tel : 886-3-5642000
Fax : 886-3-5642050
Taipei Branch :
7F, No. 137, Lane 235, Pac Chiao Rd.,
Hsin Tien City, Taipei Hsien, Taiwan, R. O. C.
Tel : 886-2-89191368
Fax : 886-2-89191369
Copyright  ANPEC Electronics Corp.
Rev. A.4 - Sep, 2005
21
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