APW7089
4A, 26V, 380kHz, Asynchronous Step-Down Converter
General Description
Features
•
•
•
•
•
•
•
•
•
•
•
•
Wide Input Voltage from 4.5V to 26V
Output Current up to 4A
The APW7089 is a 4A, asynchronous, step-down converter with integrated 80mΩ P-channel MOSFET. The
Adjustable Output Voltage from 0.8V to 90% VIN
- 0.8V Reference Voltage
device, with current-mode control scheme, can convert
4.5~26V input voltage to the output voltage adjustable
- ±2.5% System Accuracy
80mΩ Integrated P-Channel Power MOSFET
from 0.8 to 90% VIN to provide excellent output voltage
regulation.
High Efficiency up to 91%
- Pulse-Skipping Mode (PSM) / PWM Mode Op-
The APW7089 regulates the output voltage in automatic
PSM/PWM mode operation, depending on the output
eration
Current-Mode Operation
current, for high efficiency operation over light to full load
current. The APW7089 is also equipped with power-on-
- Stable with Ceramic Output Capacitors
- Fast Transient Response
reset, soft-start, and whole protections (under-voltage,
over-temperature, and current-limit) into a single package.
Power-On-Reset Monitoring
Fixed 380kHz Switching Frequency in PWM Mode
In shutdown mode, the supply current drops below 5µA.
This device, available in a 8-pin SOP-8P package, pro-
Built-in Digital Soft-Start
Output Current-Limit Protection with Frequency
vides a very compact system solution with minimal external components and good thermal conductance.
Foldback
70% Under-Voltage Protection
100
Over-Temperature Protection
100ns
-2 ~ VIN+0.3
< 100ns
-5 ~ VIN+6
VIN > 6.2V
-0.3 ~ 6.5
VIN ≤ 6.2V
< VIN+0.3
V
V
VUGND_GND
UGND to GND Voltage
-0.3 ~ VIN+0.3
V
VVIN_UGND
VIN to UGND Voltage
-0.3 ~ 7V
V
-0.3 ~ 20
V
EN to GND Voltage
FB, COMP to GND Voltage
-0.3 ~ VCC +0.3
Maximum Junction Temperature
TSTG
Storage Temperature
TSDR
Maximum Lead Soldering Temperature, 10 Seconds
V
150
o
C
-65 ~ 150
o
C
260
o
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.1 - Jan., 2012
2
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APW7089
Thermal Characteristics
Symbol
θJA
θJC
Parameter
Junction-to-Ambient Resistance in Free Air
Typical Value
Unit
(Note 2)
SOP-8P
Junction-to-Case Resistance in Free Air (Note 3)
SOP-8P
50
o
10
o
C/W
C/W
Note 2: θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. The exposed pad
of SOP-8P is soldered directly on the PCB.
Note 3: The case temperature is measured at the center of the exposed pad on the underside of the SOP-8P package.
Recommended Operating Conditions (Note 4)
Symbol
VIN
Range
Unit
VIN Supply Voltage
Parameter
4.5 ~ 26
V
VCC Supply Voltage
4.0 ~ 5.5
V
VOUT
Converter Output Voltage
0.8 ~ 90% VIN
V
IOUT
Converter Output Current
0~4
A
VCC Input Capacitor
0.22 ~ 2.2
µF
VIN-to-UGND Input Capacitor
0.22 ~ 2.2
µF
TA
TJ
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 ~ 85oC, unless
otherwise specified. VCC is regulated by an internal regulator. Typical values are at TA=25oC.
Symbol
Parameter
APW7089
Test Conditions
Unit
Min.
Typ.
Max.
1.0
2.0
SUPPLY CURRENT
IVIN
IVIN_SD
IVCC
IVCC_SD
VIN Supply Current
VFB = 0.85V, VEN=3V, LX=Open
-
mA
VIN Shutdown Supply Current
VEN = 0V, VIN=26V
-
-
5
µA
VCC Supply Current
VEN = 3V, VCC = 5.0V, VFB=0.85V
-
0.7
-
mA
VCC Shutdown Supply Current
VEN = 0V, VCC = 5.0V
-
-
1
µA
VCC 4.2V LINEAR REGULATOR
Output Voltage
VIN = 5.2 ~ 26V, IO = 0 ~ 8mA
4.0
4.2
4.5
V
Load Regulation
IO = 0 ~ 8mA
-60
-40
0
mV
Current-Limit
VCC > POR Threshold
8
-
30
mA
VIN = 6.2 ~ 26V, IO = 0 ~ 10mA
5.3
5.5
5.7
V
Load Regulation
IO = 0 ~ 10mA
-80
-60
0
mV
Current-Limit
VIN = 6.2 ~ 26V
10
-
30
mA
VIN-TO-UGND 5.5V LINEAR REGULATOR
Output Voltage (VVIN-UGND)
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
3
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APW7089
Electrical Characteristics (Cont.)
Refer to the typical application circuits. These specifications apply over VIN=12V, VOUT=3.3V and TA= -40 ~ 85oC, unless
otherwise specified. VCC is regulated by an internal regulator. Typical values are at TA=25oC.
Symbol
Parameter
APW7089
Test Conditions
Unit
Min.
Typ.
Max.
3.7
3.9
4.1
V
-
0.15
-
V
2.3
2.5
2.7
V
-
0.2
-
V
-
3.5
-
V
-
0.2
-
V
-
0.8
-
V
-1.0
-
+1.0
-2.5
-
+2.5
POWER-ON-RESET (POR) AND LOCKOUT VOLTAGE THRESHOLDS
VCC POR Voltage Threshold
VCC rising
VCC POR Hysteresis
EN Lockout Voltage Threshold
VEN rising
EN Lockout Hysteresis
VIN-to-UGND Lockout Voltage
Threshold
VVIN-UGND rising
VIN-to-UGND Lockout Hysteresis
REFERENCE VOLTAGE
VREF
Reference Voltage
o
TJ = 25 C, IOUT=0A, VIN=12V
Output Voltage Accuracy
%
o
TJ = -40 ~ 125 C, IOUT = 0 ~ 4A,
VIN = 4.5 ~ 26V
Line Regulation
VIN = 4.5V to 26V, IOUT = 0A
-
0.36
-
%
Load Regulation
IOUT = 0 ~ 4A
-
0.4
-
%
340
380
420
kHz
-
80
-
kHz
-
93
-
%
-
200
-
ns
-
400
-
µA/V
60
80
-
dB
-
0.12
-
Ω
-
80
100
mΩ
OSCILLATOR AND DUTY
FOSC
Free Running Frequency
VIN = 4.5 ~ 26V
Foldback Frequency
VFB = 0V
Maximum Converter’s Duty Cycle
Minimum Pulse Width of LX
VIN = 4.5 ~ 26V
CURRENT-MODE PWM CONVERTER
Gm
Error Amplifier Transconductance
Error Amplifier DC Gain
COMP = Open
Current-Sense Resistance
P-channel Power MOSFET
Resistance
Between VIN and Exposed Pad,
TJ=25oC
PROTECTIONS
ILIM
P-channel Power MOSFET
Current-limit
Peak Current
5.0
6.5
8.0
A
VUV
FB Under-Voltage Threshold
VFB falling
66
70
74
%
FB Under-Voltage Hysteresis
-
40
-
mV
FB Under-Voltage Debounce
-
2
-
µs
Over-Temperature Trip Point
-
150
-
o
o
TOTP
Over-Temperature Hysteresis
C
-
50
-
C
Soft-Start Interval
9
10.8
12
ms
Preceding Delay before Soft-Start
9
10.8
12
ms
-
-
0.8
V
SOFT-START, ENABLE, AND INPUT CURRENTS
tSS
EN Logic Low Voltage
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
VEN falling, VIN = 4 ~ 26V
4
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APW7089
Electrical Characteristics (Cont.)
Refer to the typical application circuits. These specifications apply over VIN=12V, VOUT=3.3V and TA= -40 ~ 85oC, unless
otherwise specified. VCC is regulated by an internal regulator. Typical values are at TA=25oC.
Symbol
Parameter
APW7089
Test Conditions
Unit
Min.
Typ.
Max.
SOFT-START, ENABLE, AND INPUT CURRENTS (CONT.)
EN Logic High Voltage
VEN rising, VIN = 4 ~ 26V
2.1
-
-
V
12
-
17
V
-
-
4
µA
EN Pin Clamped Voltage
IEN=10mA
P-channel Power MOSFET
Leakage Current
VEN = 0V, VLX = 0V, VIN = 26V
IFB
FB Pin Input Current
VFB = 0.8V
-100
-
+100
nA
IEN
EN Pin Input Current
VEN < 3V
-500
-
+500
nA
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
5
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APW7089
Typical Operating Characteristics
Switching Frequency vs. Junction Temperature
420
0.812
410
Switching Frequency, FOSC (kHz)
Reference Voltage, VREF (V)
Reference Voltage vs. Junction Temperature
0.816
0.808
0.804
0.800
0.796
0.792
0.788
0.784
-50 -25
0
25
50
75
400
390
380
370
360
350
340
-50 -25
100 125 150
Junction Temperature, TJ (oC)
Output Voltage vs. Output Current
3.36
3.35
IOUT=1A
Output Voltage, VOUT (V)
Output Voltage, VOUT (V)
Output Voltage vs. Supply Voltage
3.36
3.35
3.34
3.33
3.32
3.31
3.30
3.29
3.28
3.27
3.26
3.25
3.24
VIN=12V
3.34
3.33
3.32
3.31
3.30
3.29
3.28
3.27
3.26
3.25
3.24
4
6
0.0
8 10 12 14 16 18 20 22 24 26
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Output Current, IOUT (A)
VIN Input Current vs. Supply Voltage
Current-Limit Level (Peak Current)
vs. Junction Temperature
8.0
VFB=0.85V
Current-Limit Level, ILIM (A)
1.4
0.5
Supply Voltage, VIN (V)
1.6
VIN Input Current, IVIN (mA)
0
25 50 75 100 125 150
Junction Temperature, TJ (oC)
1.2
1.0
0.8
0.6
0.4
0.2
7.5
7.0
6.5
6.0
5.5
5.0
0.0
0
4
8
12
16
20
24
VIN Supply Voltage, VIN (V)
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
28
-50 -25
6
0
25 50 75 100 125 150
Junction Temperature, TJ (oC)
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APW7089
Typical Operating Characteristics (Cont.)
Efficiency vs. Output Current
EN Clamp Voltage vs. EN Input Current
100
18
16
90
70
EN Clamp Voltage, V EN (V)
Efficiency (%)
80
VOUT=5V
VOUT=3.3V
60
50
40
30
VIN=12v, L=10µH (DCR=50mΩ)
C1=10µF, C4=22µF
20
10
0.001
14
12
TJ = -30oC
10
TJ = 25oC
8
TJ = 100oC
6
4
2
0
0.01
0.1
1
Output Current, IOUT (A)
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
10
1
7
10
100
1000
EN Input Current, IEN (µA)
10000
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APW7089
Operating Waveforms
(Refer to the application circuit 1 in the section “Typical Application Circuits”, VIN=12V, VOUT=3.3V, L1=10µH)
Load Transient Response
Load Transient Response
I OUT = 50mA -> 3A -> 50mA
I OUT rise/f all time=10µs
I OUT = 0.5A -> 3A -> 0.5A
I OUT rise/f all time=10µs
VOUT
1
VOUT
1
3A
3A
IL1
IL1
2
2
0A
Ch1: VOUT, 200mV/Div, DC,
Voltage Offset = 3.3V
Ch2: IL1, 1A/Div, DC
Time: 50µs/Div
0.5A
Ch1: VOUT, 100mV/Div, DC,
Voltage Offset = 3.3V
Ch2: IL1, 1A/Div, DC
Time: 50µs/Div
Power On
Power Off
I OUT = 3A
1
I OUT = 3A
VIN
VIN
1
VOUT
VOUT
2
2
3
IL1
3
Ch1: VIN, 5V/Div, DC
Ch2: VOUT, 2V/Div, DC
Ch3: IL1, 2A/Div, DC
Time: 5ms/Div
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
IL1
Ch1: VIN, 5V/Div, DC
Ch2: VOUT, 2V/Div, DC
Ch3: IL1, 2A/Div, DC
Time: 5ms/Div
8
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APW7089
Operating Waveforms (Cont.)
(Refer to the application circuit 1 in the section “Typical Application Circuits”, VIN=12V, VOUT=3.3V, L1=10µH)
Enable Through EN Pin
Shutdown Through EN Pin
I OUT = 3A
I OUT = 3A
1
1
VEN
VOUT
VOUT
2
2
3
VEN
IL1
3
Ch1: VEN, 5V/Div, DC
Ch2: VOUT, 2V/Div, DC
Ch3: IL1, 2A/Div, DC
Time: 5ms/Div
IL1
Ch1: VEN, 5V/Div, DC
Ch2: VOUT, 2V/Div, DC
Ch3: IL1, 2A/Div, DC
Time: 5ms/Div
Over Current
Short Circuit
I OUT = 1 -> 6A
VOUT is shorted to ground by a short wire
VOUT
1
VOUT
1
I L1
IL1
2
2
Ch1: VOUT, 1V/Div, DC
Ch2: IL1, 2A/Div, DC
Time: 50µs/Div
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
Ch1: VOUT, 1V/Div, DC
Ch2: IL1, 2A/Div, DC
Time: 50ms/Div
9
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APW7089
Operating Waveforms (Cont.)
(Refer to the application circuit 1 in the section “Typical Application Circuits”, VIN=12V, VOUT=3.3V, L1=10µH)
Switching Waveform
Switching Waveform
I OUT = 0.2A
3A
I OUT = 3A
VLX
VLX
1
1
IL1
IL1
2
2
Ch1: VLX, 5V/Div, DC
Ch2: IL1, 1A/Div, DC
Time: 1.25µs/Div
Ch1: VLX, 5V/Div, DC
Ch2: IL1, 2A/Div, DC
Time: 1.25µs/Div
Line Transient Response
VOUT
VIN = 12V --> 24V --> 24V
VIN rise/f all time=20µ s
1
VIN
24V
12V
2
Ch1: VOUT, 50mV/Div, DC,
Voltage Offset = 3.3V
Ch2: VIN, 5V/Div, DC,
Voltage Offset = 12V
Time: 50µs/Div
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
10
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APW7089
Pin Description
PIN
FUNCTION
NO.
NAME
1
VIN
2
EN
Power Input. VIN supplies the power (4.5V to 26V) to the control circuitry, gate driver and
step-down converter switch. Connecting a ceramic bypass capacitor and a suitably large
capacitor between VIN and GND eliminates switching noise and voltage ripple on the input to
the IC.
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. Pull up with 100kΩ resistor for automatic start-up.
UGND
Gate driver power ground of the P-channel Power MOSFET. A linear regulator regulates a 5.5V
voltage between VIN and UGND to supply power to P-channel MOSFET gate driver. Connect a
ceramic capacitor (1µF typ.) between VIN and UGND for noise decoupling and stability of the
linear regulator.
4
VCC
Bias input and 4.2V linear regulator’s output. This pin supplies the bias to some control circuits.
The 4.2V linear regulator converts the voltage on VIN to 4.2V to supply the bias when no
external 5V power supply is connected with VCC. Connect a ceramic capacitor (1µF typ.)
between VCC and GND for noise decoupling and stability of the linear regulator.
5
LX
6
COMP
Output of error amplifier. Connect 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
for noise decoupling.
7
FB
Feedback Input. The IC senses feedback voltage via FB and regulate the voltage at 0.8V.
Connecting FB with a resistor-divider from the output set the output voltage in the range from
0.8V to 90% VIN.
8
GND
9
(Exposed Pad)
LX
3
Power Switching Output. Connect this pin to the underside Exposed Pad.
Power and Signal Ground.
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 Pin 5. Connect the pad to
output LC filter via a top-layer thermal pad on PCBs. The PCB will be a heat sink of the IC.
Block Diagram
VIN
Current Sense
Amplifier
4.2V Regulator
and
Power-On-Reset
VCC
Current
-Limit
VCC
POR
70%VREF
UVP
UG
Soft-Start
and
Fault Logic
Soft-Start
Gate
Driver
Inhibit
UGND
Gate
Control
FB
VREF
0.8V
Error
Amplifier
COMP
Slope
Compensation
ENOK
2.5V
EN
LX
Current
Compartor
Enable
0.8V
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
OverTemperature
Protection
FB
11
Oscillator
380kHz
VIN
Linear
Regulator
GND
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APW7089
Typical Application Circuit
1. 4.5~26V Single Power Input Step-down Converter (with Ceramic Input/Output Capacitors)
C1
10µF
1
VIN
4
VCC
UGND
C3
1µF
VIN
LX
LX
R5
100kΩ
2
6
3
C2
1µF
R4
R1
1%
7
R2
1%
GND
8
C6
VOUT
0.8V~90%VIN/4A
C4
22µF
D1
EN
FB
L1
4A
9
5
U1
APW7089
COMP
VIN
4.5~26V
C7
(Optional)
C5
Recommended Feedback Compensation Network Components List:
VIN
(V)
VOUT
(V)
L1
(µH)
C4
(µF)
C4 ESR
(mΩ)
R1
(kΩ)
R2
(kΩ)
C7
(pF)
R4
(kΩ)
C5
(pF)
C6
(pF)
24
12
15
22
5
140
10
22
62
820
22
24
12
15
44
3
140
10
22
120
820
22
24
5
10
22
5
63.4
12
33
24
1500
22
24
5
10
44
3
63.4
12
33
51
1500
22
12
5
10
22
5
63.4
12
68
24
820
22
12
5
10
44
3
63.4
12
68
51
820
22
12
3.3
10
22
5
47
15
82
15
1000
22
12
3.3
10
44
3
47
15
82
33
1000
22
12
2
4.7
22
5
30
20
56
10
2200
22
12
2
4.7
44
3
30
20
56
20
2200
22
12
1.2
3.3
22
5
7.5
15
150
6.2
3300
22
12
1.2
3.3
44
3
7.5
15
150
12
3300
22
5
3.3
3.3
22
5
47
15
68
15
560
22
5
3.3
3.3
44
3
47
15
68
33
560
22
5
1.2
2.2
22
5
7.5
15
270
5.6
1500
22
5
1.2
2.2
44
3
7.5
15
270
12
1500
22
5
0.8
2.2
22
5
0
NC
NC
2.7
2700
22
5
0.8
2.2
44
3
0
NC
NC
6.2
2700
22
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
12
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APW7089
Typical Application Circuit (Cont.)
2. Dual Power Inputs Step-down Converter (VIN=4.5~26V)
+5V
C1
10µF
D2
Schottky
Diode
1
VIN
4
VCC
UGND
C3
1µF
VIN
LX
LX
R5
100kΩ
2
6
3
C2
1µF
R4
FB
R1
1%
7
R2
1%
GND
8
C6
VOUT
0.8V~90%VIN/4A
C4
22µF
D1
EN
COMP
L1
4A
9
5
U1
APW7089
VIN
4.5~26V
C7
(Optional)
C5
3. 4.5~5.5V Single Power Input Step-down Converter
C1
10µF
1
VIN
4
VCC
UGND
C3
1µF
LX
VIN
R5
100kΩ 2
6
3
C2
1µF
L1
4A
9
U1 LX 5
APW7089
D1
R1
1%
EN
COMP
R4
C6
GND
8
FB
7
VOUT
0.8V~90%VIN/4A
C4
22µF
R2
1%
C7
(Optional)
C5
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
VIN
4.5~5.5V
13
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APW7089
Typical Application Circuit (Cont.)
4. +12V Single Power Input Step-down Converter (with Electrolytic Input/Output Capacitors)
VIN
C8 +12V
470µF
C1
2.2µF
1
C2
1µF
VIN
4
VCC
UGND
C3
1µF
VIN
LX
LX
R5
100kΩ
2
VOUT
+3.3V/4A
D1
R1
47kΩ
1%
EN
COMP
R4
56k
C5
4700pF
L1
10µH
4A
9
5
U1
APW7089
6
C6
22pF
3
FB
7
R2
15k
1%
GND
8
C4
470µF
(ESR=30mΩ)
C7
33pF
5. -8V Inverting Converter with 4.5~5.5V Single Power Input
VIN
4.5~5.5V
1
VIN
R5
100kΩ
2
4
C3
1µF
C6
22pF
6
UGND
EN
3
9
LX
LX 5
VCC U1
APW7089
COMP
R4
39kΩ
C5
560pF
GND
8
FB
7
C2
1µF
C1
10µF
L1
6.8µH
D1 4A
R1
90.9kΩ
R2
10kΩ
PGND
C8
1µF
AGND
C7
27pF
C4
22µF
VOUT
-8V/4A
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
14
www.anpec.com.tw
APW7089
Function Description
Main Control Loop
physically close to the IC to provide good noise
The APW7089 is a constant frequency current mode
switching regulator. During normal operation, the internal
decoupling. The linear regulator is not intended for
powering up any external loads. Do not connect any
P-channel power MOSFET is turned on each cycle when
the oscillator sets an internal RS latch and would be turned
external loads to VCC. The linear regulator is also
equipped with current-limit protection to protect itself dur-
off when an internal current comparator (ICMP) resets
the latch. The peak inductor current at which ICMP resets
ing over-load or short-circuit conditions on VCC pin.
VIN-to-UGND 5.5V Linear Regulator
the RS latch is controlled by the voltage on the COMP pin,
which is the output of the error amplifier (EAMP). An
The built-in 5.5V linear regulator regulates a 5.5V voltage
between VIN and UGND pins to supply bias and gate
charge for the P-channel Power MOSFET gate driver. The
external resistive divider connected between VOUT and
ground allows the EAMP to receive an output feedback
linear regulator is designed to be stable with a low-ESR
ceramic output capacitor of at least 0.22µF. It is also
voltage VFB at FB pin. When the load current increases, it
causes a slight decrease in V FB relative to the 0.8V
equipped with current-limit function to protect itself
during over-load or short-circuit conditions between VIN
reference, which in turn causes the COMP voltage to increase until the average inductor current matches the
and UGND.
new load current.
The APW7089 shuts off the output of the converters when
the output voltage of the linear regulator is below 3.5V
VCC Power-On-Reset(POR) and EN Under-voltage
Lockout
The APW7089 keeps monitoring the voltage on VCC pin
(typical). The IC resumes working by initiating a new softstart process when the linear regulator’s output voltage
to prevent wrong logic operations which may occur when
VCC voltage is not high enough for the internal control
is above the undervoltage lockout voltage threshold.
Digital Soft-Start
circuitry to operate. The VCC POR has a rising threshold
of 3.9V (typical) with 0.15V of hysteresis.
The APW7089 has a built-in digital soft-start to control the
output voltage rise and limit the input current surge
An external under-voltage lockout (UVLO) is sensed and
during start-up. During soft-start, an internal ramp,
connected to the one of the positive inputs of the error
programmed at the EN pin. The EN UVLO has a rising
threshold of 2.5V with 0.2V of hysteresis. The EN UVLO
amplifier, rises up from 0V to 1V to replace the reference
voltage (0.8V) until the ramp voltage reaches the reference
should be programmed by connecting a resistive divider
from VIN to EN to GND.
voltage.
After the VCC, EN, and VIN-to-UGND voltages exceed their
The device is designed with a preceding delay about
10.8ms (typical) before soft-start process.
respective voltage thresholds, the IC starts a start-up
process and then ramps up the output voltage to the
Output Under-Voltage Protection
setting of output voltage. Connect a RC network from EN
to GND to set a turn-on delay that can be used to sequence
In the process of operation, if a short-circuit occurs, the
the output voltages of multiple devices.
output voltage will drop quickly. Before the current-limit
circuit responds, the output voltage will fall out of the
VCC 4.2V Linear Regulator
required regulation range. The under-voltage continually
monitors the FB voltage after soft-start is completed. If a
VCC is the output terminal of the internal 4.2V linear
regulator which is powered from VIN and provides power
to the APW7089. The linear regulator is designed to be
load step is strong enough to pull the output voltage lower
than the under-voltage threshold, the IC shuts down
stable with a low-ESR ceramic output capacitor powers
the internal control circuitry. Bypass VCC to GND with a
converter’s output.
ceramic capacitor of at least 0.22µF. Place the capacitor
The under-voltage threshold is 70% of the nominal out-
Copyright ANPEC Electronics Corp.
Rev. A.1 - Jan., 2012
15
www.anpec.com.tw
APW7089
Function Description (Cont.)
Output Under-Voltage Protection (Cont.)
put voltage. The under-voltage comparator has a built-in
2µs noise filter to prevent the chips from wrong UVP shutdown caused by noise. The under-voltage protection
works in a hiccup mode without latched shutdown. The
IC will initiate a new soft-start process at the end of the
preceeding delay.
Over-Temperature Protection (OTP)
The over-temperature circuit limits the junction temperature of the APW7089. When the junction temperature exceeds TJ = +150oC, a thermal sensor turns off the power
MOSFET, allowing the devices to cool. The thermal sensor
allows the converter to start a start-up process and
regulate the output voltage again after the junction
temperature is cooled by 50 oC. The OTP is designed
with a 50oC hysteresis to lower the average TJ during continuous thermal overload conditions, increasing lifetime
of the IC.
Enable/Shutdown
Driving EN to ground places the APW7089 in shutdown.
When in shutdown, the internal power MOSFET turns off,
all internal circuitry shuts down and the quiescent supply
current of VIN reduces to
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