AP3125B
Document number: DS36659 Rev. 3 - 2
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AP3125B
A Product Line of
Diodes Incorporated
NEW PROD UCT
GREEN MODE PWM CONTROLLER
Description
The AP3125B is a current mode PWM controller which is optimized
for high performance, low standby power and cost effective offline
flyback converters.
The PWM switching frequency at normal operation is internally fixed
(about 65kHz). In middle load, the IC will enter green mode to
improve system efficiency with the help of frequency foldback. A
minimum switching frequency (about 20kHz) is set to avoid the
audible noise. In no load or light load, the IC will enter the burst mode
to minimize standby power. Furthermore, the frequency dithering
function is built-in to reduce EMI emission.
Internal slope compensation allows more stable Peak-Current Mode
control over wide range of input voltage and load conditions. Internal
line compensation ensures constant output power limit over entire
universal line voltage range.
Comprehensive protection features are included, such as cycle-by-
cycle current limit (OCP), VCC Over Voltage Protection (VOVP),
internal OTP, Over Load Protection (OLP) and pins’ fault protection.
Built-in Brownout (BNO) and Line Over Voltage Protection (LOVP)
are also integrated in AP3125B.
Features
Very Low Start-up Current
Current Mode Control
Non-audible-noise Green-mode Control
Internal Slope Compensation
Soft Start During Startup Process
Frequency Fold Back for High Average Efficiency
Secondary Winding Short Protection with FOCP
Soft Switching for Reducing EMI
VCC Maintain Mode
Brownout Protection (BNO)
Line Over Voltage Protection (LOVP)
Useful Pin Fault Protection:
SENSE Pin Floating
SENSE Pin Short to Ground
FB/Opto-coupler Open/Short
Comprehensive System Protection Feature:
VCC Over Voltage Protection (VOVP)
Over Load Protection (OLP)
Mini Size with Packages
Pin to Pin Compatible with AP3105NA/NV/NL/NR
Totally Lead-free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Pin Assignments
(Top View)
SOT26
Applications
Switching AC-DC Adapter/Charger
ATX/BTX Auxiliary Power
Set-top Box (STB) Power Supply
Open Frame Switching Power Supply
Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
1
2
3 4
5
Pin 1 Mark
6
GND
FB
BNO
GATE
VCC
SENSE
AP3125B
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AP3125B
A Product Line of
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NEW PROD UCT
Typical Applications Circuit
~
~
+
-
VCC
GND
GATE
FB
SENSE
BNO
~
AZ431
AP3125B
L2
T1
R13 C7
C6
C8
R14
R15
R16 R17
R18
C9
C10
R12R11
R10
R9
C5R6
R19
C4
R5
R4
C2
C1
VR1
NTC
R2 R3
F1
R7
C3
C11
R8
R20
C20
Pin Descriptions
Pin Number
Pin Name
Function
1
GND
Signal ground. Current return for driver and control circuits
2
FB
Feedback. Directly connected to the opto-coupler
3
BNO
Control brownout protection
4
SENSE
Current sense
5
VCC
Supply voltage of driver and control circuits
6
GATE
Gate driver output
AP3125B
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AP3125B
A Product Line of
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Functional Block Diagram
GND
GATE
250ns LEB
Driver 13V
OSC with
Frequency Jitter
0.95V
VCC_OVP
OLP
VCC
32V 28V
VCC_OVP
UVLO
16V
7.6V Internal
Bias
Auto
Recovery
Protection
AP3125B
FB
R
2R
PWM
0.3V
1.3V
Latch-off
Protection
70mS
Debounce
OLP
FOCP
OCP
SS
SS
VDD
Soft
Start
1.80V
FOCP
QD
CLK RB
DFF
OTP
VCC
VDD
OTP
150oC/125oC
BNO
0.95V
4.2V
5.5V
Line_OVP
Brownout 0.9V
50mS
Debounce
Line_OVP
Brownout
SENSE
6
3
4
1
2
5
Line
Compensation
AP3125B
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NEW PROD UCT
Absolute Maximum Ratings (Note 4)
Symbol
Parameter
Rating
Unit
VCC
Power Supply Voltage
30
V
IO
Gate Output Current
350
mA
VFB, VSENSE, VBNO
Input Voltage to FB, SENSE, BNO
-0.3 to 7
V
θJA
Thermal Resistance (Junction to Ambient)
250
°C/W
PD
Power Dissipation at TA < +25°C
500
mW
TJ
Operating Junction Temperature
-40 to +150
°C
TSTG
Storage Temperature Range
+150
°C
–
ESD (Human Body Model)
3000
V
–
ESD (Machine Model)
300
V
Note 4: Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “Recommended Operating Conditions” is not implied.
Exposure to “Absolute Maximum Ratings” for extended periods may affect device reliability.
Recommended Operating Conditions
Symbol
Parameter
Min
Max
Unit
VCC
Supply Voltage
10
25
V
AP3125B
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Electrical Characteristics (@TA = +25°C, VCC = 16V, unless otherwise specified.)
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
Supply Voltage (VCC Pin)
ISTARTUP
Startup Current
–
–
1
10
μA
ICC
Operating Supply Current
VFB=0V, CL=1nF
0.5
0.7
1
mA
VFB=3V, CL=0nF
0.6
1.2
2.0
–
UVLO (on)
–
14.5
15.8
16.5
V
–
VCC Maintain
–
8.6
9.1
9.6
V
–
UVLO (off)
–
7.1
7.6
8.1
V
–
VCC OVP
–
27
28.5
30
V
–
VCC Clamp
ICC=5mA
31
34
–
V
PWM Section/Oscillator Section
–
Maximum Duty Cycle
–
70
75
80
%
–
Oscillation Frequency
–
60
65
70
kHz
–
Green Mode Frequency
–
20
–
30
kHz
–
Frequency Temperature
Stability
-20°C to +125°C
(Note 5)
–
–
5
%
–
Frequency Voltage Stability
VCC=12V to 30V
–
–
3
%
–
Frequency Dithering
–
±4
±6
±8
%
Current Sense Section (SENSE Pin)
VCS
Maximum SENSE Voltage
VFB=4.5V
0.9
0.95
1
V
–
FOCP Voltage
–
1.5
1.7
1.9
V
–
SENSE Shorted Protection
Threshold
–
–
0.1
–
V
–
LEB Time of SENSE
–
150
250
350
ns
–
Delay to Output (Note 5)
–
–
100
–
ns
–
Soft-start Time
–
3
5
8
ms
Feedback Input Section (FB Pin)
–
The Ratio of Input Voltage to
Current Sense Voltage
–
2.5
3
3.5
V/V
–
Input Impedance
–
12
15
18
kΩ
–
Source Current
VFB=0V
-0.2
-0.27
-0.34
mA
–
Green Mode Threshold
–
–
2.1
–
V
–
Input Voltage for Zero Duty
–
1.3
1.55
1.8
V
Output Section (GATE Pin)
–
Output Low Level
IO=20mA, VCC=12V
–
–
1
V
–
Output High Level
IO=20mA, VCC=12V
8
–
–
V
–
Output Clamping Voltage
–
11
13
15
V
–
Rising Time (Note 5)
CL=1nF, VCC=13V
–
150
250
ns
–
Falling Time (Note 5)
CL=1nF, VCC=13V
–
50
100
ns
AP3125B
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AP3125B
A Product Line of
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Electrical Characteristics (Cont.) (@TA = +25°C, VCC = 16V, unless otherwise specified.)
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
Brownout Section (BNO Pin)
–
Brown-in Voltage
–
0.93
0.95
0.97
V
–
Brownout Voltage
–
0.88
0.9
0.92
V
–
Clamping Voltage
ICLAMP=1mA
–
5.5
–
V
–
Line OVP
–
4.1
4.2
4.3
V
Delay Time Section
–
Delay of Short Circuit
Protection
–
–
70
–
ms
–
Delay of Hiccup Protection
VCC OVP
–
5
–
Cycles
–
De-bounce Time of Brownout
–
–
50
–
ms
Internal OTP Section
–
OTP Enter
–
–
+150
–
°C
–
OTP Exit
–
–
+125
–
°C
Note 5: Guaranteed by design.
AP3125B
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AP3125B
A Product Line of
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Performance Characteristics
Startup Voltage vs. Ambient Temperature Shutdown Voltage vs. Ambient Temperature
Startup Current vs. Ambient Temperature Operating Current vs. Ambient Temperature
BNO Utilization for Brownout
BNO
CBUCK
-40 -20 0 20 40 60 80 100 120 140
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Startup Current (A)
Ambient Temperature (oC)
-40 -20 0 20 40 60 80 100 120 140
13
14
15
16
17
18
Startup Voltage (V)
Ambient Temperature (oC)
-40 -20 0 20 40 60 80 100 120 140
6.5
7.0
7.5
8.0
8.5
9.0
Shutdown Voltage (V)
Ambient Temperature (oC)
-40 -20 0 20 40 60 80 100 120 140
0.5
0.6
0.7
0.8
0.9
VFB=3V, CL=0
Operating Current (mA)
Ambient Tempture (oC)
AP3125B
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Operation Description
The AP3125B is specifically designed for off-line AC-DC power
supply used in LCD monitor, notebook adapter and battery charger
applications. It offers a cost effective solution with a versatile
protection function.
Start-up Current and UVLO
The start-up current of AP3125B is optimized to realize ultra low
current (1A typical) so that VCC capacitor can be charged more
quickly. The direct benefit of low start-up current is the availability of
using large start-up resistor, which minimizes the resistor power
loss for high voltage AC input.
An UVLO comparator is included in AP3125B to detect the voltage
on VCC pin. It ensures that AP3125B can draw adequate energy
from hold-up capacitor during power-on. The turn-on threshold is
16V and the turn-off threshold is 7.6V.
Current Sense Comparator and PWM Latch
The AP3125B operates as a current mode controller, the output
switch conduction is initiated by every oscillator cycle and is
terminated when the peak inductor current reaches the threshold
level established by the FB pin. The inductor current signal is
converted to a voltage signal by inserting a reference sense resistor
RS. The inductor current under normal operating conditions is
controlled by the voltage at FB pin. The relation between peak
inductor current (IPK) and VFB is:
SFBPK RVI 3/)8.0(
Moreover, FOCP with 1.8V threshold is only about 100ns delay,
which can avoid some catastrophic damages such as secondary
rectifier short test. Few drive cycles can alleviate the destruction
range and get better protection.
Leading-edge Blanking
A narrow spike on the leading edge of the current waveform can
usually be observed when the power MOSFET is turned on. A
250ns leading-edge blank is built-in to prevent the false-triggering
caused by the turn-on spike. During this period, the current limit
comparator is disabled and the gate driver can not be switched off.
At the time of turning off the MOSFET, a negative undershoot
(maybe larger than -0.3V) can occur on the SENSE pin. So it is
strongly recommended to add a small RC filter or at least connect a
resistor “R” on this pin to protect the IC (Shown as Figure 1).
FB
SENSE
GATE
GND
BNO 6
1
3
4
AP3125B
VCC
5
2
Large undershoot (more than
-0.3V) may damage the SENSE pin
R
C
Necessary
Figure 1
Built-in Slope Compensation
It is well known that a continuous current mode SMPS may become
unstable when the duty cycle exceeds 50%. The built-in slope
compensation can improve the stability, so there is no need for
design engineer to spend much time on that.
FB Pin and Short Circuit Protection
This pin is normally connected to the opto-coupler and always
paralleled with a capacitor for loop compensation. When the voltage
at this pin is greater than 4.5V and lasts for about 70ms, the IC will
enter the protection mode. For AP3125B, the system will enter
hiccup mode to wait the VCC decreasing to low UVLO level, then the
IC will try to restart until the failure removed. And when this voltage
is less than 1.55V, the IC will stop the drive pulse immediately.
Therefore, this feature can be used for short circuit protection,
which makes the system immune from damage. Normally, output
short makes the VFB value to the maximum because the opto-
coupler is cut off.
VCC Maintain Mode
During light load or step load, VFB will drop and be lower than 1.55V,
thus the PWM drive signal will be stopped, and there is no more
new energy transferred due to no switching. Therefore, the IC
supply voltage may reduce to the shutdown threshold voltage and
system may enter the unexpected restart mode. To avoid this, the
AP3125B hold a so-called VCC maintain mode which can supply
energy to VCC.
When VCC decreases to a setting threshold, the VCC maintain
comparator will output some drive signal to make the system switch
and provide a proper energy to VCC pin. The VCC maintain function
will cooperate with the PWM and burst mode loop which can make
the output voltage variation be within the regulation. This mode is
very useful for reducing startup resistor loss and achieving a better
standby performance with a low value VCC capacitor. The VCC is
not easy to touch the shutdown threshold during the startup process
and step load. This will also simplify the system design. The
minimum VCC voltage is suggested to be designed a little higher
than VCC maintain threshold thus can achieve the best balance
between the standby and step load performance。
System Protection and Pin Fault Protection
The AP3125B provides versatile system and pin fault protections.
The OCP comparator realizes the cycle-by-cycle current limiting
(OCP). In universal input line voltage, the IC realizes the constant
over load protection (OLP). VCC over voltage protection can be
applied as the primary OVP or opto-coupler broken protection. The
AP3125B also has pin fault connection protection including floating
and short connection. The floating pin protection includes the
SENSE, FB, etc. The short pin protection includes the CTRL pin
short protection. When these pins are floated or CTRL pin is
shorted to ground, PWM switching will be disabled, thus protecting
the power system.
AP3125B
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AP3125B
A Product Line of
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NEW PROD UCT
Operation Description (Cont.)
Brownout Protection Function
To avoid potential high current stress at low line voltage, AP3125B
introduces reliable brownout protection. AC line voltage information
is sampled through a voltage divider net-work, adjusting the divider
ratio to achieve expected brownout protection voltage. A typical
0.1nFcapacitor is strongly recommended to parallel with BNO pin to
bypass any accidental spike in AC line for preventing false trigger.
When the voltage across BNO pin is higher than 0.95V and VCC
reaches UVLO/ON, the GATE pin will output drive signals. If the
BNO voltage falls below 0.9V and lasts for 50ms, the GATE pin will
turn off and the system will enter hiccup mode until the line voltage
rises over its brown-in voltage again.
Internal OTP Protection Function
The AP3125B integrates an internal temperature sensor. It has a
trigger window of +150°C enter and +125°C exit. The internal OTP
protection mode is auto-recovery mode.
Ordering Information
AP3125XX XX XX - G1
Packing
Package
TR : Tape & Reel
K : SOT26 G1 : Green
Product Name RoHS/Green
Product Version*
B : AP3125B
Package
Part Number
Marking ID
Packing
SOT26
AP3125BKTR-G1
GLV
3000/Tape & Reel
*Product Version Classification (with Different Protection Functions)
Product Version
Frequency
VOVP
OLP & SOCP
BNO
LOVP
AP3125B
65kHz
Auto-Recoverable
Auto-Recoverable
Auto-Recoverable
Latch
Marking Information
(Top View)
: Logo
XXX: Marking ID (See Ordering Information)
Diodes IC’s Pb-free products with "G1" suffix in the part number, are RoHS compliant and green.
AP3125B
Document number: DS36659 Rev. 3 - 2
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AP3125B
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Package Outline Dimensions (All dimensions in mm(inch).)
(1) Package Type: SOT26
2.820(0.111)
3.100(0.122)
2.650(0.104)
3.000(0.118)
1.500(0.059)
1.700(0.067)
0.950(0.037)TYP
1.800(0.071)
2.000(0.079)
0.300(0.012)
0.500(0.020)
0.700(0.028)REF
0.100(0.004)
0.200(0.008)
0°
8°
0.200(0.008)
0.300(0.012)
0.600(0.024)
0.000(0.000)
0.150(0.006)
0.900(0.035)
1.300(0.051) 1.450(0.057)
MAX
1 2 3
4
5
6
Pin 1 Mark
AP3125B
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Suggested Pad Layout
(1) Package Type: SOT26
Dimensions
Z
(mm)/(inch)
G
(mm)/(inch)
X
(mm)/(inch)
Y
(mm)/(inch)
E
(mm)/(inch)
Value
3.600/0.142
1.600/0.063
0.700/0.028
1.000/0.039
0.950/0.037
AP3125B
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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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.
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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
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