AP3988

A Product Line of
Diodes Incorporated
AP3988
PRIMARY SIDE POWER SWITCHER FOR OFF-LINE SMPS
NEW PRODUCT
Description
Pin Assignments
The AP3988 is a performance enhanced power switcher for power
supplies with better conversion efficiency, better voltage & current
accuracy, and improved protection functions. Typical applications
include charger, adapter for ADSL, home appliance power supply,
LED lighting power supply and PC auxiliary power supplies. The
controller regulates the output voltage and current in the primary
side by piece-wise Pulse Frequency Modulation (p-PFM) in
discontinuous conduction mode (DCM). The system operating
frequency reduces linearly from heavy load to light load in each
interval of the p-PFM, and enters constant current mode when the
load current equals to the maximum system output current.
(Top View)
CPC
1
FB
2
VCC
CS
The AP3988 provides operating frequency dithering function to
improve EMC performance of power supply. It also has built-in
fixed cable voltage drop compensation (5% of nominal system
output voltage) and adjustable line voltage compensation.
7
GND
3
6
C
4
5
C
SO-7
The AP3988 solution has fewer component number, smaller size,
and lower total cost.
Applications
The AP3988 is packaged in SO-7.



Features


Primary Side Control for Eliminating
Secondary CV/CC Control Circuitry
Built-in NPN Transistor with 700VCBO









Low Start-up Current: 0.2A (Typ.)
Internal Output Cable Voltage Drop Compensation
Hiccup Function to Improve Short Circuit Protection
Better Over Voltage Protection
Better Over Temperature Protection
Low Total Cost Solution
Output Power Range (Note 1): for 5.5W Adapter
Totally Lead-free & Fully RoHS Compliant (Note 2 & 3)
Halogen and Antimony Free. “Green” Device (Note 4)
Notes:
Opto-coupler
Adapters
Set Top Boxes
Appliances
and
1. Typical continuous power in a non-ventilated enclosed adapter measured at +50°C ambient.
2. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
3. 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.
4. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
AP3988
Document number: DS36722 Rev. 4 - 2
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A Product Line of
Diodes Incorporated
AP3988
Typical Applications Circuit
Rf1
D1 to D4
L1
C11 R11
NEW PRODUCT
Vo+
J1
AC 90-264V
+
C1
+
C2
C5
R6
Np
D12
R10
+
C12
R12
R3
D5
Vo-
L2
D6
R5
T1
+
C3
C8
Nfb
U1
VCC C
R8
CPC
GND
CS
FB
R9
R7
For AP3988 (5V/1A)
Item
Function
QTY
Item
Function
QTY
C1,C2
4.7µF/400V, electrolytic
2
Rf1
10Ω/1W, fuse resistor
1
C3
4.7µF/50V, electrolytic
1
R3
3.3M/0.25W
1
C5
1nF/250V, ceramic
1
R5
3.9, 0805
1
C8
0.01µF, 0805
1
R6
150k, 1206
1
C11
1nF, 0805
1
R7
2.7, 1206
1
C12
680µF/10V
1
R8
75k, 0805
1
D1 to D6
1N4007, rectifier diode
6
R9
43k, 0805
1
D12
APD340,Schottky diode
1
R10
200, 0805
1
L1
1mH, inductor
1
R11
27, 0805
1
L2
Bead, 0805
1
R12
1.5k, 0805
1
U1
AP3988, SO-7
1
T1
EE13 core, PC40, transformer
1
AP3988
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AP3988
NEW PRODUCT
Pin Descriptions
Pin Number
Pin Name
1
CPC
2
FB
3
VCC
4
CS
5, 6
C
7
GND
Function
This pin connects a capacitor to GND for output cable compensation
The voltage feedback from auxiliary winding
This pin receives rectified voltage from the auxiliary winding of the transformer
Current sense for primary side of transformer
This pin is connected with an internal power BJT’s collector
This pin is the signal reference ground
Functional Block Diagram
VCC
3
OVP
OCkP
Output Short
OTP
Max Tonp
Rcs Short
tOSC
0.05V
FB
COMP
2
Regulator
&
Bias
OSC
tONS
tONS, NL and LL
Detector
PFM
UVLO
NL
LL
7
Pro
GND
Vload
UV
LL
UV
NL
PFM
Dynamic
Response
Dyn
CV_ctrl
5, 6
Vally
ON
(LL+NL)Bar
C
DetectON
VFB_ref
Constant Voltage Control
Cable Compensation
R
Q
Detect
Pulse
Driver
S
tosc NL LL
Vload
Line
Comp.
VCSN(N=1,2,3)
Peak Current Control
LEB
Frequency Dither
VCSN Select
Vload
CS
UV
tONS
Shutdown
Pre_Shutdown
CV_M
DetectON
CC_ctrl
Constant Current
Control
R Q
S
VCSN(N=1,2,3)
CPC
Vload
4
1
CPC
AP3988
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CS
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AP3988
Absolute Maximum Ratings (Note 5)
Symbol
VCC
VCS, VCPC
NEW PRODUCT
VFB
Parameter
Rating
Unit
Supply Voltage
-0.3 to 30
V
Voltage on CS, CPC Pin
-0.3 to 7
V
FB Input Voltage
-0.3 to 8
V
VCBO
Collector-emitter Voltage
700
V
ICDC
Collector DC Current
1.5
A
+150
°C
-65 to +150
°C
Operating Junction Temperature
TJ
TSTG
Storage Temperature
TLEAD
Lead Temperature (Soldering, 10 sec)
+300
°C
–
ESD (Machine Model)
200
V
–
ESD (Human Body Model)
2000
V
0.7
W
Total Power Dissipation
PD
Note 5: 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
–
25
V
VCC
Supply Voltage
TOP
Operating Temperature Range
-40
+85
°C
fS(MAX)
Maximum Operating Frequency
–
60
kHz
Thermal Impedance (Note 6)
Symbol
Parameter
Value
θJA
Junction to Ambient
140
θJC
Junction to Case
70
Unit
°C/W
Note 6: When mounted a standard single-sided FR4 board with 300mm2 Cu (at least 35µm thick) connected to CS pin and all collectors.
AP3988
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AP3988
Electrical Characteristics
Symbol
(@VCC=15V, TJ=+25°C, unless otherwise specified.)
Parameters
Conditions
Min
Typ
Max
Unit
STARTUP AND UVLO SECTION
VTH_ST
Turn-on Voltage
–
13
15
17
V
VOPR(MIN)
Turn-off Voltage
–
5.2
5.8
6.4
V
0
0.2
0.6
550
650
750
–
–
60
kHz
4.5
5
5.5
%
–
1.8
2
2.2
kHz
40% to 100% of full load
874
910
946
mV
17% to 40% of full load
581
605
630
mV
5% to 17% of full load
390
405
425
mV
NEW PRODUCT
STANDBY CURRENT SECTION
IST
ICC_OPR
Turn-on Current
VCC=VTH_ST-1V before
startup
Operating Current
Static current @ no load
OPERATING FREQUENCY SECTION (5% LOAD TO FULL LOAD)
Operating Frequency in Full Load
–
fS(MAX)
Condition
5% to 100% of full load
Δf/f
Frequency Dithering
range
μA
OPERATING FREQUENCY SECTION (NO LOAD TO 5% OF IOUT(MAX))
fS(MIN)
Output Voltage Detection Frequency
CURRENT SENSE SECTION
Peak Current Sense Voltage in Heavy
VCS_H
Load
Peak Current Sense Voltage in Middle
VCS_M
Load
Peak Current Sense Voltage in Light
VCS_L
Load
ΔVCS/VCS
VCS Modulation for Frequency Dithering
–
–
2.5
–
%
tMOD
VCS Modulation Period
–
225
250
275
μs
RLINE
Built-in Line Compensation Resistor
–
260
330
400
Ω
tLEB
Leading Edge Blanking
@ VCS_H and VCS_M
600
750
900
ns
Closed loop test of VOUT
4.13
4.20
4.27
V
FB Pin Input Current
VFB=4V
3.36
4.20
5.04
μA
Cable Compensation Drop
–
–
0.35
–
V
VFB=3V
–
4/7
–
–
Collector-emitter Saturation Voltage
IC=0.5A
–
–
0.3
V
hFE
DC Current Gain
–
14
17
–
–
ICEO
Leakage Current
–
–
–
60
μA
–
7.5
–
V
CONSTANT VOLTAGE SECTION
Equivalent Feedback Voltage @ 90%
VFB
Load
IFB
VCABLE
CONSTANT CURRENT SECTION
tONS/tSW
Secondary Winding Conduction Duty
POWER TRANSISTOR SECTION
VCE(SAT)
PROTECTION FUNCTION SECTION
VFB(OVP)
Over Voltage Protection
–
VFB(SCP)
Short Circuit Protection
VFB @ Hiccup
2.6
3.3
3.7
V
TOTP
Shutdown Temperature
–
+125
+160
–
°C
THYS
Temperature Hysteresis
–
–
+40
–
°C
AP3988
Document number: DS36722 Rev. 4 - 2
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A Product Line of
Diodes Incorporated
AP3988
Performance Characteristics
Turn-on Voltage vs. Ambient Temperature
Turn-off Voltage vs. Ambient Temperature
6.5
14.8
6.0
Turn-off Voltage (V)
NEW PRODUCT
Turn on Voltage (V)
14.7
14.6
14.5
5.5
14.4
5.0
14.3
14.2
-40
-20
0
20
40
60
o
80
100
4.5
-40
120
-20
0
20
40
60
80
100
120 125
o
Ambient Temperature ( C)
Ambient Temperature ( C)
Operating Current vs. Ambient Temperature
750
Operating Current (A)
700
650
600
550
500
-40
-20
0
20
40
60
80
100
120 125
o
Ambient Temperature ( C)
Operation Description
VS
Vbulk
VIN
+
C1
LM N P
NS
D1
CO
VO
+
IOUT
AP3988
VAUX
C
NAUX
Q1
RFB1
CS
GND
CPC
FB
CCPC
RCS
RFB2
Figure 1. Simplified Flyback Converter Controlled by AP3988
AP3988
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AP3988
Operation Description (Cont.)
Constant Primary Peak Current
The primary ip(t) current is sensed by a current sense resistor RCS as shown in Figure 1.
The current rises up linearly at a rate of:
dip (t )
NEW PRODUCT
dt

Vbulk (t ) ……… (1)
LM
See equation 2
IPK
ip(t)
0A
Figure 2. Primary Current Waveform
As illustrated in Figure 2, when the current ip(t) rises up to IPK, the switch Q1 turns off. The constant peak current is given by:
I PK 
VCS
………(2)
RCS
The energy stored in the magnetizing inductance LM each cycle is therefore:
1
2
Eg   LM  I PK ………(3)
2
So the power transferring from input to output is given by:
P
1
2
 LM  I PK  f SW ………(4)
2
Where fSW is the switching frequency. When the peak current I PK is constant, the output power depends on the switching frequency fSW.
Constant Voltage Operation
The AP3988 captures the auxiliary winding feedback voltage at FB pin and operates in constant-voltage (CV) mode to regulate the output voltage.
Assuming the secondary winding is master, the auxiliary winding is slave during the D1 on-time. The auxiliary voltage is given by:
V AUX 
N AUX
 VO  Vd  ………(5)
NS
Where Vd is the diode forward drop voltage, NAUX is the turns of auxiliary winding, and NS is the turns of secondary winding.
See equation 5
VAUX
0V
Portion of Tons
Tons
Figure 3. Auxiliary Voltage Waveform
The output voltage is different from the secondary voltage in a diode forward drop voltage V d which depends on the current. If the secondary
voltage is always detected at a constant secondary current, the difference between the output voltage and the secondary voltage will be a fixed Vd.
The voltage detection point is portion of Tons after D1 is turned on. The CV loop control function of AP3988 then generates a D1 off-time to regulate
the output voltage.
AP3988
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AP3988
Operation Description (Cont.)
Constant Current Operation
The AP3988 is designed to work in constant current (CC) mode. Figure 4 shows the secondary current waveforms.
NEW PRODUCT
See equation 7
Is
IOUT
0A
Tons
Toffs
Figure 4. Secondary Current Waveform
In CC operation, the CC loop control function of AP3988 will keep a fixed proportion between D1 on-time Tons and D1 off-time Toffs by discharging
or charging the built-in capacitance connected. This fixed proportion is
Tons 4 ……… (6)

Toffs 3
The relation between the output constant-current and secondary peak current IPKS is given by:
Tons
1
………(7)
I OUT   I PKS 
2
Tons  Toffs
At the instant of D1 turn-on, the primary current transfers to the secondary at an amplitude of:
I PKS 
NP
 I PK ………(8)
NS
Thus the output constant current is given by:
2 N
I OUT   P  I PK ………(9)
7 NS
Leading Edge Blanking (LEB)
When the power switch is turned on, a turn-on spike on the output pulse rising edge will occur on the sense-resistor. To avoid false termination of
the switching pulse, a typical 750ns leading edge blanking is built in. During this blanking period, the current sense comparator is disabled and the
gate driver cannot be switched off.
The built-in LEB in AP3988 has shorter delay time from current sense terminal to output pulse than those IC solutions adopting external RC filter
as LEB.
Built-in Cable Compensation
The AP3988 has built-in fixed voltage of 0.35V typical to compensate the drop of output cable when the load is changed from zero to full load. A
typical 10nF external capacitor connected to the CPC pin is used to smooth voltage signal for cable compensation.
Over Temperature Protection
The AP3988 has internal thermal sensing circuit to shut down the PFM driver output when the die temperature reaches +160°C typical. When the
die temperature drops about +40°C, the IC will recover automatically to normal operation.
AP3988
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AP3988
Ordering Information
NEW PRODUCT
AP3988 X XX - G1
Product Name
Package
Packing
RoHS/Green
M : SO-7
TR : Tape & Reel
G1 : Green
Diodes IC’s Pb-free products with "G1" suffix in the part number, are RoHS compliant and green.
Package
Temperature Range
SO-7
-40°C to +85°C
Part Number
AP3988MTR-G1
Marking ID
3988M-G1
Packing
4000/Tape & Reel
Marking Information
(Top View)
First and Second Lines: Logo and Marking ID
Third Line: Date Code
Y: Year
WW: Work Week of Molding
A: Assembly House Code
th
th
XX: 7 and 8 Digits of Batch No.
AP3988
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AP3988
Package Outline Dimensions (All dimensions in mm(inch).)
(1)
Package Type: SO-7
5.800(0.228)
1.350(0.053)
1.750(0.069)
NEW PRODUCT
6.200(0.244)
0.330(0.013)
0.510(0.020)
2.54(0.100)
TYP
4.700(0.185)
5.100(0.201)
1.270(0.050)
TYP
0.100(0.004)
0.250(0.010)
3.800(0.150)
4.000(0.157)
0.190(0.007)
0.250(0.010)
0°
8°
1.250(0.049)
1.500(0.059)
0.450(0.017)
0.800(0.031)
Note: Eject hole, oriented hole and mold mark is optional.
AP3988
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AP3988
Suggested Pad Layout
Package Type: SO-7
NEW PRODUCT
(1)
G
Z
E1
Y
X
E
Dimensions
Z
(mm)/(inch)
G
(mm)/(inch)
X
(mm)/(inch)
Y
(mm)/(inch)
E
(mm)/(inch)
E1
(mm)/(inch)
Value
6.900/0.272
3.900/0.154
0.650/0.026
1.500/0.059
1.270/0.050
2.540/0.100
AP3988
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AP3988
IMPORTANT NOTICE
NEW PRODUCT
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes
without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the
application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or
trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume
all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated
website, harmless against all damages.
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel.
Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and
hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or
indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.
Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings
noted herein may also be covered by one or more United States, international or foreign trademarks.
This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the
final and determinative format released by Diodes Incorporated.
LIFE SUPPORT
Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the
labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the
failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any
use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related
information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its
representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2014, Diodes Incorporated
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