Data Sheet

HT7A3942
High Performance
Current Mode PWM Controller
Feature
General Description
• High performance, low cost current mode PWM
controller especially designed for energy star 2.0
The HT7A3942 is a high performance, low cost
Current Mode PWM controller for providing
necessary feature to implement Off-Line application.
By Optimizing for the Energy Star 2.0 spec., the
Power Supply Unit (PSU) implemented using the
HT7A3942 can satisfy the “Energy Star No-Load
Mode” Stand-by Power standard, which is less than
0.3W within all Nameplate Output Power Range of
0~250W. Internally implemented circuits include a
trimmed Oscillator for precise frequency control,
a temperature-compensated Voltage Reference,
Slope Compensation, Leading-Edge Blanking, and
a patented Non-Audible Noise Green Mode Control
Scheme.
• High-Voltage CMOS process with excellent ESD
protection (>3KV)
• Very low startup current (<20μA) and operating
current
• ±5% trimmed oscillator for precise frequency
control
• Non-audible-noise Green Mode control
• LEB (Leading-Edge Blanking) on CS pin
• Internal slope compensation
• Programmable switching frequency
• Internally trimmed reference with UVLO
(Under Voltage Lockout) The HT7A3942 features a range of various protection
functions such Short-Circuit Protection (SCP, which
can also be used for Over-Load Protection, OLP),
Cycle-by-Cycle Current Limiting and Under Voltage
Lock-Out (UVLO).
• Cycle-by-Cycle Current Limiting
• Build-in Short-Circuit-Protection(SCP) for
Short-Circuit and Over-Load condition
• 8-Pin SOP package
Applications
• Switching AC-DC adaptor
• Open frames switching power supply
• LCD TV
Application Circuits
EMI Filter
Flyback Converter
VOUT
RT
GD
HT7A3942
GND
CS
VCC
COMP
VREF
0.1uF
FOD817
Voltage Sense
10k
Current Sense
GND
95k
TL431
25k
Rev. 1.00
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May 27, 2011
HT7A3942
Block Diagram
Pin Assignment
VREF
VCC
UVLO
Driver
Stage
RT
S
GD
Q
GND
R
Slop
Compensation
PWM
2R
COMP
14V / 8V
Green Mode
OSC
VCC
Internal Bias
& Vref
32V
R
OCP
CS
LEB
350nS
SCP
1V
Pin Description
Pin No.
Pin Name
Description
1
COMP
2
N.C
No connection
3
CS
A voltage proportional to inductor current is connected to this input. The PWM generator
uses this voltage information to terminate the output switch conduction.
4
RT
The oscillator frequency is programmed by connecting a resistor RT between this pin and
ground. A maximum frequency of 500KHz is possible.
5
GND
6
GD
7
VCC
Positive Supply.
8
VREF
Reference output.
Voltage Feedback Pin. Connected to a Photo-Coupler for close-loop control.
Combined control circuitry and power ground.
Power MOSFET gate driver output.
Absolute Maximum Ratings
Supply Voltage VCC�������������������������������������������������������������������������������������������������������������������������������� -0.3V~30.0V
COMP, RT, CS Pins����������������������������������������������������������������������������������������������������������������������������������� -0.3V~5.5V
Junction Temperature������������������������������������������������������������������������������������������������������������������������������������������ 150°C
Operating Ambient Temperature��������������������������������������������������������������������������������������������������������������� -40°C~85°C
Storage Temperature Range�������������������������������������������������������������������������������������������������������������������� -65°C~150°C
Package Thermal Resistance (8-Pin SOP)����������������������������������������������������������������������������������������������������� 160°C/W
ESD Protection:
Human Body Model���������������������������������������������������������������������������������������������������������������������������������������3kV
Machine Model��������������������������������������������������������������������������������������������������������������������������������������������200V
Note: These are stress ratings only. Stresses exceeding the range specified under “Absolute Maximum Ratings”
may cause substantial damage to the device. Functional operation of this device at other conditions beyond
those listed in the specification is not implied and prolonged exposure to extreme conditions may affect
device reliability.
Rev. 1.00
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May 27, 2011
HT7A3942
Electrical Characteristics
Unless otherwise stated, this specifications apply for 0°C ≤ Ta ≤ 70°C, VCC=15V, RT=10kW
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
VCC=12.9V
—
12
30
mA
VCOMP=0V
—
2.0
3.0
mA
VCOMP=3V
—
2.5
—
mA
Supply Voltage (VCC Pin)
IST
Startup Current
ICC
Operating Current
VTL
UVLO (Off)
—
7
8
9
V
VTH
UVLO (On)
—
13
14
15
V
Reference Section
VREF
Output Voltage
Tj = 25°C, IO = 1mA
—
5.5
—
V
∆VREF
Line Regulation
12V ≤ VCC ≤ 25V
—
3
20
mV
∆VREF
Load Regulation
1mA ≤ IO ≤ 10mA
—
4
25
mV
Current Sensing (CS Pin)
VCS(OFF)
Maximum Input Voltage, Vcs(off)
—
0.9
1.0
1.1
V
tLEB
Leading Edge Blanking Time
—
—
350
—
ns
Delay to Output
—
—
100
—
ns
Oscillator (RT pin)
fOSC
∆fOSC
∆TA
∆fOSC
∆VREF
DMAX
Oscillator Frequency
Tj=25°C, RT=10kW
49
52
55
kHz
Temp. Stability
-40°C ~105°C
—
5
—
%
Voltage Stability
VCC=10V~25V
—
0.2
1.0
%/V
—
75
—
%
Maximum Duty
—
Gate Drive Output (GD Pin)
VOL
Output Low Level
VCC=15V, Isink=20mA
—
—
1
V
VOH
Output High Level
VCC=15V, Isource=20mA
9
—
—
V
tr
Rising Time
Tj=25°C, Load Capacitance=1nF
—
50
150
ns
tf
Falling Time
Tj=25°C, Load Capacitance=1nF
—
50
150
ns
Voltage Feedback (COMP Pin)
ISINK
Short Circuit Current
VCOMP=0V
—
1.5
2.2
mA
VCOMP
Open Loop Voltage
COMP pin open
—
5.5
—
V
SCP Trip Level
VCOMP (SCP)
—
4.7
—
V
SCP Delay Time (See Note)
fS=52kHz
—
40
—
ms
SCP (Short Circuit Protection)
VCOMP
Note: These Parameters, although guaranteed, are not 100% tested in production.
Rev. 1.00
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May 27, 2011
HT7A3942
Typical Performance Characteristics
15.5
10
9.5
UVLO (off)(V)
UVLO (on)(V)
15
14.5
14
13.5
13
12.5
8
7.5
7
12
11.5
9
8.5
6.5
-40
-20
0
20
40
60
80
100
6
120
-40
10
60
Figure 1. UVLO (on) (V) vs. Temperature
Figure 2. UVLO (off)(V) vs. Temperature
57
56
55
54
53
52
51
50
49
48
47
-40
57
56
55
54
53
52
51
50
49
48
47
11
-20
0
20
40
60
80
100
120
13
15
17
Temperature (degree C)
-20
0
20
40
60
80
100
23
25
31
29
27
25
23
21
19
17
15
11
120
Temperature (degree C)
13
15
17
19
21
23
25
Vcc (V)
Figure 6. Green Mode Frequency vs. Vcc
Figure 5. Vcomp for SCP vs. Temperature
Rev. 1.00
21
Figure 4. Frequency vs. Vcc
Green Mode Frequency (KHz)
4.9
4.85
4.8
4.75
4.7
4.65
4.6
4.55
4.5
4.45
4.4
-40
19
Vcc (V)
Figure 3. Frequency vs. Temperature
Vcomp (V)
110
Temperature (degree C)
Frequency (KHz)
Frequency (KHz)
Temperature (degree C)
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May 27, 2011
HT7A3942
Application Information
Base on device field test demo board results, for the
Full-Range (115V, 230V Vac) input, the Stand-by
Power will remain less than [email protected]=60W(as
shown in Table 2).This is within the Energy Star 2.0
criteria.
Operation Overview
The HT7A3942 is an excellent, low power off-line
PWM Controller. With a high degree of functional
integration, the external component requirement is
greatly reduced resulting in excellent performance/
cost ratios. The device integrates many enhanced
features such as a Non-Acoustic-Noise Green Mode
Oscillator, Internal Slope Compensation, Internal
Leading-Edge Blanking, Short-Circuit Protection
and a wide industrial operating temperature range
(-40°C to 85°C). The device is designed for primary
side control / secondary side feedback applications
and is optimized for the Energy-Star 2.0 specification,
this ensures that any EPS (External Power Supply)
implemented using the HT7A3942 can fully satisfy
the Energy Star 1.1/2.0 Stand-by (No-Load) criteria.
Demo Board
Input Condition
(Pno=60 watts)
0 to < 50 watts
≥ 50 to ≤ 250 watts
Stand-by Power
115V VAC
< 0.3W
230V VAC
< 0.3W
Table 2. Demo Board Stand-by Power Results
Advanced Precise-Oscillator for GreenMode Switching and Non-Acoustic Noise
Requirement
A Trimmed Precise Green Mode Oscillator is
implemented in the device to enhance the conversion
efficiency under conditions of light loads. As the
data shown in Fig. 8, the efficiency difference of the
traditional current mode PWM Controller between
light loads and heavy loads is more than 8%, while
the average efficiency is only 82%, the efficiency
difference of the HT7A3942 is only 1%, while
average efficiency is up to 87.5%.
Energy Consumption Criteria for No-Load
Nameplate Output
Power (Pno)
Input Range
Maximum Power in No-Load
AC-AC EPS
AC-DC EPS
≤ 0.5 watts
≤ 0.3 watts
≤ 0.5 watts
≤ 0.3 watts
Table 1. Energy Star 2.0 No-Load Criteria
Ultra Low Stand-by Power for Energy
Star 2.0 and Later Energy Star
Requirement
The device contains many advanced control schemes
for Low Stand-by Power like tiny Operating/Standby Current, Green Mode for Light-Load, etc. By
choosing an appropriate Stand-by resistor (as shown
in Figure 7), EPS implemented by the device can fully
satisfy the Energy Star 2.0 No-Load criteria.
Figure 8. Efficiency Comparison between
Figure 7. Stand-by Resistor
HT7A3942 & Traditional Current Mode PWM
Controller (Measured at HT7A3942 Demo Board)
Rev. 1.00
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May 27, 2011
HT7A3942
The Green Mode Oscillator types supplied by other
PWM Controller providers are plagued by the
problems of Acoustic-Noise. This is because, under
the conditions of light loads, the frequency will keep
decreasing through Human Acoustic Range (from
20Hz to 20kHz), these audio frequencies may create
audible noise in the transformer. Holtek’s HT7A3942
patented Green Mode Oscillator designed using an
advanced Non-Acoustic Noise Scheme to prevent
the generation of frequencies in the audio frequency
band, thus eliminating any transformer noise.
Figure 10. UVLO Scheme and Start-Up Current
Current Sense and Leading-Edge
Blanking (LEB)
A Leading-Edge Blanking Scheme is integrated in
the device to prevent false triggering due to feedback
current spikes which may appear on the CS pin,
further eliminate the need for R-C filter which is
always a requirement in the traditional current mode
PWM Controller applications.
Figure 9. Oscillator Behavior Compared with
HT7A3942 and other Green Mode PWM Controller
Under Voltage Lockout (UVLO)
An UVLO comparator is implemented in to ensure
that the device is fully functional before the output
stage is enabled. As shown in Fig. 10, a hysteresis
is provided to prevent the PWM Controller from
shutting down during any voltage dips which might
occur during startup process. The turn-on and turnoff threshold levels are set at 16.0V and 10.0V,
respectively.
Rev. 1.00
Figure 11. LEB with R-C Filter Removed
6
May 27, 2011
HT7A3942
Internal Slope-Compensation
Oscillator Frequency Tuning
An important issue with the current mode control
schemes is the instability due to Sub-Harmonic
Oscillation when the Duty-Cycle > 50%. To prevent
this problem from occurring, a Slope-Compensation
function is always necessary. In traditional current
mode PWM Controller application, many external
components are necessary for Slope-Compensation
function, but in HT7A3942 the internal SlopeCompensation eliminates the need for these external
components resulting in simplified the application
circuit design.
By choosing an appropriate value of an external
resistor between the RT Pin and GND, a suitable
operating frequency can be generated. The
relationship between the value of RT and the operating
frequency is provided in the Figure 13.
Short-Circuit Protection (SCP) and
Over-Load Protection (OLP)
To protect all the devices of a system from being
damaged under over load or short circuit conditions,
a smart SCP function is implemented in the device.
Here the feedback system will force the voltage loop
to move toward a saturation value and then pull up
the voltage on the COMP pin. Whenever the VCOMP
increases to the SCP threshold of 4.7V and remains
there for longer than 40ms, the protection scheme will
activate and then turn off the gate output to stop the
switching of power circuit. By using such a protection
mechanism, the average input power can be reduced
to a very low level so that the component temperature
and stress can be controlled within safe operating
levels.
Figure 13. RT Resistor value vs.
Operating Frequency
Figure 12. SCP Function Behavior
Rev. 1.00
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May 27, 2011
HT7A3942
Package Information
8-pin SOP (150mil) Outline Dimensions
MS-012
Symbol
Nom.
Max.
A
0.228
―
0.244
B
0.150
―
0.157
C
0.012
―
0.020
C'
0.188
―
0.197
D
―
―
0.069
E
―
0.050
―
F
0.004
―
0.010
G
0.016
―
0.050
H
0.007
―
0.010
α
0°
―
8°
Symbol
Rev. 1.00
Dimensions in inch
Min.
Dimensions in mm
Min.
Nom.
Max.
A
5.79
―
6.20
B
3.81
―
3.99
C
0.30
―
0.51
C'
4.78
―
5.00
D
―
―
1.75
E
―
1.27
―
F
0.10
―
0.25
G
0.41
―
1.27
H
0.18
―
0.25
α
0°
―
8°
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May 27, 2011
HT7A3942
Reel Dimensions
SOP 8N (150mil)
Symbol
Description
Dimensions in mm
A
Reel Outer Diameter
330.0±1.0
B
Reel Inner Diameter
100.0±1.5
C
Spindle Hole Diameter
13.0 +0.5/-0.2
D
Key Slit Width
T1
Space Between Flange
T2
Reel Thickness
Rev. 1.00
2.0±0.5
12.8 +0.3/-0.2
18.2±0.2
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May 27, 2011
HT7A3942
Carrier Tape Dimensions
 SOP 8N (150mil)
Symbol
Description
W
Carrier Tape Width
P
Cavity Pitch
E
Perforation Position
F
Cavity to Perforation (Width Direction)
Dimensions in mm
12.0+0.3/-0.1
8.0±0.1
1.75±0.10
5.5±0.1
D
Perforation Diameter
1.55±0.1
D1
Cavity Hole Diameter
1.50 +0.25/-0.00
P0
Perforation Pitch
4.0±0.1
P1
Cavity to Perforation (Length Direction)
2.0±0.1
A0
Cavity Length
6.4±0.1
B0
Cavity Width
5.2±0.1
K0
Cavity Depth
2.1±0.1
t
Carrier Tape Thickness
C
Cover Tape Width
Rev. 1.00
0.30±0.05
9.3±0.1
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May 27, 2011
HT7A3942
Holtek Semiconductor Inc. (Headquarters)
No.3, Creation Rd. II, Science Park, Hsinchu, Taiwan
Tel: 886-3-563-1999
Fax: 886-3-563-1189
http://www.holtek.com.tw
Holtek Semiconductor Inc. (Taipei Sales Office)
4F-2, No. 3-2, YuanQu St., Nankang Software Park, Taipei 115, Taiwan
Tel: 886-2-2655-7070
Fax: 886-2-2655-7373
Fax: 886-2-2655-7383 (International sales hotline)
Holtek Semiconductor (China) Inc. (Dongguan Sales Office)
Building No.10, Xinzhu Court, (No.1 Headquarters), 4 Cuizhu Road, Songshan Lake, Dongguan, China 523808
Tel: 86-769-2626-1300
Fax: 86-769-2626-1311, 86-769-2626-1322
Holtek Semiconductor (USA), Inc. (North America Sales Office)
46729 Fremont Blvd., Fremont, CA 94538, USA
Tel: 1-510-252-9880B
Fax: 1-510-252-9885
http://www.holtek.com
Copyright© 2011 by HOLTEK SEMICONDUCTOR INC.
The information appearing in this Data Sheet is believed to be accurate at the time of publication.
However, Holtek assumes no responsibility arising from the use of the specifications described.
The applications mentioned herein are used solely for the purpose of illustration and Holtek makes
no warranty or representation that such applications will be suitable without further modification,
nor recommends the use of its products for application that may present a risk to human life due to
malfunction or otherwise. Holtek's products are not authorized for use as critical components in life
support devices or systems. Holtek reserves the right to alter its products without prior notification. For
the most up-to-date information, please visit our web site at http://www.holtek.com.tw.
Rev. 1.00
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May 27, 2011