Green-Mode PWM Controller: General Description Features
Green-Mode PWM Controller: General Description Features
Green-Mode PWM Controller: General Description Features
Features
Protection
Current Limiting
power applications.
load condition.
Applications
DIP-8 package.
Patent pending
Typical Application
AC
input
EMI
Filter
VCC
40V
OUT
UVLO
16.0V/
11.4V
RT
COMP
LD7552
OSC
Control
Logic
Divider
photocoupler
CS
GND
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Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
TL431
Pin Configuration
OUT
VCC
CS
NC
TOP MARK
RT
COMP
GND
VCC
YYWWPP
Ordering Information
Part number
Package
TOP MARK
Shipping
LD7552 IS
SOP-8
LD7552IS
LD7552 BS
LD7552BS
LD7552 IN
DIP-8
LD7552IN
LD7552 BN
LD7552BN
Pin Descriptions
PIN
NAME
GND
FUNCTION
COMP
VCC
RT
NC
Unconnected pin
CS
VCC
OUT
Ground
Voltage feedback pin (same as the COMP pin in UC384X), By connecting a
photo-coupler to close the control loop and achieve the regulation.
Supply voltage pin
This pin is to program the switching frequency. By connecting a resistor to ground
to set the switching frequency.
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Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
Block Diagram
VCC
UVLO
40V
internal bias
& Vref
16.0V/
11.4V
RT
OSC
EN
Vref OK
EN
OUT
Green-Mode
Oscillator
COMP
2R
R
CS
Leading
Edge
Blanking
PWM
Comparator
+
Ramp from
Oscillator
GND
36V
COMP, RT, CS
-0.3 ~7V
150 C
-65 C to 150 C
100 C/W
160 C/W
230 C
260 C
Caution:
Stresses beyond the ratings specified in Absolute Maximum Ratings may cause permanent damage to the device. This is a stress only
rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not
implied.
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LD7552-DS-00 February, 2005
Electrical Characteristics
o
CONDITIONS
MIN
TYP
MAX
UNITS
25
VCOMP=0V
mA
VCOMP=3V
VCOMP=open
mA
0.7
mA
UVLO (off)
10.4
11.4
12.4
UVLO (on)
14.8
16.0
17.5
2.2
3.0
mA
VCOMP=0V
5.0
2.35
0.80
0.85
0.90
250
nS
Input impedance
50
Delay to Output
300
nS
RT=100K
Fs=66.5KHz
61.5
66.5
71.5
Temp. Stability
(-30 C ~85 C)
Voltage Stability
(VCC=12V-30V)
20
KHz
KHz
VCC=15V, Io=20mA
VCC=15V, Io=20mA
Rising Time
Load Capacitance=1000pF
160
nS
Falling Time
Load Capacitance=1000pF
60
nS
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LD7552-DS-00 February, 2005
12.2
16.8
16.4
11.8
12.0
11.6
11.4
16.0
15.6
15.2
14.8
11.2
14.4
11.0
-40
-20
20
40
60
80
100
14.0
-40
120
-20
Temperature ( C)
Fig. 2
72.0
18.2
71.0
18.0
Frequency (KHz)
Frequency (KHz)
Fig. 1
70.0
69.0
68.0
-20
20
Fig. 3
40
60
80
100
80
100
120
17.6
17.4
17.0
-40
120
-20
Fig. 4
75.9
75.6
60
17.8
Temperature ( C)
75.3
75.0
74.7
74.4
-40
40
17.2
67.0
66.0
-40
20
Temperature ( C)
UVLO (On) vs. Temperature
-20
20
40
60
80
100
120
Temperature ( C)
Fig. 5
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Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
20
40
60
80
100
120
Temperature ( C)
Green-Mode Frequency vs. Temperature
Application Information
special circuit design, the maximum startup current of
Operation Overview
LD7552 is only 25 A.
startup time.
AC
input
EMI
Filter
R1
Cbulk
D1
Vcc
VCC
UVLO(on)
OUT
UVLO(off)
LD7552
GND
t
I(Vcc)
operating current
(~ mA)
CS
Fig. 7
startup current
(~uA)
Fig. 6
is not only for the peak current mode control but also for the
pulse-by-pulse
LD7552.
current
limit.
maximum
voltage
Therefore, the
The
IPEAK (MAX)
0 .85 V
RS
The lower
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Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
Vin
Cbulk
D1
fSW
C1
VCC
OUT
LD7552
Comp
66.5
100(KHz)
RT(K )
CS
GND
Rs
Fig. 8
pin of LD7552.
V (PWMCOMPARATOR )
2 VF )
VCC
OUT
LD7552
CS
GND
the
internal
slope
compensation
circuit
has
been
On/Off Control
Fig. 9
There
are
many
difference
topologies
has
been
requirements
such
as
burst-mode
control,
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Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
switching frequency.
What LD7552 used to implement the power-saving
"Set" Signal
(to OSC & Nor gate)
from OSC
In such
Level-detector
& Counter
VCO
Green-Mode
Oscillator
Vgreen
V+
V+
Normal Mode
Under the
Ramp of
OSC
Green-Mode
Oscillator activated
EN=1
EN
OUT
Green-Mode
Osc
Ramp of
VCO
Set
Reset
2R
V-
CS
V+
COMP
LEB
Fig. 11
PWM
Comparator
+
Ramp from
Oscillator
Fig. 10
As shown in Fig. 11, the green-mode oscillator detects the
Comp pin signal to determine if it is within the green-mode
operation. When the detected signal V+ is lower than the
green-mode threshold Vgreen, the green-mode oscillator is
on. The green-mode oscillator, implemented by a VCO
(voltage controlled oscillator), is a variable frequency
oscillator. The rising time of the VCO is proportional to
(Vgreen-V+), thus the lower voltage on V+ will generate
longer rising time on VCO as well as lower frequency on
VCO.
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Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
Vgreen
Green Mode
V-
Package Information
SOP-8
H
C
I
D
Dimensions in Millimeters
Dimensions in Inch
Symbols
MIN
MAX
MIN
MAX
4.801
5.004
0.189
0.197
3.810
3.988
0.150
0.157
1.346
1.753
0.053
0.069
0.330
0.508
0.013
0.020
1.194
1.346
0.047
0.053
0.178
0.229
0.007
0.009
0.102
0.254
0.004
0.010
5.791
6.198
0.228
0.244
0.406
1.270
0.016
0.050
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Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
DIP-8
A
Dimension in Millimeters
Dimensions in Inches
Symbol
Min
Max
Min
Max
9.017
10.160
0.355
0.400
6.096
7.112
0.240
0.280
-----
5.334
------
0.210
0.356
0.584
0.014
0.023
1.143
1.778
0.045
0.070
2.337
2.743
0.092
0.108
2.921
3.556
0.115
0.14
7.366
8.255
0.29
0.325
0.381
------
0.015
--------
Important Notice
Leadtrend Technology Corp. reserves the right to make changes or corrections to its products at any time without notice. Customers should
verify the datasheets are current and complete before placing order.
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Leadtrend Technology Corporation
LD7552-DS-00 February, 2005