2/21/2005
1
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
Green-Mode PWM Controller
General Description
The LD7552 is a low cost, low startup current, current mode
PWM controller with green-mode power-saving operation.
The integrated functions such as the leading-edge blanking
of the current sensing, internal slope compensation and the
small package provide the users a high efficiency, minimum
external component counts, and low cost solution for AC/DC
power applications.
The special green-mode control does not only achieve low
power consumption but also offer a non-audible-noise
operation when the LD7552 operates under light load or no
load condition.
The LD7552 is designed for the switching adaptor with
30W~60W output. The LD7552 is offered in both SOP-8 and
DIP-8 package.
Patent pending
Features
High-Voltage CMOS Process with Excellent ESD
Protection
Very Low Startup Current (Typical 5 A)
Under Voltage Lockout (UVLO)
Current Mode Control with Cycle-by-Cycle Peak
Current Limiting
Leading-Edge Blanking on CS Pin
Programmable Switching Frequency
Internal Slope Compensation
Proprietary Green-Mode Control for Power Saving
Non-audible-noise Green Mode Control
500mA Driving Capability
Applications
Switching AC/DC Adaptor and Battery Charger
Open Frame Switching Power Supply
384X Replacement
Note: Please see Application Information
Typical Application
OSC
16.0V/
11.4V
UVLO
Divider
40V
Control
Logic
EMI
Filter
RT
OUT
CS
VCC
GND
COMP
LD7552
photocoupler
AC
input
TL431
2
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
Pin Configuration
SOP-8 & DIP-8 (TOP VIEW)
YY: Year code (D: 2004, E: 2005
...
..)
WW: week code
PP: production code
1
8
2
3
4
7
6
5
TOP MARK
YYWWPP
G
N
D
C
O
M
P
V
C
C
R
T
O
U
T
V
C
C
C
S
N
C
Ordering Information
Part number
Package
TOP MARK
Shipping
LD7552 IS
SOP-8
LD7552IS
2500 /tape & reel
LD7552 BS
SOP-8 (PB Free)
LD7552BS
2500 /tape & reel
LD7552 IN
DIP-8
LD7552IN
3600 /tube /carton
LD7552 BN
DIP-8 (PB Free)
LD7552BN
3600 /tube /carton
Pin Descriptions
PIN
NAME
FUNCTION
1
GND
Ground
2
COMP
Voltage feedback pin (same as the COMP pin in UC384X), By connecting a
photo-coupler to close the control loop and achieve the regulation.
3
VCC
Supply voltage pin
4
RT
This pin is to program the switching frequency. By connecting a resistor to ground
to set the switching frequency.
5
NC
Unconnected pin
6
CS
Current sense pin, connect to sense the MOSFET current
7
VCC
Supply voltage pin
8
OUT
Gate drive output to drive the external MOSFET
3
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
Block Diagram
OSC
COMP
CS
OUT
internal bias
& Vref
VCC
GND
PWM
Comparator
RT
16.0V/
11.4V
UVLO
Green-Mode
Oscillator
Leading
Edge
Blanking
2R
R
40V
R
S
Q
Vref OK
EN
EN
+
+
Ramp from
Oscillator
Absolute Maximum Ratings
Supply Voltage VCC
36V
COMP, RT, CS
-0.3 ~7V
Operating Junction Temperature
150 C
Storage Temperature Range
-65 C to 150 C
Package thermal resistance (DIP-8)
100 C/W
Package thermal resistance (SOP-8)
160 C/W
Lead temperature (LD7552IS & LD7552IN, Soldering, 10sec)
230 C
Lead temperature (LD7552BS & LD7552BN, Soldering, 10sec)
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.
4
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
Electrical Characteristics
(T
A
= +25
o
C unless otherwise stated, V
CC
=15.0V)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage (Vcc Pin)
Startup Current
5
25
A
V
COMP
=0V
3
4
mA
V
COMP
=3V
2
mA
Operating Current
V
COMP
=open
0.7
mA
UVLO (off)
10.4
11.4
12.4
V
UVLO (on)
14.8
16.0
17.5
V
Voltage Feedback (Comp Pin)
Short Circuit Current
V
COMP
=0V
2.2
3.0
mA
Open Loop Voltage
COMP pin open
5.0
V
Green Mode Threshold VCOMP
2.35
V
Current Sensing (CS Pin)
Maximum Input Voltage
0.80
0.85
0.90
V
Leading Edge Blanking Time
250
nS
Input impedance
50
K
Delay to Output
300
nS
Oscillator (RT pin)
Frequency
RT=100K
61.5
66.5
71.5
KHz
Green Mode Frequency
Fs=66.5KHz
20
KHz
Temp. Stability
(-30 C ~85 C)
5
%
Voltage Stability
(VCC=12V-30V)
2
%
Gate Drive Output (OUT Pin)
Output Low Level
VCC=15V, Io=20mA
1
V
Output High Level
VCC=15V, Io=20mA
9
V
Rising Time
Load Capacitance=1000pF
160
nS
Falling Time
Load Capacitance=1000pF
60
nS
5
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
Typical Performance Characteristics
-40
-20
0
20
40
60
80
100
120
11.0
11.2
11.4
11.6
11.8
12.0
12.2
U
V
L
O
(
O
f
f
)
(
V
)
Temperature ( C)
Fig. 1 UVLO (Off) vs. Temperature
U
V
L
O
(
O
n
)
(
V
)
Fig. 2 UVLO (On) vs. Temperature
-40
-20
0
20
40
60
80
100
120
14.0
14.4
14.8
15.2
15.6
16.0
16.4
16.8
17.0
Temperature ( C)
F
r
e
q
u
e
n
c
y
(
K
H
z
)
Temperature ( C)
Fig. 3 Frequency vs. Temperature
-40
-20
0
20
40
60
80
100
120
66.0
67.0
68.0
69.0
70.0
71.0
72.0
F
r
e
q
u
e
n
c
y
(
K
H
z
)
Fig. 4 Green-Mode Frequency vs. Temperature
Temperature ( C)
-40
-20
0
20
40
60
80
100
120
17.0
17.2
17.4
17.6
17.8
18.0
18.2
M
a
x
.
D
u
t
y
-
C
y
c
l
e
(
%
)
Temperature ( C)
Fig. 5 Duty-Cycle (max.) vs. Temperature
-40
-20
0
20
40
60
80
100
120
74.4
74.7
75.0
75.3
75.6
75.9
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