LD7552
2/21/2005
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 5µA)
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
Non-audible-noise Green Mode Control
500mA Driving Capability
Proprietary Green-Mode Control for Power Saving
1
Applications
Switching AC/DC Adaptor and Battery Charger
Open Frame Switching Power Supply
384X Replacement
1
Note: Please see Application Information
Typical Application
AC
input
EMI
Filter
VCC
40V
16.0V/
11.4V
UVLO
OUT
RT
COMP
LD7552
OSC
Control
Logic
photocoupler
Divider
CS
GND
TL431
1
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
LD7552
Pin Configuration
SOP-8 & DIP-8 (TOP VIEW)
VCC
OUT
NC
5
8
7
CS
6
TOP MARK
YYWWPP
1
2
3
4
YY: Year code (D: 2004, E: 2005…..)
WW: week code
PP: production code
GND
VCC
Ordering Information
Part number
LD7552 IS
LD7552 BS
LD7552 IN
LD7552 BN
Package
SOP-8
SOP-8 (PB Free)
DIP-8
DIP-8 (PB Free)
TOP MARK
LD7552IS
LD7552BS
LD7552IN
LD7552BN
Shipping
2500 /tape & reel
2500 /tape & reel
3600 /tube /carton
3600 /tube /carton
Pin Descriptions
PIN
1
2
3
4
5
6
7
8
NAME
GND
COMP
VCC
RT
NC
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.
Unconnected pin
Current sense pin, connect to sense the MOSFET current
Supply voltage pin
Gate drive output to drive the external MOSFET
FUNCTION
COMP
RT
2
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
LD7552
Block Diagram
VCC
40V
16.0V/
11.4V
UVLO
internal bias
& Vref
RT
OSC
EN
Vref OK
EN
OUT
Green-Mode
Oscillator
S
COMP
2R
R
PWM
Comparator
+
+
R
Q
CS
Leading
Edge
Blanking
∑
Ramp from
Oscillator
GND
Absolute Maximum Ratings
Supply Voltage VCC
COMP, RT, CS
Operating Junction Temperature
Storage Temperature Range
Package thermal resistance (DIP-8)
Package thermal resistance (SOP-8)
Lead temperature (LD7552IS & LD7552IN, Soldering, 10sec)
Lead temperature (LD7552BS & LD7552BN, Soldering, 10sec)
36V
-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.
3
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
LD7552
Electrical Characteristics
(T
A
= +25 C unless otherwise stated, V
CC
=15.0V)
PARAMETER
Supply Voltage (Vcc Pin)
Startup Current
V
COMP
=0V
Operating Current
UVLO (off)
UVLO (on)
Voltage Feedback (Comp Pin)
Short Circuit Current
Open Loop Voltage
Green Mode Threshold VCOMP
Current Sensing (CS Pin)
Maximum Input Voltage
Leading Edge Blanking Time
Input impedance
Delay to Output
Oscillator (RT pin)
Frequency
Green Mode Frequency
Temp. Stability
Voltage Stability
Gate Drive Output (OUT Pin)
Output Low Level
Output High Level
Rising Time
Falling Time
VCC=15V, Io=20mA
VCC=15V, Io=20mA
Load Capacitance=1000pF
Load Capacitance=1000pF
9
160
60
1
V
V
nS
nS
RT=100KΩ
Fs=66.5KHz
(-30°C ~85°C)
(VCC=12V-30V)
61.5
66.5
20
5
2
71.5
KHz
KHz
%
%
0.80
0.85
250
50
300
0.90
V
nS
KΩ
nS
V
COMP
=0V
COMP pin open
2.2
5.0
2.35
3.0
mA
V
V
V
COMP
=3V
V
COMP
=open
10.4
14.8
5
3
2
0.7
11.4
16.0
12.4
17.5
25
4
µA
mA
mA
mA
V
V
CONDITIONS
MIN
TYP
MAX
UNITS
o
4
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
LD7552
Typical Performance Characteristics
12.2
17.0
16.8
12.0
16.4
UVLO (On) (V)
UVLO (Off) (V)
11.8
16.0
15.6
15.2
14.8
11.6
11.4
11.2
14.4
14.0
-40
11.0
-40
-20
0
20
40
60
80
100
120
-20
0
20
40
60
80
100
120
Temperature (°C)
Fig. 1
72.0
UVLO (Off) vs. Temperature
18.2
Fig. 2
Temperature (°C)
UVLO (On) vs. Temperature
71.0
18.0
Frequency (KHz)
Frequency (KHz)
70.0
17.8
69.0
17.6
68.0
17.4
67.0
17.2
66.0
-40
-20
0
20
40
60
80
100
120
17.0
-40
-20
0
20
40
60
80
100
120
Temperature (°C)
Fig. 3
Frequency vs. Temperature
Fig. 4
Temperature (°C)
Green-Mode Frequency vs. Temperature
75.9
75.6
Max. Duty-Cycle (%)
75.3
75.0
74.7
74.4
-40
-20
0
20
40
60
80
100
120
Temperature (°C)
Fig. 5
Duty-Cycle (max.) vs. Temperature
5
Leadtrend Technology Corporation
LD7552-DS-00 February, 2005
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