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PDF LD7531A Data sheet ( Hoja de datos )
| Número de pieza | LD7531A | |
| Descripción | Green-Mode PWM Controller | |
| Fabricantes | Leadtrend Technology | |
| Logotipo |  |
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LD7531A
7/6/2009
Green-Mode PWM Controller with Frequency Trembling
and Integrated Protections
REV: 00
General Description
The LD7531A is built-in with several functions, protection
and EMI-improved solution in a SOT-26/ DIP-8 package.
It takes less components counts or circuit space,
especially ideal for those total solutions of low cost.
The implemented functions include low startup current,
green-mode power-saving operation, leading-edge
blanking of the current sensing and internal slope
compensation. And the LD7531A features more
protections like OLP (Over Load Protection) and OVP
(Over Voltage Protection) to prevent the circuit damage
from the abnormal conditions.
Furthermore, the frequency trembling function is to reduce
the noise level and thus helps the power circuit designers
to easily deal with the EMI filter design by using minimum
component cost and developing time.
Features
z High-Voltage CMOS Process with Excellent ESD
protection
z Very Low Startup Current (<20μA)
z Current Mode Control
z Non-audible-noise Green Mode Control
z UVLO (Under Voltage Lockout)
z LEB (Leading-Edge Blanking) on CS Pin
z Programmable Switching Frequency
z Internal Trembling (±4KHz)
z Internal Slope Compensation
z OVP (Over Voltage Protection) on Vcc Pin
z OLP (Over Load Protection)
z 300mA Driving Capability
Applications
z Switching AC/DC Adaptor and Battery Charger
z Open Frame Switching Power Supply
Typical Application
AC EMI
input Filter
VCC
RT
100K Ohm
COMP
32V
16.0V
/10.0V
UVLO
LD7531A
FM OSC
Divider
Control
Logic
GND
OUT
CS
Leadtrend Technology Corporation
LD7531A-DS-00 July 2009
1
www.leadtrend.com.tw
photocoupler
TL431
1 page  
Electrical Characteristics
(TA = +25oC unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
Supply Voltage (Vcc Pin)
Startup Current
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V
VCOMP=3V
Protection tripped (OLP)
Protection tripped (OVP)
UVLO (off)
UVLO (on)
OVP Level
Voltage Feedback (Comp Pin)
Short Circuit Current
Open Loop Voltage
VCOMP=0V
COMP pin open
Green Mode Threshold VCOMP
Current Sensing (CS Pin)
Maximum Input Voltage, VCS_Off
Leading Edge Blanking Time
Input impedance
Delay to Output
VCOMP>1.9V
VCOMP<1.8V
Oscillator for Switching Frequency
Frequency
Green Mode Frequency
Trembling Frequency
Temp. Stability
Voltage Stability
RT=100KΩ
Fs=65kHz
(-40°C ~105°C)
(VCC=11V-25V)
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
OLP (Over Load Protection)
OLP Trip Level
OLP Delay Time at start-up
VCOMP (OLP)
Fs=65kHz
OLP Delay Time
Fs=65kHz
* RT value is in proportion to OLP delay time.
Leadtrend Technology Corporation
LD7531A-DS-00 July 2009
5
www.leadtrend.com.tw
LD7531A
MIN TYP MAX UNITS
12 20
2.65 3.5
3.0
0.45
0.55
9.0 10.0 11.0
15.0 16.0 17.0
26.8 28.0 29.2
μA
mA
mA
mA
mA
V
V
V
1.3 2.2
5.9
2.85
0.8 0.85 0.9
240
1400
1
100
mA
V
V
V
ns
ns
MΩ
ns
60 65 70
21
± 4.0
5
1
kHz
kHz
kHz
%
%
1V
8V
170 350
ns
50 100 ns
5.0 V
70 ms
40 ms
5 Page 
LD7531A
Over Load Protection (OLP)
To protect the circuit from being damaged under over load
condition or short condition, a smart OLP function is
implemented in the LD7531A. The Figure 19 shows the
waveforms of the OLP operation. In this case, the
feedback system will force the voltage loop proceed
toward the saturation and then pull up the voltage on
COMP pin (VCOMP). Whenever the VCOMP trips up to the
OLP threshold 5V and stays longer than the OLP delay
time, the protection will activate and then turn off the gate
output to stop the switching of power circuit. The OLP
delay time is to prevent the false trigger from the power-on
and turn-off transient. Typically the OLP delay time will be
around 40mS. In order to provide the more start-up
capability, the OLP delay time at start-up will be around
70ms.
By such protection mechanism, the average input power
can be reduced to very low level so that the component
temperature and stress can be controlled within the safe
operating area.
Fault Protection
There are several critical protections were integrated in
the
LD7531A to prevent the power supply or adapter had
being damaged. Those damages usually come from open
condition on the pins of LD7531A.
Under the conditions listed below, the gate output will turn
off immediately to protect the power circuit ---
1. RT pin floating
2. CS pin floating
Fig. 19
Leadtrend Technology Corporation
LD7531A-DS-00 July 2009
11
www.leadtrend.com.tw
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LD7531A.PDF ] | |
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