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PDF LD7530 Data sheet ( Hoja de datos )
| Número de pieza | LD7530 | |
| Descripción | Green-Mode PWM Controller | |
| Fabricantes | Leadtrend Technology | |
| Logotipo |  |
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LD7530/LD7530A
12/5/2007
Green-Mode PWM Controller with Integrated Protections and
Adjustable OLP Delay Time
REV: 04
General Description
The LD7530/LD7530A are specifically designed for the low
total system cost by integrating many functions, protections,
and the EMI-improved solution in a tiny SOT-26 package
which usually need a lot of extra components or circuits on
the general designs.
Furthermore, the LD7530/7530A features green mode
operation, leading edge blanking time, internal slope
compensation and adjustable over load protection (OLP)
delay time to minimize the component counts for switching
power supply.
And to satisfy different designs, 2 versions of OVP levels are
implemented as ---
z LD7530 --- 28.0V ± 1.2V.
z LD7530A --- 21.0V ± 1.2V.
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 Internal Slope Compensation
z OVP (Over Voltage Protection) on Vcc Pin
z OLP (Over Load Protection)
z 300mA Driving Capability
z Adjustable OLP Delay Time
Applications
z Switching AC/DC Adaptor and Battery Charger
z Open Frame Switching Power Supply
Typical Application
Leadtrend Technology Corporation
LD7530&LD7530A-DS-04 December 2007
1
1 page  
Absolute Maximum Ratings
Supply Voltage VCC
COMP, CT, CS
Junction Temperature
Operating Ambient Temperature
Storage Temperature Range
Package Thermal Resistance (SOT-26)
Package Thermal Resistance (DIP-8)
Power Dissipation (SOT-26, at Ambient Temperature = 85°C)
Power Dissipation (DIP-8, at Ambient Temperature = 85°C)
Lead temperature (Soldering, 10sec)
ESD Voltage Protection, Human Body Model
ESD Voltage Protection, Machine Model
Gate Output Current
LD7530/LD7530A
30V
-0.3 ~7V
150°C
-40°C to 85°C
-65°C to 150°C
250°C/W
100°C/W
250mW
650mW
260°C
2.5 KV
250 V
300mA
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.
Recommended Operating Conditions
Item
Supply Voltage Vcc (LD7530)
Supply Voltage Vcc (LD7530A)
CT Value
Min.
11
11
0.047
Max.
25
18
0.1
Unit
V
V
μF
Leadtrend Technology Corporation
LD7530&LD7530A-DS-04 December 2007
5
5 Page 
LD7530/LD7530A
Internal Slope Compensation
In the conventional application, the problem of the stability is
a critical issue for current mode controlling, when it operates
in higher than 50% of the duty-cycle. As UC384X, It takes
slope compensation from injecting the ramp signal of the
RT/CT pin through a coupling capacitor. It therefore requires
no extra design for the LD7530/LD7530A since it has
integrated it already.
On the other hand, if the OVP condition is removed, the Vcc
level will get back to normal level and the output will
automatically return to the normal operation.
On/Off Control
The LD7530/LD7530A can be turned off by pulling COMP
pin lower than 1.2V. The gate output pin of the
LD7530/LD7530A will be disabled immediately under such
condition. The off-mode can be released when the pull-low
signal is removed.
Dual-Oscillator Green-Mode Operation
There are many different topologies has been implemented
in different chips for the green-mode or power saving
requirements such as “burst-mode control”, “skipping-cycle
mode”, “variable off-time control “…etc. The basic operation
theory of all these approaches intended to reduce the
switching cycles under light-load or no-load condition either
by skipping some switching pulses or reduce the switching
frequency.
What LD7530/LD7530A use to implement the power-saving
operation is Leadtrend Technology’s own IP. By using this
dual-oscillator control, the green-mode frequency can be
well controlled and further to avoid the generation of audible
noise.
OVP (Over Voltage Protection) on Vcc
The VGS ratings of the nowadays power MOSFETs are often
limited up to max. 30V. To prevent the VGS from the fault
condition, LD7530/LD7530A are implemented an OVP
function on Vcc. Whenever the Vcc voltage is higher than
the OVP threshold voltage, the output gate drive circuit will
be shutdown simultaneously thus to stop the switching of
the power MOSFET until the next UVLO(on).
The Vcc OVP function in LD7530/LD7530A is an
auto-recovery type protection. If the OVP condition,
usually caused by the feedback loop opened, is not
released, the Vcc will tripped the OVP level again and
re-shutdown the output. The Vcc is working as a hiccup
mode. The figure 18 shows its operation.
Fig. 18
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 LD7530/LD7530A. 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, set by CT
pin, is to prevent the false trigger from the power-on and
turn-off transient. Higher CT value will generate longer OLP
delay time. For the recommended CT value, the OLP delay
time is around 90mS when CT=0.1μF and will be around
50mS if CT=0.047μF.
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.
Leadtrend Technology Corporation
LD7530&LD7530A-DS-04 December 2007
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet LD7530.PDF ] | |
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