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PDF LD7660J Data sheet ( Hoja de datos )
| Número de pieza | LD7660J | |
| Descripción | Low Power Off-line Switcher | |
| Fabricantes | Leadtrend | |
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LD7660J
5/21/2009
Low Power Off-line Switcher
P03 (Internal use only)
General Description
The LD7660J integrated a 600V power MOSFET and a
current mode PWM controller in a DIP-8 package. It’s
operating at fixed frequency of 65 kHz. It provides important
functions needed for a low output power applications such
as leading-edge blanking of the current sensing, internal
slope compensation, and green-mode power-saving
operation under light load or no load condition. This highly
integrated device provides the users a high efficiency, low
external component counts, and low cost solution for low
power adaptor or charger applications.
The special green-mode control is not only to achieve the
low power consumption but also to offer a non-audible-noise
operation when the LD7660J is operating under light load or
no load condition.
Features
z Built-in 600V/1A Power MOSFET
z Secondary-side/Primary-side feedback control
z Switching Frequency at 65KHz
z Fixed Internal Frequency Trembling
z Built-in Load Regulation Compensation
z Built-in Slope Compensation with 75% max duty-cycle
z Low Startup Current (<20μA)
z Current Mode Control with Cycle-by-Cycle Current
Limit
z Non-audible-noise Green Mode Control
z UVLO (Under Voltage Lockout)
z LEB (Leading-Edge Blanking) on CS Pin
z OVP (Over Voltage Protection) on Vcc
z OLP (Over Load Protection)
Applications
z Switching AC/DC Adaptor
z LCD TV or PC Standby Power
Typical Application
Secondary-side Feedback
Leadtrend Technology Corporation
LD7660J-DS-P03 May. 2009
1
1 page  
Absolute Maximum Ratings
Supply Voltage VCC
FB, S
Drain
Continuous drain current1, TC=25°C
LD7660J
Single Pulse Avalanche Energy2
LD7660J
Total Power Dissipation of DIP-8, Ta=25°C
Package thermal resistance (DIP-8)
θJA
θJA
θJC
Maximum Junction Temperature
Operating Junction Temperature Range
Operating Ambient Temperature Range
Storage Temperature Range
Lead temperature (DIP-8, Soldering, 10sec)
ESD Voltage Protection, Human Body Model
ESD Voltage Protection, Machine Model
1. Repetitive rating: Pulse width limited by maximum junction temperature
2. L=60mH, IDS=1A, VDD=150V, Starting TJ=25°C
3. w/o heat-sink, under natural convection
4. Infinite cooling Condition, refer to SEMI G30-88
5. Measured on the package top surface
LD7660J
30V
-0.3 ~7V
-0.3~600V
1.3A
30mJ
1.2W
80°C/W3
20°C/W4
35°C/W5
150℃
-40°C to 125℃
-40°C to 85°C
-50°C to 150°C
260°C
2.5 KV
250 V
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
limited.
Leadtrend Technology Corporation
LD7660J-DS-P03 May. 2009
5
5 Page 
Application Information
Operation Overview
The LD7660J is an excellent primary side feedback
controller. It meets the green-power requirement and is
intended for the use in those modern switching power
suppliers and linear adaptors that demand higher power
efficiency and power-saving. It integrated more functions to
reduce the external components counts and the size. Its
major features are described as below.
Under Voltage Lockout (UVLO)
An UVLO comparator is implemented in it to detect the
voltage on the VCC pin. It would assure the supply voltage
enough to turn on the LD7660J PWM controllers and further
to drive the power MOSFET. As shown in Fig. 13, a
hysteresis is built in to prevent the shutdown from the
voltage dip during startup. The turn-on and turn-off
threshold level are set at 16.0V and 10.0V, respectively.
LD7660J
Where Ra and Rb are top and bottom feedback resistor
value, Ns and Na are the turns of transformer secondary
and auxiliary (as shown in the figure 14).
The load regulation and line regulation for primary side
feedback control is sensitive to the structure of transformer.
For getting good regulation and efficiency, the sandwich
structure by two secondary separate parallel layer windings
surrounding primary winding is recommended.
Vcc
UVLO(on)
UVLO(off)
I(Vcc)
t
operating current
(~ mA)
startup current
(~uA)
t
Fig. 13
Output Voltage setting
The LD7660J monitors the auxiliary fly-back signal at FB pin
through a resistor divider pair Ra and Rb. An error signal
representing the difference between the voltage at FB and
the reference voltage is generated by LD’s patent-pending
circuitry, which is then integrated by the Error Amplifier and
used to control switching duty cycle.
The output voltage is determined by the following
relationship. For improving the output voltage accuracy, the
transformer leakage inductance should be reduced as much
as possible.
Fig.14
Startup Current and Startup Circuit
The typical startup circuit to generate the LD7660J Vcc is
shown in Fig. 15. During the startup transient, the Vcc is
lower than the UVLO threshold thus there is no gate pulse
produced from LD7660J to drive power MOSFET.
Therefore, the current through R1 will provide the startup
current and to charge the capacitor C1. Whenever the Vcc
voltage is high enough to turn on the LD7660J and further to
deliver the gate drive signal, the supply current is provided
from the auxiliary winding of the transformer. Lower
startup current requirement on the PWM controller will help
to increase the value of R1 and then reduce the power
consumption on R1. By using CMOS process and the
special circuit design, the maximum startup current of
LD7660J is only 20μA.
Leadtrend Technology Corporation
LD7660J-DS-P03 May. 2009
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet LD7660J.PDF ] | |
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