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PDF LD7575 Data sheet ( Hoja de datos )
| Número de pieza | LD7575 | |
| Descripción | Green-Mode PWM Controller | |
| Fabricantes | Leadtrend | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LD7575 (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
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LD7575
6/5/2007
Green-Mode PWM Controller with High-Voltage
Start-Up Circuit
REV: 04a
General Description
www.DataSheeTt4hUe.coLmD7575 is a current-mode PWM controller with
excellent power-saving operation. It features a high-
voltage current source to directly supply the startup current
from bulk capacitor and further to provide a lossless startup
circuit. 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.
Furthermore, the embedded over voltage protection, over
load protection and the special green-mode control provide
the solution for users to design a high performance power
circuit easily. The LD7575 is offered in both SOP-8 and
DIP-8 package.
Features
z High-Voltage (500V) Startup Circuit
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 Slope Compensation
z OVP (Over Voltage Protection) on Vcc
z OLP (Over Load Protection)
z 500mA Driving Capability
Applications
z Switching AC/DC Adapter and Battery Charger
z Open Frame Switching Power Supply
z LCD Monitor/TV Power
Typical Application
Leadtrend Technology Corporation
LD7575-DS-04a June 2007
1
1 page  
LD7575
Electrical Characteristics
(TA = +25oC unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
High-Voltage Supply (HV Pin)
High-Voltage Current Source
Vcc< UVLO(on), HV=500V
Off-State Leakage Current
Vcc> UVLO(off), HV=500V
www.DataSheet4U.cSoumpply Voltage (Vcc Pin)
Startup Current
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V
VCOMP=3V
Protection tripped (OLP, 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
Leading Edge Blanking Time
Input impedance
Delay to Output
Oscillator (RT pin)
Frequency
RT=100KΩ
Green Mode Frequency
Fs=65.0KHz
Temp. Stability
(-40°C ~105°C)
Voltage Stability
(VCC=11V-25V)
Gate Drive Output (OUT Pin)
Output Low Level
VCC=15V, Io=20mA
Output High Level
VCC=15V, Io=20mA
Rising Time
Load Capacitance=1000pF
Falling Time
Load Capacitance=1000pF
OLP (Over Load Protection)
OLP Trip Level
OLP Delay Time (note)
Fs=65KHz
MIN
TYP
MAX UNITS
0.5 1.0 1.5 mA
35 µA
100 µA
2.0 3.0 mA
2.5 4.0 mA
0.5 mA
9.0
10.0
11.0
V
15.0
16.0
17.0
V
25.0
27.5
30.0
V
1.5
6.0
2.35
2.2 mA
V
V
0.80
0.85
0.90
V
350 nS
1 MΩ
100 nS
60.0
65.0
70.0 KHz
20 KHz
3%
1%
1V
9V
50 160 nS
30 60 nS
5.0 V
30 mS
Note: The OLP delay time is proportional to the period of switching cycle. So that, the lower RT value will set the higher switching
frequency and the shorter OLP delay time.
Leadtrend Technology Corporation
LD7575-DS-04a June 2007
5
5 Page 
LD7575
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. Figure 18 shows its
operation.
On the other hand, if the OVP condition is removed, the Vcc
level will get back to normal level and the output is
automatically returned to the normal operation.
www.DataSheet4U.com
VCC
OVP Level
UVLO(on)
UVLO(off)
OUT
OVP Tripped
t
This external pull-low resistor is to prevent the MOSFET
from damage during power-on under the gate resistor is
disconnected. In such single-fault condition, as show in
figure 21, the resistor R8 can provide a discharge path to
avoid the MOSFET from being false-triggered by the current
through the gate-to-drain capacitor Cgd. Therefore, the
MOSFET is always pull-low and kept in the off-state
whenever the gate resistor is disconnected or opened in any
case.
Switching
Non-Switching
Fig. 18
Switching
t
Fault Protection
A lot of protection features have been implemented in the
LD7575 to prevent the power supply or adapter from being
damaged caused by single fault condition on the open or
short condition on the pin of LD7575. Under the conditions
listed below, the gate output will be off immediately to
protect the power circuit ---
y RT pin short to ground
y RT pin floating
y CS pin floating
Pull-Low Resistor on the Gate Pin of MOSFET
In LD7575, an anti-floating resistor is implemented on the
OUT pin to prevent the output from any uncertain state
which may causes the MOSFET working abnormally or false
triggered-on. However, such design won’t cover the
condition of disconnection of gate resistor Rg thus it is still
strongly recommended to have a resistor connected on the
MOSFET gate terminal (as shown in figure 19) to provide
extra protection for fault condition.
Leadtrend Technology Corporation
LD7575-DS-04a June 2007
11
Fig. 19
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LD7575.PDF ] | |
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