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PDF LD7575A Data sheet ( Hoja de datos )
| Número de pieza | LD7575A | |
| Descripción | Green-Mode PWM Controller | |
| Fabricantes | Leadtrend | |
| Logotipo |  |
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LD7575A
11/29/2007
Green-Mode PWM Controller with High-Voltage
Rev.00a
Start-Up Circuit
General Description
The LD7 575A is a c urrent-mode PWM con troller with
excellent pow er-saving o peration. It fea tures 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 le ading-edge
blanking of the current sensing, internal slope compensation,
and the small package provide the users a high effic iency,
minimum external component counts, and low cost solution
for AC/DC power applications.
Furthermore, the e mbedded over volt age protection, o ver
load protection and the special green-mode control provide
the solution fo r users to design a hig h performance po wer
circuit easily. The LD7575A 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
LD7575A-DS-00a November 2007
1
www.leadtrend.com.tw
http://www.Datasheet4U.com
1 page  
LD7575A
Electrical Characteristics
(TA = +25oC unless otherwise stated, VCC=15.0V)
PARAMETER CO
NDITIONS
High-Voltage Supply (HV Pin)
High-Voltage Current Source
Vcc< UVLO(on), HV=500V
Off-State Leakage Current
Vcc> UVLO(off), HV=500V
Supply 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
200 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
LD7575A-DS-00a November 2007
5
www.leadtrend.com.tw
5 Page 
LD7575A
The Vcc OVP function in LD7575A is an auto-recovery type
protection. If the OVP condi tion, usu ally c aused 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 mod e. Figure 18 shows its
operation.
On the other hand, if the OVP condition is removed, the Vcc
level will ge t back to normal lev el a nd th e ou tput is
automatically returned to the normal operation.
VCC
OVP Level
UVLO(on)
UVLO(off)
OUT
OVP Tripped
t
MOSFET ga te termina l (a s s hown in figu re 19 ) to provide
extra protection for fault condition.
This ex ternal pull-low resistor is to prevent the MOSF ET
from d amage during p ower-on und er the gate resis tor is
disconnected. In su ch s ingle-fault cond ition, as show in
figure 2 0, the re sistor R8 ca n provide a d ischarge path t o
avoid the MOSFET from being false-triggered by the current
through the g ate-to-drain ca pacitor Cg d. Therefore, the
MOSFET is always p ull-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 pr otection features h ave b een implemented in th e
LD7575A to prevent the power supply or adapter from being
damaged c aused b y single fau lt condition on th e o pen or
short condition on the pin of LD7575A. Under the conditions
listed b elow, the gate out put will be of f imm ediately 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 LD7575A, an anti-floating resistor is imple mented on the
OUT pin to p revent th e o utput fro m a ny uncertain state
which may causes the MOSFET working abnormally or false
triggered-on. Howeve r, such de sign won’t co ver the
condition of disconnection of gate resistor Rg thus it is still
strongly recommended to have a resistor connected on the
Leadtrend Technology Corporation
LD7575A-DS-00a November 2007
11
www.leadtrend.com.tw
Fig. 19
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet LD7575A.PDF ] | |
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