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PDF LD7522 Datasheet ( Hoja de datos )

Número de pieza LD7522
Descripción Smart Green-Mode PWM Controller
Fabricantes Leadtrend Technology 
Logotipo Leadtrend Technology Logotipo

Total 18 Páginas
		
LD7522 Hoja de datos, Descripción, Manual
LD7522
12/5/2008
Smart Green-Mode PWM Controller with Multiple Protections
REV:04
General Description
The LD7522 is a low startup current, current mode PWM
controller with green-mode power-saving operation. The
SOP-8/DIP-8 package integrated functions such as the
leading- edge blanking of the current sensing, internal slope
compensation, line compensation, and several protection
features. The protection functions include cycle-by-cycle
current limit, OVP, OTP, OLP, and brownout protection. It
provides the users a high efficiency, low external component
counts solution for AC/DC power applications.
Furthermore, to satisfy various protection requirements,
both latch-mode protection and auto-recoverable protection
can be easily achieved by configuring LD7522 on different
operation modes.
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 LD7522 is operating under light load or
no load condition.
-Patent Pending
Features
z High-Voltage CMOS Process with Excellent ESD
protection
z Very Low Startup Current (< 35μA)
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 Programmable Line Compensation
z OVP (Over Voltage Protection)
z OLP (Over Load Protection)
z OTP (Over Temperature Protection) through a NTC
z Brownout Protection
z Flexibility on Latch/Auto-Recoverable Protection Mode
z 500mA Driving Capability
Applications
z Switching AC/DC Adaptor and Battery Charger
z Open Frame Switching Power Supply
z LCD Monitor/TV Power
Typical Application
AC EMI
input Filter
www.DataSheet4U.com
OVP
8
VCC
7
LD7522
6
OUT
1
BNO
3
(-)LATCH
CS
4
52
GND COMP
Leadtrend Technology Corporation
LD7522-DS-04 December 2008
1
www.leadtrend.com.tw
photocoupler
TL431

1 page

LD7522 pdf
LD7522
Electrical Characteristics
(TA = +25oC unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
MIN
Supply Voltage (VCC Pin)
Startup Current
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V
VCOMP=3V
Protection Mode (note 1)
UVLO (off)
9.0
UVLO (on)
15.0
Voltage Feedback (Comp Pin)
Short Circuit Current
Green Mode Threshold VCOMP
VCOMP=0V
Current Sensing (CS Pin)
Maximum Input Voltage, VCS(OFF)
VBNO=0V (note 2)
VBNO=1.30V
0.800
0.748
VBNO=3.75V
0.650
Leading Edge Blanking Time
Input impedance
1
Delay to Output
Gate Drive Output (OUT Pin)
Output Low Level
Output High Level
Rising Time
VCC=15V, Io=20mA
VCC=15V, Io=20mA
Load Capacitance=1000pF
9.0
Falling Time
Load Capacitance=1000pF
Oscillator
Frequency
60
Green Mode Frequency
Frequency Temp. Stability
(-40°C –85°C)
Frequency Voltage Stability
(VCC=12V-30V)
Latch Protection ((-)LATCH Pin)
(-)LATCH Pin Source Current
92
Turn-On Trip Level
3.3
Turn-Off Trip Level
2.40
www.Data(S-)hLeAeTt4CUH.cpoimn de-bounce time
100
De-latch Vcc Level
(PDR, Power Down Reset)
6.8
Note 1: When OVP, OLP, or Latch Protection is tripped.
Note 2: Guaranteed by design because Vcs(off) can’t be measured when VBNO=0V.
Leadtrend Technology Corporation
LD7522-DS-04 December 2008
5
www.leadtrend.com.tw
TYP
MAX UNITS
20
3.5
3.0
0.7
10.0
16.0
35 μA
5.0 mA
mA
mA
11.0 V
17.0 V
2.5
2.35
4.0 mA
V
0.850
0.798
0.700
350
150
0.900
0.848
0.750
V
V
V
nS
MΩ
nS
1.0 V
V
50 160 nS
30 60 nS
65 70 KHz
20 KHz
3%
1%
100
3.50
2.50
8.0
108
3.7
2.60
8.7
μA
V
V
μS
V

5 Page

LD7522 arduino
LD7522
the EMI performance, thermal treatment, component sizes
and transformer design.
Voltage Feedback Loop
The voltage feedback signal is provided from the TL431 in
the secondary side through the photo-coupler to the COMP
pin of LD7522. The input stage of LD7522, like the
UC384X, has 2 diodes voltage offset before feeding into the
voltage divider with 1/3 ratio, that is,
V+ (PWM COMPARATOR
)
=
1
3
× (VCOMP
2VF )
A pulling-high resistor is embedded internally to eliminate
the requirement of another resistor in the external circuit.
Dual-Oscillator Green-Mode Operation
There are many different topologies 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 intends to reduce the
switching cycles under light-load or no-load condition either
by skipping some switching pulses or reduce the switching
frequency.
By using this dual-oscillator control, the green-mode
frequency can be well controlled and further to avoid the
generation of audible noise.
and achieve regulation. The LD7522 detects the primary
MOSFET current from the CS pin, which is not only for the
peak current mode control but also for the pulse-by-pulse
current limit. The maximum voltage threshold of the current
sensing pin is set as 0.85V. Thus the MOSFET peak current
can be calculated as:
IPEAK(MAX)
=
(0.85
VLINE _ COMPENSATION )
RS
A 350nS leading-edge blanking (LEB) time is included in the
input of CS pin to prevent the false-trigger due to the current
spike. However, the total pulse width of the turn-on spike is
decided by the output power, circuit design and PCB layout.
It is strongly recommended to adopt a smaller R-C filter (as
shown in figure 21) to avoid the CS pin being damaged by
the negative turn-on spike.
Internal Slope Compensation
A fundamental issue of current mode control is the stability
problem when its duty-cycle is higher than 50%. To stabilize
the control loop, slope compensation is needed in the
traditional UC384X design by injecting the ramp signal from
the RT/CT pin through a coupling capacitor. In the LD7522,
the internal slope compensation circuit has been internally
implemented to simplify the external circuit design.
www.DCautarSrheenett4SUe.cnosming, Leading-edge Blanking
The typical current mode PWM controller feeds back both
current signal and voltage signal to close the control loop
Fig. 21
Brownout Protection & Line Compensation
BNO pin plays 2 different roles in LD7522. The major
function is to set the brownout protection point, and at the
same time, the second function provides the line
compensation function like in LD7520.
Leadtrend Technology Corporation
LD7522-DS-04 December 2008
11
www.leadtrend.com.tw

11 Page


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