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PDF LD7536S Data sheet ( Hoja de datos )
| Número de pieza | LD7536S | |
| Descripción | Green-Mode PWM Controller | |
| Fabricantes | Leadtrend | |
| Logotipo |  |
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LD7536S
4/5/2012
Green-Mode PWM Controller with Frequency Swapping
and Integrated Protections
Rev. 00a
General Description
The LD7536S is built-in with several functions, protection
and EMI-improved solution in a tiny package. It takes less
components counts or circuit space, especially ideal for
those total solutions of low cost.
The implemented functions include low startup current,
green-mode power-saving operation, leading-edge
blanking of the current sensing and internal slope
compensation. It also features more protections like
OLP (Over Load Protection) and OVP (Over Voltage
Protection) to prevent circuit damage occurred under
abnormal conditions.
Furthermore, the Frequency Swapping function is to
reduce the noise level and thus helps the power circuit
designers to easily deal with the EMI filter design by
spending minimum amount of component cost and
developing time.
Features
High-Voltage CMOS Process with Excellent ESD
protection
Very Low Startup Current (<20A)
Current Mode Control
Green Mode Control
UVLO (Under Voltage Lockout)
LEB (Leading-Edge Blanking) on CS Pin
Internal Frequency Swapping
Internal Slope Compensation
OVP (Over Voltage Protection) on Vcc Pin
OTP (Over Temperature Protection) through a NTC
OLP (Over Load Protection)
300mA Driving Capability
Applications
Switching AC/DC Adaptor and Battery Charger
Open Frame Switching Power Supply
Typical Application
AC
input
EMI
Filter
OTP
VCC
OUT
COMP
LD7536S
CS
GND
Leadtrend Technology Corporation
LD7536S-DS-00a April 2012
1
www.leadtrend.com.tw
DC
Output
photocoupler
1 page  
LD7536S
Electrical Characteristics
(TA = +25C unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Supply Voltage (Vcc Pin)
Startup Current
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V
VCOMP=3V
OLP Tripped/ Auto
OVP Tripped/ Auto
12 20 A
1.0 mA
2.0 mA
0.4 mA
0.4 mA
OTP Pin Tripped/Latch
0.85 mA
Holding Current
UVLO (off)
Vcc=7V (latched)
430
7.5 8.5 9.5
A
V
UVLO (on)
15 16 17
V
OVP Level
25 26 27
V
Latch-Off Release Voltage
3.25 V
Voltage Feedback (Comp Pin)
Short Circuit Current
Open Loop Voltage
VCOMP=0V
COMP pin open
0.25 mA
5.4 V
Green Mode Threshold VCOMP
*
2.2 V
Zero Duty Threshold VCOMP
1.4 V
Zero Duty Hysteresis
100 mV
Current Sensing (CS Pin)
Maximum Input Voltage, VCS_OFF
Maximum Input Voltage, VCS_min
Leading Edge Blanking Time
For High Line
0.85 V
0.65 V
230 ns
Internal Slope Compensation
Input impedance
Delay to Output
0% to DMAX. (Linearly increase)*
*
*
1
300
100
mV
M
ns
Oscillator for Switching Frequency
Frequency, FREQ
60 65 70 kHz
Green Mode Frequency, FREQG
22 kHz
Trembling Frequency
Temp. Stability
Voltage Stability
(-20C ~85C)*
(VCC=11V-25V)*
4.0
5
1
kHz
%
%
Leadtrend Technology Corporation
LD7536S-DS-00a April 2012
5
www.leadtrend.com.tw
5 Page 
LD7536S
threshold values. As a result, the current limit will be
lowered at high-line inputs. This compensation control
mechanism is developed with patents pending by
Leadtrend Technology.
The maximum voltage threshold of the current sensing pin
is set at 0.85V for low-line input. Thus the MOSFET peak
current can be calculated as:
IPEAK(MAX)
0.85V
RS
Voltage Feedback Loop
The voltage feedback signal is provided from TL431 at the
secondary side through the photo-coupler to the COMP
pin of the LD7536S. Similar to UC3842, the LD7536S
would carry a diode voltage offset at the stage to feed the
voltage divider at the ratio of RA and RB, that is
V(PWMCOMPARATOR )
RB
RA RB
(VCOMP
VF )
A pull-high resistor is embedded internally and can be
eliminated externally.
Fig. 16
A 230nS leading-edge blanking (LEB) time is included in
the input of CS pin to prevent false-trigger from the current
spike. In those low power applications, if the total pulse
width of the turn-on spikes is less than 230nS and the
negative spike on the CS pin below -0.3V, then, the R-C
filter is free to eliminate. (As shown in Fig.17).
However, the total pulse width of the turn-on spike is
determined according to output power, circuit design and
PCB layout. It is strongly recommended to adopt a
smaller R-C filter (as shown in Fig. 18) for larger power
application to avoid the CS pin being damaged by the
negative turn-on spike.
Output Stage and Maximum Duty-Cycle
An output stage of a CMOS buffer of 300mA driving
capability typically is incorporated to drive a power
MOSFET directly. And the maximum duty-cycle of
LD7536S is limited to 75% to avoid the transformer
saturation.
Leadtrend Technology Corporation
LD7536S-DS-00a April 2012
11
www.leadtrend.com.tw
Fig. 17
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet LD7536S.PDF ] | |
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