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PDF LD7536E Data sheet ( Hoja de datos )
| Número de pieza | LD7536E | |
| Descripción | Green-Mode PWM Controller | |
| Fabricantes | Leadtrend | |
| Logotipo |  |
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LD7536E
6/26/2012
Green-Mode PWM Controller with Frequency Swapping
and Integrated Protections
Rev. 01a
General Description
The LD7536E 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 will
reduce the noise level and thus help 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
DC
Output
OTP
VCC
OUT
COMP
LD7536E
CS
GND
photocoupler
Leadtrend Technology Corporation
LD7536E-DS-01a June 2012
1
www.leadtrend.com.tw
1 page  
LD7536E
Electrical Characteristics
(TA = +25C unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Supply Voltage (Vcc Pin)
Startup Current
12 20 A
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V
VCOMP=3V
OLP Tripped/ Auto
1.0 mA
2.0 mA
0.47 mA
OVP/OTP Tripped/ Auto
0.47 mA
UVLO (off)
7.5 8.5 9.5
V
UVLO (on)
15 16 17
V
OVP Level
25 26 27
V
Voltage Feedback (Comp Pin)
Short Circuit Current
Open Loop Voltage
VCOMP=0V
COMP pin open
0.2 0.25
4.8 5.4
mA
V
Green Mode Threshold VCOMP
2.4 V
Zero Duty Threshold VCOMP
1.5 V
Zero Duty Hysteresis
100 mV
Current Sensing (CS Pin)
Maximum Input Voltage, VCS_OFF
0.8 0.85 0.9
V
Leading Edge Blanking Time
230 ns
Internal Slope Compensation
Input impedance
0% to DMAX. (Linearly increase)
300
1
mV
M
Delay to Output
100 ns
Oscillator for Switching Frequency
Frequency, FREQ
60 65 70 kHz
Green Mode Frequency, FREQG
22 kHz
Trembling Frequency
4.0
kHz
Temp. Stability
(-20C ~85C)
5%
Voltage Stability
(VCC=11V-25V)
1%
PARAMETER
Gate Drive Output (OUT Pin)
Output Low Level
Output High Level
Output High Clamp Level
Rising Time
CONDITIONS
VCC=15V, Io=20mA
VCC=15V, Io=20mA
VCC=20V
Load Capacitance=1000pF
MIN TYP MAX UNITS
0 1V
8
VCC
V
16 V
-- 170 350 ns
Leadtrend Technology Corporation
LD7536E-DS-01a June 2012
5
www.leadtrend.com.tw
5 Page 
LD7536E
Internal Slope Compensation
In the conventional applications, the problem of the
stability is a critical issue for current mode controlling,
when it operates over 50% duty-cycle. As UC384X, It
takes slope compensation from injecting the ramp signal
of the RT/CT pin through a coupling capacitor. It therefore
requires no extra design for the LD7536E since it has
integrated it already.
On/Off Control
The LD7536E can be turned off by pulling COMP pin
lower than 1.5V. The gate output pin of the LD7536E will
be disabled immediately under such condition. The
off-mode can be released when the pull-low signal is
removed.
Over Load Protection (OLP) - Auto
Recovery
To protect the circuit from damage due to over-load
condition and short or open-loop condition, the LD7536E
is implemented with smart OLP function. It also features
auto recovery function; see Fig. 18 for the waveform. In
case of fault condition, the feedback system will force the
voltage loop toward the saturation and then pull the
voltage high on COMP pin (VCOMP). When the VCOMP
ramps up to the OLP threshold of 4.5V and continues over
OLP delay time, the protection will be activated and then
turn off the gate output to stop the switching of power
circuit.
With the protection mechanism, the average input power
will be minimized to remain the component temperature
and stress within the safe operating area.
VCC
UVLO(on)
UVLO(off)
COMP
4.5V
OUT
OLP
UVLO(off)
OLP Reset
OLP delay time
OLP trip Level
t
t
Switching
Non-Switching
Switching
t
Fig. 18
OVP (Over Voltage Protection) on Vcc -
Auto Recovery
The maximum VGS ratings of the power MOSFETs are
mostly for 30V. To prevent the VGS enter fault condition,
LD7536E series are implemented with OVP function on
Vcc. Whenever the Vcc voltage is higher than the OVP
threshold, the output gate drive circuit will be shutdown
simultaneously and the switching of the power MOSFET
is disabled until the next UVLO(on).
The Vcc OVP functions of LD7536E are auto-recoverable.
If the OVP condition, usually caused by open-loop of
feedback, is not released, the Vcc will tripped the OVP
level again and re-shutdown the output. The Vcc works
in hiccup mode. Figure 19 shows its operation.
Otherwise, when the OVP condition is removed, the Vcc
level will be resumed and the output will automatically
return to the normal operation.
Leadtrend Technology Corporation
LD7536E-DS-01a June 2012
11
www.leadtrend.com.tw
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LD7536E.PDF ] | |
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