Leadtrend LD7537GL, LD7537GN Schematics
Rev. 01a
LD7537
12/15/2011
Green-Mode PWM Controller with Frequency Swapping
and Integrated Protections
General Description
The LD7537 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
z High-Voltage CMOS Process with Excellent ESD
protection
z Very Low Startup Current (<20μA)
z Current Mode Control
z Green Mode Control
z UVLO (Under Voltage Lockout)
z LEB (Leading-Edge Blanking) on CS Pin
z Internal Frequency Swapping
z Internal Slope Compensation
z OVP (Over Voltage Protection) on Vcc Pin
z Brownout Protection
z OLP (Over Load Protection)
z 300mA Driving Capability
Applications
z Switching AC/DC Adaptor and Battery Charger
z Open Frame Switching Power Supply
Typical Application
AC
input
Leadtrend Technology Corporation www.leadtrend.com.tw
LD7537-DS-01a December 2011
EMI
Filter
BNO
COMP
VCC
OUT
LD7537
CS
GND
1
photocoupler
DC
Output
Pin Configuration
LD7537
DIP-8 (TOP VIEW)
SOT-26 (TO P VIEW )
Ordering Information
Part number Package Top Mark Shipping
LD7537GL SOT-26 Green Package YWP/37 3000 /tape & reel
LD7537GN DIP-8 Green Package LD7537GN 3600 /tube /Carton
The LD7537GL is ROHS compliant.
Protection Mode
Switching Freq. VCC OVP OLP BNO Pin
65kHz Latch Auto recovery/ 65ms Auto recovery
GND
COMP
NC
7 6 5
TOP MARK
YYWWPP
1 8 2 3 4
OUT
NC
VCC
BNO
CS
YY, Y : Year code ( D: 2 004, E: 2005 …..)
WW, W : Week code
PP : Production code
P37 : LD7537
OUT VCC CS
YWP
123
GND CO MP BNO
37
pp
456
Pin Descriptions
SOT-26 DIP-8 NAME FUNCTION
1 8 GND Ground
2 7 COMP
3 5
BNO
4 4 CS Current sense pin, connect it to sense the MOSFET current
5 2 VCC Supply voltage pin
6 1 OUT Gate drive output to drive the external MOSFET
Leadtrend Technology Corporation www.leadtrend.com.tw
LD7537-DS-01a December 2011
Voltage feedback pin (same as the COMP pin in UC384X). Connect
a photo-coupler to close the control loop and achieve the regulation.
Brownout Protection Pin. Connect a resistor divider between this pin
and bulk capacitor voltage to set the brownout level. If the voltage is
less than threshold voltage, the PWM output will be disabled.
2
∑
Block Diagram
LD7537
3
Leadtrend Technology Corporation www.leadtrend.com.tw
LD7537-DS-01a December 2011
LD7537
Absolute Maximum Ratings
Supply Voltage VCC -0.3V ~29V
COMP, BNO, CS -0.3V ~6V
OUT
Maximum Junction Temperature 150°C
Operating Ambient Temperature -40°C to 85°C
Operating Junction Temperature
Storage Temperature Range -65°C to 150°C
Package Thermal Resistance (SOT-26, θJA) 250°C/W
Package Thermal Resistance (DIP-8, θ
Power Dissipation (SOT-26) 250mW
Power Dissipation (DIP-8) 650mW
Lead temperature (Soldering, 10sec)
ESD Voltage Protection, Human Body Model 2.5 KV
ESD Voltage Protection, Machine Model 250 V
Gate Output Current 300mA
) 100°C/W
JA
-0.3V ~Vcc+0.3V
-40°C to 125°C
260°C
Caution:
Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only
rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification
is not implied.
Recommended Operating Conditions
Item Min. Max. Unit
Supply Voltage Vcc 10 24 V
Start-up resistor Value 540K 1.8M Ω
4
Leadtrend Technology Corporation www.leadtrend.com.tw
LD7537-DS-01a December 2011
LD7537
Electrical Characteristics
(TA = +25°C unless otherwise stated, VCC=15.0V)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Supply Voltage (Vcc Pin)
Startup Current 12 20 μA
V
=0V 1.0 mA
COMP
V
Operating Current
(with 1nF load on OUT pin)
Holding Current Vcc=7V (latched) 430 μA
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 V
Open Loop Voltage COMP pin open 5.4 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, V
0.8 0.85 0.9 V
CS_OFF
Leading Edge Blanking Time 230 ns
Internal Slope Compensation 0% to D
Input impedance 1 MΩ
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 (-20°C ~85°C) 5 %
Voltage Stability (VCC=11V-25V) 1 %
=3V 2.0 mA
COMP
OLP Tripped/ Auto 0.47 mA
OVP Tripped /Latch 0.85 mA
=0V 0.25 mA
COMP
. (Linearly increase) 300 mV
MAX
5
Leadtrend Technology Corporation www.leadtrend.com.tw
LD7537-DS-01a December 2011
LD7537
PARAMETER CONDITIONS MIN TYP MAX UNITS
Gate Drive Output (OUT Pin)
Output Low Level VCC=15V, Io=20mA 1 V
Output High Level VCC=15V, Io=20mA 8 V
Output High Clamp Level VCC=20V 16 V
Rising Time Load Capacitance=1000pF -- 170 350 ns
Falling Time Load Capacitance=1000pF 50 100 ns
Max. Duty 75 %
OLP (Over Load Protection)
OLP Trip Level 4.3 4.5 4.7 V
OLP Delay Time
Brownout Protection (BNO Pin)
55 65 75 ms
Brownout Turn-On Trip Level
Brownout Turn-Off Trip Level
BNO Pin De-bounce Time 250 us
On Chip OTP (Over Temperature)
OTP Level 140 °C
OTP Hysteresis 30 °C
Soft Start Duration
Soft Start Duration 2 ms
1.00 1.05 1.10 V
0.75 0.80 0.85 V
6
Leadtrend Technology Corporation www.leadtrend.com.tw
LD7537-DS-01a December 2011
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